Fuel Systems

Question 1

What are the two main subsystems?

Answer 1

Distribution

Control

Question 2

What mechanical adjustments can be carried out on a FADEC FMU?

Answer 2

None

Question 3

What prevents cavitation of the HP fuel pump when a booster pump fails?

Answer 3

LP pump

Question 4

What is the purpose of the servo fuel heater?

Answer 4

To prevent blockages from ice forming

Question 5

Why is the PRV fitted to the HP fuel pump?

Answer 5

To relieve the pressure at 1250 psi

Question 6

What happens to the un-metered fuel in an FCU?

Answer 6

It’s sent down the bypass line back to the pump or the tank

Question 7

If a bypass is used to cool the IDG oil, what is usually fitted and why?

Answer 7

Fuel recirculating valve

To cool the fuel before it sends it back to the fuel tanks, as warm fuel

Question 8

What is the advantage in having an oil cooler in stalled on the fuel pump?

Answer 8

Keeps the fuel in the tanks from getting too hot

Question 9

What section of the FCU is responsible for engine speed control?

Answer 9

Computing/governing

Question 10

Speed governed constant speed control uses which two signals?

Answer 10

N2 demand

N2 feedback

Question 11

Where on a FADEC engine would you normally find the FCU?

Answer 11

Mounted on the fuel pump near the gearbox

Question 12

As well power, what else may the PMA supply to the ECU?

Answer 12

Stall protection system
Clearance control system 
Thrust reverser system
Engine starting system
Engine indication system