Airframe Flashcards
What is the fuselage
The body of the aircraft to which the wings, tail section, engine and landing gear are attached, it normally contains a cabin and cockpit, instruments and baggage lockers
Requirements of the fuselage
It needs to be light but strong enough to to be able to stand the bending and twisting loads of flight without becoming deformed or breaking
What construction is commonly used for the fuselage
semi-monocoque/stressed skin
Semi-monocoque construction
A light metal framework usually covered by an aluminium alloy skin riveted to it
Benefits of semi-monocoque
Incorporates the best feature of truss type and monocoque structure
Truss type structure
Internal framework carries almost all the stress
Monocoque structure
No internal framework, stress carried by the skin
Composite materials
Combination of materials which are bonded together to provide a new material with the required characteristics
What composites are used in aviation
Glass fibre reinforced plastics and carbon fibre reinforced plastics
Advantages of composites
They offer high strength for reduced weight, better resistance to fatigue, corrosion and impact damage
Disadvantages of composites
High cost
Spars
They attach to the fuselage extending to the wingtips, they carry the major loads, which bend the wings upwards, downwards, and twist them
External struts
Some light aircraft have external struts connecting the wings to the fuselage, this provides extra strength by bracing the wings and transferring some of the wing bending loads from the wing roots to other parts of the fuselage
Ribs
They are attached to the wing spars, and provide the required aerofoil shape as well supporting the skin which envelopes the frameworks
Stringers
Run in-between the ribs and assist in supporting the skin
Ailerons
Control surfaces attached to the outer trailing edge of the wing. They are able to be moved simultaneously in opposite directions to allow the pilot to control roll
Flaps
Installed on the inner trailing edges of the wings and are lowered symmetrically to increase lifting ability of the wing or to increase its drag
Where are the fuel tanks installed in most light aircraft
In the wings because it is an efficient use of space and in high-wing aeroplanes it enables the use of gravity feed of fuel to the engine
Monoplanes
One set of wings
Biplanes
Double set of wings
Classification of monoplanes
High-wing, low-wing or mid-wing
Empennage
Tail section
Tail section
Consists of the fin which has a movable rudder attached, tailplane which has a movable elevator attached
Vertical stabiliser
Fin
Horizontal stabiliser
Tailplane
Trim tab
Small control surface on the trailing edge of the elevator and sometimes rudder which aerodynamically balances control in steady flight so that the need to hold a constant steady pressure on the control column to maintain a given altitude is eliminated, reducing the workload of the pilot
What are the main flight control surfaces
Elevator, ailerons and rudder
What do stops do
Prevent excessive movement to control surfaces
Types of undercarriage
- Tricycle type (nose wheel)
- Tail wheel type
Disc brakes
Fitted to each main wheel operated hydraulically and independently through the upper portion of the rudder pedal
Advanced aircraft have a ____ undercarriage to improve performance by ____ ____
Retractable, reducing drag
What type of undercarriage do training aircraft have
Fixed, which cant be retracted
What is the recommended taxiing speed
Walking pace
Control in a tricycle type undercarriage
Visibility is good, and with nose wheel steering and the use of brakes control is reasonably easy to achieve, however because the tips of the propeller are fairly close to the ground caution must be taken when crossing line depressions to avoid propeller tip strike
Control in a tail wheel type undercarriage
Forward viability is usually restricted, so the aircraft must be weaved when taxiing to enable the pilot to see the area ahead, directional control may be lost in what is called a ground loop if the pilot allows a large swing to develop.
How is the engine separated from the cockpit
Firewall
Propeller in training aircraft
Fixed pitch propeller
Constant speed propeller
In more advanced aircraft, the pitch of the blades can be varied and controlled by the pilot
What is meant by stressed skin airframes are designed to be fail safe
They are designed and constructed in a way that over-stressing will result in gradual failure of a part of the structure, and not a sudden or catastrophic failure of the whole
Flexibility of aluminium alloy structures
Withstands tension (stretching) well, but is susceptible to buckling under compression. It is also susceptible to fatigue as an alloy component that is repeatedly bent or subjected to fluctuating stress such as vibration will eventually crack and then fail in the area where the bending is the greatest
Composite structures
Less prone to fatigue and corrosion and because of they aren’t as ductile minor damage won’t be visible, they are prone to delamination through the failure of the bonding matrix
How can delamination identified
Dull colour, bubbled/depressed, light tapping may produce a different sound
What are fabric airframes affected by
UV light, Moisture, pollution, spilled aircraft fluid, battery acid and fumes as well as the passage of time.
Fabric airframes inspection
- Check seems and lapped joints
- Surface tapes in place
- Check lacing cords
- Drain holes unobstructed
- Surface free from cuts + tears
- Check for signs of dope separation, whorls, cracks, spits
Picketing procedure
- Park into wind
- Choke wheels, park brake on
- Lock control surfaces
- Tie plane down (angle ropes attached to wings forward, drive pegs on an angle, need slack with manilla rope)
- Fit pitot cover
- Cover engine openings
- Secure loose equipment and lock doors
