Future design requirements and trends to overcome challenges of helicopter operations BY Wg Cdr (Retd) NS Krishna YSM

Transcription

1 Future design requirements and trends to overcome challenges of helicopter operations BY Wg Cdr (Retd) NS Krishna YSM

2 WHAT ARE THE DESIRED QUALITIES IN AN IDEAL AEROPLANE? Ideal Aero plane Aero foil design for high lift or high speed Wing adaptable for various stages of flight Should be Trimmable Fuel Efficient Minimum noise Minimal Loss of Power Helicopters Usually symmetrical.. Neither high lift or high speed NO.. In addition, various part of rotor move at different speeds NO Fuel efficiency per seat is over 5 times a A 320 HA HA HA Substantial losses by the time power is delivered to Rotors

3 Ideal Aeroplane Minimum Drag Sealed and capable of being pressurized Effect of Controls-Minimal Cross couplings Should be statically and Dynamically stable Range should be large Vertical/short Takeoff and Landing Helicopter Very draggy, primarily due to gearbox Not designed to be pressurized Each movement cyclic, collective and rudder pedals has a primary, secondary and tertiary response Dynamic unstable.. Diverges rapidly Very limited ranges YES YES YES!!!!

4 Helicopters are different from planes. An airplane by it's nature wants to fly, and if not interfered with too strongly by unusual events or by a deliberately incompetent pilot, it will fly. A helicopter does not want to fly. It is maintained in the air by a variety of forces and controls working in opposition to each other If there is any disturbance in this delicate balance the helicopter stops flying; immediately and disastrously. This is why airplane pilots are open, clear-eyed, buoyant extroverts helicopter pilots are brooding introspective anticipators of trouble.

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6 So, why fly helicopters at all? Helicopters differ from Aeroplanes in that they :- Can Hover Can move sideways and backwards Can fly very slow without stalling Can fly very low to avoid radar detection Can maneuver in small spaces

7 MAIN USAGE OF HELICOPTERS Usage in civil is mainly for operations to/from places where big landing surfaces cannot be built Mountains Offshore oils rigs Emergency Medical Services from unprepared accident sites to nearest Hospital ( roof top or nearby helipad) Trump Towers to JFK Airport Disaster relief

8 Exotic Civil Uses Policing and Traffic management Helitourism.. Such as ride to the Grand Canyon Lifting heavy tree logs from Jungles or mountains to nearest processing plants HT cables laying Cattle rounding Clearing water logging and snow from runways

9 MILITARY USAGES Casualty Evacuation Remember M*A*S*H? OF course you would not.. Even I was a kid then!! Battlefield Air Support Fighter Aircraft cannot fly low and slow as required Anti Tank- Very effective as they can use a fire and forget missile, and duck after firing Air Superiority ie protect own troops and tanks from enemy helicopters and fighters using ATAMs For direct attacks, as a Command post and for transporting troops during Anti Terrorist operations

10 The helicopter approaches closer than any other vehicle to the fulfillment of mankind s ancient dreams of the flying horse and the magic carpet Igor Sikorsky However, during all these roles, helicopters face certain operational limitations Speed Relatively costlier due to Fuel Inefficiency in terms of seat per mile Relatively lower payload capability Lower cabin volumes for the same AUW Maintenance intensive due to more rotating parts Noisy- this is more noticeable as helicopters operate close to ground Adverse weather operations in hills and to helipads carry great risks

11 SEEMS UGLY IS BEAUTIFUL!! FUTURE TRENDS OF HELICOPTER DESIGN

12 All the future trends are towards :- Overcoming Speed limitations Reducing Noise Improving Power to Weight ratio Using Fly BY Wire and advanced Autopilots to artificially improve stability while retainingg maneuverability. Improving fuel efficiency All weather capability

13 VTOL X PLANE : A PROGRAM BY US DOD VTOL X-Plane challenges industry and innovative engineers to create a single hybrid aircraft that would concurrently push the envelope in four areas: Speed: Achieve a top sustained flight speed of kt Hover efficiency: Raise hover efficiency from 60 percent to at least 75 percent Cruise efficiency: Present a more favorable cruise lift-todrag ratio of at least 10, up from 5-6 Useful load capacity: Maintain the ability to perform useful work by carrying a useful load of at least 40 percent of the vehicle s projected gross weight of 10,000-12,000 pounds Several companies have been funded for initial research, after which a short list will be made for competing for US Govt contract

14 EFFORTS TO INCREASE SPEED Speed in helicopter is limited because :- Dissymmetry of lift between advancing and retreating blade Forward Control limits being reached as flap back is overcome Retreating blade Stall Compression effects on advancing tip ALL CURRENT PROJECTS ADDRESS THE ABOVE ISSUES

15 Trends in Speed Improvement Compound helicopters 253 KTs Eurocopter X3 Uses two puller propellers with differential pitch to provide antitorque Stub wings offload rotors by %, also preventing retreating blade stall Rotors are slowed down to prevent drag from advancing blade tip

16 Trends in Speed Improvement Sikorsky X2 ( S (& Raider) 260 Kts Rigid Contra-rotating rotors about 2 ft apart Rear prop provides most of forward thrust requiring very little forward tilt of rotors Resultant vibrations damped by active dampers Instability countered by FBW and highly advanced AP

17 Trends in Speed Improvement Bell V280 Valor Designed for 280 Kts Tilt Propellers at ends of a straight wing Since control laws would be very complicated, specially for transition f rom hover mode to forward flight, it has triple reduntant FBW system V tail for maneuverability Range of 2600 nm highest of any new development of Future Vertical Lift ( FVL) aircraft

18 Boeing Concept :Phantom Swift Employs a wide, blended body incorporating two large lifting fans, which are covered in forward flight. It has ducted fans in swiveling nacelles at the end of the short wings. Boeing has already built and flown scaled-down model of the Phantom Swift.

