A/C SYS 2017

airframe, engine and systems

Structure, vehicle system, avionic system

- complex and integrated set of structural components
- supports the mass of systems and PAX
- carries loads and stresses
- also known as the “platform”

- also known as general or utility system
- enables the A/C to fly safely
- provides an adequate environment for crew and PAX

provides information, control and communication functions that enable the aircraft to fulfil its operational role

- nowadays usually a Fly-by-Wire (FBW) system
- pilot control input is elaborated on the basis of air data, A/C attitude etc. to issue the proper control surface deflections that will effect the desired aircraft motion

in most recent aircraft a Full Authority Digital Engine Control (FADEC) system

provides airspeed, altitude, air temperature, rate of climb or descent information

provides information on pitch, yaw and roll angles, rates and accelerations

provides electrical power for flight and engine control computers, air data system, attitude systems, hydraulic servo-valves and (on some A/C) electrically driven hydraulic pumps

provides motive power for the actuators that move the flight control surfaces, or the engine thrust reversers

The functions whose loss would reduce the capability of the A/C or its crew to cope with adverse operating and environmental conditions (i.e. loss of cabin pressurization or loss of the anti-icing system)

Functions which could cause the loss of the aircraft or fatal injuries to the occupants (i.e. a complete loss of engine power)

The severity of a failure condition must be inversely proportional to ist probability

- Effects on the airplane
- Effects on the crew members
- Effects on the occupants

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

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

- Safe-Life
- Fail-Safe
- Fault-Tolerant

systems or components will survive a specific design life with no failures

a failure will cause no (or minimum) harm to other parts and systems or danger to personnel

a system can continue operating in the event of the failure of one or more of its components

- the angle of incidence

- the aerofoil shape

- (where present) the deflection of control or lift augmentation surfaces (such as ailerons, spoilers, flaps or slats)

At the centre of pressure (c.p.)

For a cambered aerofoil, c_m0 is usually negative (which means that for positive lift the centre of pressure lies behind the aerodynamic centre)

- 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.

- for taxiing, take off ground roll, landing

- through landing gear (reduce loads to a level that can be absorbed without damage)

- design of the landing gear

- structure of the A/C

- attachment points

1. level landing condition
2. lateral drift landing condition
3. one-gear landing condition
4. side load condition
5. braked roll conditions
6. forward acting horizontal load (during towing)

The maximum load that the test specimen can withstand before the material fails.