Project Flight Controls

Hogeschool van Amsterdam Amsterdamse Hogeschool voor techniek Aviation studies Project Flight Controls ALA Group: 2A1Q Jelle van Eijk Sander Groenendijk Robbin Habekotte Rick de Hoop Wiecher de Klein Jasper Schoen Rogier Stoelman Bill de Vries Amsterdam, March 19 2008

List of contents Project Flight controls Summary 1 Introduction 2 1. DEFINITION FLIGHT CONTROLS 3 1.1 Aerodynamics 3 General laws The wing 1.2 Primary flight controls 6 Elevators Ailerons Rudders Trim 1.3 Secondary Flight Controls 10 Flaps Leading edge devices Spoilers 1.4 Regulations and demands 12 Regulations Demands 1.5 Functional analysis 15 2. FLIGHT CONTROL ANALYSIS 16 2.1 Hydro mechanical system 16 Input Transport Convert Output Power Supply Control laws & limitations 2.2 Fly-By-Wire system 19 Input Convert Processing Transport Convert Output Power Control laws 2.3 Pro s and Con s 23 Pro s and Con s per system Pro s and Con s table 2.4 Comparison 24 Weighing factors table System compared 3. Modification plan 26 3.1 System overview 26 Modifications Construction overview 3.2 Designing aspects 28 Safety Maintenance Environment Planning 3.3 Cost and Benefits 29 Cost Benefits Break-even-point 3.4 Conclusion 30 3.5 Recomendation 31 Bibliography 32 2A1Q 2008

SUMMARY Project Flight controls 1 The project contains the definition and analysis of the flight controls as found in the Boeing 737 Next Generation (NG) and Airbus A320. When this is done, an actual modification and recommendation is made to the customer. The flight controls works on an aerodynamic force. The flow of air around a subject creates forces; these forces are explained with help of Bernoulli s law and the law of continuity. Important characteristics of the wing are the leading edge, the trailing edge, chord, mean camber line, camber, thickness and nose radius. The length or positions of these characteristics are important for the lift and drag. The airplane can move around three different axles; the longitudinal axis, the normal axis and the lateral axis with help of the primary flight controls. The elevator is used to turn the airplane around the lateral axis. The ailerons are the control surfaces mounted on the rear of each wing and are designed to make the airplane roll around its longitudinal axis. The rudder is the control surface on the tail of the airplane that can make the airplane yaw around its normal axis. There are also trim functions, these are used for lighten the control for the pilot. Altering the shape of the wings, which can be done by flaps, slats and spoilers can change the aerodynamic forces of the wings. These controls are named secondary flight controls. Flaps are used during take-off and landing. They increase the lift so the airplane can fly at a lower speed. There are two different types of spoilers; flight spoilers and ground spoilers. They enhance the working of ailerons and can be used as speed brakes. The system must meet the regulations by the European Aviation Safety Agency (EASA). This contains forces, controls and safety. The demands are made by the constituent they can be flexible and fixed. The flexible demands are wanted but not necessary. The fixed demands should always be met. The system of the Boeing 737NG and Airbus A320 consists of seven steps: input, convert, transport, process, convert, transport and output. First the analysis of the Boeing 737NG. There are two inputs; one of the pilot, using the steering column, and one of the autopilot. The signal of the pilot is mechanically transported by means of steel cables and pulleys. The autopilot signal is analog electrical. A Power Control Unit (PCU) amplifies the mechanical movement. The signal of the autopilot is transported to a servo. Both these signals move the control surface. The system receives its power of the engines during flight and the Auxiliary Power Unit (APU) on the ground. The Airbus A320 also has two inputs: the pilot and the autopilot. Both inputs are electrical and transported by the ARINC 429 protocol. They are transported to the flight computers that correct the input values. After the conversion step the signal is converted into a hydraulic signal and it is transported. The movement of the hydraulic fluid is converted into a movement, which is done by means of the actuators. Airbus programmed the flight computers to protect the pilot from abnormal control inputs, but this also gives the pilot more control in abnormal situations. To make a good overview, a pro s and con s table is set up. The hydro mechanical system of the Boeing 737NG scores 64%. The fly-by-wire system scores 71.5%. These scores are based on safety, maintenance, fuel efficiency, comfort, marketing and feedback. In order to advice Amsterdam Leeuwenburg Airlines (ALA) whether or not they should modify their fleet of 737 s, all aspects that are changed are known. Numerous systems, like the cable systems, must be removed and/or modified. Also the whole function analysis has been made for the modified fly-by-wire system. The new fly-by-wire system of the Boeing 737 s has been tested and certified. Because of the modification, the maintenance procedures for the Boeing 737 s change. The new fly-by-wire system makes the Boeing 737 s more fuel-efficient, so there is less carbon dioxide emission. From a marketing perspective, this is a positive aspect. Also the complete period of the modification process is planned. The feasibility of the modification of the Boeing 737 s depends on the costs and benefits. Therefore the costs of the modification need to be analyzed. Besides the costs, the modification to a fly-by-wire system also has benefits. Once the fly-by-wire system has been implemented, the maintenance costs drop. The fly-by-wire computers also improve the fuel efficiency, which saves ALA 3% on fuel costs. 2A1Q 2008

Introduction Project Flight controls 2 The airliner Amsterdam Leeuwenburg Airlines (ALA) has gathered a project group to create a way to make a modification from the hydro mechanical flight control system to fly-by-wire. ALA wants to modify their Boeing 737NG to use fly-by-wire just like an Airbus A320. The project group exists out of eight students of the Amsterdam School of Technology. The students in this project group have been carefully selected to realize this modification. An airplane uses flight controls to adjust and control the airplane s flight attitude. These controls exist of surfaces on the outside of the airplane that are moveable. The pilot can move these surfaces by means of cables that are attached to the surfaces outside the airplane. The older airplanes used to fly with this conventional flight system. The problem with everything in the world of engineering is that some systems get old and that there are newer better systems like fly-by-wire. The project group has chosen a Cessna 172 as an example to get an understanding of the basics of flight controls. With the use of this information, learned from the Cessna, the Airbus A320 fly-by-wire system will be analyzed to find out how it works. With the knowledge from these two systems it is possible to modify a Boeing 737NG to realize a fly-by-wire system. The report is divided into three chapters. In order to draw up the report the project group has first examined the aerodynamic forces that work on the control surfaces and the way those forces come to be. Knowing what a flight control really is, the project group has taken a Cessna 172 as an example. This helped to find out that the flight controls consist of primary and secondary flight controls. It is also important to know what kind of restrictions and demands there are on flight controls. To know what kind of parts there are used in the flight controls, a functional examination (1) is made. In the second chapter a comprehensive description is given about how a hydro mechanical and a fly-by-wire system work. Using this information the pro s and con s for the hydro mechanical and fly-by-wire system are determined. The advantages and drawbacks of each system have been put in a pro s and con s table in order to compare them to each other (2). In the final chapter a modification plan is created to fit a fly-by wire system in a Boeing 737NG. First, a system overview is made to look at what components are replaced and what can remain. The design of this system needs to have some demands that are put into designing aspects. With all the new parts that are ordered, the crews that need to be hired to make this modification possible cost money. An assessment on how much the entire system costs is made and in order to know if it s worth to replace the system or not, a recommendation to ALA (3) is given. For the project the book of Siers (2004) is used for structure. Also the HvA weekberichten are used. For a complete list of information sources, refer to page 32. In the appendix map the complete assignment given by ALA (Appendix I) and the pyramid model (Appendix II) can be found. 2A1Q 2008

Project Flight controls 3 1 Definition of flight Controls The airplane has a system that controls the movement around the three axis: the flight control system. In order to understand how the flight controls work, you need to understand which forces and laws of physics work on the controls (1.1). There are two types of flight controls. First the primary flight controls, consisting of rudder, ailerons, elevator and trim (1.2), and secondary flight controls, the slats, flaps and spoilers (1.3). Before the flight controls are modified, they have to meet the requirements of the law and the demands of ALA (1.4). There are two flight control systems, the hydro mechanical and the fly-by-wire system. These systems consists of various sub functions which are important to describe in analyses (1.5). The main sources that are used are: Vliegtuigen B1 en B3, The air pilot s manual 4 / The aeroplane-technical and the websites from FAA and the EASA. 1.1 Aerodynamics Before the flight controls are described, the theory behind the Aerodynamics is explained. The Aerodynamic laws (1.1.1) are the basics behind the flight controls. The theory behind the wing (1.1.2) is needed to understand the how the flight controls let the airplane move. 1.1.1 General laws There are two general laws for flight controls: the law of continuity (1.1.1a) and Bernoulli (1.1.1b). These two laws have effect on the lift of the plane and the way it handles. These two laws combined is called a venturi effect (1.1.1c). An airplane reacts on the center of gravity (1.1.1d). Some forces act in the center of pressure (1.1.1e). 1.1.1a Law of continuity In a stationary air stream the product of the surface and speed is constant. When the surface (A) decreases the speed (v) increases, this works the other way around too. This effect is referred as the Continuity law [1] and is also called: the law of containment of volume. [1] A = surface (m 2 ) ρ = air density (kg/m 3 ) v = speed (m/s) c = constant 1.1.1b Law of Bernoulli The law of Bernoulli [2] states that the energy per volume unit is constant. In other words the product of speed and static pressure is equal. [2] v= speed (m/s) c = constant ρ = air density (kg/m 3 ) p = Pressure (n/m 2 ) 2A1Q 2008

Project Flight controls 4 The law of Bernoulli can only be used if it meets these requirements: The air is incompressible. When reaching high speeds the air becomes compressible (around mach 0.5). Bernoulli is only useable at low speeds. Bernoulli's equation is not applicable when there is viscosity. Viscous means friction between different air layers so there mustn t be any friction between the air layers. The airflow is stationary. This means that each air particle flies in the same direction and at the same speed. The airflow is adiabatic. Adiabatic airflow can t receive incoming energy or outgoing. Bernoulli gives the relationship between speed and static pressure. When the speed, which is kinetic energy, increases the static pressure, which is potential energy, decreases. This works the other way around too. 1.1.1c Venturi effect The law of continuity and Bernoulli s law together is called the venturi (Figure 1.1) effect. This means that in a converging air stream (1), the surface between the different air streams becomes smaller. When this occurs the speed of the incoming air (2) increases and the static pressure decreases. In this case the pressure difference is measured by the tube under the venturi. The fluid in the tube goes up (3) (because of the pressure difference) when the static pressure (4) becomes higher. 1.1.1d Center of gravity Figure 1.1 Venturi 1. Venturi throat 2. Incoming air (m/s) 3. Pressure difference (N/ m 2 ) 4. Static pressure (N/m 2 ) Every object on earth stays on this planet because of gravity. Every little molecule of that object has got his gravity. For calculations we use the center of gravity. That is a point in the object where in theory the gravity grabs the object. This point is important for the balance of the airplane. 1.1.1e Center of pressure Not all the forces are going through the center of gravity, the sum of the total aerodynamic forces are going through the center of pressure. Because there is no distance between the force and this point there is no moment. 1.1.2 Aerodynamic profiles Every wing has got its own characteristics (1.1.2a). Small adjustments on the shape length etc. can lead to a different behavior of the airflow around it. But before looking at these differences between wings, it is examined how the air flows around a wing profile. Also the angle of attack and the boundary layer (1.1.2b) are explained. The boundary layer is split up in laminar and turbulent airflows (1.1.2c). The change of airflow is calculated with a Reynolds number (1.1.2d). 1.1.2a Lift and Drag Important sections of the wing (Figure 1.2) are, the leading edge (1), trailing edge (2), chord (3), mean camber line (4), camber (5), thickness (6) and nose radius (7). The length or positions (8) of these sections are important for the lift and drag. The most important function of the wing is to provide the airplane with lift. This is realized by a difference in pressure above and below the wing. 1. Leading edge 2. Trailing edge 3. Chord 4. Main camber line 5. Camber 6. Max. Thickness 7. Position on chord 8. Nose radius Figure 2.2 Wing profile Figure 1.2 Wing profile 2A1Q 2008

Project Flight controls 5 When there is no viscosity, the air molecules do not disturb each other. This means the speed of layers of air does not decrease or increase when the adjacent layer is faster or slower. In this situation there is no lift and drag. When this profile is placed in a narrow angle with the incoming airflow, the air travels faster at the trailing edge at one side of the wing. However, without viscosity the air flows to the other side and creates a pressure point. The pressure point found at the leading edge is in the opposite direction of the one at the trailing edge, so the two pressure points cancel each other out, resulting in no lift. In presence of viscosity, the flow on the end is not there so there is only one force, which is lift. This force is separated in a horizontal and vertical force, the lift and drag. This depends on: 1. Angle of attack 2. Wing characteristics Ad 1 Angle of Attack The definition (Figure 1.3) of the angle of attack (1) is the angle that the chord (2) of the wing makes with the incoming airflow (3). This angle can increase or decrease the lift of the wing. This also effects the drag. A greater angle creates more drag. 1. Angle of attack 2. Chord 3. Direction of incoming airflow Figure 1.3 Angle of attack Ad 2 Wing characteristics To compare wings of different sizes, realistic forces cannot be used because the surface of the wing is needed as part of calculating this force. To be able to compare wings of different sizes, a realistic number with no dimension is needed so the size is not important. To create this, the surface and the dynamic pressure are equaled out [3]. A Cl and a Cd coefficient are left. This indicates the lift and drag for different wing profiles so they can be compared. CF = F / q.s [3] When you replace the Lift or drag for force you get a Lift and drag coefficient CL = L / q.s and CD = D / q.s 1.1.2b Boundary layer If a wing is placed in an air flow, the air close to the surface is influenced by resistance from the wing. On the surface of the wing the speed of the air is reduced to zero. The speed of the higher layers in the airflow increases until the speed of the undisturbed airflow is reached. This layer is called the boundary layer. The dynamic viscosity plays a significant role here, without it the airplane would not experience friction and flying would become impossible. There are two types of boundary layers (Figure 1.4), laminar (1) and turbulent (2). A laminar layer is a layered stream of air moving over a surface, where the space between each layer is equal. The longer the laminar flow is, the more air layers it influences. 1. Laminar boundary layer 2. Turbulent boundary layer Figure 1.4 Turbulent and laminar boundary layer. A laminar boundary layer turning into a turbulent layer is called the change of air flow. The reason why this happens is that the air particles on a wing profile accelerate at the leading edge. When the air particles passes the point of the lowest pressure they slow down. When the low kinetic energy air particles reach the trailing edge, the higher static pressure at the trailing edge causes the flow to go from laminar to turbulent. 2A1Q 2008

