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FA50: Fuel system

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Under typical operation, each wing tank is connected to its respective feeder tank and the
corresponding XFER PUMP is on. Likewise, each feeder tank is connected to its respective engine and
the corresponding BOOSTER Pump is on.

From manual 1.4 above it is very simple, with this setup we should check the wing fuel quantity and when empty, the feeder tanks quantity.

fuel.jpg

If I am not wrong with this setup above, the wing tanks do not seems feed their respective feeder tanks. Did you notice something wrong there?

Pascal

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I saw in a coast to coast flight that the wing tanks won't transfer fuel to their corresponding feed tank until the quantity of that said feed tank was down to 609lbs.

I think it's built in to avoid CG displacement aft to out of limits.

Edited by Guevorkyan
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My understanding is the fuel in the feeder tanks decrease until there is about 600 pounds of fuel in each feeder tank.  When that level is reached,  a float activated switch in the feeder tank regulates the transfer of fuel (using the transfer pump) from the respective wing tank so to keep the feeder tank fuel level at 600 pounds. This happens until the wing tank is empty.  If a transfer pump fails, fuel will still be transferred from the wing tank to the feeder tank (although at a reduced rate) because the wing tanks are pressurized with bleed air to a higher value then the feeder tanks. You should turn off the transfer pumps when the wing tanks are empty.

I'm sure Jim Barrett can elaborate in more detail how all this really works.

Al

Edited by ark
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Thanks Martin, I missed this Scott's nice tresor 😃

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5 hours ago, ark said:

My understanding is the fuel in the feeder tanks decrease until there is about 600 pounds of fuel in each feeder tank.  When that level is reached,  a float activated switch in the feeder tank regulates the transfer of fuel (using the transfer pump) from the respective wing tank so to keep the feeder tank fuel level at 600 pounds. This happens until the wing tank is empty.  If a transfer pump fails, fuel will still be transferred from the wing tank to the feeder tank (although at a reduced rate) because the wing tanks are pressurized with bleed air to a higher value then the feeder tanks. You should turn off the transfer pumps when the wing tanks are empty.

I'm sure Jim Barrett can elaborate in more detail how all this really works.

Al

Your explanation is spot on. 

The feeder tank for engine 2 is physically larger than the feeders for engines 1 and 3. On refueling, the system will put the same amount of fuel (weight wise) in each of the three tank groups, and the total weight in each of the three groups will be the combined weight of the respective wing and feeder tank.

But when refueling, the main/feeder “split” will be different in number 2 than in number 1 and 3. There will be less fuel in the number 2 wing tank, and more in the feeder tank compared to the other two. 

This is indeed done for CG management. In flight, the number 1 and 3 feeders will reach the 600 pound transfer point well before the number 2. Eventually when all the wing fuel is consumed, all three feeders will be at 600 pounds.

Hopefully, the aircraft will be in descent for the destination airport by that time, because there is less than one hour fuel remaining once the wing tanks are empty.

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