Name the types of fuel pumps and explain one of them.

(1) Gear type :

Gear type pump is a positive displacement pump which takes in inlet fuel and
rotates in a direction which allows fuel to move between the gear teeth and pump
inlet case until fuel is deposited in the outlet.

(2) Multi-Plunger/swash plate type :

(a) It is a variable displacement pump, driven by the engine gear train.
(b) Output depends on rotational speed and also pistons.
(c) Rotor assembly fitted with several plungers.
(d) Ends of plungers bear onto non-rotating cam plate and biased by spring to give full stroke position of plungers.
(e) Servo pistons subjected to pump delivery pressure on one side and spring end servo pressure on the other.
(f) Variation in pressure difference across the servo piston causes it to move with corresponding variation in cam plate angle therefore piston stroke.


2. Explain crack inspection on turbine blades.

1. Visually inspect for stress rupture cracks on turbine blades leading/trailing edge.
2. Minute hairline cracks at right angles to the blade length.
3. Check for turbine blade creep.
4. Check for nipping of the trailing edge.
5. Check for pitting, metal deposits, erosion and heat damage.
6. Check for signs of gas leaks across shroud indicated by streaks.
7. With a strong spotlight and viewing equipment e.g. magnifying glass access hole through a strategic position through which a boroscope or intrascope inspection can be carried out.


3. Describe the checks necessary on engine power controls after installation.

1. Check for proper cable routing and tensioning.
2. Check for security/safety of attachments.
3. Check for full and free movements.
4. Check for correct sense of operation of controls with respect to the lever movement.
5. Check for spring back, smoothness and static friction.
6. Check that clearance of stops are within limits at extreme travel of controls.
7. Under static condition, check the throttle stagger.
8. Carry out engine ground run.
9. Check for correct operation of system, proper indication.
10. Parameters normal, record result/adjustments.
11. Of satisfactory, carry out duplicate inspection.