Aircraft Layout Choices Prof. Rajkumar S. Pant Aerospace - PowerPoint PPT Presentation

Aircraft Layout Choices Prof. Rajkumar S. Pant Aerospace Engineering Department IIT Bombay

Many letters of English Alphabet !!! TAIL PLANE LAYOUT AE-332M / 714 Aircraft Design Capsule-2

Requirements from the Tailplane  Horizontal Tail  Vertical Tail  Trim  Trim o Wing pitching moment o Engine failure o Single engine asymmetry  Stability  Stability o Pitching motion o Yawing motion  Control o Dutch roll damping o Nosewheel liftoff  Control o Low speed flight with flaps down o Engine out flight at low speeds o Transonic maneuvering o Maximum roll rate o Spin recovery

Aft Tailplane Configuration Options Conventional tail is seen in nearly 70% a/c

T-Tail  Smaller vertical tail due to end-  Heavier plate effect  Deep stall  Clear of wing and prop wash  Ease in mounting of rear engines http://en.wikipedia.org/wiki/Deep_stall#Deep_stall Source: Wikipedia

T-Tail v/s Conventional Tail  Advantages (of T-Tail)  Disadvantages  Looks Faster  Pilots don’t like it o When pilots add power on a  Lesser FOD from Eng. & LG single-engined aircraft, they  Allow rear-mounted engines get additional control authority  Bad for maintenance o Alaska MD-83's accident o http://www.ntsb.gov/publictn /2002/AAR0201.htm AE-332M / 714 Aircraft Design Capsule-2

Some aircraft with T-Tail F101-Voodoo ETA glider Canadair CRJ Piper Tomahawk

Cruciform Tail  Compromise between Conventional & T-Tail JS-31, DHC-6, Falcon 20, ATR-42 

Twin Tail  Lower overall height  Avoid fuselage wake on rudder  spin resistance  higher structural weight Many examples AN-225, F-15, MiG-25 http://www.atlasaerospace.net/image/f_pilotag8.jpg http://en.wikipedia.org/wiki/File:Buran_On_Antonov225.jpg http://en.wikipedia.org/wiki/File:F-15,_71st_Fighter_Squadron,_in_flight.JPG

H and Triple Tail  H Tail Triple Tail  undisturbed airflow on VT at lower VT to fit into hangers high AOA  VT in propwash to enhance engine-out controllability  Smaller HT due to endplate effect P-38 Lockheed Constellation

Butterfly or V- Tail  Reduction of one tail surface  Lower interference drag  Lower weight  Higher Complexity o Mixing unit required Beechcraft Bonanza F-117A

Other Aircraft with V Tail Eclipse 400 Cirrus Vision SF 50 Fouga CM 120 Magister RQ4/MQ4 Global Hawk AE-332M / 714 Aircraft Design Capsule-2

WING GEOMETRY AE-332M / 714 Aircraft Design Capsule-2

C 0 = root chord Wing Geometry C T = tip chord b = wing span s = wing semi-span S = wing ref. area t = thickness c = chord α = angle of attack Λ = Taper Ratio = C T /C 0 AR = Aspect Ratio = b 2 /S t/c = Thickness Ratio Source: Fielding, J. P., Introduction to Aircraft Design AE-332M / 714 Aircraft Design Capsule-2

Effect of Wing Geometry: Aerodynamics and Weight Geometrical Effecting on wing Trends Effecting on wing Range of Values polar and C L weight Parameter Airfoil Camber C L W wing ~ const C L 0 – 6 % C D α 5 - 18 % subs. Airfoil C L max W wing 3 - 7 % supers. C L Thickness ratio C D α 7 – 9 subs. Aspect Ratio C D ind W wing C L 2 – 4 supers. K C D 4 - 14 subs. Taper Ratio C Di W wing C L 2 - 5 supers. C D 0 - 35 subs. Leading-edge C D0 W wing C y C L 35 - 70 supers. sweep angle C Di C D subs. = subsonic flight supers. = supersonic flight AE-332M / 714 Aircraft Design Capsule-2

Wing Layout Parameters  Reference wing planform = Trapezoidal  Aspect Ratio (b 2 /s or b/c for rectangular wing) o Increase in AR  Reduces induced drag  Reduces stalling AOA  Increases subsonic (L/D) max  Increases wing weight  Sweep  Taper Ratio  Twist  Incidence  Dihedral

Taper ratio  λ = tip chord / root chord  (root chord / tip chord in USA)  λ = 1 (Rectangular wing)  Heavy  Ease in construction  Low λ  Lower wing root BM  lighter wing  tip stalls before root  poor stalling behavior  Compromise Value: usually 0.4 to 0.6

Number of Engines  No clearcut indication from Accident/Emergency stats  > Airlines prefer smallest number of engines  Often dictated by availability  2 engines for extended over-water flights  ETOPS clearance

Illustration of ETOPS D. AL T E.ALT 1 Destination ETP2 E.ALT 2 (CP) EEP Departure ETP 1 EEP : ETOPS Entry Point ETOPS Segment ETP : Equitime Point 60 minute circles E.ALT : En-route Alternate Airport Maximum diversion time circles D.ALT: Destination Alternate Unauthorised area Area of Operation AE-332M / 714 Aircraft Design Capsule-2

Choose your pick ! MANY CONFIGURATIONS AND LAYOUT POSSIBILITIES EXIST AE-332M / 714 Aircraft Design Capsule-2