Aircraft Design: A Systems Engineering Approach, M. Sadraey, Wiley, 2012 Chapter 12 Design of Control Surfaces Tables No Term 1 Trim, balance, equilibrium Definition When the summations of all forces exerting on an aircraft; and the summations of all moments about aircraft center of gravity are zero, the aircraft is in trim. 2 Control A desired change in the aircraft trim condition from an initial trim point to a new trim point with a specified rate. 3 Stability The tendency of an aircraft to oppose any input and return to the original trim point, if disturbed by an undesired force or moment. 4 Static stability The tendency of an aircraft to oppose any input if disturbed from the trim point. 5 Dynamic stability The tendency of an aircraft to return to the original trim point if disturbed. Table 12.1. Definition of fundamental terms 1
No Control surface Symbol Positive control surface deflection 1 Elevator E Producing a negative pitching moment; (Down: + E ; Up: - E ) 2 Aileron A Generating a positive rolling moment; Left and right aileron are considered ( A left-down, A right-down ); A = 0.5 ( Aleft + Aright ) 3 Rudder R Producing a positive side-force and a negative yawing moment(left:+ R, right: - R ); Table 12.2. Convention for positive control surface deflections 2
Control Surface Elevator Aileron Rudder Control surface area/lifting surface area S E /S h = 0.15-0.4 S A /S = 0.03-0.12 S R /S V = 0.15-0.35 Control surface span/lifting surface span b E /b h = 0.8-1 b A /b = 0.2-0.40 b R /b V = 0.7-1 Control surface chord/lifting surface chord C E /C h = 0.2-0.4 C A /C = 0.15-0.3 C R /C V = 0.15-0.4 Control surface maximum -25 deg (up) 25 deg (up) - 30 deg (right) deflection (negative) Control surface maximum deflection (positive) +20 deg (down) 20 deg (down) +30 deg (left) Table 12.3. Typical values for geometry of control surfaces 3
No Control Surface Configuration Aircraft Configuration 1 Conventional (aileron, elevator, Conventional (or canard replacing elevator) rudder) 2 All moving horizontal tail, rudder, Horizontal tail and elevator combined aileron 3 All moving vertical tail, elevator, Vertical tail and rudder combined aileron 4 Flaperon, Elevator, Rudder Flap and aileron combined (e.g. X-29 and F- 16 falcon) 5 Taileron, Rudder All moving horizontal tail (elevator) and aileron combined (e.g. F-16 Falcon) 6 Elevon, Rudder (or equivalent) Aileron and elevator combined (e.g. Dragon, F-117 Night Hawk, Space Shuttle) 7 Ruddervator, Aileron V-tail (e.g. UAV Global Hawk and Predator) 8 Drag-Rudder, Elevator, Aileron No vertical tail (e.g. DarkStar) 9 Canardvator, Aileron Elevator as part of canard, plus aileron 10 Four Control Surfaces Cross (+ or ) tail configuration (e.g. most missiles) 11 Aileron, Elevator (or equivalent), Split Rudder No vertical tail. Aileron-like surfaces that is split into top and bottom sections (e.g. bomber B-2 Spirit) 12 Spoileron, Elevator, Rudder Spoiler and aileron combined (e.g. B-52) 13 Thrust vector control Augmented or no control surfaces, VTOL UAV Table 12.4. Control Surface Configuration Options 4
Class Aircraft characteristics I Small, light aircraft (maximum take-off mass less than 6,000 kg) with low maneuverability II Aircraft of medium weight and low-to-medium maneuverability (maximum take-off mass between 6,000 and 30,000 kg) III Large, heavy, low-to-medium maneuverability aircraft (maximum take-off mass more than 30,000 kg) IV Highly maneuverable aircraft, no weight limit (e.g. acrobatic, missile, and fighter) Table 12.5. Aircraft Classes 5
