B737NG Fuel System Flashcards
How many fuel pump ‘low pressure’ lights is required to activate master caution light.?
Two ‘LOW PRESSURE’ lights illuminated in same main tank. If one CENTRE TANK low pressure light remains illuminated for 10 seconds or more.
One LOW PRESSURE light causes MASTER CAUTION and FUEL system annunciator lights to illuminate on pressing recall.
In which tank is the fuel temperature measured?
No. 1 tank.
What is the purpose of the crossfeed system?
Connects engine No. 1 and No. 2 fuel feed lines.
How much fuel should be in a tank that indicates ‘Fuel LOW’ Alert?
907 kgs in related tank.
Max allowable fuel imbalance?
453kg /1000 lbs
What will cause kFuel Configuration (CONFIG)’ Alert?
- either engine running
- centre fuel tank quantity greater than 726 kgs; and
- both center fuel tank pump switches positioned OFF
How many measuring sticks are installed?
16:
6 are installed in each main tank and 4 are installed in center tank
How is fuel fed to the engines?
Pressure fed from the center tank first. The engines are then pressure fed from their respective main tanks.
How does the system ensure the proper direction of fuel flow and to prevent transfer of fuel between tanks.
Check valves (like diodes). Center tank pumps produce higher pressure than main tank pumps.
If the centre tank pumps sense a low pressure, do the u ps shut down automatically or manually?
Each center tank pump will automatically shut off, after a short delay, when that pump’s sensor detects low output pressure. Switches still require manual switching off.
What happens if the fuel pumps struggle to supply fuel to the engines at high altitudes?
Each engine can draw fuel from its corresponding main tank through a suction feed line that bypasses the pumps if the pressure is low.
How many fuel shut off valves are there and where are they located?
Four. 2 spar valves located in each wing and 2 engine shut off valves located in the pylons.
How are the shut off valves closed?
Whenever their respective engine fire switch is pulled or engine start lever is placed to CUTOFF.
When does the scavenge pump start pumping fuel into the left main tank?
When the centre tank quantity reaches 50%. (The main tank fuel pump No. 1 FWD Switch must be ON)
With loss of Transfer bus 1, how many fuel pumps will be operable?
One in each tank.
