LOW COST FLIGHT TEST INSTRUMENTATION FOR EDUCATION PURPOSES

Transcription

1 LOW COST FLIGHT TEST INSTRUMENTATION FOR EDUCATION PURPOSES Jesús Javier Fernández Orío Head of Military Transport Unit. Airworthiness Department INTA Instituto Nacional de Técnica Aerospacial Cra. Ajalvir km.4 Torrejón de Ardoz Madrid Spain Lt. Col. Rafael Gómez Blanco Spanish Air Force Logistics Command. Combat Airplanes & School of Aeronautics. Universidad Politécnica de Madrid Pza Cardenal Cisneros Madrid. Spain Juan B. Terrones Aragón School of Aeronautics. Universidad Politécnica de Madrid. Pza Cardenal Cisneros Madrid. Spain 1. ABSTRACT The Spanish aeronautics industrial evolution has not been accompanied by the corresponding progress in Flight Testing education. In 2005, the main Flight Testing Spanish Actors (the Spanish Air Force; INTA, the MoD airworthiness technical authority; DGAC the Civilian airworthiness technical authority and EADS) came together to analyze how to establish a Spanish Flight Testing educational framework. Started formally on 2006, the MsC was designed with three main general objectives: To provide an educational stuff, with a multi-disciplinary approach, where theory and praxis should have a similar weight. To have a rigorous theoretical formation on classical Flight Testing areas, paying special attention to systems and airworthiness. To adjust the praxis, mainly flight hours, to reduce the overall cost of the course. An important part of the learning activities is the actual flight tests. These tests are carried out by the students on several platforms. INTA instrumentation laboratory has the responsibility of providing the FTI for the students flight tests. This equipment and installation has unique requirements. They have to reflect enough the state of the art and to do so in an affordable way for the assigned resources. The installation has to take in account that the instrumentation will be managed not by professionals but by students. At the same time, it has to be flexible enough to represent as much different kind of tests as possible. J. B. Terrones Page 1 of 14

2 A particular development based on the combination of standard Garmin-1000 data plus with additional specific sensors has been performed and applied for Cessna C172. The design, selection and integration of this instrumentation for the Spanish Flight Test Master are detailed in this paper. 2. ACRONYMS, ABBREVIATIONS, SYMBOLS AGARD: Advisory Group for Aerospace Research and Development, ARINC: Aeronautical Radio Inc. DGAC: Dirección General de Aviación Civil (Civil Aviation National Board) EADS: European Aeronautic Defence and Space. FTE: Flight Test Engineer FTI: Flight Test Instrumentation. INTA: Instituto Nacional de Técnica Aeroespacial (National Institute for Aerospace Technology) LRU: Line Replaceable Unit MFD: Multi Functional Display MoD: Ministry of Defense MSC: Master Course PFD: Primary Flight Display TPS: Test Pilot School 3. INTRODUCTION The objective of the present paper is the preliminary design of an onboard instrumentation for performances and handling qualities flight testing, from a bunch of economic sensors and the required instrumentation architecture which collects the necessary data, intended for a motorized fixed wing airplane with typical configuration. This design is originally intended for the instrumentation of already built airplanes with the purpose of training in the flight test techniques and analysis to future flight test pilots and engineers, but it could be used as well for normal flight testing with various motives, like the evaluation of the suitability of a given airplane for a determinate mission, the acceptance of acquired airplanes, or the integration of systems or equipment for development or certification/qualification. 4. GENERAL DESCRIPTION OF FTI FOR PERFORMANCES AND HANDLING QUALITIES 4.1 General description of instrumentation architecture for Flight Test purposes Any flight test program requires always to have clearly stated the needed parameters that will have to be recorded along with its specifications, creating a measurement list. In section 4.2 a parameters list will be defined for a certain kind of aircraft for general flight tests, and on section 4.3 the full measurement list will be defined for that aircraft. J. B. Terrones Page 2 of14