Category Examples of flight operation A 1. Air-to-air combat (CO); 2. Ground attack (GA); 3. Weapon delivery/launch (WD); 4. Aerial recovery (AR); 5. Reconnaissance (RC); 6. In-flight refueling (receiver) (RR); 7. Terrain following (RF); 8. Antisubmarine search (AS); 9. Close formation flying (FF); and 10. Lowaltitude parachute extraction (LAPES) delivery. B 1. Climb (CL); 2. Cruise (CR); 3. Loiter (LO); 4. In-flight refueling in which the aircraft acts as a tanker (RT); 5. Descent (D); 6. Emergency descent (ED); 7. Emergency deceleration (DE); and 8. Aerial delivery (AD). C 1. Takeoff (TO); 2. Catapult takeoff (CT); 3. Powered approach (PA); 4. Wave-off/go-around (WO); and 5. Landing (L). Table 12.6. Flight phase categories [8] 6
Level Definition 1 Flying qualities clearly adequate for the mission Flight Phase. 2 Flying qualities adequate to accomplish the mission Flight Phase, but some increase in pilot workload or degradation in mission effectiveness, or both, exists. 3 Flying qualities such that the airplane can be controlled safely, but pilot workload is excessive or mission effectiveness is inadequate, or both. Category A Flight Phases can be terminated safely, and Category B and C Flight Phases can be completed. Table 12.7. Levels of acceptability 7
Level Meaning Pilot Comfort Level Pilot Status 1 Very comfortable 1 to 3 2 Hardly comfortable 4 to 6 3 Uncomfortable 7 to 10 Table 12.8. Levels of acceptability and pilot comfort 8
No Aircraft type Rotation time during take-off (second) Take-off pitch angular acceleration (deg/sec 2 ) 1 Highly maneuverable (e.g. 0.2 0.7 12-20 acrobatic GA and fighter) 2 Utility; semi-acrobatic GA 1-2 10-15 3 Normal General Aviation 1-3 8-10 4 Small transport 2-4 6-8 5 Large transport 3-5 4-6 6 Remote control, model 1-2 10-15 Table 12.9. Take-off angular acceleration requirements 9
Level of acceptability Requirement 1 Damping ratio of phugoid mode ( ph ) 0.04 2 Damping ratio of phugoid mode ( ph ) 0.0 3 The time-to-double the amplitude of at least 55 seconds. Table 12.10. Phugoid mode requirement 10
Flight phase Short period damping ratio ( s ) Level 1 Level 2 Level 3 Minimum Maximum Minimum Maximum Minimum Maximum A 0.35 1.3 0.25 2.0 0.15 No maximum B 0.3 2.0 0.2 2.0 0.15 No maximum C 0.35 1.3 0.25 2.0 0.15 No maximum Table 12.11. Short period mode damping ratio specification 11
Level Flight Phase Category A B C Time to achieve a bank angle of 60 o Time to achieve a bank angle of 45 o Time to achieve a bank angle of 30 o 1 1.3 seconds 1.7 seconds 1.3 seconds 2 1.7 seconds 2.5 seconds 1.8 seconds 3 2.6 seconds 3.4 seconds 2.6 seconds a. Time to achieve a specified bank angle change for Class I Level Runway Flight Phase Category A B C Time to achieve a bank angle of 45 o Time to achieve a bank angle of 45 o Time to achieve a bank angle of 30 o Time to achieve a bank angle of 25 o 1 Land-based 1.4 seconds 1.9 seconds 1.8 seconds - Carrier-based 1.4 seconds 1.9 seconds 2.5 seconds - 2 Land-based 1.9 seconds 2.8 seconds 3.6 seconds - Carrier-based 1.9 seconds 2.8 seconds - 1.0 seconds 3 Land-based 2.8 seconds 3.8 seconds - 1.5 seconds Carrier-based 2.8 seconds 3.8 seconds - 2.0 seconds Level b. Time to achieve a specified bank angle change for Class II Speed range Flight Phase Category A B C 1 Low 1.8 seconds 2.3 seconds 2.5 seconds Medium 1.5 seconds 2.0 seconds 2.5 seconds High 2.0 seconds 2.3 seconds 2.5 seconds 2 Low 2.4 seconds 3.9 seconds 4.0 seconds Medium 2.0 seconds 3.3 seconds 4.0 seconds High 2.5 seconds 3.9 seconds 4.0 seconds 3 All 3.0 seconds 5.0 seconds 6.0 seconds c. Time to achieve a 30 o bank angle change for Class III 12
