Prime/boost Pump

Question 1

Describe operation of the prime/boost pump

Answer 1

1 and #2 FUEL switches set to ON energise fuel shutoff valves allowing them to open. Fuel flows to engine boost pumps

Primes engine fuel lines by building pressure and acts as boost pump for APU start up

Prime boost switch set to on

Draws fuel from rh fuel cell and routes it to APU, #1 and 2 engine shutoff valves

Builds up pressure to 4psi and closes pressure switch contacts. ITAS monitors pressure

APU set to ON APU fuel shutoff valve opens allowing fuel to flow to APU fuel inlet

Is set to off during normal flight

Question 2

Describe prime boost pump

Answer 2

Electrically actuated centrifugal pump 28v

Pump supplies pressurised fuel to 1 and 2 engine fuel lines. Fuel lines are interconnected slowing priming of engine 1

Delivers fuel to APU, engine 1&2

Question 3

What Is boost control switch

Answer 3

Switch in cockpit

Question 4

What is crossfeed solenoid valve

Answer 4

Controlled by boost pumswitch

When energised to open position is allows crossfeed to LH and RH fuel lines

When deenergised it closes and seperate paths for each engine are maintained

Question 5

What are fuel shutoff valves

Answer 5

Reversing ball type valves

Used to control fuel flow

Valves are closed in event of fire

Question 6

What is prime boost pressure switch

Answer 6

Sense fuel pressure

When pressure exceeds 4psi it sends a message to ITAS initiating status indicators

Question 7

What are relief check valves

Answer 7

Prevent overpressuritation due to thermal expansion of fuel