Project Flight controls 6 1.1.2c Comparison of the laminar and turbulent layer The two boundary layers (Figure 1.5) have different properties. It is important to know which flow goes over the surface of an object because it affects the aerodynamic characteristics. For example a laminar layer has lower friction then a turbulent layer. This shows that for lesser fuel consumption a laminar layer is better than a turbulent layer. Figure 1.5 Speed profile of a laminar and turbulent air layer Laminar layer A layered profile. The speed profile shows the true speed. It is a thin layer. Low speed close to the wing surface. An equal increase of the speed. Little friction. The average speed of the air particles in the boundary layer is low. The boundary layer has little kinetic energy. Turbulent layer The speed profile shows the average speed. It is a thick layer. Higher speed close to the wing surface. A very high speed increase Much friction. The average speed is high. The particles in the boundary layer have more kinetic energy. 1.1.2d Reynolds number It is possible to calculate the change of air flow with the Reynolds formula [4]. When the Reynolds number is greater than 530.000, the air stream changes from laminar to turbulent. At low speed the length (l) of the laminar air flow is greater than at high speed. At greater height the dynamic viscosity (µ) increases which influences the length (l) of the laminar to turbulent air flow. [4] ρ = air density (kg/m 3 ) v= speed (m/s) l = length of the air flow (m) µ = Dynamic viscosity (N/ρ) 1.2 Primary flight controls The primary flight controls are the most important controls of an airplane, without them the airplane would be uncontrollable. There are four types of primary flight controls; the elevator (1.2.1) for the control around the lateral axis, the ailerons (1.2.2) to move the airplane around the longitudinal axis, the rudder (1.2.3) to move the airplane around the normal axis and finally the trim tabs (1.2.4) to maintain a direction and/or height. 1.2.1 Elevator The elevator is used to turn the airplane around the lateral axis. In the Cessna 172 the elevator is controlled via a system of cables and pulleys. They connect the yoke to the control surface located on the horizontal stabilizer on the back of the airplane. 2A1Q 2008

Project Flight controls 7 1. Purpose 2. System Ad1 Purpose The purpose of the elevator is to create a moment of forces along the lateral axis of the airplane (Appendix VI). This movement is created by the change in lift on the horizontal stabilizer. When for example the elevator moves up, the camber of the profile changes thus providing more lift. In the case of an elevator with negative camber (like the Cessna). This means the elevator creates a downward force pushing the nose of the plane upwards. Ad2 System The movement is controlled by the pilot and is transported via cables and pulleys (Figure 1.6). When the pilot moves the yoke (1), the movement is transported via a lever (2), to the cables (3 & 4). There is one cable for the upward, and one for the downward motion. These cables run through the airplane guided by pulleys and are connected to the elevator (5) which is located on the back of horizontal stabilizer (6). 1.2.2 Ailerons Figure 1.6 Elevator control on a Cessna 172 1. Yoke 2. Lever 3. Cable for upward motion 4. Cable for downward motion 5. Elevator 6. Horizontal stabilizer The ailerons are the control surfaces mounted on the rear of each wing and are designed to make the airplane roll around it s longitudinal axis. They are controlled by the wheel on the yoke in the cockpit and linked to that wheel via a mechanical system of wires and pulleys. Also there are many different kinds of ailerons, they all are different designs to counter the side effect that occurs (which is yawing caused by a difference in drag between the left and right wing when the ailerons are used), thus making the airplane more controllable. 1. Purpose 2. System 3. Variations Ad1 Purpose The ailerons (Figure 1.7) are the control surfaces at the rear of each wing. They serve only one purpose and that is to make the airplane roll controlled around its longitudinal axis. If the pilot wants the airplane to roll to the right for example, he or she turns the wheel on the yoke clockwise. This makes the aileron. On the left wing (1) move downward, which increases the effective camber of the left wing which in its turn increasing the lift (2), while the aileron on the right wing (3) moves upward, decreasing the effective camber and thus the lift (4) on the right wing. The difference in lift between the left and the right wing makes the airplane roll (5). There is a limit set to the maximum angle the ailerons can handle, this varies on different types of airplane, but on a Cessna its 30 upward and 30 downward from the horizontal position. Figure 1.7 The workings of the ailerons 1. Left aieron 2. Increased lift 3. Right aileron 4. Decreased lift 5. Rolling direction Ad2 System 1. Control wheel 2. Cables 3. Pulleys 4. Ailerons The control surfaces are linked to the controls in the cockpit using a system of cables and pulleys (Figure 1.8). When the pilot turns the control wheel (1), two cables (2) guided by a series of pulleys (3) move in opposite direction of each other. Each cable is attached to an aileron (4). Because the cables move in opposite direction of each other, the one attached to the left aileron moves in the opposite direction of the one attached to the right aileron, thus one aileron is pulled downwards and the other aileron is pulled upwards. Figure 1.8 Aileron controls 2A1Q 2008

Project Flight controls 8 Ad3 Variations When an aileron moves downwards the drag in produces increases, while the drag of the up going aileron is reduced. Because of the difference in drag between the left and right wing the airplane starts to roll in the opposite direction of the intended turn. This side effect is called adverse yaw. There are several options for an airplane designer to choose from to counter this effect, the usage of differential ailerons, the usage of frise-type ailerons or a system where the rudder and ailerons are combined. Differential ailerons are designed to minimize adverse yaw by increasing the drag on the up going aileron (which is the down going wing). This is achieved by deflecting the up going aileron through a greater angle than the down going aileron. Because of this the difference in drag between the left en right wing is decreased which eliminates most of the adverse yaw. With this type of aileron not all adverse yaw is eliminated. To counter all the adverse yaw the rudder needs to be used. Frise-type ailerons (Figure 1.9) are another solution to the problem of adverse yaw. Frise-type ailerons also increase drag on the up going aileron to make the difference in drag between the left and the right wing as small as possible. Because of the shape of friseailerons and the positioning of the hinge a part of the aileron protrudes into the airstream beneath the wing Figure 1.9 Frise-ailerons when the aileron moves upward, causing more drag. On the other wing that part does not protrude in to the airstream causing no extra drag. Frise-type ailerons may also be designed to operate like differential ailerons, eliminating adverse yaw all together. The rudder and ailerons also can be linked together so that when the pilot starts to bank the airplane using the ailerons, the rudder automatically compensates for the adverse yaw. 1.2.3 Rudder The rudder is the control surface on the tail of the airplane that can make the airplane yaw around its normal axis. The rudder is controlled by two paddles found at the feet of the pilot in the cockpit. If for example the pilot pushes the right pedal forward, the left pedal moves the same distance in the opposite direction. The pedals are connected to the rudder by the same kind of system of pulleys and wires used for the elevator and ailerons. When the pilot pushes the right paddle forward, the rudder moves to the right thus yawing the airplane to the right. A side effect occurs when using the rudder which is the airplane starting to bank in the direction of the yawing motion the airplane is doing. 1. Purpose 2. System Ad1 Purpose The rudder (Figure 1.10) is mounted on the rear end of the airplane. Its purpose is to make the airplane yaw, which means rotating around its normal axis. This works by for example pushing the left pedal (1), which moves the rudder to the left (2). This alters the rudder airfoil from a symmetrical shaped airfoil to a positively cambered one, creating sideways lift (3) so the airplane starts to yaw (4). The effectiveness of the rudder increases with the airplane s speed. When flying slowly, a large rudder deflection is needed to get the same effect as a small rudder deflection at high speeds. This is because the amount if lift generated (in this case sideways) also depends on the speed of the air flowing around an airfoil. In propeller driven airplane where the propeller is mounted in front of the nose (so also in front of the rudder), the slipstream from the propeller flowing over the rudder also increases its effectiveness. Figure 1.10 Yaw 1. Left pedal 2. Rudder 3. Lift 4. Yaw 2A1Q 2008

Project Flight controls 9 Ad2 System 1. Pedal 2. Cable 3. Pulley 4. Rudder Figure 1.11 Rudder controls The system (Figure 1.11) to link the pedals in the cockpit to the rudder on the back of the airplane is similar to the system used to control the elevator and ailerons. When a pedal (1) is pushed forward, it pulls on the cable (2) it is attached to. There is one cable fitted to each of the pedals. Those cables are guided by a series of pulleys (3) and move in an opposite direction of each other. The cable attached to the left pedal is attached to the left side of the rudder (4) and the cable on the right pedal to the right side of the rudder. Because of this the rudder is pulled on one side and pushed on the other, thus moving it. When an airplane is yawing to the left for example, the right wing is traveling faster than the left wing. Because the amount of lift a wing generates is also dependent on air speed, the right wing starts generating more lift than the left wing, thus banking the airplane to the left. The only way to counter this is to use the ailerons to counter the rolling motion. 1.2.4 Trim Trim tabs are devices on the trailing edge of the control surfaces of an airplane. Trim is used to lighten the controls for the pilot, by holding the control surfaces in a position which normally required an input force by the pilot. Most airplanes come with a trimmable elevator and a trimmable rudder, larger passenger planes also come with aileron trim. 1. Purpose 2. System 3. Variations Ad1 Purpose Trim is used to lighten the controls for the pilot. By moving the trim on the elevator the pilot can hold the elevator and thus the airplane in level flight, controlled climb or controlled descend without the need of an input force. When installed on the rudder, trim is used to hold a steady course when changing the power setting on a single engine airplane or in the event of crosswind. The aileron trim is used to hold the airplane straight along its longitudinal axis when for example the airplane is unbalanced due to a difference in weight between the left and the right side of the airplane. Ad2 System The movement of the elevator trim tab is controlled by a system of cables and pulleys (Figure 1.12). When the pilot moves the trim wheel (1) the movement is transported via two cables (2 & 3). There is one cable for upward motion (2) and one for downward motion (3). These cables run through the airframe and horizontal stabilizer on pulleys (4) and are connected to the trim tab (5). Figure 1 Trim control on a Cessna 172 Figure 1.12 Elevator trim control 1. Trim wheel 2. Cable for upward motion 3. Cable for downward motion 4. Pulley 5. Trim tab Ad3 Variations The trimming of an airplane is done with the help of various devices. The most common way to lighten the control, and trim the airplane is with the use of tabs (Figure 1.13). In the case of a balance tab the elevator or rudder (1) Figure 1.13 Balance tab 1. Elevator 2. Trim/balance tab as well as the balance tab (2) are connected to the controls, they work in opposite direction of each other. When used as a servo tab, only the balance tab is connected to the controls. In this case the tab is driven by a servo. Controlling the elevator or rudder with the help of tabs reduces the input force needed, and holds the elevator in the desired position without the need of a constant input force. The controls are much lighter because the tab gives the elevator more or less lift, pulling the control surface up or down. 2A1Q 2008

Project Flight controls 10 Another way to lightening the controls is with the use of an inset hinge (Figure 1.14) or horn balance. Whit an inset 1. Hinge 2. Aerodynamic force hinge (1), the elevator or rudder is Figure 1.14 Inset hinge pushed in the desired direction by the air dynamic force (2). The force is created by the air flowing around the profile, which pushes on the back of the control surface. In the case of a horn balance there is only a small part with an overlay on the edge of the elevator or the top of a rudder. A third way of lightening the controls is with weight balancing, this method is often used on airplanes with a stabilizer (Figure 1.15). This design uses the whole horizontal stabilizer as an elevator. The stabilizer rotates along an axis (1), the weight (2) keeps the stabilizer in balance. In this example there is also a tab installed (3). 1.3 Secondary flight controls Figure 1.15 Weight balanced stabilizer 1. Pivot point 2. Weight 3. Servo tab Secondary flight controls are flight controls that are not essential for flying an airplane. The main function of secondary flight controls is to improve control of the airplane. The aerodynamic forces generated by the wings can be changed by altering the shape of the wings, which is done by flaps (1.3.1), slats (1.3.2) and spoilers (1.3.3). 1.3.1 Flaps Flaps are used during take-off and landing. They increase lift so the airplane can fly at a slower speed. There are various types of flaps that are used on airplanes. Each type of flap has its own Cl-α and Cl-Cd diagram (Appendix VII). On take-off and landing, an airplane uses different flap settings. 1. Purpose 2. Types of flaps 3. Operation Ad1 Purpose The purpose of flaps is to increase lift at a lower airspeed. By extending the flaps, which are located at the trailing edge of the wings, the camber increases so the wing produces more lift at the same speed or the same amount of lift at a lower speed. Besides increasing lift, extended flaps also increase drag. In the first stages of extension the lift increases more than the drag, while in the last stages of extending the drag increases more than the lift. Depending on the type of flap used the lift/drag ratio varies. Ad2 Types of flaps There are four common flap types. The plain flap (Figure 1.16a) is the simplest type of flap. The flap (1) rotates around a hinge which is located partly inside the wing (2). This increases the wing camber and results in a increase in both lift and drag. The surface of the wing decreases when the flap is extended. The split flap (Figure 1.16b) (1) deflects from the lower surface of the wing (2). Like the plain flap this type increases the lift but produces even more drag. When the flap is extended the camber increases but the surface of the wing stays equal. The slotted flap (Figure 1.16c) is almost the same as the plain flap. The difference is that the flap (1) does not only rotate but also moves backwards. This is an advantage compared to the plain flap because when extended, the slot (2) between the flap and the airfoil makes it possible for high energy air from beneath the wing (3) to flow to the upper surface. There it accelerates the boundary layer which results in a delay in air separation and thus increases lift. Large airplanes use double or even triple slotted flaps (Appendix VIII). 2A1Q 2008