3 Once established this measurement list, the instrumentation design has to be created as well, attending to the specifications to assign the adequate sensors and recording systems for each parameter to fulfill the objectives. Flight test instrumentation systems have to be onboard the airplane which results in various problems like the available space, weight, energy consumption, etc and has to measure the precise parameters needed for the study of the airplane behavior. In a typical measurement process for flight test purposes the physical parameter has to be measured by a sensor, which provides an analogical or digital signal. This signal generally has to be converted in a digitalized signal compatible with our signal processing system, and will commonly be processed again to combine it with other measurements (formatting and multiplexing), for finally being stored, processed and/or sent by telemetry. During this process the measurement can t suffer any modifications or losses that may affect the subsequent data analysis. Additionally, the system is powered by energy that may be or may not be provided by the airplane power system. Finally the sensors must be correctly calibrated. In the next figure, adapted from AGARD 160 Vol.1 (reference [1]), a typical block diagram of the information evolution in general onboard flight test instrumentation is presented. 4.2 Parameters needed for performance & handling qualities tests After a study of the performances problem of an airplane, and evaluating the specific necessities for typical handling qualities flight testing, the parameters list for performances and handling qualities flight tests should include, at least, the following: Time 1. Reference time Weight parameters 2. Total weight 3. Remaining fuel Engine parameters 4. Fuel flow 5. Outside air temperature 6. Control parameters: RPM, EGT, oil pressure, nozzle position J. B. Terrones Page 3 of14

4 Movement parameters 7. Velocity 8. Linear acceleration 9. Angular velocity 10. Angular acceleration 11. Angle of attack 12. Sideslip angle 13. Euler angles 14. Pressure altitude 15. Altimeter setting 16. Geographic position 17. Height Piloting parameters 18. Control surfaces deflection 19. Controls position 20. Forces over the controls 21. Pilot s seat accelerations 4.3 Measurement list to instrument for a Cessna 172 type of aircraft Therefore, and using as a model a characteristic Class I airplane (small and light aircrafts), a Cessna 172R, a single engine aircraft with 4 seats capacity, designed for private aviation and pilot s training, a measurement list is written with the parameters listed on section 4.2, giving the range, precision and frequency considered enough for the study of performances and flying qualities for that particular aircraft. Obtaining these ranges, precisions and frequencies is not an easy work, especially for certain parameters. With some of them it has been possible to find reliable data from type certificates or airplane manuals. Information was also available in well recognized bibliography like Jane's all the World's Aircraft series (reference [2]). When these data wasn t enough, estimations were made according to the case, supported by reference documentation on flight testing like the US Navy TPS series (references [3] and [4]). Finally, for the remaining values and the final check, help from professionals with huge experience in the field of flight testing has been used. A confidence margin for estimating mistakes was established. These are the results: J. B. Terrones Page 4 of14

5 5. LOW COST FTI FOR PERFORMANCES AND HANDLING QUALITIES FOR A CESSNA 172 TYPE OF AIRCRAFT The purpose of this chapter is to show the preliminary design of a complete viable, economic and reliable instrumentation system that fully meets the previously exposed objectives. Some further work will have to be performed: Detailed description of the installation and mounting in the aircraft. J. B. Terrones Page 5 of14

