Aircraft fuselage

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

4. 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

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

6. Types

7. 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

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

9. 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

10. 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

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

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

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

16. 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

18. 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

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

20. 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

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

22. Windows (flight deck)
Stepped:

23. Windows (flight deck)
Exception:

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

25. 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

26. Windows

27. 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

28. Doors

29. 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

30. 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

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

32. 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

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

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

35. 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

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

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

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

41. Tail bumper:
 For protection during
rotation
 Fixed or retractable

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

43. Fuselage mounted engines
 Rear bulkhead mounted act as pusher

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

45. 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

46. Fuselage mounted engines