Project Flight controls 11 The Fowler flap (Figure 1.16d) (1) slides backwards on tracks from underneath the wing (2). This increases both camber and wing area. In the first stages of extension the lift increases more than the drag. Like the slotted flap the Fowler flap has a slot (3) which delays airflow separation. 1. Flap 2. Wing 1. Flap 2. Wing Figure 1.16a The plain flap Figure 1.16c The slotted flap 1. Flap 2. Wing 3. Slot Figure 1.16b The split flap Figure 1.16d The Fowler flap 1. Flap 2. Wing 3. Slot Ad3 Operation In the cockpit the pilot operates the flaps by selecting the degree of flap with a lever or switch. In smaller airplanes the flaps can also be operated manually by a handle which is connected by means of cables to the flaps. Before take-off, the flaps are lowered to the required take-off position. By doing this the wings produce more lift so the airplane takes-off at a lower speed and therefore uses less runway. After take-off the flaps can only be retracted when the airplane has gained enough speed. When the flaps are retracted at a too low speed, the airplane may stall. On approach the flaps are lowered to generate more lift so the airplane can have a lower approach speed. The flaps can only be lowered if the airplane is flying below the maximum flap extension speed (VFE), otherwise the flaps are damaged. When the flaps are lowered a side effect called ballooning occurs, unless the pilot lowers the pitch attitude. If an airplane is ballooning, the extension of flaps causes a short period of much more increased lift then drag. The result is an unpleasant short climb. Shortly after the climb the drag increases which slows the airplane down. With flaps extended, the angle of attack which causes the airplane to stall is lower than when the flaps are retracted. 1.3.2 Leading edge devices An airplane has several devices on the leading edge of the wing. The purpose of this devices is to prevent the airplane from stalling when flying slowly. The slats come out on the front of the wings and increase the camber, nose radius and sometimes the surface of the wing. There are also flaps on the leading edge. These are the Krueger flaps and they also increase the camber, nose radius and surface of the wing. There are also nose flaps and fixed slots to increase the angle of attack. Leading edge devices cannot be used without the trailing edge devices because then the airplane s tail would touch the ground during take off and landing and the pilot would only be able to see the sky and not the airstrip. The Cl-α graph shows the angle of attack (Appendix IX). 1. Slats 2. Krueger flaps 3. Nose flaps 4. Fixed slots Ad1 Slats A Cessna is a small airplane and does not have slats. Every big airplane like a Boeing or Airbus is equipped with slats. These slats increase lift and camber, nose radius and the surface of the wing. Slats are controlled by the pilot or by the auto slat computer. The slats are not used during cruise flight, only during take-off and landing. With slats extended an airplane can fly slower without stalling or it can fly with the same speed but with an bigger angle-of-attack. The slats have three settings (Figure 1.17): up (1), extended (2) and fully extended (3). The slats are operated by a hydraulic system. Retracting and extending is done using hydraulic actuators. When the airplane is near a stall, auto slat computers or the pilot gives a signal, which activates the servo valves. When this happens, pressure is applied to the main pumps. This results in extending of the slats and prevents or delays a stall. 3 2 Figure 1.17 Slats 1 1. Slats up 2. Slats extended 3. Slats fully extended 2A1Q 2008

Project Flight controls 12 Ad2 Krueger flaps The Krueger flaps drop down from the underside of the wing at the leading edge (Figure 1.18). They increase the nose radius of the wing and the camber line. Figure 1.19 Nose flap Ad3 Nose flap The nose flap (Figure 1.19) lowers the leading edge so it increases the camber of airfoil by increasing the mean camber line. Figure 1.18 Krueger flap Ad4 Fixed slots The fixed slots are not adjustable (Figure 1.20). These are made to increase the angle of attack. But with the fixed slots the surface is not extended but air flows through the gap so it provides more energy to the boundary layer to delay a stall. Figure 1.20 Fixed slots 1.3.3 Spoilers Commercial airplanes have two kinds of spoilers: flight spoilers which are used during flight and ground spoilers which are only used on ground or during landings. The ground spoilers also have an important function; this is to counter the ground effect. 1. Flight spoilers 2. Ground spoilers 3. Ground effect Ad1 Flight spoilers Flight spoilers (Figure 1.20) are located on the upper wing surface of the airplane (1). They enhance the working of ailerons and can also be used as speed brakes. If the spoilers are made to improve the working of the ailerons, they must work in the opposite way of the ailerons. For example, if the control wheel is moved right, the left aileron deflects downwards and the right aileron deflects upwards. To increase this effect, the right flight spoilers deflects when aileron deflection exceeds 10. As a result of the deflection, the right wing looses lift and gains drag. The right wing falls down and the airplane rolls to the right. Flight spoilers can also be used as speed brakes, to reduce speed or to increase the descent angle while maintaining the same speed. Figure 1.20 Spoilers 1 1. Spoilers Ad2 Ground spoilers Ground spoilers are also located on the upper wing surface, next to the flight spoilers. Ground spoilers are used as speed brakes when the airplane is on the ground during its roll-out after landing. Just before the airplane makes contact with the ground, the ground spoilers deflect. This removes the lifting properties of the wing so all the weight of the airplane is on the wheels, increasing the wheel brake effectiveness. Ad3 The ground effect When the airplane lands there is a lot of air flowing around it. This air acts like a cushion between the ground and the wings. This prevents the airplane from touching the ground. To make the airplane touch the ground the spoilers are deflected. This enables the air between the airplane and the ground to escape through the wings, thus eliminating ground effect. 1.4 Regulations & Demands Before designing a multifunctional fly-by-wire system, the system is tested to meet specific regulations (1.4.1). Also the constituent has made some demands (1.4.2) to make the design a success. 2A1Q 2008

1.4.1 Regulations Project Flight controls 13 The modification of the flight controls needs to comply with numerous regulations. These regulations can be found in the documents of the European Aviation Safety Agency (EASA), the parts which are relevant to the modification are found in the CS 25 (Appendix X). The regulations of the CS 25 suit the certification specifications for large airplanes on which every airplane must comply. All paragraphs mentioned in the CS25 can be divided in several factors like forces (1.4.1a) or cockpit controls (1.4.1b) but also safety (1.4.1c). The regulations mentioned by the Federal Aviation Authority (FAA) are almost full integrated in the regulations made by EASA. 1.4.1.a Forces As described in the CS25.397 the flight controls need to comply with several (feedback) forces (table 1). Also the forces which come up when designing flight controls are calculated, CS25.395 states that the forces are calculated at 25% above the maximum forces. In the CS25.457 is described how wing flaps, their operating mechanisms and their supporting structures are designed for critical loads. When designing the flight control system, all flaps and those operating mechanisms are checked and recalculated for the existing and possible new installed components. All the cables, pulleys, turnbuckles or fairleads which may have given greater forces when the system is redesigned, have to comply with the regulations in CS25.689. The used cables must also match these regulations. When the flaps or slats are operated, they are interconnected to each other as written in CS25.701. This compensates unsymmetrical loads or prevents damage to the flight controls. These regulations comply when programming software for the fly-by-wire flight contol system. Primary Flight Controls Control: Maximum Pilot Forces: Minimum Pilot Forces: Aileron - Stick - Wheel* Elevator - Stick - Wheel 445 N 356 DNm 178 N 178 DNm 1112 N 1335 N 445 N 445 N Rudder 1335 N 578 N Secondary Flight Controls Control: Limit Pilot Forces: Miscellaneous: Crank, wheel, or lever. Not less than 222 N nor more than 667 N. Dependent of kind of control. Twist 15 N Push-Pull To be chosen by applicant. Table 1 *D = wheel diameter in m 1.4.1.b Cockpit controls During the design, the regulations in CS25.399 must be respected in order to meet the safety requirements of EASA. The cockpit is designed with the right controls and correct labels. The flap handle for example should be labeled as flaps and the motions are labeled as up for flaps up and down for flaps down. In CS25.779 the motions and effects of the flight controls are mentioned. The primary and secondary flight controls respect the regulations in order to meet the safety requirements. All the motions of the designed flight controls match the effects described (table 2). When the controls in the cockpit are integrated, it is considered that the controls must comply with the regulations in CS25.781; the controls must be placed in the right order and labeled correctly. The knobs must have the described dimensions and should have enough room to move. 2A1Q 2008

Project Flight controls 14 Primary Flight Controls: Aileron Elevator Rudder Trim tabs Secondary Flight Controls Controls: Flaps Table 2 Motion and effect: Right (clockwise) for right wing down. Rearward for nose up. Right pedal forward for nose right. Rotate to produce similar rotation of the airplane about an axis parallel to the axis of the control. Motion and effect: Forward for wing-flaps up; rearward for flaps down. 1.4.1c Safety All the regulations mentioned in the CS25 are made for safety reasons. CS25.671 describes which safety requirements apply when the flight controls jam. Even when the engines fail, the airplane must still be controllable. When designing the flight control system, it is considered necessary to install a back-up system. CS25.865 also mentions that essential flight controls and other flight structures, located in designated fire zones or in adjacent areas, which would be subjected to the effects of fire in the fire zone, are constructed of fireproof material or shielded, so they are capable of resisting the effects of fire. 1.4.2 Demands The ALA staff would like to know if the 737NG fly-by-wire modification has enough benefits and is financial reliable. All demands required, flexible or desirable, are assessed (table 3). ALA Demands Required Flexible Desirable The newly designed system needs a better in-flight comfort than the old system. The newly designed system must fly more fuel-efficient than a hydro-mechanical flight control system. Reduction of CO2 emission. The design is at least as safe as the regular Boeing 737NG or Airbus A320 Maintenance costs are lower than the maintenance costs of a hydro mechanical system. The break-even point is reachable before the aircraft is taken out of service. The newly designed system should be more reliable and far more durable than the hydro mechanical system. The fly-by-wire systems are as uniform as possible, to insure lower maintenance costs. The implementation costs of the fly-by-wire system are as low as possible. X X X X X X X X X Table 3 2A1Q 2008

1.5 Function analyses Project Flight controls 15 The flight control system consists of a range of steps which are carried out to let the system function. The main function is controlling the movement of the airplane during flight. This main function is divided in five steps, the so called sub functions. These sub functions are all different, each step has a different function, and together they for fill the task of the main function. The different functions are placed in a function-block-diagram (Appendix XI). The sub functions are the following 1. Input 2. Convert 1 3. Transport 1 4. Process 5. Transport 2 6. Convert 2 7. Output 8. Feedback Ad1 Input When the pilot wants to change direction by using the pedals, yoke and/or control wheel, he creates an input. Ad2 Convert 1 The input is converted to a binary signal so it can be transported through electrical wires. A binary signal cannot move the flight controls, therefore it is converted back to a motion. The input can also be a motion and is converted to another motion to amplify the signal or to make it more easy to transport. Ad3 Transport 1 The binary signal is transported through electrical wires. The Motion signal is transported threw a series of cables and pulleys. Ad4 Process In the case of a Binary signal, a computer corrects the input signals, maximizing performance or preventing dangerous manoeuvres. The computer in the 737 process the information of all the instruments on the airplane when the pilot exceeds the limits an alarm go s off. Ad5 Transport 2 The transport method is for both systems mechanical. Ad6 Convert 2 A binary signal can t move the flight controls therefore it is converted back to a motion. The motion is converted to an other motion that amplify the signal Ad7 Output The movement of the flight control leads to a change/movement in one of the three axes of the airplane. Ad8 Feedback The fly-by-wire system has no physical feedback. There for sensors are placed on the flight control to tell the computer that it s moved. 2A1Q 2008

Project Flight controls 16 2 Flight Control Analysis Before ALA can be advised in changing their fleet 737 planes flight control systems, it is important to know how the conventional hydro mechanical systems works (2.1). To change the flight control system into a newer and possibly more efficient fly-by-wire system the workings of this fly-by-wire system and its computers is critical (2.2). When changing the flight control system it is very important to know the benefits and possibly drawbacks of the system change (2.3). The final step to the modification is the comparison in which the advantages and disadvantages are discussed (2.4). The system used to control the elevator is used as a reference. The main sources used to make this chapter are the manuals of the Boeing 737-NG and the Airbus A320 as well as the website smartcockpit.com. 2.1 Hydro mechanical system The hydro mechanic system as found in the Boeing 737NG can be divided in several subsystems. This system splits up in a input (2.1.1) from the pilot or the auto pilot. These signals are transported (2.1.2), this is done mechanical, electrical or hydraulically. These signals are not strong enough for the output so they are amplified. (2.1.3) This motion eventually becomes an output (2.1.4). The system is powered by hydraulics and electricity (2.1.5) and it has certain limitations (2.1.6). 2.1.1 Input Every system has an input and output. To explain the hydro mechanical system of the flight controls in a Boeing 737NG, we use the elevator as a reference. All other flight controls work the same way. In the Boeing 737 the flight control system has 2 inputs: the pilot (2.1.1a) and the autopilot (2.1.1b). 2.1.1a Steering column The pilot and co-pilot have their own control column (Figure 2.1). This column (1) can move forwards and backwards. On the same column the yoke (2) is situated. The steering column is connected with the other column, so when the pilot moves it, the column of the copilot moves in the same direction. This movement makes the pulley (3) move. This rotation of the pulley in turn moves the steel cable (4). That transfers the input to the control surfaces to the back of the aircraft. Figure 2.1 steering column 1. Steering column 2. Yoke 3. Pulley 4. Steel cable 2.1.1b Autopilot The autopilot is the second input for the elevators. Unlike the steering column this input device is analog electrical. The autopilot creates an input value for the autopilot actuators. The autopilot compares the data from the pitot tubes and gyroscopes with the inputted values in the flight control unit or flight management computer. The autopilot calculates how much the elevator, rudder and ailerons must move to hold the aircraft in the desired direction. 2.1.2 Transport After the input from the pilot or autopilot this motion or value is transferred for a correction or amplification. In a Boeing 737NG there are three ways to transfer a signal: electrical (2.1.2a), mechanical (2.1.2.b) and hydraulic (2.1.2.c). 2A1Q 2008

