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7890 - Aircraft Systems Design > Module 7890 > Flashcards

Module 7890 Flashcards

1
Q

State the Ideal System (6)

A

1) Should function correctly under all conditions of operation
2) Reliability of components should not be affected due to delicacy
3) Light and compact
4) Ease of maintenance, testing and repair
5) Does not reduce performance or interfere with other services
6) Immune to external interferences and contamination

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2
Q

List the external interferences (6)

A

1) Vibration
2) Contamination
3) Heat
4) Electrical Induction
5) Radiation
6) Acoustics

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3
Q

Explain what must NOT happen when a component fails

A

Must not cause damage to other equipment, endanger personnel or cause failure of the system

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4
Q

What methods are employed to protect the integrity of systems and components? (5)

A

1) Mechanically driven components fitted with waisted drives
2) Pressure and thermal relief valves, fuses and circuit breakers used to prevent or protect from overloading
3) Pressure transmitters used to isolate dangerous fluids from entering the cockpit
4) Filters used to stop contamination
5) Emergency or duplicated systems installed where flight safety could be affected

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5
Q

What are the system classifications and define them?

A

Primary/Essential - Critical to flight safety
Secondary - Primary but does not necessarily mean the system cannot be degraded
Utilities -

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6
Q

What are the system classifications and define them?

A

Primary/Essential - Critical to flight safety
Secondary - Primary but does not necessarily mean the system cannot be degraded
Utilities - Considered expendable after failure

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7
Q

Three types of A/C systems

A

Power
Supply
Information

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8
Q

What are the requirements of the power system? (4)

A

1) Reduce aircrew workload
2) Overcome excessive flight load
3) Give automatic control of the system
4) Give remote operation of the system

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9
Q

Advantages of HP air (3)

A

1) cheap, clean, light and safe
2) Easy to test and maintain
3) Can absorb shock loads

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10
Q

Disadvantages of HP air (3)

A

1) Too compressible causing inefficiency
2) Limited reserve available
3) Requires routine servicing

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11
Q

What is low pressure air used for?

A

Boundary layer control
Air conditioning
Fuel tank pressurisation
Weapon cooling

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12
Q

Advantages of LP air (4)

A

1) Those stated in HP air
2) Continual source of supply
3) Hot, used for de-icing and air conditioning
4) High volumes of flow can be obtained

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13
Q

Disadvantages of LP air (4)

A

1) Output varies with engine speed and altitude
2) Medium is compressible
3) High temperatures are a disadvantage to some systems
4) High water content

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14
Q

Hydraulic System Advantages (3)

A

1) Good power/weight ratio due to operating at high pressures
2) One power source can operate numerous systems
3) Simple to arrange a hydraulic lock

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15
Q

Hydraulic System Disadvantages (4)

A

1) Problems with sealing can occur
2) Leakage can lead to total system failure
3) flammable - fire risk
4) susceptible to contamination

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16
Q

Advantages of Electrical systems (6)

A

1) Light and flexible
2) Easily and accurately controlled
3) Power source is self governing
4) Ease of fault diagnosis (BITE)
5) High speed operation
6) Not normally subject to contamination

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17
Q

Disadvantages of the Electrical System (2)

A

Heavy components required for some systems operating under heavy loads

Fault diagnosis can be more difficult on complex systems

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18
Q

What is the basic requirement of the supply system?

A

To accurately control the flow to meet the demand under all operating conditions i.e correct temperature, pressure and flow rate

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19
Q

What methods are used to transfer the supply system medium?

A

Pumps
Gravity

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20
Q

What is the purpose of the Information system?

A

Provide information on serviceability, condition and status/position of a system or component

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21
Q

Where is information supplied to?

A

Aircrew via cockpit gauges, indicators and warning lights

ACS

22
Q

For a fluid system to operate, what must take place?

A

flow or movement of the system medium

23
Q

How are errors caused and give examples? (3)

A

1) System Conditions - change in temperature, pressure, flow rate and work load on the fluid

2) Environment - Weather conditions , geographic location, altitude, forward speed and G loading

3)Flight Pattern - change in altitude, forward speed, G loading and attitude

24
Q

What will error sensing devices respond to?

A

Changes in pressure, temperature, speed, flow rate selection and attitude

25
Q

What are the 3 methods of error sensing?

A

Mechanical Offset Lever
Hydraulic - Differential Area
Electrical Amplification

26
Q

Define how to overcome “hunting”

A

A proportion of the output of the corrective device is fed back to the error detector and partially opposes the original error. It will continue to do this and act as a dampening effect until the error is cancelled and the system is at the desired condition

27
Q

What does the amplifier do?

A

Increases the size of the signal to be corrected by the corrective device

28
Q

What is the purpose of a pump?