Level Speed range Flight Phase Category A B C 30 o 50 o 90 o 90 o 30 o 1 Very Low 1.1 sec - - 2.0 sec 1.1 sec Low 1.1 sec - - 1.7 sec 1.1 sec Medium - - 1.3 sec 1.7 sec 1.1 sec High - 1.1 sec - 1.7 sec 1.1 sec 2 Very Low 1.6 sec - - 2.8 sec 1.3 sec Low 1.5 sec - - 2.5 sec 1.3 sec Medium - - 1.7 sec 2.5 sec 1.3 sec High - 1.3 sec - 2.5 sec 1.3 sec 3 Very Low 2.6 sec - - 3.7 sec 2.0 sec Low 2.0 sec - - 3.4 sec 2.0 sec Medium - - 2.6 sec 3.4 sec 2.0 sec High - 2.6 sec - 3.4 sec 2.0 sec d. Time to achieve a specified bank angle change for Class IV Table 12.12. Roll control requirements 13
Level Class Crosswind speed 1 I 20 knots II, III, and IV 30 knots 2 I 20 knots II, III, and IV 30 knots 3 I, II, III, and IV One-half the value for levels 1 and 2 Table 12.13. Crosswind velocity requirements 14
Flight Phase Aircraft Class T R (seconds) Level 1 Level 2 Level 3 A I, IV 1.0 1.4 10 II, III 1.4 3.0 10 B All 1.4 3.0 10 C I, IV 1.0 1.4 10 II, III 1.4 3.0 10 Table 12.14. Roll mode time constant specification (maximum value) 15
Aircraft Class Flight Phase Minimum time to double amplitude in spiral mode Level 1 Level 2 Level 3 I and IV A 12 seconds 8 seconds 4 seconds B and C 20 seconds 8 seconds 4 seconds II and III A, B, C 20 seconds 8 seconds 4 seconds Table 12.15. Time to double amplitude in spiral mode 16
Level Flight Phase Aircraft Class min d min d nd (rad/s) min (rad/s) 1 A I,IV 0.19 0.35 1.0 II, III 0.19 0.35 0.4 B All 0.08 0.15 0.4 C I, II, IV 0.08 0.15 1.0 III 0.08 0.15 0.4 2 All All 0.02 0.05 0.4 3 All All 0.02 No limit 0.4 Table 12.16. Dutch roll mode handling qualities n d 17
No Aircraft Type m TO b C A /C Span ratio Amax (deg) (kg) (m) b i /b/2 b o /b/2 up down 1 Cessna 182 Light GA 1,406 11 0.2 0.46 0.95 20 14 2 Cessna Citation Business 9,979 16.31 0.3 0.56 0.89 12.5 12.5 III jet 3 Air Tractor AT- Agriculture 7,257 18 0.36 0.4 0.95 17 13 802 4 Gulfstream 200 Business 16,080 17.7 0.22 0.6 0.86 15 15 jet 5 Fokker 100A Airliner 44,450 28.08 0.24 0.6 0.94 25 20 6 Boeing 777-200 Airliner 247,200 60.9 0.22 0.32 1 0.76 2 30 10 7 Airbus 340-600 Airliner 368,000 63.45 0.3 0.64 0.92 25 20 8 Airbus A340-600 Airliner 368,000 63.45 0.25 0.67 0.92 25 25 Table 12.17. Characteristics of aileron for several aircraft 1 Inboard aileron 2 Outboard aileron 18
No Aircraft Type m TO S E /S h C E /C h Emax (deg) (kg) down up 1 Cessna 182 Light GA 1,406 0.38 0.44 22 25 2 Cessna Citation III Business jet 9,979 0.37 0.37 15 15.5 3 Gulfstream 200 Business jet 16,080 0.28 0.31 20 27.5 4 AT-802 Agriculture 7,257 0.36 0.38 15 29 5 ATR 42-320 Regional airliner 18,600 0.35 0.33 16 26 6 Lockheed C-130 Hercules Military cargo 70,305 0.232 0.35 15 40 7 Fokker F-28-4000 Transport 33,000 0.197 0.22 15 25 8 Fokker F-100B Airliner 44,450 0.223 0.32 22 25 9 McDonnell Douglas DC- 8 Transport 140,600 0.225 0.25 10 25 10 McDonnell Douglas DC- 9-40 Transport 51,700 0.28 0.30 15 25 11 McDonnell Douglas