Project Flight controls 17 2.1.2a Electrical For the electrical part of the system electrical wires are used to transport the signal from A to B. This signal is binary or analog. In the Boeing 737NG there are only analog electrical connections. That means that the signals are not encoded with a data bus. With this method only one signal can be sent at a time through a cable. An analog signal is a variation in voltage of the signal. A binary signal has got two options; on or off. This means one or zero. The combination of zero s and one s gives the computer information. 2.1.2.b Mechanical Mechanical transport needs some basic parts. These are cables, pulleys, springs and other mechanical connections. Cables are used to transfer a force between two parts of the mechanical system. Pulleys are used to change the direction of the force, and guide the control cables trough the airplane. They can also be used to amplify the force. The mechanical part of the system is spring loaded to bring the controls and control column in a neutral position when no force is applied. 2.1.2.c Hydraulic For transport and controlling of forces, a hydraulic system is used. In the Boeing 737NG there are three separate systems (Appendix XII) for safety reasons. There are two different parts: 1. Rotating pumps 2. Actuator Ad 1 Rotating pumps Rotating pumps (Figure 2.2) use sprockets. These pumps create hydraulic pressure with the help of a mechanical motion. Both sprockets (1) rotate in a different direction. The rotation of the wheels transports the liquid from the left (2) to the right side (3) of the pump. 1. Sprockets 2. Incoming fluid 3. Outgoing pump Ad 2 Actuator Figure 2.2 Rotating pump Figure 2.3 Actuator 1. System A 2. System B 3. Increased pressure side A 4. Less pressure than side A 5. Actuator rod 6. Elevator An actuator is filled with hydraulic fluid. When there is more pressure on one side of the actuator, the volume of that part increases, which makes the actuator rod move. When every side is connected with a separate hydraulic system there is a backup system to make sure the actuator is still operational. There are actuators that move hydraulically one way and are pushed back mechanically the other way. Another type (Figure 2.3) is moved in both directions by hydraulic pressure. In this type there are two hydraulic systems; system A (1) and system B (2). When the pressure and volume of system A increases (3) and gets greater than system B (4), the actuator rod (5) moves to the right and give a mechanical movement to, for instance, an elevator (6). 2.1.3 Convert In the Boeing 737NG the amplification of the elevator controls is done by means of the mechanism close to the elevator itself. The control columns are used to control the elevator; the movement of those columns is transported and amplified. This amplification process is done by several hydro mechanical components such as a power control unit (PCU) (2.1.1.a) and a mach trim actuator for trimming the horizontal stabilizer (2.1.1.b). 2.1.3.a Power Control Unit The PCU in the Boeing 737NG is used for several flight controls such as the rudder and the elevator. A PCU (Figure 2.4) is based on the principle of leverage. Due to the use of hydraulics, the pilot has to apply little force to move the elevator. Figure 2.4 PCU unit 1. Input rods 2. Piston 3. Actuator rod 4. Elevator 2A1Q 2008

Project Flight controls 18 The pilot s input is transferred by means of the input rods (1) to the mechanical system that is used for the elevator. The hydraulic unit has two pistons (2) on an actuator rod (3) that moves the elevator (4). Powered by both of the hydraulic systems, the elevator can be used at full strength at all time. Also the advantage of using both hydraulic systems is when system A fails, system B can take over. That way the pilot never has to use excessive force to control the elevator on the aircraft and the elevator can never jam in a certain position. 2.1.3.b Trim actuator In the Boeing 737NG the horizontal stabilizer can also be used as a trim surface. Because of this, there is no need for a trim surface on the elevator. The trim actuator of the horizontal stabilizer is used to correct the movement or unbalance in the aircraft. It is also used to amplify the working of the elevator; however it s not common on a regular flight. When trimming the horizontal stabilizer, the pilots can use the control knob positioned on the column wheel (Figure 2.5). When the knob (1) is pressed, the servo (2) of the trim actuator is activated and it adjusts the angle of attack of the horizontal stabilizer (3). 2.1.4 Output The Boeing 737NG has two mechanical units to control the elevator, one mechanism and elevator on each side of the rudder, also there is one mechanical system located in the tail of the aircraft that controls the movement of the horizontal stabilizer. 2.1.5 Power supply Electric power is very important. Some components of the system work electrically, so it is important to have electrical power at all times. Therefore there are multiple energy sources available. Electric power is normally supplied by one of the two main generators driven by the engines. When the airplane is on the ground an external power source or the generator driven by the auxiliary power unit (APU) is used. A Boeing 737NG has got an APU in the back of the tail. This APU is a small gas turbine which provides the aircraft with electricity and hydraulic pressure. This gas turbine is installed in a fireproof and sound-reducing shroud. To start this turbine, electricity from the aircraft battery and fuel from the primary tank is used. This APU is used to start the engines of the airplane. The APU provides the engines of compressed air. This compressed air and fuel starts the engine. Each of the three generators can power the whole electric system of the aircraft when needed. But normally either the APU, or two engines drive the system. All three generators provide the same output and are individually connected to a generator control unit (GCU), which provide a stable voltage and frequency. When all three generators are out of order power from the main batteries are used to supply the aircrafts main systems, or the ram air turbine is used to power the most critical systems on board. The generators in the Boeing provide alternating current (AC), but important systems like the computers need direct current (DC) to operate. Therefore the Boeing is equipped with transformers, which convert AC the DC. In a situation where no generators are available there are static inverters, which convert DC to AC. 2.1.6 Control laws and limitations. Figure 2.5 Trim actuator 1. Trim control knob 2. Servo motor 3. Horizontal stabilizer The Boeing 737 can be fully operated manually; there are almost no limitations which the flight control computers (FCC) can set. The pilot is always able to set all functions of the flight controls, even in normal conditions. The FCC gathers all information from the sensors, which monitor the position of all flight controls and other flight information. The FCC checks the position and circumstances of the airplane for possible faults or miscalculations from the pilot. Then the FCC gives the pilot information about the conditions of the flight controls and how the airplane performs. The FCC can also check the hydraulic and electrical systems involving with the flight controls. 2A1Q 2008

Project Flight controls 19 When for example there is a leak in the hydraulics, the low pressure lights are lit to inform the pilot (Figure 2.6). The pilot then can reroute the hydraulic current to still maintain control over the used flight controls. There are multiple checklists available in the Boeing 737 Quick Reference Manual (QRM). The most common used checklist when a abnormal situation does occur is the Non-Normal Checklist (NNC). The NNC explains which functions come available in specific mentioned conditions. All of the pilot s controls do have multiple functions, for example if the flight spoilers become jammed, the control wheel of the First Officer now can control the ailerons. This way the pilot and the first officer maintain full control over the flight controls at any time. Also there are some limitations of the flight controls, these are found in the Aircraft Flight Manual. For example some in flight limitations; - Max flap extension altitude is 20,000 ft. - Holding in icing conditions with flaps extended is prohibited. - Do not deploy speed brakes in flight at radio altitudes less than 1000 ft. 2.2 Fly-by-wire Figure 2.6 Warning lights panel The fly-by-wire system, as found in the Airbus A320, starts with input from the side stick or the autopilot (2.2.1). The output signal from the side stick is converted using an A/D converter (2.2.2). The binary signal is transported to the flight computers where the input values are corrected (2.2.3). After the conversion step, the signal is converted to a hydraulic signal and transported (2.2.4). The movement of the hydraulic fluid is converted to a movement (2.2.5) which is done with the help of actuators. The last step is the output (2.2.6), in this case of the elevator. The system is powered by hydraulics and electricity (2.2.7), and it works with different control laws (2.2.8) in various situations 2.2.1 Input The input in the airbus is done through one of the two side stick s (2.2.1a), or by the auto-pilot (2.2.1b). The side stick converts the movement from the pilot to an analog electrical signal using a transducer, which is converted to a binary signal. The autopilot directly puts out a digital signal. 2.2.1a Side stick The side stick (Figure 2.7) is a method to convert the movement of the pilot into a usable analog electrical signal for the computers used in the fly-by-wire system. The side stick replaces the function of the steering column and control wheel on a hydro mechanical system. Unlike the hydro mechanical system, the side sticks are not linked to each other. Therefore the priority button is used to select the side stick used to control the aircraft. When both side sticks are used, the sum of the two inputs goes to the computer. To prevent this there are several warning systems to signal the pilots. The stick (1) is connected to an Figure 2.7 Side stick unit 1. Stick 2. Universal joint 3. Forward motion 4. Sideward motion 5. Connection rods 6. Transducer units universal joint (2) which separates the movements in forward (3) and sideward motion (4). The axes are connected to rods (5) which are connected to the transducer unit (6). This unit converts the movements from the rods to an electrical signal using pot meters. 2.2.1b Autopilot The second input method is the autopilot. Data is put in directly by the pilot via the flight control unit (FCU) or indirectly via the flight management computer (FMC). Since the output of the autopilot is already a binary signal, it is directly linked to the computers without the need of a converter. The FCU is used to select an altitude, heading or course and airspeed of the airplane. When for example the pilot wants the airplane to fly 280 knots at an altitude of 30.000 ft. with a heading of 210, he simply puts in the values after which the airplane controls itself. 2A1Q 2008

Project Flight controls 20 The FMC is a more sophisticated version of the FCU. A big advantage of the FMC over the FCU is that the route can be programmed after which the airplane follows this route. For safety there are three autopilots available in the A320, which are selected by the buttons on the FCU (Appendix XIII). 2.2.2 Convert Since the signals from the side stick s transducer are analog electrical, they are converted to binary signals. This conversion is done by an A/D converter. The A/D converter converts the analog input signal into a binary output code which is used by the computers in the airplane. The A/D converter splits the input signal in little steps, the accuracy depends on the number of bits used for this process. For example a four bits converter splits the signal in 2 4 =16 steps, and an eight bit converter does the same only with 2 8 =256 steps. 2.2.3 Processing The Airbus A320 has a very advanced computer system on board, used to control the airplane. This system makes the airplane different than planes like the Boeing 737. The airplane has seven primary flight control computers installed: Two elevator aileron computers (ELAC) These computers controls the elevator and ailerons. Three spoiler elevator computer (SEC) These computers controls the spoilers, the trim system and it is the backup computer for the elevator. Two flight augmentation computer (FAC) These computers control the rudder. Only the ELAC s are discussed. The computers contain several chips and processors (2.2.2a). These processors work together and are part of the elevator system (2.2.2b). 2.2.3a Computer content The ELAC s contain three processors, the main processor, the ARINC processor and the co-processor. The main processor receives the commands from the pilot and deals with the servo controls. The ARINC processor is dedicated to deal with the ARINC 429 data busses, which is necessary for the transport. Last, there is the co-processor. This processor deals with the flight control laws (2.2.8). The software for these computers is placed on On-Board Replaceable Modules (OBRM s). These modules are slotted in the back of the computer and can easily be pulled out (like a USB-Stick) so the software can easily be updated. 2.2.3b Electrical flight controls 1. Side stick 2. Main processor 3. Servo 4. Sensors Figure 2.8 Electrical flight controls The computers are part of a bigger system (Figure 2.8). If the pilot wants to go up for example, he pulls on the side stick (1). The signal is sent to the computers main processor (2). Then the signal is sent to the co-processor. The co processor checks the signal. If the system is within the limit of the flight envelope the signal is sent back to the main processor. If it is not within limits, the signal is corrected. After the correction the signal is sent back to the main processor. Finally the signal is sent to the ARINC processor, which converts the signal to be sent using the ARINC 429 protocol (2.2.4a), to the servo (3). The servo deflects the elevator upwards, which makes the airplane pitch up. The sensors read the new angle of attack and they send a feedback signal (4) back to the computers so the computers know the position of the elevator. 2.2.4 Transport There are two types of transport in the flight control system of the Airbus 320. The transport of digital electric signals (2.2.4a), and hydraulic fluids (2.2.4b). 2A1Q 2008

Project Flight controls 21 2.2.4a Electric transport Transport from the computers to the hydraulic system is done using electrical cables. To limit the amount of cables needed the signals are transported via the ARINC protocol. This means that the packages sent by the system are send via the same cable with pauses in between. The ARINC data bus system consists out of senders and receivers. The packages are called data words, the data bus sends data words with an address so only the receiver with the right address receives the package. The ARINC 429 system used by airbus is a one way system, so for feedback to the computers there are still two lines needed where a newer ARINC system like the 629 only uses one cable for two directions. 2.2.4b Hydraulic transport The hydraulic pressure is transported via aluminum or rubber tubes. They connect the actuators to the hydraulic reservoir. The tubes are made of special high strength material because the pressure in them is high; normally 3000 psi, or 2500 psi when powered by de ram air turbine. 2.2.5 Convert The last conversion is from a movement of the hydraulic fluids into a movement of the actual control surface. This conversion is done using actuators, which is very similar to the hydro-mechanical system. The only big difference to the cylinders used in the Boeing 737 is the way the actuators are controlled. Since the airbus is a fly-by-wire airplane, the cylinders are driven by servo valves controlled by the computers. The actuators in the airbus system are the only devices connecting the control system to the elevator. In case of a complete hydraulic failure the elevators are uncontrollable and pitching is done with the mechanical trim system. 2.2.6 Output In the case of the elevator, the output is done by the elevators. The airbus has two elevators, both connected to two actuators. One actuator per side of the airplane is active while the other acts as a damper. In case of an emergency when one of the actuators has failed, the other one can take over while the broken one can still act as a damper. The actuator of the Airbus is very similar to that of the Boeing, the only big difference is that the valve controlling the flow of hydraulic fluids is a servo valve. 2.2.7 Power The flight control system, as described above needs power to operate. Power is available in two different variations, hydraulic (2.2.7a) and electric power (2.2.7b). 2.2.7a Hydraulic power The hydraulic system in a fly-by-wire airplane like the A 320 is very similar to the hydraulic system used in the Boeing 737. There are three hydraulic systems and the control surfaces are driven by actuators. In the airbus there are three hydraulic systems like used in the 737, a blue labeled system driven by engine one, an electric driven blue system, and a yellow system driven by engine two (Appendix XIV). In case of an emergency the yellow system can also be driven by engine one and vice versa or the blue system can driven by the ram air turbine. 2.2.7b Electric power Electric power is very important for the working of the fly-by-wire system because the key components of the system are working electrically. To ensure electrical power at all times there are multiple energy sources available. The electrical system of the Airbus is build very similar to that used in the Boeing. There are three generators installed in the airplane, which al have the same output, so that the fly-by-wire system can work on any generator. The Airbus has two batteries for supplying power when the generators are turned off. When all systems fail, the ram air turbine can supply electrical power at speeds above 100 knots. 2A1Q 2008