6 Airworthiness studies Aerodynamics interferences with flight controls. Electronic interferences with the avionic system. Development and integration of software for data storage and processing. The instrumentation system general scheme is showed here on the next figure of the chosen Preliminary Design for the flight test instrumentation system for a Cessna 172R. All the equipment that takes part on the system, with the interconnections between them, is shown here. Colored lines have been used to differentiate the kind of connection or relation between the equipment whether is an Ethernet connection, analog data transmission, manually entered data or power supply. 5.1 Data storage and processing For this system, in which the data is going to be stored and processed, two options were considered: A PC/104 architecture or a commercial rugged laptop. The chosen option was the commercial rugged laptop, which is a laptop specifically designed for operating in hostile environments, not suitable for a normal laptop. These laptops can stand extreme temperatures, humidity, dust, falls, etc. Rugged laptops are designed in advance, and are available including the needed network cards, storage and processing capacity for its tasks. With this option an operator (FTE) can directly analyze in real time the flight data, perform calculations and execute any software that may be useful during the flight test. Attending to the hardware election, rugged option is not as flexible as the PC/104, but there are enough alternatives in the market from a lot of manufacturers with multiple options that will allow us to fulfill the specifications without problems for affordable prices. The figures in this paper means euros, taxes included and delivered on site. Finally it has been chosen, between the alternatives in the market, the Panasonic CF-31 model. This model counts with the technical characteristics showed in the following figure. This equipment is both powerful and versatile, showing ample compliance with the special specifications needed to be embarked on a flight test, collect the data and J. B. Terrones Page 6 of14

7 run the needed software for real time analysis, with an autonomy of 13.5 hours, enough for a full test working day. The price of this equipment is around Garmin G1000 Avionics System installed in Cessna 172R The Cessna 172R has installed a Garmin 1000 avionic system that provides the flight and navigation necessary for the safe operation of the airplane. This system is formed by LRUs, each one with a specific function inside the system, interconnected between them with avionic buses following the ARINC 429 protocol. From the following figure (reference [5]) it is interesting to focus on the four main components: the two GIA 63 modules, which are the integrated avionic units, serving as hubs or nexus ports between the different instrumentation and communication modules with the two GDU 1040 displays, the PFD and the MFD. These four components are interconnected by an Ethernet network which sends the information between them. The J. B. Terrones Page 7 of14

8 system is redundant, so if any of the modules stops working, there will still be at least one display to show the information to the pilot. This Ethernet information could be used to gather the information from all the instrumentation embedded on the Garmin 1000 avionic system. The Garmin 1000 system itself offers however another alternative that consists in the storage in an SD memory card installed in the MFD of all the information stored by the system. This alternative could allow obtaining by an insignificant inversion a great amount of the flight data after the end of the flight. This alternative, attractive at first sight, is discarded because according to the specifications, the data is stored once a second, and that does not meet the specifications of most of the parameters of the measurement list presented previously. This list shows the parameters that could be extracted from the Garmin 1000 avionic system installed in the Cessna 172R: Time Reference time Weight parameters Remaining fuel Engine parameters Fuel flow Outside air temperature Control parameters: RPM, EGT, oil pressure, nozzle position Movement parameters Velocity Linear acceleration Angular velocity Angular acceleration Angle of attack Euler angles Pressure altitude Altimeter setting Geographic position Height 5.3 Data acquisition unit and associated sensors For the other group of parameters remaining a Preliminary Design of an instrumentation system is presented in which each parameter will be measured by a sensor that meets the measurement specifications, connecting all of them to a data acquisition unit that will be connected at the same time to the storage and processing unit. Nowadays a lot of sensors and architecture manufacturers exist that can provide, with limited inversions, compact and reliable systems with which the measurement objectives can be fulfilled. In this section a proposal for the measurement of the J. B. Terrones Page 8 of14

9 remaining parameters to be measured is presented attending reasons as reliability, safety and price. Data acquisition system: A DEWESOFT s DS-NET data acquisition unit has been chosen, integrated by a DS- GATE unit, which receives all the information from the other modules and sends it via Ethernet to another equipment connected to it, in this case the rugged laptop. A DS- GATE unit cost To this DS-GATE module three DS-NET BR4-D modules are joined. These DS-NET BR4-D modules are formed by signal entrances that allow different kinds of signals, among them the ones given by the sensors chosen. Each module has a capacity to collect four different entries, with a sampling frequency of 10 khz and a resolution of 24 bits. DSUB connectors option has been chosen, because these connectors have the advantage that they can power the sensors without needing any additional equipment. It has to be said that from the 12 channels only 10 are used in this design, as will be shown later on, so 2 channels are free in case any additional sensor has to be joined to the system without extra inversion, if the measuring entrance is compatible with the module. Each of this DS-NET BR4-D modules cost The DS-NET system needs power supplied by an external battery, with power specifications that are met with SAFT s PV Module 20S battery, which offers a nominal continuous current voltage of 24 V, for a capacity of 10 A h and an energy of 240 W h, being able to stand regular charge and discharge cycles, and it is easily portable to mount it on the plane as needed. This battery model cost is J. B. Terrones Page 9 of14