DC- Transport 251,700 0.225 0.25 16.5 27 10-40 12 McDonnell Douglas MD-11 Transport 273,300 0.31 0.35 20 37.5 13 Boeing 727-100 Transport 76,820 0.23 0.25 16 26 14 Boeing 737-100 Transport 50,300 0.224 0.25 20 20 15 Boeing 777-200 Transport 247,200 0.30 0.32 25 30 16 Boeing 747-200 Transport 377,842 0.185 0.23 17 22 17 Airbus A-300B Transport 165,000 0.295 0.30 17 30 18 Airbus 320 Transport 78,000 0.31 0.32 17 30 19 Airbus A340-600 Airliner 368,000 0.24 0.31 15 30 20 Lockheed L-1011 Tristar Transport 231,000 0.215 0.23 0 25 21 Lockheed C-5A Cargo 381,000 0.268 0.35 10 20 Table 12.18. Specifications of elevators for several aircraft 19
E Tail-to-elevator-chord ratio; C E /C h (deg) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 0 0 0 0 0 0 0 0 0 0 0 ±5 0 0.3 0.5 1.1 1.6 2.2 2.7 3.3 3.9 4.4 5 ±10 0 0.6 1 2.1 3.2 4.4 5.5 6.6 7.7 8.9 10 ±15 0 0.9 1.5 3.2 4.9 6.5 8.2 9.9 11.6 13.3 15 ±20 0 1.2 2 4.2 6.5 8.7 11 13.2 15.5 17.7 20 ±25 0 1.6 2.5 5.3 8.1 11 13.7 16.5 19.4 22.2 25 ±30 0 1.9 3 6.4 9.7 13.1 16.5 19.9 23.2 26.6 30 Table 12.19. Reduction in tail stall angle ( h E ) in degrees when elevator is deflected 20
No Aircraft Type m TO (kg) S R / S V C R /C V Rmax (deg) Max cross wind speed (knot) 1 Cessna 182 Light GA 1,406 0.38 0.42 ±24 2 Cessna 650 Business jet 9,979 0.26 0.27 ±25 3 Gulfstream 200 Business jet 16,080 0.3 0.32 ±20 4 Air Tractor AT-802 Regional airliner 18,600 0.61 0.62 ±24 5 Lockheed C-130E Military cargo 70,305 0.239 0.25 ±35 - Hercules 6 DC-8 Transport 140,600 0.269 35 ±32.5 34 7 DC-10 Transport 251,700 0.145 38 ±23/±46 3 30 8 Boeing 737-100 Transport 50,300 0.25 0.26 9 Boeing 777-200 Transport 247,200 0.26 0.28 ±27.3 10 Boeing 747-200 Transport 377,842 0.173 0.22 ±25 30 11 Lockheed C-5A Cargo 381,000 0.191 0.2-43 12 Fokker 100A Airliner 44,450 0.23 0.28 ±20 30 13 Embraer ERJ145 Regional jet 22,000 0.29 0.31 ±15 14 Airbus A340-600 Airliner 368,000 0.31 0.32 ±31.6 Table 12.20. Characteristics of rudder for several aircraft Tandem rudder 3 21
No Requirements Brief description Aircraft 1 Asymmetric thrust When one engine fails, the aircraft must be able to overcome the asymmetric thrust. Multi-engine aircraft 2 Crosswind landing An aircraft must maintain alignment with the All runway during a crosswind landing. 3 Spin recovery An aircraft must be able to oppose the spin rotation and to recover from a spin. Spinnable aircraft 4 Coordinated turn The aircraft must be able to coordinate a turn. All 5 Adverse yaw The rudder must be able to overcome the All adverse yaw that is produced by the ailerons. 6 Glide slope adjustment Aircraft must be able to adjust the glide slope by increasing aircraft drag using a rudder deflection. Glider aircraft Table 12.21. Rudder design requirements 22
No Aircraft The most critical flight condition 1 Glider/sailplane Glide slope adjustment 2 Single engine Normal GA Crosswind landing 3 Single engine Utility/Acrobatic GA Spin recovery 4 Multi-engine Normal GA Asymmetric thrust 5 Multi-engine Utility/Acrobatic GA Asymmetric thrust/ Spin recovery 6 Multiengine transport (fuselageinstalled Crosswind landing engines) 7 Multiengine transport (winginstalled Asymmetric thrust/ Crosswind landing engines) 8 Military fighter Directional maneuverability/spin recovery 9 Remote controlled/ model Coordinated turn Table 12.22. The most critical flight condition for a rudder 23