2.2.8 Control laws Project Flight controls 22 The fly-by-wire system has a lot to do with computers. But this is also a big disadvantage, the pilot is not in total control of the airplane. So it can happen that the pilot pulls on his stick and nothing happens because the airplane will not allow it. For all these kind of problems Airbus came up with a solution called control laws. Written in these laws is what kind of rights and protection the system has. There are different control laws for different parts of flight or circumstances. The normal law is the standard configuration and is up when everything is normal (2.2.8a). If errors occur the system can degrade into the alternate law (2.2.8b), abnormal alternate law (2.2.8c) or the direct law (2.2.8d). When there is no computer anymore to control the controls there is a mechanical back up left (2.2.8e). Each law is shown different on the displays (Appendix XV). 2.2.8a Normal law This is the main flight control law and is in normal circumstances active. This law has three modes depending on the phase of the flight and also has some protection systems: 1. Ground mode 2. Flight mode 3. Flare mode 4. Protection Ad 1 Ground mode This mode is active when the airplane is on the ground. It gives the pilot direct control over the flight controls. Shortly after take-off this mode deactivates and shortly before the airplane touches the ground for landing this mode is activated. In ground mode the stabilizer trim system resets automatically. Ad 2 Flight mode This mode starts shortly after take-off and ends shortly before touch-down. The side stick movements are directed to the computer after which the corrected signals are directed to the flight controls. With the side stick in neutral position and the wings at the same level there is a gravitation of 1g. This means that the airplane always flies straight when there is no input. There are no requirements needed to change the pitch trim if changes are made in the airspeed, because the computer does that for the pilot. In flight mode the roll rate is not depended on the airspeed. With a full backwards or forwards deflection of the side stick the flaps automatically fully extend, to help keep the airplane from stalling. Ad 3 Flare mode The flare mode activates 50 ft. above the ground during the landing. It helps the pilot to decrease the vertical speed. When a go-around is made the flare mode reactivates itself again at 50 ft. above the ground. Ad 4 Protection Airbus has made a protection system to make the airplanes a lot more safer. The system has a load factor limitation. This prevents the pilot from overstressing the airplane, even if he gives a full deflection on his side stick. There is the attitude protection, the pitch is limited for 30 0 up and 15 0 down, also the banking is limited, in this case 67 0. The pilot can see these limits on his primary flight display (PFD) with green stripes. The airplane can never reach a higher angle of attack then the alpha max (after this point the airplane will stall). Last there is an overspeed protection, the pilot can never fly faster than the maximum airspeed set in the computer. 2.2.8b Alternate law When errors occur, the system degrades to the alternate law. On the Electronic Centralized Aircraft Monitoring (ECAM) displays a message appears, warning the pilots that they do not have the protection of the normal laws. The alternate law has only two modes, ground mode and flight mode, depending on the phase of the flight. There is another protection in alternate law: 1. Ground mode 2. Flight mode 3. Protection Ad 1 Ground mode This mode is totally identical to the normal law ground mode. 2A1Q 2008

Project Flight controls 23 Ad 2 Flight mode This mode starts shortly after take-off and ends shortly before touch-down. The alternate law of the pitch control degrades to the direct law when the landing gear is down. This is the backup system for the flare mode because this mode does not exist anymore. There is no longer any turn coordination available. Ad 3 Protection The load factor maneuvering is lost so the pilot can overstress the airplane. The green stripes on the PFD for the limits are now replaced by orange crosses and the stall limits are being displayed in red. The normal angle of attack protection is lost and replaced by a low speed stability function: The system has a new command which can pull the nose down to prevent the speed from decaying further. This command can be ignored by the pilot, he can pull on the side stick and this overrides the command. So the airplane can stall in alternate law. An audio stall warning becomes active. It also has a nose up command to prevent the airplane from overspeed. This can also be overridden by the pilot. The bank angle protection is also lost. There are failures in the system that can cause the low speed stability function to be lost in alternate law. 2.2.8c Abnormal alternate law This mode is activated when the airplane reaches an unusual attitude. This mode is to get the airplane back to a normal attitude. The pitch law becomes alternate law. The roll law becomes direct law and gets its own mechanical yaw system. When the airplane is back on normal attitude the following settings are active: pitch becomes alternate law, yaw also becomes alternate law and roll becomes direct law. The direct law is not activated when the landing gear is down. 2.2.8d Direct law This is the lowest level of flight control law and becomes active after a lot of failures. All the flight control inputs from the pilot are sent unmodified to the control surfaces. The sensitivity of the side stick is linked to the airspeed. On the PFD appears a message: Use manual pitch trim!. If the control law degrades to alternate law the direct law automatically becomes active when the landing gear is down. But if the autopilot is turned on the alternate law remains active until the autopilot is turned off. All protections are lost in direct law, but the errors still appear on the displays. 2.2.8e Mechanical back up If all the electrical flight controls are lost, the airplane can be temporally be controlled by the mechanical back up. The pitch control now is operated by the manual trim wheel. Lateral control is operated by the rudder pedals. Both controls must have hydraulic power. 2.3 Pro s and con s Both systems have their pro s and con s (2.3.1). The pro s and con s of both systems are compared together (2.3.2). 2.3.1 Pro s and con s per system To get a good overview of both systems advantages and disadvantages the positive and negative sides of the hydro mechanical (2.3.1a) and the fly-by-wire (2.3.1b) system are described. 2.3.1a Hydro mechanical system The hydro mechanical system has been around for a long time and is used on the bigger airplanes before the arrival of the new fly-by-wire system. The hydro mechanical system still has some benefits. The hydro mechanical flight controls give feedback to the pilot. The system also can fly without a power source without losing full control of the airplane. This is because the controls are still mechanical, and only rely on hydraulics for amplification. The hydro mechanical system also has some drawbacks. The system makes the airplane more thirsty, because the pilot continually needs to correct every tracking error, and the mechanical components are heavy. This is bad for the marketing aspect of the airliner, the consumer wants greener flights so lesser fuel consumption reduces carbon oxide emission. Because the hydro mechanical system uses cables to control the flight controls, the parts of this system will wear. Therefore the hydro mechanical system is checked regularly by hand, and the cables are changed frequently. Also the steel cables have friction, this friction influences the controllability of the flight controls. 2A1Q 2008

Project Flight controls 24 2.3.1b Fly-by-wire The first advantage of the fly-by-wire system is the precision, the computer can make very small corrections which help keep the airplane in the desired direction. This reduces fuel consumption and increases the comfort of the airplane. Another side effect of this efficiency is that with lesser fuel consumption the carbon dioxide emissions get lower, which is a good marketing point. Another advantage is the reliability of the fly-by-wire system, there is no friction because of the lack of mechanical parts. When something eventually breaks down in the airplane, with a fly-by-wire system the defect can easily be detected with the help of the built in test equipment (BITE). The lack of moving components is also an advantage because those wear out. Another advantage is safety, because the computers stand above the pilot, the pilot can never push the airplane beyond its boundaries. The last advantage is uniformity, the feel of the controls is very similar to any of the other new airplanes, equipped with a fly-by-wire system. Some of the drawbacks of the fly-by-wire system are the lack of feedback to the pilot. This is because of the electronic controls, the plane is controlled using a side stick. If there is a power failure the plane is not fully controllable, it is only possible to steer the airplane with the rudder and elevator trim. The last disadvantage is the price, a fly-by-wire system is expensive because of the complex electronic equipment that is needed to make this system. 2.4 Comparison Both systems are compared before conclusions are made. Therefore the systems are compared with the desired and flexible demands. This is done in a weighing factors table (2.4.1). The systems are compared to each other (2.4.2). 2.4.1 Weighing factors table The pro s and con s table (Appendix XVI) is made with the use of ten different factors. Each factor gets a rating, this rating is put into an weighing model which gives an accurate score of each system. To test both systems a close look at each system is needed. The best way to do this is by making a pro s and con s table. The table tests the system with the use the following factors: 1. Safety How safe each system is. 2. Modification Cost How much the modification costs. 3. Maintenance How easy it is to fix a problem. 4. Dependence on the source of electricity How much the airplane controls need to rely on a power source to control the airplane. 5. Fuel efficiency Here is taken a look at the fuel consumption of each system. 6. Uniform How easy it is for pilots and maintenance crew to switch from the modified Boeings to Airbuses of the air fleet. 7. Control feedback Airplane feedback, is the way the airplane controls gives feedback to the pilot. 8. Marketing Here is taken a look at what s possible on the marketing area. In other words if the fuel consumption gets lower, the greener the airplane becomes. This is because of lesser exhaustion gasses that makes the airplane more environment friendly. which can be used in commercials. 9. Wear and tear How long each system lasts before it must be replaced. 10. Comfort The comfort of the airplane for the passengers and the pilots. Each factor gets a rating from one to ten with each system. In this case a ten is the highest score and one the lowest. This gives each system a score, unfortunately this score is not the kind of score which is interesting. Because not every factor is as important as the other. For example the costs are more important than comfort so it is logical to calculate these ratings with a weighing factor. The weighing factor has been sorted from the highest percentage which stands on top of the table to the lowest which stands at the bottom of the table. With the use of the mark calculated together with the weighing model it is possible to create a realistic comparison between the systems. 2A1Q 2008

2.4.2 Systems compared Project Flight controls 25 The hydro mechanical system scores 64% after looking at the factors and weighing factors. The fly-by-wire system scores 71.5%. This means that this system is better. When it comes to the safety factor both systems are sufficient, it would be strange if it was not, but the airbus scores better here because of its protection systems built into the computer. On the other hand, the modification costs are very high for the fly-by-wire system and there are no costs to build an already built in system into the Boeing so the hydro mechanical system has a ten out of ten score. Then, the maintenance crew is better off with the newer fly-by-wire system because it is a lot easier to maintain and it needs fewer maintenance. With the hydro mechanical system the pilot is in total control of the airplane, even without electricity, which is not the case with fly-by-wire. With fly-by-wire the pilot has a small selection of controls without electricity. However the electricity can almost not lost completely, so this system is still adequate for this factor. The fly-by-wire system is also more efficient with fuel consumption because it is kept in a straight line better by the computers than a pilot can do. And if the newer fly-by-wire system is built into the Boeing there are only fly-by-wire controlled airplanes in the fleet, so the uniformity is high. The hydro mechanical system gives the pilot feedback through the steering column. The side stick of the fly-by-wire system does not have this feedback system because the airplane is controlled by the computers. Also on marketing the modification can be a huge role-playing factor. The fly-by-wire creates a lower fuel consumption so it is better for the environment, also the comfort is better because the airplane flies in a straighter line in comparison to the hydro mechanical system. Last, there is the wear level of the components; with the fly-by-wire system there are fewer moving parts in the system so they can be used for a longer time before they wear out. The fly-by-wire system is better but on many points is the hydro mechanical system on the better hand. So a real conclusion cannot be made at this point of research. 2A1Q 2008

Project Flight controls 26 3 Modification plan All aspects that are changed are known (3.1). There are several designing aspects that are taken into consideration (3.2). To get a good view of what kind of costs and how much these are a cost and benefits analyses is done (3.3). Advice is given in whether or not ALA should go ahead with the modification (3.4). 3.1 System overview Numerous systems are removed and/or modified (3.1.1). All these new systems are placed somewhere in the Boeing 737NG (3.1.2). 3.1.1 Modifications To modify the hydro mechanical system to a fly-by-wire system there are components removed (table 3.1) and also new components that are installed. Both systems have some kind of control limitation (3.1.1a). The following modifications are applied: Hydro mechanical system Modifications Input Steering column Removed Transport Cables and pulleys Removed Process Flight control computers Removed Convert Power control unit Stay Output Movement of elevator Stay Fly-by-wire system Modifications Input Side stick + transducer Instal Convert 1 A/d converter Instal Transport 1 Electric wires Instal Process Advanced flight control computers Instal Transport 2 Electric wires Instal Convert 2 Servo valve + Power control unit Instal + Stay Output Movement of elevator Stay Feedback Movement sensors Instal Table 3.1 Modification overview Ad1 Input A hydro mechanical flight control system uses a yoke with a control wheel mounted on it. This is removed and replaced with a side stick as used in the Airbus. The rudder pedals don t change as they are the same for both systems. Ad2 Convert 1 There for a A/d converter is placed to convert the analogue signal to a binary signal. Ad3 Transport 1 The input signal is transported to the computers. Normally the signal is transported through mechanical cables coming from the yoke and control wheel. With the fly-by-wire-system this signal is now binary, so the cables are replaced by electrical wires. The electrical wires are connected to the sensors and the computers. The binary signal is send using the ARINC 429 protocol. 2A1Q 2008

Project Flight controls 27 Ad4 Process Processing the binary signal is done by the Flight control computers. The flight control computers from the 737 are removed because the computer can not work with the new installed flight control system. An advanced computer system is installed to control the airplane. Ad5 Convert 2 The Power control unit can stay. It is only controlled differently. In the hydro mechanical system it is controlled by cables and in the fly-by-wire system they are controlled by servo valves. Ad6 Output The hydraulic system moves a series of actuators that move the control surfaces. These can remain the same as they are used both in the hydro mechanical system as in the fly-by-wire system. Ad7 Feedback The sensors on the elevator send a signal back to the computers to let the computer now if the elevator has moved. 3.1.1a Control limitation Both systems have different control limitations. The a320 has control laws, these set limitations to the control of the aircraft. The control laws are executed by the computers in the a320. The 737 has no control laws, it is more like a checklist. However the limitations of 737 are not controlled by computers, the pilot is alerted when he exceeds the limits of the airplane. The checklist is converted to control laws. After that a software program is written the new computers in the 737 can use the new control laws. 3.1.2 System overview To know where all the parts are placed in the 737 a schematic image is made (Appendix XVII). The input through the side stick is converted to an analog signal. The analog signal is send through intern transport to the a/d converter. The signal is now binary and send to the computers via ARINC protocol to process. The processed signal is send through electric cables (5) to the Servo valve and the PCU (6). The Servo valve makes the PCU move and the PCU moves the elevator (7).The movement of the elevator is measured by the position sensor(8) on the elevator. This signal is send to the flight control computer to now if the elevator is in the correct position. In the overview (Figure 3.1) of the entire system the various components are displayed with the boxes. The box with FCC are all the flight computers bundled together to make a clearer picture. If the pilot pulls the side stick backwards for example, the resulting signal is sent to the FCC. The FCC then checks this signal using the air and gyro data coming from the instruments, the control laws, the autopilot input, the elevator position sensor and other flight system computers. Then the signal is corrected and sent to the actuator. This in turn moves the elevator up. The elevator position sensor sends a signal back to the FCC so it knows what position the elevator is in. Figure 3.1 System overview 2A1Q 2008

