11.2b Airframe Construction Methods Flashcards
what are frames or formers ?
Lateral fuselage or nacelle members giving a cross sectional shape which is often circular. They are used to give shape and provide strong attachment points.
Monocoque construction was very heavy, in order to combat this what was used?
Semi-monocoque construction using stringers and other components to transfer loads.
What are bulkheads?
Give shape to the fuselage but do not have an aperture and usually act to close off or Partion an area. E.g pressure bulkheads or fireproof bulkheads
What are longerons?
Main longitudinal member of a fuselage or nacelle.
What type of loads do longerons take?
The main support for bending loads
What can longerons be supplemented by ?
Stringers
What are stringers ?
Smaller and lighter than longerons and serve as stiffeners that assist sheet materials to carry loads along their length however they mainly create the shape of the skin
What are used to attach the skin to the frame and stringers?
Clips and cleats
What are doublers?
Additional sections of material used to reinforce ares of skin that require a little extra strength
Where are doublers often found ?
Around apertures such as doors or windows
What can also be used as a crack stopper ?
Doublers, placed at 90° to the path of the anticipated crack, which reduces the rate of further propergation
What are struts and what are they used for ?
Load bearing components that primarily handle compression forces, typically transmits loads from one part of the fuselage to another
What are ties ?
Elements that handle tension forces employed to maintain the structural integrity of various parts of the fuselage
When ties and struts are used in conjunction what can this form ?
Truss like structures that effectively distribute loads and provide stability
What are ties typically made from ?
Steel or titanium
What do ties ensure ?
Resist tension forces and rigidity
What are floorboards made of ?
Honeycomb composite construction which are screwed down to floor beams made from aluminium or composite
What do floor beams do ?
Primary structure that carry tension loads during pressurisation
How are floorboards protected from corrosion ?
Foam tape on the underside around the edges where they contact the structure or sealed in “wet areas”
What must be considered when considering the structure of an aircraft ?
Strength to weight ratio
What ways can we reinforce structures ?
-doublers
-butt straps
-cleats
-gussets
-fishplates
-angles
-stiffeners
What principle is wing construction based on ?
Semi- monocoque construction. With spars and ribs giving shape.
What are ribs ?
a fore-and-aft structural member of an aerofoil that has the primary purpose of maintaining the correct contour of the covering but is usually also a stress-bearing component of the main structure.
What are wings often covered with?
Stressed skin forming a box section that is then able to house integral fuel tanks
What are the two types of general fuselage construction?
Truss type
Monocoque
What is a truss ?
A truss is a rigid framework made up of members of :
Struts, beams and bars
Where is the the truss type wing construction method used mostly ?
In fabric aircraft
What is a strut?
Any rod or member designed to take compression loads
What are the two types of monocoque construction?
True monocoque construction and more common semi monocoque
What does true monocoque construction consist of?
Formers, frame assemblies and bulkheads to give shape
On a monocoque construction what carries the stress?
The skin
What is important about semi monocoque construction?
Skin is reinforced by longitudinal members and loads are shared between the skin and framework
When a fuselage structure comes in structures, and the joints need to be reinforced, what is this called ?
Manufacturers joint or production break
What is a semi monocoque type construction generally made from?
Aluminium alloys or steel and titanium in elevated temperatures
What are the main advantages of a semi-monocoque construction?
-the bulkheads, frames, stringers and longerons give shape to the skin
-because of the way stresses are distributed throughout the skin, this construction method gives a lot more strength and rigidity
How may a frame work be skinned ?
What is the most likely method of skinning in modern composite skin aircraft ?
-filament wound into the frame or preformed and fastened to the frame with special fasteners and bonding techniques
Why is aluminium widely used throughout aircraft ?
For its passivation property (passive film) an it’s strength
What surface treatments can you perform to prevent corrosion ?
-Painting
-anodising
-using sealants
What three sections are there to a pair of wings ?
Left wing ,centre wing box, right wing
How many spars do a wing have ?
Front spar and rear spar. Some may also have a false spar for an attachment point for the landing gear
The spars make up a “box” and are linked by formers, what are these called ?
Ribs
What else does the construction of a wing often give space for ?
Fuel storage
How are control surfaces connected to the wing ?
Control surfaces are attached to the rear wing spar
What supports the centre wing box?
The keel beam and a series of heavy frames
Despite holding the wings what other jobs do the centre wing box do ?
-can provide area for fuel storage
- help absorb impacts during flight such as turbulence
How are the horizontal stabilisers attached ?
Following a similar construction the the wing, horizontal stabilisers attach to a centre box
How is the vertical stabiliser attached ?
Attached using large machined fittings that align with the fuselage frames and longerons
What is a engine pylon ?
Also known as the strut consist of a torque box, firewall, fire-seal, fairings, strut drains , a fan cowl support beam and engine attachment fittings.
What is the primary function of an engine nacelle ?
To provide a streamline shape to the engine pylon, engine and all of their components