10 Associated Sensors: o Sideslip Angle: For the measurement of this parameter, a vane (which could be made by a flat plane) oriented with the wind installed in the symmetry plane of the aircraft, joined to the axis of an angle sensor, an ASM s AWS1-90º - R1K angular potentiometer has been chosen. It has a measurement range of 0-90º and gives an analogical potentiometer output of 1 kω with reduced dimensions (97,5x68x68mm). This sensor cost is o Controls and control surfaces position: The Cessna 172R has a wheel-shaped kind of control, which allows the commanding of displacement to the elevator and the ailerons, and pedals to command the displacement of the rudder. To measure all the displacements an ASM s WS31C R1K - L35 - KAB2M cable displacement sensor has been chosen. This sensor gives a potentiometer output of 1 kω and a measuring range of 0-250mm. Other characteristics are its low weight (90 g), its reduced dimensions (31x31x60mm) and a collecting force of only 1.5 N. This sensor is made by a box that has to be fixed to one of the relatively moving parts, and a cable coming out that must be tied to the other moving part regarding where the box has been fixed. The cost is each. o Forces over the pedals: To determine the forces applied to the pedals two Measurement Specialties XFL225D - 1KN miniature load cells have been chosen. This sensor is a load cell with reduced dimensions (25 mm of diameter and 3 mm of depth), with a range of N that J. B. Terrones Page 10 of14

11 measures the compression load applied over its sensor. This load cells can be easily installed in the pedals thanks to its reduced dimensions, assuring that the pilot acts over the cell every time he acts over the pedals. Each of this sensor costs Rest of parameters Total Weight Through a procedure previous to the flight, calculating or measuring the total weight before the flight, and with the measuring of the remaining fuel already in the instrumentation system, the total weight can be calculated in every moment of the flight. Forces over the controls J. B. Terrones Page 11 of14

12 A pilot s force gauge has been chosen to measure the force over the controls. Cool City Avionics Model 916C, that has a measuring range of lbs (0-890 N), costs about Total budget One of the main objectives of this Preliminary Design was to be as affordable as possible regarding the sensors and equipment. So a list of the budget that would allow purchasing all the sensors and equipment needed for this Preliminary Design is displayed bellow: 5.5 Next steps in the design process The design presented on this paper is preliminary, and therefore it stays pending for the remaining actions for the system final design. In this section a brief description is going to be presented summing the next steps that would follow this Preliminary Design for the consecution of the final objective of having an onboard instrumentation system mounted on the aircraft and collecting all the necessary data: J. B. Terrones Page 12 of14