19 Avatar Planes? My Take? The Avatar helicopter/plane looks deadly, but cannot possibly be ideal for high speed! Stub wings cannot give much lift Rotors look too draggy for high speed Rotors have very little tilt, and no propellor to give forward speed DON T SEE WHERE THE FORWARD THRUST IS COMING FROM

20 FUSELAGE SIZE The space required for landing is determined by the rotor diameter and length Requirement of an anti torque Tail Rotor and a supporting tail boom decreases available space for the cabin Usable cabin space is steadily increasing with alternate solutions for anti-torque These solutions could enable shuttles from heliport to heliport between city centres carrying 100 plus passengers

21 Trends in Rotor Blades New thoughts in Rotor Design are required for Optimising blade performance in advancing and retreating sides Reduce vibrations Reduce noise Smart blades, which change shape Chordwise, or camber wise, are being developed These use Local Mod of aerodynamic characteristics of a blade such as flaps, slots and boundary layer control to optimise performance across the full revolution in forward Smart Blades use piezoelectric actuators mechanical devices incorporating a material that changes shape when subjected to an electrical field

22 Trends in Rotor Blades FLAPS- FOR MODIFYING LIFT AND REDUCING VIBRATIONS GURNEY FLAPS- FOR INCREASING LIFT ON REREATING SIDE DROOP - FOR PREVENTING DYNAMIC STALL ON RETREATING SIDE AND REDUCING VIBRATIONS SLOTS FOR RE-ENERGISING BOUNDARY LAYER

23 Trends in Rotor Blades NASA, in collaboration with Boeing and DARPA, has tested smart blades in a wind tunnel. However, there is a long way to go as there are many challenges Weight and Space constraints Centrifugal loads Reliability ( more than flight hours at failure rate < 10-9 per hour) Challenge greater for actuator which need to work more than once during a rotation cycle, for eg those used for active vibration control Failures must not result in uncontrollability or adverse decrease in performance A SMART TEST PILOT WOULD BE VERY CAUTIOUS FLIGHT TESTING THESE!!

24 Efforts towards Reduction Of Noise Sources of Noise

25 DESIGN TRENDS FOR REDUCTION OF NOISE Modulated Blade Spacing Frequencies in equally spaced blades are related to spacing Modulated blade spacing reduces noise by Lower peak sounds Distribution of acoustic energy over wider spectrum of frequencies Reduced tip speed Tip redesign mainly for reducing vortices and reducing noise impact of blade passing through vortices Aerofoil tailoring as in smart blades

26 OTHER INTERESTING AREAS OF NEW DESIGNS Engine power Use of Silicon carbide ceramic materials in turbine blades Electric Distributed Propulsion One/Two main engines producing Electric power and charging batteries 6-8 ducted propellers driven by batteries and producing thrust Very light weight super conducting cables Management according to flight mode Take off- use power Cruise charge Descent idle/windmilling Land - use

27 OTHER INTERESTING AREAS OF NEW DESIGNS Increasing of the AFCS autonomy Possible A/RPC problems. Clear definitions of when pilot has override needed Low Visibility Flying Autonomous Landings based on LIDAR and Hybrid Nav systems with a specified RNP ( Required Navigational Performance) Tactile cues Pilot wears a vibrating vest As the pilot comes into land, if a drift starts, say on his right hand side, he would feel a vibration on his right hand side.

28 Electric Helicopter The e-volo VC200 has become the first electric helicopter to make a successful maiden flight, with multiple flights lasting several minutes and reaching heights of nearly 22 meters high. Together with 18-rotor blades and a disassemblable architectural system, the volocopter has been designed to host two passengers for distances of up to 100km and a flight altitude of up to 6500 ft. Equipped with a sophisticated automated control system requiring minimum piloting skills Click here

29 I have covered a few of the design efforts already in progress However the biggest problem facing helicopters today is adverse weather operations Most of the current aids available, such as EGPWS, Autopilot coupled modes, etc are still not enough to prevent Controlled Flight into Terrain ( CFIT) as pilots often delay or are unable to process all the information available No effective landing aids while landing at helipads in low visibility Potential exists to develop autonomous systems using LIDAR etc to fly in adverse weather in hills, or take over/suggest action when a potential CFIT situation is imminent. signal

30 Research and academic institutions, such as IIT K, could look into the needs of the hours, concepts of the future and conduct research to enable this vision I leave you with a video outlining a possible futuristic military scenario, which may possible give you some thoughts on the direction design efforts need to take Aviation 2050 Vision