Project Flight controls 28 3.2 Designing aspects An important aspect of the modification is safety. The modified Boeing 737 s is tested and certified (3.2.1). Because of the modification, the maintenance procedures for the Boeing 737 s change (3.2.2). The new fly-by-wire system makes the Boeing 737 s more fuel efficient, so there is less carbon dioxide emission. This is a very positive aspect from a marketing perspective (3.2.3). The most efficient time for modification is during a D-check (3.2.4). 3.2.1 Safety When the airplanes of ALA switch from hydro mechanical to fly by wire a lot of the flight control systems are changed, that can affect the safety if the system is not installed correctly. If the modification goes wrong the airplane is not useable. Because the airplane does not fit the required safety standard. When the airplane is stripped it is checked. When this check is complete and certified, the installation of the new fly-by-wire begins. This work is performed by a hired crew that has done this work before and are certified by EASA. The components used to create the fly-by-wire system need to fit the requirements stated by the law. With the right parts, the assembly of the fly-by-wire system starts. When the construction of the flyby-wire system ends, another safety check is preformed. When this phase is completed, a final test flight is preformed. When this series of test flight are completed without any problems the airplane is certified for normal use. A lot of things change for the pilot because the fly-by-wire system has more restrictions then the hydro mechanical system. The pilot steers the plane with a side stick instead of a steering column. Because the system is so different from the hydro mechanical system the pilots of the Boeing 737NG are educated for the usage of the new fly-by-wire system. Not only the pilots are educated, the engineers are re-trained as well. There is also a difference in components, the fly-by-wire system is almost fully electrical. The maintenance crew is educated to be able to do repairs on this system by computers. With all these safety precautions for implementation of the system and the re-educating of the flight crew and mechanics the fly-by-wire airplane is safer than a hydro mechanical system. The computers of the fly-by-wire system never exceeds the limits that have been programmed in the FCC s. If a computer failure occurs then the airplane has a total of three SEC s, two FAC s and two ELAC s which can take over each-others tasks. In case of a complete power failure the airplane still is controllable by using the rudder and elevator trim. The chance of a complete power failure is small because there are two batteries and three generators. 3.2.2 Maintenance The hydro mechanical flight control system, as found in the Boeing 737, is checked completely manually. This costs a lot of hours to preform. The airbus A320 uses a Build-In Test Equipment. This is part of the Central Fault Display System (CFDS), which facilitates troubleshooting and information about component replacement. This system is a great advantage because failed equipment is much faster identified. The on-board diagnostics and testing in fly-by-wire systems aircraft produces reliability that allows components to be replaced on condition and not according to a designated life cycle. Most electronic line replaceable units (LRUs) have a 30- minute remove and replace requirement. What is unique to fly-by-wire is testing the primary flight control processor (PFCP). The A320 has seven PFCPs (2.2.3). The PFCPs are tested with automated test equipment (ATE). The ATE simulates digital signals, measure their value and compare them to specifications in the component maintenance manual. This test takes about two to four hours and there are 4.000 to 5.000 test results. This results in a shorter duration of the maintenance on a fly-by-wire system and because there is less wear, the maintenance intervals become longer. The time between a C-check for the fly-by-wire system is 15 months or 6,000 flight hours, compared to 12 months or 2,800 flight hours for the hydro mechanical system. The flight controls of the fly-by-wire system are checked every 2 C-checks. 3.2.3 Environment An airplane with a fly-by-wire system is more environmental friendly than an airplane with hydro mechanical flight controls. The cables from the hydro mechanical flight controls needed a lot of grease every maintenance check. With the fly-by-wire system installed, the flight controls make no longer use of cables, so on an annual basis the environmental pollution is reduced. The fly-by-wire computers cause less deflection in the flight controls. This makes the fly-by-wire system more fuel efficient than an airplane that is controlled by hydro mechanical flight controls. Because the modified Boeing 737NG uses less fuel, there is a useful side effect for marketing. Global warming is a hot issue these days, so a more fuel-efficient airplane is positive for ALA. 2A1Q 2008

Project Flight controls 29 3.2.4 Planning schedule for modification. The airplanes of ALA need to be modified from a hydro mechanical flight control system to fly-by-wire during a logical time schematic (Appendix XVIII). The best time to build in the system is during a D-check (starts 2009). During a D-check the whole airplane is stripped into bare components and then rebuild. During this phase the modification crew is given time to build in the fly-by-wire system (42 days). A D-check takes approximately 28000 man hours and a total of six weeks to finish. At the end of these six weeks the build in phase is completed and the certification/testing phase starts. During these scheduled two months (62 days) the airplane is tested and certified. If all goes well and the first plane passes certification, the modification for the rest of the Boeing 737 NG starts. The other four Boeing 737NG s are modified like the first airplane, only the time of the testing and certification is shorter. The first modification is an example for the other airplanes so when the modification is approved the certification and testing period is shortened by a month (31 days). This is a total time of around three months (108 days) for the first airplane and the other four airplanes around two months (72 days). The modification can go faster with each plane because of the learning curve. The modification crew gain experience for each aircraft they modify, so this reduces the modification time with a day (24 hours) for each airplane that follows. 3.3 Costs & Benefits The feasibility of the modification of the Boeing 737 s depends on the costs and benefits. Therefore the costs of the modification are analyzed (3.3.1). Besides the costs, the modification to a fly-by-wire system also brings benefits (3.3.2). To conclude if the modification meets the demands of ALA, the break-even-point is calculated (3.3.3). To complete the report assumptions are made (Appendix XIX) 3.3.1 Costs When the modification of the flight control system is designed, also the cost aspects (Appendix XX) are provided. The costs can be divided up to direct cost (3.3.1.a) and fixed costs (3.3.1.b). 3.3.1.a Direct costs Before the total cost of the modification can mentioned, all costs are investigated. When the direct costs are calculated, all factors like material costs, maintenance costs, equipment costs and replacement costs are completely reported. All cost consuming the materials, man-hours and safety inspections of the project are compiled to give an impression of the overall material costs (table1). To give an indication of the savings for maintenance costs which occur when starting the modification the flight controls, both systems are compared (table2). Both systems do have multiple identical maintenance costs, but also there are some specific costs which occur on only one of the two systems. To give the operation a better working flow, transportation of workers and employees are considered. The transportation costs of the workers or equipment from the worksite and back are calculated as equipment costs. Also the rental of special equipment which the average worker does not have in his toolbox, like hydraulic pumps or specialized working gear, are calculated as equipment costs (table 3). Also all of the costs which can come up when the airplane is set to non active due to the modification of the flight controls are specified (table 4). In this specification the option is used to rental or short lease an airplane. This helps to make the modification more interesting because the non active costs, when the airplane is kept out of service, are as low as possible. When all costs are filled in, the total direct cost can be calculated (table 5). 3.3.1.b Fixed costs When designing a flight control system not only material and man hours count. To give more perspective, the complete overhead cost is calculated, meaning that for example the marketing costs, financing costs and administration costs are calculated (Table 6). Also the retraining is financed, those costs would come up when retraining the pilots and mechanics (table 7). Due the total overview, ALA has a clear vision over which fixed cost the whole project has (table 8). 3.3.2 Benefits Besides the costs, the modification of the Boeing 737 s provides ALA with benefits as well. The fly-by-wire system makes the airplane safer and because the computers are more accurate. With the fly-by-wire system implemented, the maintenance costs drop. The fly-by-wire computers improve the fuel-efficiency: this saves ALA 3% on fuel (3.3.2.a). Also the pilots, passengers and environment profit from the fly-by-wire system (3.3.2.b). 2A1Q 2008

Project Flight controls 30 3.3.2a Quantitative benefits 19% 22% Fuel Landing Navigation 21% 5% 8% Station Maintenance Flight crew 8% Cabin crew 17% Graph 3.1 Airplane operating costs. The highest benefits are realized when the airline saves on fuel and maintenance. Debits as flight crew and maintenance crew are not so much influenced by the modification (graph 3.1) The fly-by-wire system is more accurate, which reduces the fuel consumption of the airplane by 3%. Since the fuel prices are very high and increasing every day, this is a benefit for ALA. Each Boeing 737NG flies approximately 8000 kilometers a day. This results in a fuel consumption of 24.752.000 liters a year and costs ALA 12.376.000,00. When the airplanes use 3% less fuel, the benefit is 371.280,00 a year. The lower fuel consumption also reduces the CO2 emission of the Boeing 737NG. For ALA, this is positive from a marketing perspective. The maintenance costs are lower after the modification. Every year ALA saves 64.720,00 on each modified Boeing 737. The maintenance crew has to maintain only one system. Because the fly-by-wire system can be easily checked by computers, the duration of maintenance is shorter. The fly-by-wire computers can be easily replaced in case of a failure and the software on the computers can also easily be updated. The flight control system of the Boeing 737 is after the modification almost identical to the flight control system of the Airbus A320. 3.3.2b Qualitative benefits After modification the flight controls of the Boeing 737NG and the Airbus A320 are identical. This improves the productivity of the maintenance crew, because they have no longer to maintain two different flight control systems. The fly-by-wire system makes the airplane also more stable which improves the flight comfort for the passengers and reduces the workload for the pilots. With the fly-by-wire system installed, the airplane is more fuel efficient (3.2.3). This is not only positive for the image of ALA, but also attracts more environment aware passengers, so the total amount of CO2 emission is reduced. 3.3.3 Break-even-point To meet the demands of ALA a break-even-point (Appendix XXI) is calculated. A break-even-point needs some factors like the total savings (table 9) and total costs (table 10). Both have been calculated to give the right amount of relevant information for the project. When merging all cost and setting it into a multiple year plan, the break-even-point becomes visible (graph 1). The break-even-point is calculated for about 23 years, this calculation does not involve any form of inflation or other forms of financial devaluation. 3.4 Conclusion After a long period of research becomes clear how the flight controls work. Also the hydro-mechanical system, fly-by-wire system and what they contain becomes clear. After the research of both systems there was looked at the pro s and con s of both systems. By the pro s and con s is looked at the flexible demands like the costs, comfort, safety and fuel consumption. Then the project group took a look at the costs and benefits, now can become clear if the system after the modification is profitable or not profitable. The fly-by-wire system comes better out the test then the hydro mechanical system but the costs for the modification are very high. This can be earned back with the fuel consumption and better marketing. The receivings would be too low to make the system profitable in the period that the airplanes are operative. So the conclusion is not to build the fly-by-wire system into the B737 fleet. This would be too expensive. There are enough advantages for ALA to do the modification but the high costs make it unprofitable to do the modification. This is our conclusion that restricts to the demands of ALA. 2A1Q 2008

3.5 Recommendation Project Flight controls 31 As seen in previous paragraphs, the replacement of the Boeing 737 hydro mechanical flight control system with the more advanced fly-by-wire system has a lot of advantages. The new system is more reliable, lighter, and cheaper to maintain. But in the end, the modification is too expensive. When ALA would modify their 737 s, the invested money is only earned back when all five airplanes stay in service for another 23 years. Because the 737 fleet s average age is now six years, that means that the 737 s need to fly with ALA for 29 years which is too long. The expected life of the 737 is 20 years when used on a daily base, like the ALA 737 fleet. With this in mind project group 2A1Q can make two recommendations, which both not include the modification of the current fleet, and therefore need further investigation over the next seven weeks. 1. Keep all 737 s in service for the next 14 years. 2. Sell the current 737 fleet 737 s Ad1 Keep all 737 s in service for the next 14 years. In this situation everything stays the way it is, which means that no large investments are made. The current fleet costs a little bit more to maintain than a fleet with only A320 s and modified 737 s. Ad2 Sell the current fleet of 737 s In this situation, all five 737 s are sold. The airplanes are replaced with A320 s about the same age. This means that a large investment is made, but the maintenance and lower fuel consumption mean less flexible costs. This option brings the risk of not being able to sell the current fleet, or not being able to buy used A320 s for a reasonable price. 2A1Q 2008

Bibliography Books Anderson, John D., jr. Introduction to Flight 5e druk New York, 2005 Project Flight controls 32 Davis, D.P. Handling the Big Jets 3e druk London, 1988 Civil Aviation Authority, United Kingdom Kermode, A.C. Mechanics of Flight 8e druk London, 1979 Langedijk, C.J.A. Vliegtuigen voor B1 en B3, deel A Amsterdam, 1995 Hogeschool van Amsterdam Langedijk, C.J.A. Vliegtuigsystemen 2 Amsterdam, 1991 Hogeschool van Amsterdam McCormick, Barnes W. Aerodynamics Aeronautics and Flight Mechanics 2e druk Canada, 1995 Mosbach, B. Theorie voor privévliegers 10e druk Wassenaar, 1996 Thom, Trevor The air pilot s manual 4 / The aeroplane-technical 3e druk Shrewsbury, 2002 Underdown, R.B. Ground studies for pilots Navigation General and Instruments (Vol. 3) 5th edition Oxford, 1993 Wentzel, Tilly Het projectgroepsverslag Amsterdam, 2007 Hogeschool van Amsterdam Amsterdamse Hogeschool voor Techniek Docent kamer Aviation studies Continental 737 flight manual Hogeschool van Amsterdam 2A1Q 2008

Flight control jaar 1 Airbus presentaties internet Hogeschool van Amsterdam Docenten kamer Aviation studies Maintenance manuals Airbus a320 Hogeschool van Amsterdam Project Flight controls 33 Websites European Aviation Safety Agency (EASA) http://www.easa.eu.int Visited: 03-02-2008 Last update: 02-10-06 Smartcockpit http://www.smartcockpit.com/ Visited: 04-02-2008 Last update: 02-2008 http://www.pilotosdeiberia.com/areatec/airbus_sfo/23fbw_evol.htm visited: 03-2008 last update:unknown FAA Pilot's Handbook of Aeronautical Knowledge http://www.faa.gov/library/manuals/aviation/pilot_handbook/ visited: 02-2008 last update: 01-07-2008 http://personales.upv.es/juaruiga/teaching/tfc/material/trabajos/airbus.pdf visited: 03-2008 last update: unknown http://www.kls2.com/cgibin/arcfetch?db=sci.aeronautics.airliners&raw=1&id=%3cairliners.1993.180@ohare.chicago.com%3e visited: 03-2008 last update: unknown http://airsimmer.com/support/index.php?s=20e21baebaacad94126e502084b9998d&showtopic=269&pid=3379&st=0&#entry 3379 visited: 03-2008 last update: unknown http://www.airbusdriver.net/ visited:03-2008 last update: unknown 2A1Q 2008