A

converts mechanical rotational energy to fluid energy. Creates fluid flow.

29
Q

The size of pressure in a fluid is influenced by? (2)

A

1) The amount of resistance to fluid flow

2)The ability of the pump to maintain flow against resistance

30
Q

The quantity of the flow of fluid induced by the pump is influenced by? (3)

A

1) The capacity of the pump

2) The operation of the pump

3) Design limits

31
Q

What factors are considered when selecting a pump to a system? (5)

A

1) System Flow Rates

2) System Operating Pressures

3) Speed of operations

4) Required efficiency

5) Cost, quietness and smoothness of operation

32
Q

Name and describe the 2 types of pumps

A

Positive Displacement Pump - total quantity of fluid in = total quantity of fluid out

Non-positive Displacement Pump - Fluid going in meets some resistance and pump allows eddying inside the pump body (fluid to circulate the pump)

33
Q

Positive displacement pumps can be further sub divided into…?

A

1) Constant Delivery pumps

2) Variable delivery pumps

34
Q

State the 2 ways mechanically driven pumps can be driven

A

1) Rotary driven

2) Linearly driven

35
Q

What type of pump is an external spur gear pump and what type of delivery does it provide?

A

Positive Displacement pump
Constant delivery at a constant speed

36
Q

When are external spur gear pumps most effective?

A

When pumping liquids

37
Q

External spur gear pumps are designed to operate to what pressures?

A

3000-5000 psi

38
Q

Describe how the external spur gear pump works

A

1 driven gear and one driver gear.
As the driver gear rotates clockwise, the driven gear rotates the opposite way allowing the fluid to pass through the space between their teeth and out the outlet port.
Due to no clearance of the teeth and the housing, it can cause wear and contamination to the fluid.

39
Q

What factors affect the efficiency of an external spur gear pump?

A

1) Pump speed of rotation

2) Viscosity of the fluid being used

40
Q

What type of pump is a gerotor pump and state its delivery type

A

Positive displacement pump
Constant delivery

41
Q

Describe how a gerotor pump works

A

One driver gear (6 teeth) and one driven gear (7 teeth).
Gears turn clockwise together As the gears turn, they form a partial vacuum due to the increase in size, sucking in fluid from the kidney shaped inlet and transfer it to the kidney shaped outlet once the pockets decrease in size

42
Q

What type of pump is an internal gear pump and state its delivery type

A

Positive displacement pump
Constant delivery
Constant speed

43
Q

Give 4 comparisons of the internal gear pump and the external spur gear pump

A

1) Can give a larger displacement

2) Quieter in operation

3) Higher operating pressures

4) More costly

44
Q

Describe how the internal gear pump works

A

An eccentric driving piston is mounted to the internal gear located inside the outer gear ring and is free to rotate.
The tip of each internal gear tooth is always in contact with the inner surfaces of the outer gear ring.
A crescent shaped wedge seals the clearance space and prevents pack pressure.
Rotation creates contracting and expanding pockets, acting as a vacuum, transferring from the inlet to the outlet.

45
Q

What type of pump is an eccentric vane pump and state its delivery type

A

Positive displacement pump
Constant delivery
Constant Speed

46
Q

Describe how an eccentric vane pump works

A

Mainly operates with gases.

Rotor mounted off centre in a pump body. The rotor is fitted with vanes which its outer edges keep in contact with the pump body via centrifugal force or with springs.
Fluid comes from the inlet and is trapped between 2 adjacent vanes and transferred around the pump body as the rotor rotates, as it rotates the vanes begin to drop, allowing the fluid to pass through to the outlet port.

47
Q

What causes a loss in efficiency in an eccentric vane pump?

A

Vane tip wear can cause contamination
Sealing problems - can be overcome by spring loaded vanes

48
Q

What type of pump is a piston pump and state its delivery type

A

Positive Displacement pump
Constant delivery
Constant speed

49
Q

What are the advantages of a multi piston pump over a single piston pump? (4)

A

1) Reduction in pulsations

2) Effective sealing

3) Long close tolerance pistons

4)High volumetric efficiency

50
Q

Explain how a multi piston radial pump works

A

Offset eccentric drive allows the piston to reciprocate its motion as it rotates about the bearing and slip assembly.
The depression caused by this movement allows each piston to receive a full charge of fluid into its cylinder. As it rotates, the fluid in the piston gets pushed out to the outlet line. The pressure overcomes the non return valve and opens the lines to transfer the fluid to the outlet port.

51
Q

What type of pump is the multi-piston axial pump (fixed swashplate) and what delivery type is it?

A

Positive displacement pump
Constant delivery
Constant speed

7890 - Aircraft Systems Design (1 decks)

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