Fuel System Flashcards
There are _____ separate wing fuel systems, _____ for each engine, that are connected by a _____________ _____system.
2, one, Valve-controlled crossfeed
What is the usable fuel capacity?
384 gallons
How many modes of operation on the fuel system is available?
3 - normal, auto crossfeed, and suction feed
Describe the modes of fuel operation:
Normal - Each engine receives fuel from corresponding fuel cells and boost pump
Auto Crossfeed - In the case of boost pump failure, boost pressure is obtained by supplying fuel to both engines through the crossfeed valve, from one boost pump. A drop in output pressure from the failed pump is sensed by a pressure switch, which then automatically pens the crossfeed valve when the pressure drops below 10psi and illuminates the low pressure annunciation. When pressure is restored, the annunciation extinguishes.
Suction - may be used for boost pump failure. It allows use of fuel from tanks on the side with the failed pump. It moves the crossfeed valve control from AUTO to CLOSED. A vacuum created by the engine driven pump draws fuel from the nacelle fuel tank. Suction feed is limited to 10 hours cumulative between engine driven pump overhauls.
What are the different fuel tanks?
Leading edge bladder-type tank (40gals), two outboard-wing panel bladder-type tanks (23 & 25 gals), one center section bladder-type tank (44gals), and the nacelle tank (61gals)
What tanks supply the center section and nacelle tanks?
The outboard wing tanks
What is fuel transferred to the nacelle tank by?
The fuel transfer pump in the low point of the center section tank
Fuel for each engine pumped directly from where?
The nacelle tank by an electric fuel boost pump
If a full load of fuel is needed, which tank do you fill first?
The nacelle tank, then the wing tank because fuel can only flow into the nacelle tank and not back into the wing tank
What does each engine have inside of the nacelle tank?
A boost pump
What is the boost pump pressure provided inside of the nacelle?
30psi
What color annunciation is associated with the boost pump and how many?
Red and 2
What does it mean when the FUEL PRESS annunciation pops up?
There is low fuel pressure on the side indicated.
When crossfeed is in AUTO, how is a boost pump failure identified?
Momentary illumination of the FUEL PRESS annunciation and fault warning flasher, then the FUEL CROSSFEED annunciation
How can you identify the failed boost pump during AUTO crossfeed?
Place crossfeed in the CLOSED position. The annunciation will pop up on the side that of the engine that is having the failure.
In the case of a boost pump failure what else can be done with the crossfeed switch?
It can be closed and the flight can be continued by relying on the engine-driven high pressure pump.
How is the fuel level in the nacelle automatically maintained?
By a fuel transfer system, whenever the tank drops by 10 gallons
Fuel is transferred automatically when the __________ switches are placed in AUTO, unless the nacelle tanks are full
TRANSFER PUMP
What do the nacelle tanks fill up to?
Fill until the fuel reaches the upper transfer limit and a float switch turns the TRANSFER PUMP off.
What will automatically turn off the transfer pump?
A pressure switch, when the pressure is not obtained within 30 seconds after the pump is turned on, or if the transfer pump drops below a preset pressure due to empty wing tanks or pump failure
Why do the NO FUEL XFR annunciators illuminate?
No pressure after 30 second time delay due to empty wing tanks or transfer pump failure. It illuminates when the fuel pressure to the sensor reaches a minimum pressure of 2.5psi.
What does the NO FUEL XFR annunciation mean during normal operation?
The wing tanks are empty and the fuel transfer switch should be turned off
What happens when the nacelle tank drops down to 22 gallons?
The gravity port in the nacelle tank opens and the gravity flow from the wing tank starts.
All wing fuel, except 28 gallons from the center section tank, will transfer during gravity feed.
What is the total amount of fuel the system can hold?
What is the weight of jet fuel?
387 gallons - 384 usable
6.7lbs (2572.8lbs usable fuel - 1286.4lbs per side)
What is the fuel system vented through?
A recessed ram scoop vent, coupled to a heated external vent, located on the underside of the wing, adjacent to the nacelle.
How do the wing tanks fuel flow to the center section tank?
Gravity fed
What prevents back flow of fuel into the wing tanks?
A flapper-type check valve in the end of the gravity feed line
What is the fuel pressured provided by to operate the engine?
An engine driven fuel pump, mounted in conjunction with the fuel control unit on the accessory case
Where is the engine driven fuel pump located on the engine?
The accessory case, along with the fuel control unit
During shutdown, why must both boost pump switches and crossfeed be turned off?
Prevent discharge of the battery
What is the purpose of a firewall shutoff valve?
It can cut off all fuel to the engine.
What is the fuel purge system?
It assures any residual fuel in the fuel manifold is consumed during engine shutdown
How does the purge system work?
During engine start, the fuel manifold pressure closes the manifold poppet valve, allowing P3 air to pressurize the purge tank. During shutdown, the poppet valve is opened, then the pressure differential from the purge tank and the fuel manifold causes the air to be discharged from the purge tank, forcing the residual fuel out of the engine manifold lines, through the nozzles, and into the combustion chamber.
What fuel quantity prohibits takeoff?
When the selector is in the total position and it reads in the yellow arc or when there is less than 265 pounds in each wing system.
How many hours of operation is allowed while using aviation gas?
150 hours
What does using aviation gas do to the engine?
Creates buildup of lead deposits on the turbine wheels and this causes a reduction in power.
Where are the fuel pump drains?
Nacelle tank, center-section tank transfer-pump, wheelwell, inboard end of the outboard wing-tank
