What are the four probability terms and how are they defined?
1. Probable: occur one or more times during the entire operational life of each A/C
2. Remote: may occur several times when considering the total operational life of a number of airplanes of this type
3. Extremely Remote: may occur a few times when considering the total operational life of all airplanes of this type
4. Extremely Improbable: not anticipated to occur during the entire operational life of all airplanes of one type
What are the probability ranges for commuter and transport aircraft?
Probable: 10-5 to 10-3
Remote: 10-7 to 10-5
Extremely remote: 10-9 to 10-7
Extremely Improbable: lower than 10-9
Which main design concepts are applied in aviation?
Explain the concept "Safe-Life"
systems or components will survive a specific design life with no failures
Explain the concept "Fail-Safe"
a failure will cause no (or minimum) harm to other parts and systems or danger to personnel
Explain the concept "Fault-Tolerant"
a system can continue operating in the event of the failure of one or more of its components
Aerodynamic loads result mainly from a pressure distribution over the external surfaces. What does this pressure distribution depend on?
- the angle of incidence
- the aerofoil shape
- (where present) the deflection of control or lift augmentation surfaces (such as ailerons, spoilers, flaps or slats)
Where is the point of application of the lift and drag component?
At the centre of pressure (c.p.)
Explain the pitching moment coefficient (cm0) of a cambered aerofoil
For a cambered aerofoil, cm0 is usually negative (which means that for positive lift the centre of pressure lies behind the aerodynamic centre)
What happens to the compressibility and the a.c. at Mach numbers above 0.5 - 0.6?
- compressibility effects become important
- a.c. starts to move backwards, slowly at first, then quite rapidly when zones of supersonic flow appear on the aerofoil (transonic regime). In supersonic flow, the position of the a.c. tends to 50% of the chord.
Explain "Ground loads"
- for taxiing, take off ground roll, landing
- through landing gear (reduce loads to a level that can be absorbed without damage)
What parts of the A/C do the ground load conditions influence?
- design of the landing gear
- structure of the A/C
- attachment points
List some of the main load conditions to be considered according to airworthiness regulations.
- level landing condition
- lateral drift landing condition
- one-gear landing condition
- side load condition
- braked roll conditions
- forward acting horizontal load (during towing)
Explain "ultimate load"
The maximum load that the test specimen can withstand before the material fails.
What is the common unit of the "aircraft lift curve slope" [CLα]?
The shear and bending loads are independent of speed.