13 1. First of all, it will be necessary to determine the real possibilities of the Garmin 1000 avionic system, both the measurement characteristics of the parameters that the system measures and the way to extract the information from it. This step may force to go back to the Preliminary Design step to modify or add unconsidered elements to the system. 2. Secondly, an integration study of all the equipment and sensors in the system will have to be done. After buying the equipment, a bench should be built to prove that interconnections and behavior are compatible among all the sensors and equipment, and that we can obtain all the measurements in the desired way. 3. In third place, a study of the physical installation of all the sensors and equipment, both its installation onboard the airplane and the path of the cables connecting them. 4. In parallel to the physical installation, the programming and/or installation of the software that is going to be used in the tests must be done. In this step it will be fundamental to know already the objectives of the tests that are going to be performed to test and validate the software used in them. 5. Lastly the calibration process of the instruments could be started, and afterwards the full system calibration and tests, first on ground, and afterwards in air. Once this step is finished the plane would be ready for the start of the flight tests. 6. LESSONS LEARNED 1. There are a lot of possibilities in the market to fulfill small necessities. 2. The work and effort used in searching the different possibilities improve the skills of the students in the understanding of the problems. 3. Go shopping make the students gather a lot of knowledge on the different approaches for the same problem. 7. CONCLUSIONS 1. The good results of this first experience, make us decide to go ahead with this way of teach, real testing involvement. 2. A possible way of improving the results of the task is to make different teams working in parallel. Competence could improve the effort and benefits. 3. To make the full process, with the real work of installing and integrating the instrumentation, would increase the costs of the training, with not such a big added value for the students. 8. REFERENCES [1] AGARDograph 160 Vol. 1: Basic Principles of Flight Test Instrumentation Engineering. AGARD/NATO, [2] Jane's All the World's Aircraft, & previous. Jane's Information Group, J. B. Terrones Page 13 of14

14 [3] USNTPS-FTM-No. 103 Fixed Wing Stability and Control. U.S. Naval Test Pilot School, [4] USNTPS-FTM-No. 108 Fixed Wing Performance. U.S. Naval Test Pilot School, [5] Garmin G1000 Pilot s Guide for Cessna Nav III. Garmin, BIOGRAPHY/PHOTOGRAPH Juan B. Terrones Aragón was born in Madrid, Spain, in October He got a M. Sc. Degree in Aerospace Engineering by the Polytechnic University of Madrid in One year later in 2013 he accomplished the Master for Flight Testing, delivered by Polytechnic University of Madrid. Currently he is working with a scholarship in the Flight Test Department at Airbus Military (EADS-CASA). Jesús Javier Fernández Orío was born in Logroño, Spain, in October He got a M. Sc. Degree in AEROSPACE ENGINEERING by the Polytechnic University of Madrid. After one year in IBERIA airlines, he joined INTA Flight Test Department in Since then, he has been involved as Flight Test Engineer in most of the Spanish military certification aircraft programs (C-212, CN-235 and C-295). He also has worked for the EUROFIGHTER 2000 program as part of the Official Test Center role for INTA. Right now he participates in the Military Certification and Qualification Program for the A400M, as panel coordinator for Low Level Flight, Air to Air Refuelling and Aerial Delivery, he is also the representative of Spain in the CQC (Certification and Qualification Committee) for the A400M. Some of the short courses attended along the past years are: NTPS Rotary Wing Introduction To Flight Test and SFTE Handling Qualities Testing. He is the Spanish member of Flight Test Technical Team from the SCI (Systems in RTO (Research and Technology Organization) from NATO since He is SFTE member and currently Vice-president of the European Chapter. In 2010 he became Head of the Military Transport Aircraft Airworthiness Area. Now he is also in charge of the A400M program in INTA. Rafael Gomez Blanco was born in Madrid in December He joined Spanish Air Force (SAF) in 1992 and was promoted to Aerospace Engineers Corps Lieutenant in He was promoted to Lieutenant Coronel in He was assigned to the SAF Flight Test Center in 1994, as a Flight Test Engineer, where he has been involved in different activities related to Flight Testing, Systems Integration, development, verification and validation of Operational Flight Programs. He has flown about 700 flight hours as a Flight Test Engineer, in about 25 different airplanes, including EF-18, Mirage F-1, Northrop F-5, C-101, USAF F-16, USAF F- 15, US Navy F/A-18, US Navy Blackhawk, French Air Force C-160 Transall, French Air Force KC-135 tanker or Italian Air Force B707TT. He was assigned to the Spanish Air Force Engineering Command in Graduated Command and Staff Course, PhD. Aerospace Engineer, BsC in Labor Risk Prevention, Cryptology and Infosec Specialist. He has attended to various national and international courses on Flight Testing, Fighter Airplanes Design and Weapons J. B. Terrones Page 14 of14