Fuel Flashcards
Where is the Nitrogen Generation System Operability indicator?
Main wheel well adjacent to the APU fire control panel
Green light: fully operational
Blue light: degraded but still operational
Amber light: inop. (No lights, also inop)
The NGS system converts bleed air to nitrogen enriched air during all phases of flight to reduce the possibility of fuel vapor ignition in the center fuel tank.
From left bleed air manifold. Bleed air passes through ozone converter, heat exchanger (71 degrees C), and air separator to reduce oxygen below combustible level. Excess oxygen exhausted overboard.
What do IMBAL, CONFIG, and LOW (Amber) lights indicate?
IMBAL: main fuel tank quantities differ by more than 1000 lbs for greater than 60 seconds. remains until imbalance reduced below 200 lbs. inhibited with LOW
CONFIG: center tank fuel is greater than 1600 lbs and both CTR FUEL PUMP switches OFF and either engine running. Remains on until:
-both engines shutdown
-center fuel qty less than 800 lbs
-one center pump ON
LOW: when respective main fuel tank less than 2000 lbs for more than 30 sec. Remains til tank increases to 2500 lbs
With all pumps operating, which fuel tank is burned first? Why?
Center tank. Fuel pump output pressure differential. Center tank pumps higher PSI
-center 25-41 psi and min flow 20,000 lbs/hr
-main 10-24 psi and min flow 20,000 lbs/hr
Fuel qty indicator accurate within 2%. Calibrated to read 0 (empty) when fuel remaining is equivalent to unusable fuel in level flight.
Center tank unusable fuel approx 350-500 lbs
*after takeoff with center pumps OFF (less than (1000 lbs), if pumps turned ON during climb, pump may become unsubmerged causing pump to draw air and become deprimed
When do the Center Tank Fuel Pumps automatically shut off?
Approximately 15 seconds after a continuous LOW PRESSURE signal has been detected, auto shutoff
*after 10 continuous seconds master caution and LOW PRESSURE light come on
What causes the Center Tank Fuel Scavenge Jet Pump to activate?
No. 1 Main Tank Fuel Pump FWD switch ON, scavenge pump operates automatically
Main Tank 1 float valve opens below 4500 lbs or less. This allows scavenge transfer of any remaining center tank fuel to main tank No. 1.
Once started it continues for remainder of flight at 220-450 lbs/hr
With AC power loss, how is fuel provided to the engines?
With a Main Tank suction feed line (each side) that bypasses the respective boost pumps.
*suction feeding at high altitude, thrust deterioration or engine flameout may occur due to decreased air pressure which reduces suction feed fuel flow.
What is the purpose of the Crossfeed Valve?
Interconnects engine fuel manifolds. DC motor operated by Battery Bus
Allows fuel to feed from any tank to either engine.
What is indicated by a bright blue Crossfeed VALVE OPEN light?
Bright blue: valve in transit, or valve position disagrees with selector position
Dim blue: valve open, selector positioned open
What does the Engine Start Lever control? What occurs in each position?
Fuel Shutoff Valves
-SPAR VALVE: forward spar outboard of engine pylon. DC motor operated by Hot Battery Bus. Backup power source is NICAD battery pack (also provides backup to APU fuel SOV)
-ENG VALVE: high pressure, fuel actuated solenoid controlled. Battery Bus located on Engine HMU (hydro-mechanical unit)
Positions: IDLE, CUTOFF
*the start lever must be positioned to IDLE to provide power to the igniters.
What do ENG VALVE CLOSED (blue) and SPAR VALVE CLOSED (blue) indicate?
Bright blue: valve in transit, or position disagrees with start lever/fire switch position.
Dim blue: valve closed
Extinguished: valve open
What tank can the APU suction feed fuel from?
Main tank No. 1
*with AC pumps operating, APU can be fed from any tank with selective use of fuel pumps and the Crossfeed valve
How is fueling and defueling accomplished?
Single point pressure fueling station in the right wing provides for rapid fueling and defueling.
Also used for ground transfer between fuel tanks.
Power control relay, hot battery bus.
Can be fueled
-external power connected and powering buses
-external power connected but not applied to buses
-APU power
-BAT switch on