Hogeschool van Amsterdam Amsterdamse Hogeschool voor techniek Aviation studies Project Flight Controls Appendixes ALA Group: 2A1Q Jelle van Eijk Sander Groenendijk Robbin Habekotte Rick de Hoop Wiecher de Klein Jasper Schoen Rogier Stoelman Bill de Vries Amsterdam, March 19 2008

Project Flight Controls _ LIST OF APPENDIXES I. Project assignment 1 II. Pyramid model 2 III. Planning 3 IV. Project lay-out 4 V. Group information 5 VI. Axis 6 VII. C l-α and C l/c d diagram 7 VIII. Slotted flap 8 IX. C l-α diagram (leading edge) 9 X. CS 25 Flight controls 10 XI. Function block diagram 14 XII. Hydraulic system (B737) 15 XIII. Autopilot (A320) 16 XIV. Hydraulic system (A320) 17 XV. Control laws (A320) 18 XVI. Weighing factors table 19 XVII. Construction overview 20 XVIII. Planning modification 21 XIX. Assumptions 22 XX. Costs 23 XXI. Break-even point 26 XXII. Proces report 27 XXIII. Tasks table 29 XXIV. Zelfsturende opdracht (Dutch) 30 2A1Q Maart 2008

Project Flight Controls 1 APPENDIX I Project assignment Uitgangssituatie De projectgroep is werkzaam bij de Technische Dienst, afdeling Engineering, van de luchtvaartmaatschappij Amstel Leeuwenburg Airlines [ALA]. Deze maatschappij heeft twee typen vliegtuigen operationeel: vijf Boeing 737's en zeven Airbus A320 s. Binnen ALA is een vereniging actief, die bestaat uit liefhebbers van de kleine luchtvaart. Deze maakt gebruik van de eenmotorige ALA Cessna C-172. Opdrachtformulering De projectgroep krijgt van de directie van ALA, aan de hand van een aantal specifiek gegeven richtlijnen (zie p. 5), opdracht uit te zoeken wat precies het doel van de Flight Controls is en hoe de werking ervan tot stand komt. Omdat deze per type vliegtuig verschilt, wil men inzicht krijgen in de voor- en nadelen van een conventioneel systeem (737) ten opzichte van het modernere fly-by-wire (A320). Bovendien wil de directie weten wat de consequenties zijn van een eventuele modificatie van het conventionele systeem naar een all fly-by-wire vloot. Hierbij denkt zij naast het aan de grond houden van een vliegtuig voor het uitvoeren van zo n modificatie tevens aan omscholing van het onderhouds- en vliegend personeel en wil zij een idee krijgen van alle kosten, die daarmee gemoeid zijn. De directie van ALA geeft het projectteam hiervoor in totaal een kleine zeven weken de tijd, waarna met een eindrapport het resultaat van het onderzoek wordt gepresenteerd. Interpretatie De projectgroep krijgt van de directie van ALA, aan de hand van een aantal specifiek gegeven richtlijnen, opdracht uit te zoeken wat precies het doel van de Flight Controls is en hoe de werking ervan tot stand komt. Omdat deze per type vliegtuig verschilt, wil men inzicht krijgen in de voor- en nadelen van een conventioneel systeem (737) ten opzichte van het modernere fly-by-wire (A320). Bovendien wil de directie weten wat de consequenties zijn van een eventuele modificatie van het conventionele systeem naar een all fly-by-wire vloot. Hierbij denkt zij naast het aan de grond houden van een vliegtuig voor het uitvoeren van zo n modificatie tevens aan omscholing van het onderhouds- en vliegend personeel en wil zij een idee krijgen van alle kosten, die daarmee gemoeid zijn. De directie van ALA geeft het projectteam hiervoor in totaal een kleine zeven weken de tijd, waarna met een eindrapport het resultaat van het onderzoek wordt gepresenteerd. 2A1Q 2008

Project Flight Controls 2 APPENDIX II Pyramid model Flight controls 1 Definition flight controls 1.1 Aerodynamics 2 Flight control analysis 2.1 Hydro mechanical system 3 Implementation flyby wire system 3.1 System overview 1.1.1 General laws 1.1.2The wing 1.2 Primairy flight controls 1.3 Secondary flight control 1.4 Regulation & Demands 1.5 Function analysis 1.2.1 Elevators 1.2.2 Ailerons 1.2.3 Rudders 1.2.4 Trim 1.3.1 Flaps 1.3.2 Leading edge devices 1.3.3 Spoilers 1.4.1 Regulations 1.4.2 Demands 2.2 Fly by wire system 2.3 Pro s and Con s 2.4 Comparison 1.1.1 General laws 1.1.2The wing 1.2.1 Elevators 1.2.2 Ailerons 1.2.3 Rudders 1.2.4 Trim 1.3.7 Power 1.3.8 Control laws 2.3.1 Pro s and Con s per system 2.3.2 Pro s and Con s table 1.3.1 Input 1.3.2 Convert 1.3.3 Processing 1.3.4 Transport 1.3.5 Convert 1.3.6 Output 2.4.1 Weighing factors table 2.4.2 System Compared 3.1.1 Modifications 3.1.2 System overview 3.2 Designing aspects 3.3 Costs and Benefits 3.4 Recommendation 3.5 Conclusion 3.2.1 Safety 3.2.2 Maintenance 3.2.3 Envoirement 3.2.4 Planning 3.3.1 Costs 3.3.2 Benefits 3.3.3 Break even point 2A1Q 2008

Project Flight Controls 3 APPENDIX III Planning 2A1Q 2008

Project Flight Controls 4 APPENDIX IV Project lay-out Font Part Subpart Font Size Style Note Headers Chapter Tahoma 12 Bold CAPS One decimal Tahoma 12 Bold Two decimals Arial Narrow 11 Bold Text Normal text Arial Narrow 10 Ad Arial Narrow 10 Italic TAB References Paragraphs Arial Narrow 10 Bold Subparagraphs Arial Narrow 10 Bold Blue Images Arial Narrow 10 Bold (.. ) Annexes Arial Narrow 10 Bold / Italic Term list Arial Narrow 10 Italic * Images List legend Arial Narrow 10 Bold Text legend Arial Narrow 10 Numbers in the images Arial Narrow 10 Bold Formulas Formula numbers Arial Narrow 10 Bold [.. ] Formula and magnitudes Arial Narrow 10 Bold Explanation formula Arial Narrow 10 Images Part Subpart Font Size Style Note Numbers Unclear image Line to the numbers Clear image Numbers in image Characters Big and small images Arial Narrow 12 Bold Header and footer Part Note Footer Frontpage and index nothing. Pagenumbering starts at page one. Header - Space between the headers and text After a chapter three enters Tahoma. After a paragraph (one decimal, example: 1.3) two enters Tahoma. After a subparagraph (two decimals, example: 1.3.2) two enters Arial Narrow. 2A1Q 2008

Project Flight Controls 5 APPENDIX V Group information Group members A Jelle van Eijk Jelle.van.Eijk@hva.nl jellevaneijk@gmail.com 06-16606410 B Sander Groenendijk Sander.Groenendijk2@hva.nl sander@hccnet.nl 06-27064551 C Robbin Habekotte Robbin.Habekotte@hva.nl rhabekotte@hotmail.com 06-20217685 D Rick de Hoop Rick.de.hoop@hva.nl rickdehoop@gmail.com 06-49616831 E Wiecher de Klein Wiecher.de.Klein@hva.nl wiecher10@hotmail.com 06-46571627 F Jasper Schoen Jasper.Schoen@hva.nl jasper_japser@live.nl 06-10565199 G Rogier Stoelman Rogier.Stoelman@hva.nl rogier56@hotmail.com 025-1237577 H Bill de Vries Bill.de.vries@hva.nl billdevries1989@hotmail.com 06-40434607 Supervisor Frenchez Pietersz f.pietersz@hva.nl Picture E H C A B D G F Rules Everything will be saved in.doc (word 97 2003). There is a point system. Two points is a serious conversation. You must pay an euro fine when you are not on time. Everything will be in English. Every week there will be two meetings. Everyone checks and corrects the files on BSCW. After every chapter there will be a group correction. We are making a standalone annexes book. BSCW will get the structure of our pyramid model. 2A1Q 2008

Project Flight Controls 6 APPENDIX VI Axis The airplane moves over three different axis, they come together in the centre of gravity (1) of the airplane. The normal axis (2) is the vertical axis around which the airplane yaws. The longitudinal axis (3) is the horizontal axis around which the airplane rolls. The lateral axis (4) is the horizontal axis around which the airplane pitches. 1. Centre of gravity 2. Normal axis 3. Longitudinal axis 4. Lateral axis 2A1Q 2008

Project Flight Controls 7 APPENDIX VII C l -α and C l /C d diagram 1. No flaps 2. Plain flap 3. Split flap 4. Slotted flap 5. Fowler flap Figure 1 Cl-α diagram 1. No flaps 2. Plain flap 3. Split flap 4. Slotted flap 5. Fowler flap Figure 2 Cl-Cd diagram With no flaps (1) selected, the wings produces the least lift and drag. The plain (2) and split flap (3) produce almost the same amount of lift and drag. The slotted flap (4) will stall at an lower angle of attack, but also much more lift. The Fowler flap (5) produces the most lift. 2A1Q 2008

Project Flight Controls 8 APPENDIX VIII Slotted flap 1. Flap 2. High energy flow 3. Slot 4. Boundary layer 5. Accelerated airflow 6. Separation flow 4 5 6 2 3 1 Figure 1 High energy air delays airflow separation When the flap (1) is extended, the high energy airflow (2) from underneath the wing flows through the slot (3) between the wing and the lowered flap. In the airflow above the wing there is a boundary layer (4) which contains low energy airflow. The high energy airflow accelerates this low energy airflow (5). This results in a delay in airflow separation (6). This improves the value of Cl,max. 1 1. Slots 2. Flaps 2 Figure 2 Triple slotted flap on a Boeing 737 When fully extended (Figure 2), there appear three slots (1) between the flaps (2). 2A1Q 2008

Project Flight Controls 9 APPENDIX IX C l -α diagram The leading edge devices always work together with the trailing edge devices. Here is shown what the effect is of the leading edge devices. 2A1Q 2008

Project Flight Controls 10 APPENDIX X CS 25 Flight controls 2A1Q 2008

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Project Flight Controls 14 APPENDIX XI Function block diagram The steps from pilot movement to elevator movement. Manoeuvre aeroplane Input Transport Output Input Convert 1 Transport Convert 2 Transport Output Input Convert 1 Transport 1 Process Convert 2 Feedback Output Transport 2 2A1Q 2008

Project Flight Controls 15 APPENDIX XII Hydraulic system (B737) The Boeing 737NG has three separate systems; system A, system B and the standby system. All the systems are supporting different functions. But all the functions are connected to at least 2 systems. So when a system fails there is no lost in hydraulic control. 2A1Q 2008

APPENDIX XIII Autopilot (A320) Project Flight Controls 16 The autopilot system of the Airbus consist out of the two autopilot computers (FMGC) which are connected to the FCU and the flight management computers (MCDU). 2A1Q 2008

Project Flight Controls 17 APPENDIX XIV Hydraulic system (A320) The hydraulic system of the Airbus consists out of three separate systems. When one system fails, it can be isolated with the help of valves. 2A1Q 2008

Project Flight Controls 18 APPENDIX XV Control laws (A320) The displays shows different things in different fases of the flight control laws, the mechanical back up (Figure 1), the alternate law (Figure 2) and the direct law (Figure 3). Here is shown how this is displayed on the displays. Figure 1 Mechanical back up Figure 2 Alternate law 2A1Q 2008 Figure 3 Direct law

Project Flight Controls 19 APPENDIX XVI Weighing factors table The pro s and con s table. All the advantages and drawback of each system have been put in one table. Factors Weighing factor Score hydro mechanical Score hydro mechanical with weighing factor Score fly-by-wire Score fly-by-wire with weighing factor Safety 25% 6 15,0% 8 20,0% Modification costs 10% 10 10,0% 1 1,0% Maintenance 15% 5 7,5% 9 13,5% Dependence on the source of electricity 10% 9 9,0% 6 6,0% Fuel efficiency 10% 6 6,0% 8 8,0% Uniformity 10% 5 5,0% 9 9,0% Control feedback 5% 10 5,0% 1 0,5% Marketing 5% 1 0,5% 10 5,0% Wear and Tear 5% 6 3,0% 9 4,5% Comfort 5% 6 3,0% 8 4,0% 100% 64 64,0% 69 71,5% 2A1Q 2008

APPENDIX XVII Construction overview Project Flight Controls 20 In this overview the position of the different parts that will be modificated is described. 1. Sidestick 2. Internal transport 3. A/d converter 4. Computer 5. Electric cables 6. Servo valve + PCU 7. Elevator 8. Sensor 2A1Q 2008

APPENDIX XVIII Planning modification Project Flight Controls 21 2A1Q 2008

Project Flight Controls 22 APPENDIX XIX Assumptions To complete the report assumptions are made. The d-check takes approximately 28000 man hours and the d-check will be finished in six weeks. D-check will take place every five years (20,000 Hour). Certification phase will take two months and a crew of four persons will work each day for four hours. Ala purchased every year a Boeing 737 NG. The planes are an average of six years old. Each Boeing 737 flies approximately 8000 kilometers a day Each Boeing 737 flies approximately 340 days a year This results in a consumption of 24.752.000 liters a year The average fuel consumption of the Boeing 737NG is 8,6 Liter on 1 kilometer. All prices are estimated. All man hours are estimated. The fuel savings will be 3% a year. All posts in the cost paragraph are estimated. Purchase and maintenance costs of both type of airplanes is estimated on 14 years. 2A1Q 2008

