2016 PC Guide - Fuel System Flashcards
Although the CL and NG aircraft both have 2 fuel boost pumps in each tank, what is the difference in operation?
The CL has 6 identical pumps. The center tank check valves open at a lower pressure than do the main tank check valves. This ensures that center tank fuel is used before main tank fuel even though all fuel pumps are operating at the same time pressure.
In the NG aircraft, the center tank pumps produce higher pressure than the main tank pumps. This ensures that center tank fuel is used before main tank fuel, even thought all fuel pumps are operating.
As you are completing your originating cockpit flow, you notice the crossed valve does not open. As you investigate the cause you find the crossed valve circuit breaker has tripped. Can you reset it.
Contact Mtx (through Dispatch, if necessary).
If Mtx is in agreement, the crossed valve can be reset. Resetting the circuit breaker requires a logbook entry including the Maintenance Controller’s name.
During your cockpit setup you position the center tank fuel pumps on and the low pressure light for the left center pump remains illuminated. You check circuit breakers, and find the Center Left circuit breaker tripped. Can you try resetting the circuit breaker? Can we dispatch?
A pilot may not reset a fuel pump circuit breaker even on the ground. Contact Mtx, record the tripped circuit breaker in the logbook.
While at cruise altitude, the aircraft fuel temperature drops to -38C. Would you receive any type of warning that the fuel tank temp had dropped below the minimum of -37C? What would you do in this situation?
No
There is not a warning for low fuel temperature. It is necessary to be cognizant of fuel tank temp, especially while at high cruise altitudes for extended time. If the fuel temp drops below -37C, refer to the QRH: Fuel Low Temp checklist. The QRH directs the pilot to increase airspeed, descend or deviate to a warmer airmass to achieve a TAT equal to or higher than the fuel pump temp limit. TAT will increase 0.5 to 0.7 C for each 0.01 Mach airspeeds increase. In extreme conditions, it may be necessary to descent to as low as FL250
After holding, you are on a vector for the approach and should land with about 4100 pounds of fuel. After you program the approach into the FMC, it shows landing at 3800 lbs. Should you declare min fuel with ATC?
You should verify the routing in the FMC is truly the distance you will fly. These are situations where quickly programing an approach will add 30 or more miles to your routing that you will not actually fly. If the CA (or Dispatcher) determines that landing fuel will be less than 4000 lbs, the CA will declare Min Fuel.
During cruise flight in an NG, you notice that you have a 300 lb fuel imbalance. You open the crossfeed valve verifying operation and then turn off the pumps on the low side without informing your FO. Thirty minutes later you notice that one of the fuel gauges amber and IMBAL is displayed. What does this mean and will it go away?
When the fuel imbalance reaches 1000 lbs, the low side gauge will indicate amber and IMBAL will display. Inform your FO, then turn all main pumps on ensuring the crossed valve remains open and then turn OFF the low side pumps. When the imbalance is restored within 200 lbs the amber indication will cease.
You have just landed your -700 in San Diego in the summer after a long flight and the fuel temp reads 0 degrees C. What must you think about and accomplish?
When the fuel tank temperature is less than 5 degrees C, check for cold soaked fuel frost (CSFF) on both surfaces of the wing. The Boeing 737 is susceptible on both upper and lower surfaces, most notable between the fuselage and engine pylon. Check the wings for CSFF ten to fifteen after gate arrival.
CSFF up to 1/8” on the lower wing is permissible, but no CSFF on the upper wing surface is allowed. Three methods are approved for CSFF removal:
- Radiant Heating
- Adding fuel to raise the fuel tank temp to 5C
- Type 1 deicing
What are the 2 methods of de-fueling?
De-fueling may be accomplished by boost pump pressure or suction. Both methods may be used together for more rapid de-fueling.
How do you transfer fuel from the center tank to the right main tank?
You use the manual de-fuel valve, the refuel station, and the fuel control panel to transfer fuel between tanks per AMO Chapter 16.
You are operating an aircraft with ions #1 fuel quantity indicator. It is required to dipstick the tank. What must the CA do?
The CA must monitor any fueling operation requiring the use of dipsticks to ensure the accuracy of the readings.
Where do you find the dipstick tables?
They are available on the OPC, found in the MEL section.
