aircraft structures - fuselage Flashcards
What is Fuselage
Main structure of the aircraft that carries the aircraft payload: passengers, frieght, crew, instruments, accessories, controls, equipment
It transfers loads to the wings, tailplanes, landing gears, fin and powerplants
Pressurized aircraft - has Axial and Hoop stress
when an aircraft is pressurized, the structure goes through:
Axial Stress: Longitudinal stress that puts tension/elongates the fuselage
Hoop stress: it’s a radial stresses that ‘expands’ the fuselage cross section area
Fuselage can be designed / built in a number of cross sections:
In order from less stable to stable:
Rectangular
* Usually for non pressurized ACs
* Cheaper to build
* High weight to strength ratio
Oval:
Less efficient than Circular
Frequently used to complete pressure hull construction in read bulkhead
Double Bubble
* Figure of eight
* Good use of space forpassenger/cargo configuration
* Does not have increased drag
* cost effective
Side by Side bubble
* Even chearper to build
* allows for larger # of passengers/cargo
* further reduced drag
* Engine are rear mounted
Circular
* For pressurized ACs - pressure distributed evenly
* Hoop stresses are spread out
* Can produce high drag
* Some space wasted due to passenger/cargo configuration
* Easy to build
* cheaper tooling
Fuselage Construction
For non pressurized aircrafts: TRUSS / FRAMEWORK
For Light Aircraft: Monocoque
For widely used ones: STRESSED SKIN / SEMI MONOCOQUE
Framework
light gauge steel tubes welded together to form traingular shapes for rigidness
each tube carries load, its magnitutude depends on whether the aircraft is airborn or on ground
basic, strong, light weight (aluminium) or fabric skin
aerodynamic
Monocoque construction
for smaller aircraft/light weight
The outside skin takes the load
Inside is the ‘Formers’ which give the shape
**damage to the ski weaks the structure **, therefore extra strength is required for windowns, doors and undercarriages as these weak the structure.
Semi monocoque
handle load much better than monocoque
Additional structures (STRINGERS/STIFFNERS AND LONGERONS) are added lengthwise along the fuselage - joining frames together
the skin is then attached to the frames and stringers by riveting or adhesive bonding
**Skin is stiffened and and load carried length wise **
Note:
Longerons: beems along the length of fuselage, put below the floor which takes the bending loads of the aircraft
What’s a FrAME
vertical structures that are open in the centre
take the amjor load of teh aircraft
gives aircraft the shape
Bulkheads
like Frames but solid
take some of the main loads
may have access doors
give shape to the AC
Front and back bulkheads which split the pressurized from non pressurized areas
Firewalls
separates the flight deck/cabins from the engine
made in titanium alloy or stainless steel
withstand moderate temps for pronlonged period
withstand high temp (ie 3000 degrees) for short period
cross beams
beams that add strength to the cargo/passenger floors
floor venting
blow out panels
opens authomatically to equalize pressure across the floor structure
help avoid distortion of floor during decompression