Project Flight Controls 23 APPENDIX XX Costs Table of the direct, fixed and total costs. Also an break-even point graph is displayed. Material Costs Parts Quantity Unit price Total Costs Extra Cockpit controls: - Side stick 2 80.000,00 160.000,00 - Pedals 2 80.000,00 160.000,00 - Handles 4 58.000,00 232.000,00 - Autopilot module 1 137.000,00 137.000,00 Fuselage: - Electrical wiring - 98.000,00 98.000,00 - Electrical data bus cables - 155.000,00 155.000,00 - Hydraulics tube - 78.000,00 78.000,00 Could be re-used from old flight control system. - ELAC 2 170.000,00 340.000,00 - SEC 2 190.000,00 380.000,00 - FAC 2 180.000,00 360.000,00 Wing & tail controls: - Servo motors 8 32.000,00 256.000,00 - Servo valves 14 45.000,00 630.000,00 - Actuator 14 60.000,00 840.000,00 Man-hours: - Supervisor 280 120,00 33.600,00 Quantity calculated an hour - Workers 2800 90,00 252.000,00 Quantity calculated an hour Safety inspection: - First inspection 8 145,00 1.160,00 Quantity calculated an hour - Second inspection 8 145,00 1.160,00 Quantity calculated an hour - Final inspection 8 145,00 1.160,00 Quantity calculated an hour Extra: - Software modification 1 300,000,00 300,000,00 - Mounting materials 1 132.000,00 132.000,00 Total: 4.547.080,00 Table 1 Material costs Maintenance Costs Items Hydro mechanical costs Fly-by-wire Extra costs - Electronics 30.000,00 40.000,00 Calculated a year. - Mechanics 70.000,00 30.000,00 Calculated a year. - Hydraulics 35.000,00 35.000,00 Calculated a year. - Software - 20.000,00 Calculated for one service - Man hour (C-Check) 25.000,00 10.000,00 Calculated a year. - Maintenance time (C-Check) 45.000,00 20.000,00 Calculated a year. Total: 205.000,00 155.000,00 Savings: 0,00 + 50.000,00 Total savings Table 2 Maintenance costs 2A1Q 2008

Project Flight Controls 24 Equipment Costs Items Quantity Unit price Total Costs Extra Rental special equipment 5 500,00 2.500,00 Rental transportation 16 200,00 3.200,00 Total: 5.700,00 Table 3 Equipment costs Replacement Costs Items Quantity Unit price Total Costs Extra Replacement airplane short lease 1 600.000,00 600.000,00 Quantity calculated a week Replacement extra costs 1 50.000,00 50.000,00 Extra on ground employee costs 90 100,00 9.000,00 Quantity calculated an hour Total: 659.000,00 Table 4 Replacement costs Total direct costs Items Total Costs Extra Material costs 4.547.080,00 Maintenance costs - Equipment costs 5.700,00 Replacement costs 659.000,00 Total: 5.211.780,00 Table 5 Total direct costs Reposted transfers Items Quantity Unit price Total Costs Extra Reposted transfers - Administration - 8.000,00 8.000,00 - Staff & Employees 38 170,00 6.460,00 Quantity calculated an hour - Depot costs 1 15.000,00 15.000,00 Quantity calculated a week - Secondary transport costs 8 250,00 2.000,00 Quantity calculated a week - General costs 1 10.000,00 10.000,00 - Marketing 1 8.000,00 8.000,00 Depreciation costs - Depreciation of real estate 1 4.000,00 4.000,00 Quantity calculated a week - Depreciation of equipment 0 0 0 Is covered by equipment costs Total: 53.460,00 Table 6 Reposted transfers 2A1Q 2008

Project Flight Controls 25 Retraining Items Quantity Unit price Total Costs Extra Retraining costs - Retraining pilots 15 350,00 5.250,00 Quantity calculated an hour - Retraining Mechanics 20 320,00 6.400,00 Quantity calculated an hour Continuing paying - Pilots 15 140,00 2.100,00 Quantity calculated an hour - Mechanics 20 125,00 2.500,00 Quantity calculated an hour Total: 16.250,00 Table 7 Retraining Total fixed costs Items Total Costs Extra Reposted transfers 53.460,00 Retraining costs 16.250,00 Total: 69.710,00 Table 8 Total fixed costs 2A1Q 2008

Project Flight Controls 26 APPENDIX XXI Break-even point Graph 1 Break-even-point Total savings Items Savings Extra Maintenance 50.000,00 For one airplane a year Fuel 186.000,00 For one airplane a year Total: 236.000,00 For one airplane a year Table 1 Total savings Total costs Items Total Costs Extra Direct costs 5.211.780,00 Fixed costs 69.710,00 Total: 5.281.490,00 Table 2 Total costs 2A1Q 2008

Project Flight Controls 27 APPENDIX XXII Proces report The First day the project team met there was a brainstorm session everybody was used too brainstorm. That was different in comparison with the first project then we needed to learn how to do that. The brainstorm session was good everything what lacked at the first projects was discussed. Strict rules where made and a point system was brought up by one of the team members. If your work is not finished you get a point, when you are to late and have no good reason you get a point. Three points and your name are not listed in the report. Most team members had an average knowledge about the subject. Before the project could start we had to read and find information. The week after the first meeting the team had a go and could begin Chapter one. After six weeks and a few days almost everyone had put a lot of time in the project. A few people had one of the three points. Nevertheless everything was finished on time. The team consists of eight members. We stayed together until the end. Fortunately no one has quite that would messed-up the whole schedule. To know how each member of the team performed, each person is individually comment. 1. Jelle van Eijk 2. Sander Groenendijk 3. Robbin Habekotté 4. Rick de Hoop 5. Wiecher de Klein 6. Jasper Schoen 7. Rogier Stoel 8. Bill de Vries Ad1 Jelle van Eijk Jelle was very observing in the beginning. He is not planned to finish this study but he is still motivated. It was no obstacle for this project. When something was wrong with his part he corrected it quick and learned from his mistakes. He also was not aggressive to critic. He did not always believe what someone said but thought about it and came with his own conclusion. He met his deadlines and the quality was good. But sometimes he made it to hard for himself and to difficult. The solution was sometimes for easier than he thought. He was clear and consequent as chairman. Ad2 Sander Groenendijk From the first day of this project Sander was present. He studied on the University of Enschede so he had experience with project work. He also kept his head to the project when a meeting became a little to easy going. His English was excellent so Sander changed most of the weird lines. He was clear and very present and was up to date with the work of the other group members. He met his deadlines and his work was qualitative good. He was motivated for the group. Sander is very sure off his own ideas but sometimes he can try to listen more to other people of the group. Ad3 Robin Habekotté Robin is a very motivated and present person. He likes to talk and sometimes this can be a little confusing in a meeting. His motivation was huge. He made everything on time and did everything what need to be done what was left behind. His work was qualitative fine and he read corrected lot parts of others. Robin says what he thinks and that can sometimes sound a little negative but at least he is honest and clear. Ad4 Rick de Hoop Rick is a guy with a lot of energy. He is very motivated to the study and this project. He thinks things over and his work is most of the time of good quality. Because he is busy with sport his planning is not always good. It happened a few times that his work was not completely done. Rick can also be quite cocksure. 2A1Q 2008

Project Flight Controls 28 Ad5 Wiecher de Klein Wiecher is a quiet guy it took the group a while to get to know him. The things he did were of good quality. He was always present and met his deadlines. He also was almost every time present on our Friday noon drink. Critic was not a problem he listened and changed his work. He was a little to quit as chairman but he was clear in his emails and regulations. Ad6 Jasper Schoen Jasper was almost always present a view times he was not present because he had personal problems Sometimes he was too easy with writing the report he is satisfied with a five when he can get a ten with a little bit more work. His parts where written like it was for children this needed to be more businesslike. Some times his Mac did not work properly with the other computers. Not only did he learn more about the flight controls he learned to plan his work. Nevertheless he always had his work finished on time. Ad7 Rogier Stoel Rogier was most of the time present on the meetings. His work was most of the time done but not always from good quality. It had to be corrected more times than other parts of this project. Also thought Rogier that things that were corrected by other team members were good at the way that he made it. So he could be a little cocksure. He looked a lot to other projects, that was not always reliable. But he learned some things this project like appreciating critic and learning from mistakes. Ad8 Bill de Vries Bill was almost always present the only times he was not present was for his driving exam. When he could not be present his work was already done and most of the time fine. When something was corrected Bill changed his part over and over until it was right. Sometimes he answered a phone call under a meeting that caused for some disturbance. This project was for us a big success. The planning was almost perfect, we had enough time and there was almost no increasing of work pressure. There were little errors but there were no big mistakes. 2A1Q 2008

Project Flight Controls 29 APPENDIX XXIII Tasks table Here are the tasks shown from the team members. Jelle Sander Robbin Rick Wiecher Jasper Rogier Bill 1.1 Aerodynamics X X 1.2 Primary flight controls X X 1.3 Secondary Flight Controls X X 1.4 Regulations and demands X 1.5 Functional analysis X 2.1 Hydro mechanical system X X 2.2 Fly-By-Wire system X X 2.3 Pro s and Con s X X X X X 2.4 Comparison X X 3.1 System overview X X 3.2 Designing aspects X X 3.3 Cost and Benefits X X 3.4 Conclusion X 3.5 Recommendation X Front page X Index X X X Preface X Introduction X Summary X Proces development X X Zelfstuderende opdracht X X X X English correction (big part) X 2A1Q 2008

APPENDIX XXIV Zelfsturende opdracht Mechanica Project Flight Controls 30 Opdracht 1 Eenvoudige situatieschets R1 / R2 = 5 R2 = 0,2 R1 = 5 * R2 = 5 * 0,2 = 1 Dus: Geldt voor alle tekeningen Opdracht 2 De liftkracht berekenen Om de liftkracht te berekenen [formule 1] zijn een aantal gegevens nodig. De CL waarde, dichtheid, snelheid en het vleugeloppervlak. -De CL waarde staat al in de tabel. Dit is voor alpha = 1 0,3 en voor de maximale uitslag (23 ) 1,2. -De snelheid 90 kts = 90 x 1,852 = 166,68 km/h 166,68/3,6 = 46,3 m/s -De dichtheid van de lucht op 3000ft hoogte is uit een isa tabel af te lezen. Dit is 1,121 kg/m3 -Het oppervlak is te berekenen door lengte maal breedte. Er mag vanuit gegaan worden dat de elevator rechthoekig is. L = CL * ½ * ρ * v² * S (1) CL= liftcoëfficiënt ρ = luchtdichtheid v = vliegsnelheid s = vleugeloppervlak uitwerking: alpha = 1 : s = l x b + 2 * (lhornbalance x bhornbalance) = 2,915 * 0,39 + 2 * (0,47 * 0,00225) = 1,158m2 CL = 0,3 ρ = 1,121kg/m3 v = 46,3m/s L = CL * ½ * ρ * v² * S L = 0,3 * 0,5 * 1,121 * 46,3^2 * 1,158 = 417,4N 2A1Q 2008

Max uitslag: s = l x b + 2 * (lhornbalance x bhornbalance) = 2,915 * 0,39 + 2 * (0,47 * 0,00225) = 1,158m2 CL = 1,2 ρ = 1,121kg/m3 v = 46,3m/s L = CL * ½ * ρ * v² * S L = 1,2 * 0,5 * 1,121 * 46,3^2 * 1,158 = 1669,66N Project Flight Controls 31 Opdracht 3 Bereken de kracht Fk Om de krachten in de kabels te berekenen [formule 2] moet bekend zijn waar het center of pressure ligt. Deze ligt op een kwart koordlijn (gegeven). Dit moet worden berekend bij alpha = 1 en bij maximale uitslag. Om Fk te weten moet eerst het moment berekend worden en vervolgens kan Fk berekend worden. M = F x r (2) M = moment = Nm F = kracht = N r = arm = meter Uitwerking: alpha = 1 : a = 0,21 x = 25% Mc (elevator) = 0,25 * 0,39 = 0,0975m M = 0 = Fk * a + L * x M = 0 = 0,21 * Fk + 417,4 * 0,0975 Fk = -(417,4 * 0,0975) / 0,21 = -193,79N Aangezien er een negatief getal uitkomt betekent dat dat de lift de andere kant op werkt (een negatieve kracht bestaat niet). Max uitslag: M = 0 = Fk * a + L * x M = 0 = 0,21 * Fk + 1669,66 * 0,0975 Fk = (1669,66 * 0,0975) / 0,21 = 775,2N Opdracht 4 Trekspanning in de stuurkabels De trekspanning Fs moet nu worden berekend [formule 3] bij alpha = 1 en bij maximale uitslag. Deze kan worden berekend met de eerder gevonden gegevens. Ook moeten er nog een aantal andere gegevens zoals het oppervlak berekend worden. 2A1Q 2008

Project Flight Controls 32 - Fk = kracht in de stuurkabels = - M = moment = - A = oppervlak = σ = F/A σ = Trekspanning = N/ m² F= kracht= N A = oppervalkte= m² (3) Uitwerking: alpha = 1 : Fk = 193,79N σ = Fk / A A = ¼ * d^2 * π A = ¼ * (5/32 * 2.54)^2 * π = 0,1237cm2 σ = 193,79 / 12,37 = 15,665N/mm2 Max uitslag: Fk = 775,2N σ = Fk / A A = ¼ * d^2 * π A = ¼ * (5/32 * 2.54)^2 * π = 0,1237cm2 σ = 775,2 / 12,37 = 62,67N/mm2 Opdracht 5 Kracht op het roer bij maximale uitslag Als het roer zich in zijn maximale uitslag bevindt, werkt er een kracht op. De piloot moet hierdoor een kracht uitoefenen op de stuurkolom. Dit kan berekend worden door middel van een vrije lichaam structuur te maken van de situatie. Het is in evenwicht, anders zou de knuppel bewegen. [Formule 4]. F1 x r1 = F2 x r2 (4) F= kracht = N r = arm= meters of Som van het moment = 0 2A1Q 2008

Project Flight Controls 33 Uitwerking: Fx = 0 = Fk + Fs Fx1 Fy = 0 = Fy M = 0 = R2 * Fk - R1 * Fs = 0,2 * 775,2 1 * Fs Fs = 0,2 * 775,2 = 155,04N Opdracht 6 Kracht op het trimvlak bij maximale uitslag Het trimvlak is er voor om de kracht op de stuurknuppel tot 0 te reduceren zodat de piloot geen kracht meer op de controls hoeft uit te oefenen om in een rechte lijn rechtdoor te vliegen. Hier is weer de liftformule [formule 1] nodig om de lift die het trimvlak genereert te berekenen. Uitwerking: s = l x b = 1,195 * 0,1165 = 0,1392m2 CL = 1,2 ρ = 1,121kg/m3 v = 46,3m/s L = CL * ½ * ρ * v² * S L = 1,2 * 0,5 * 1,121 * 46,3^2 * 0,1392 = 200,73N 2A1Q 2008