Fuel

Question 1

How much fuel can be in each tank?

Answer 1

Forward = 1,300 lbs
Header = 204 lbs
Aft = 790 lbs
Wings (inboard/outboard) = 735 lbs each wing

Question 2

How is fuel quantity determined?

Answer 2

Fuel quantity is both measured and calculated

Measured = values indicated by fuel probes/floats
Calculated = “mapped” fuel stored in RCM memory minus fuel sent to the engine measured by the mass flow sensor

When the GCS ignition is set to HOT the RCM stores the measured values in memory as the calculated fuel level

Question 3

How accurate is the mass flow sensor?

Answer 3

+/- 10 lbs/hr

Question 4

What is the “fuel map”?

Answer 4

The theoretical distribution of calculated fuel quantity that is used by the RCM for calculating CG and fuel remaining

Question 5

What is the electric fuel pump control algorithm?

Answer 5

One runs for 20 min then a 10 sec overlap before the other one runs for 20 min

Question 6

What happens if both electric pumps fails?

Answer 6

Engine will only continue to run until the fuel in the header tank is depleted
Also can not jettison fuel

Question 7

What is the automatic mode fuel burn pattern?

Answer 7

Wing tanks, then forward tank, then aft tank

Question 8

How is fuel heated?

Answer 8

Two fuel heaters (one on the fuel feed line to the fuel feed manifold/one on return line from header tank)

Also fuel/oil heat exchanger

Question 9

How is fuel moved between tanks?

Answer 9

Jet pumps in each tank use motive flow from return fuel to increase fuel flow to the header tank

Question 10

What is the header tank normally pressurized to?

Answer 10

2-3 psi (<1.5 psi in shutdown)

Question 11

How are the tanks constructed?

Answer 11

Rubber bladder supported by surrounding composite structure

Question 12

What is unusable fuel?

Answer 12

1-2% (60 lbs)

Question 13

When will the caution and warning for fuel level in the header tank come on?

Answer 13

Caution = 194 gal
Warning = 184 gal

Question 14

When will the header tank over pressure warning come on?

Answer 14

> 4.2 psi and again if >4.6 psi

Question 15

What would cause a fuel header tank level or pressure low?

Answer 15

-fuel feed solenoid failed closed
-return manifold failed open
-RCM selecting an empty tank

Question 16

What will be the indications of a fuel pump failure?

Answer 16

Warning on HDD
System will automatically run both pumps
Monitor fuel feed pressure on VIT 1

Question 17

What would be the indication of a return fuel solenoid failed open?

Answer 17

Fuel increasing in a non-selected tank

Question 18

What would be the indication of a return fuel solenoid failed closed?

Answer 18

Excessive pressure in header fuel tank

Question 19

What would be the indication of a feed fuel solenoid failed closed?

Answer 19

Low header tank fuel level

Question 20

What happens if a feed or return solenoid is stuck closed?

Answer 20

You would have only one problem tank

Feed solenoid closed = low fuel level in header tank

Return solenoid closed = over pressure in header tank

Question 21

What happens if a feed or return solenoid is stuck closed?

Answer 21

Problem with all but one tank

Feed solenoid open = low level in header and extra fuel in another tank

Return solenoid open = over pressure in header tank and extra fuel in another tank