Questions

Question 1

Most important indication to monitor when starting a piston engine?

Answer 1

Oil pressure (more critical than starter warning light)

Question 2

CHT measured at which cylinder?

Answer 2

The hottest

Question 3

Power output of a petrol piston engine is a function of what?

Answer 3

• mass of charge packed into the cylinders
• no. of times per second that the mass of charge

P - Pressure (mean effective pressure)
L - Length
A - Area
N - Number
E - Effective number of power strokes. (RPM/2 because only one revolution of crankshaft creates a power stroke)

Question 4

Function of ‘low pitch stops’?

Answer 4

To prevent the pilot inadvertently entering beta range. Low pitch stops withdrawn once a/c is ‘weight on wheels’.

Question 5

What checks would you consider necessary to establish correct functioning of a variable pitch propeller prior to takeoff?

Answer 5

• once engine warm, exercise rpm level to circulate warm oil into PCU.
• with constant throttle check rpm alters with rpm lever movement
• with mid-speed set on rpm lever check rpm doesn’t change with throttle movement
• set rpm to max for taxi

Question 6

Operational issues concerning the subsonic air inlet?

Answer 6

A. Flow separation 
B. May become choked if air leading in approaches Mach 1.
C. FOD
D. Ice formation
E. Heavy Turbulence
F. Inlet damage

Question 7

Why are fan blades fitted with snubbers?

Answer 7

Prevents aerodynamic instability caused by flexing

Question 8

Ideal flame rate in combustor

Answer 8

3m/sec

Question 9

air/fuel ratio in combustor?

Answer 9

45-130:1

Question 10

Describe the purpose and operation of Active Clearance Control (ACC)?

Answer 10

It’s a method for controlling turbine blade tip clearance in the turbine section, by adjusting the bleed air flow, the internal circumference of the casing can be finely controlled. This system improves cruise fuel consumption.

Question 11

State the methods employed to minimise blade tip losses?

Answer 11

Shrouding blade tips and ACC (active clearance control)

Question 12

Three types of thrust reverser?

Answer 12

A. Blocker doors
B. Reverser buckets
C. Clamshell doors

Question 13

What sequence of indicator lights are presented to the pilots during normal reverse thrust operation?

Answer 13

Amber warning light “REV unlocked” caption reverser doors are unlocked followed by a full REV caption in green.

Question 14

What controls are provided and what interlocks are employed in reverse thrust systems?

Answer 14

Three interlocks - one operated from flight deck, two controlled by engine.
System can’t deploy until a/c on ground and engine at idle rpm. Throttle levers control thrust reverse by selecting a power lever angle below idle once interlocks removed and full reverse thrust not selected until thrust reverser mechanism has fully travelled.

Question 15

Why do scavenge pumps have higher volumetric capacity than the pressure pump?

Answer 15

In order to ensure hotter (expanded) and possibly aerated oil is returned to reservoir

Question 16

Explain the principle of operation of a labyrinth seal?

Answer 16

Labyrinth seals use high pressure bleed air and a groove and thread system to block any oil escape. This may require a centrifugal breather to remove air which may mix with the oil as a result.

Question 17

List some of the inputs used by the FCU to achieve a given thrust or power setting?

Answer 17

1. Engine speed
2. Air temp and pressure
3. Exhaust gas temp
4. Thrust lever position angle
5. Compressor delivery pressure
6. Rate of engine acceleration/deceleration

Question 18

Reasons for APU auto-shutdown?

Answer 18

1. Excessive EGT
2. High oil temperature
3. Fire warning
4. Altitude limit exceeded

Question 19

What is the source of air from an APU and how is it driven?

Answer 19

A centrifugal compressor driven by the APU spool (Gas Turbine output shaft)