Fuselage structures

Aircraft fuselage

1. Fuselage Structures

2. Introduction Forms main body of aircraft to which wings, tail plane, engines and gears are attached In modern aircraft forms a tube structure housing flight deck, pax cabin, hold and equipment Also acts as a pressure hull in pressurized aircraft

3. Types Frame structure: A box frame made up of a series of vertical, horizontal, diagonal and longitudinal tubular steel pipes Design produces a square profiled fuselage Used in old aircraft and light modern aircraft Frame takes up all the loads

4. Types Heavier if shape altered Covered with fabric, fiberglass, aluminum, Kevlar e.t.c .

5. Types

6. Types Monocoque structure: Skin takes up all flight and ground loads and shape gives structure its rigidity Any damage to skin directs effects its load carrying capacity Complications in designing doors windows and hatches

7. Types Inherently heavy and fragile by design, not used in airliners.

8. Types Semi-Monocoque structure: Loads shared by skin, frames, stringers and formers Tolerant to damage Good strength to weight ratio More redundancy then monocoque construction

9. Types Reinforces shell structure: Best redundancy in shell structure Reinforced windows, doors and hatch attachment points Longerons added for further load distribution, prevent crack propagation

10. Joining methods Riveting: Old process, time consuming, more drag Bonding: Using an adhesive to attach metallic parts

11. Joining methods Milling: To remove unnecessary material Material retention adds rigidity

12. Joining methods Etching: Using chemicals to remove material or create design or shapes in billets

13. Pressure bulkheads Pressure cabin terminates at the front and rear bulkheads Usually dome shaped for better pressure distribution In some designs floor part of pressure hull, un- pressurised hold in this case

14. Cabin floors In modern designs are not used as bulkheads Series of panels attached to supporting beams of aircraft Honeycomb panels used for best weight to strength ratio

15. Blow out bungs Plastic blowout bungs to equalize pressure in case of decompression

16. Windows Flight deck: Heated for de-icing JAR approved for bird strikes Laminated like car windscreens Stepped nose profile used in most subsonic airliners Helps in: Aerodynamic profiling

17. Windows (flight deck) Better ground and forward visibility Reduction in size of screen windows Sheds water better Reduces impact force Reduces pressure loads

18. Windows (flight deck) Stepped:

19. Windows (flight deck) Exception:

20. Windows Direct vision window: For maintaining clear vision Opened from inside Can also be used as emergency exits

21. Windows Passenger cabin windows: Form a part of pressure shell of fuselage Reinforced surrounding structure Windows fitted from inside and larger then apertures Two panes with air filled gap in between them

22. Windows

23. Doors Commonly plug type doors used in commercial aircraft Closed from inside with locking pins engaging into door frame Open by pulling back on inside and turning/sliding sideways

24. Doors

25. Doors Some requirements are: Must not be located near propellers Must be able to open with people surrounding it In emergency, external handle must be able to unlock door Must open from both sides, handles to be flushed to skin

26. Doors Must be a visual indication of doors being secured and locked, both externally and internally. E.g. flushing handle on outside, warning light on the crew warning panel Must not jam in emergencies Must b a means of safe-guarding against inadvertent operation in flight

27. Sealing Pressurization costs fuel/energy Every item passing through a hole is sealed

28. Seat mountings Must withstand loads e.g. Forward 3.0g Upward 9.0g Downward 6.0g Sideward 4.0g Seat mountings attached to crossbeams below floor structure

29. Spar attachment The strongest part of fuselage where wings are attached All flight loads converge at this point

30. Fuselage shapes Streamlined tapering design Suitable undercarriage/fuselage for smaller payloads

31. Fuselage shapes Fuselages became more cylindrical to carry more payloads Engines had to be added which added weight penalties Large piston engines give diminishing returns

32. Fuselage shapes Jet engine: With its advent fuselage became cylindrical with rounded nose and a tapered tail Advantages: Easy manufacturing Lower operating costs

33. Fuselage shapes Better power to weight ratio Greater cargo and passenger capacity Easier loading and unloading of aircraft

34. Fuselage shapes Tricycle undercarriage: Upward tapering tail till reaching the tip of tailcone Top of fuselage remains unchanged

35. Tail bumper: For protection during rotation Fixed or retractable

36. Fuselage mounted engines Front mounted engines act as a tractor, pull aircraft Support frame takes vibrations and engine loads

37. Fuselage mounted engines Rear bulkhead mounted act as pusher

38. Fuselage mounted engines Jet engines can also be mounted in fuselage, usually reserved for combat aircraft

39. Fuselage mounted engines For twin engine aircraft, engines can also be mounted to sides of fuselage Mounted on stub wings Reduces drag and cabin noise as compared to wing mounted aircraft But early onset of stall

40. Fuselage mounted engines

41. End of chapter