Trapped fuel

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Cliff Wimberly
Airman
Posts: 42
Joined: 10 Jul 2015, 16:56

Trapped fuel

Post by Cliff Wimberly »

With #2 engine shut down fuel was being trapped in tank #2. I needed to use that trapped fuel to power my remaining engines. I thought that I could free up the fuel by changing the #2 tank selector from "tank to engine" to " tank to manifold " and the remaining fuel in tank #2 would flow into tanks #1, #3 and #4. That's what made sense to me but it didn't work fuel is still trapped or at least appears that way because fuel amount in tank is not being used. Plz help.

TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: Trapped fuel

Post by TreeTops »

Did you switch on No.2 Fuel booster pump?
The fuel doesnt flow into the other tanks but to the engines which are set to take fuel from the manifold.

A2A B337 Pilots_Manual_For_COTS pg 62-67.
pg 4 Restrictions/Rules - 2. Do not connect more than two engines to the manifold system. 3. Turn on the booster pump if a tank feeds the manifold (positions: TANK TO MAN or TANK TO ENG AND MAN).
Follow the fuel Balancing operations pg 65-67.
Last edited by TreeTops on 01 Oct 2020, 13:39, edited 1 time in total.
Cheers
Trev

Cliff Wimberly
Airman
Posts: 42
Joined: 10 Jul 2015, 16:56

Re: Trapped fuel

Post by Cliff Wimberly »

Thanks for the reply Tree.
I did have #2 boost pump on and the selector was in tank to manifold position so that fuel would flow into the manifold so that engines 1, 3, and 4 could use it. Selectors for 1, 3, and 4 were set to manifold to engine. When I landed the plane I had 130 - 138 lbs remaining in the tanks. Tank #2 still had 1350 lbs and had not budged since I shut down.
If I had kept on flying and run tanks 1, 3, and 4 dry would the engines start taking fuel from the manifold??

TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: Trapped fuel

Post by TreeTops »

Every time I have flown long distance I have used the fuel tanks as specified in the manual. I record all my settings and levels every half hour. I have never had a problem with using fuel out of any tank through the manifold to feed other engines.
You should be only running 2 engines off the manifold at any one time.
The point where you couldn't take any fuel from tank 2 can only mean that the selector wasn't allowing fuel through. Are you absolutely sure it was set to tank to manifold. Can you post a picture of the position you had it set to?

Why was the fuel allowed to get so low anyway? This plane carries a massive amount of fuel.

Do another short test flight and run through each of the tanks feeding to manifold to eliminate there is something sinister going on with the sim.

I assume you are fully up to date with the COTS install?
Cheers
Trev

flapman
Staff Sergeant
Posts: 457
Joined: 10 Oct 2013, 21:35

Re: Trapped fuel

Post by flapman »

This could be related to not using a default flight. There could be a fuel selector somewhere in the simulation code that A2A isn't controlling, that keeps you from moving that fuel.
How do you start the simulator Cliff?

Cliff Wimberly
Airman
Posts: 42
Joined: 10 Jul 2015, 16:56

Re: Trapped fuel

Post by Cliff Wimberly »

I'm going to do a test flight with minimum amount of fuel onboard. I will shut down one engine and feather the prop. I will turn the selector to tank to manifold and see if the other 3 engines are able to use the fuel from the dead engine tank.
I wonder why the Manual specifies that only two engines at a time can use manifold fuel. It only makes sense that the fuel from the dead engine tank should be available to all remaining engines.
I will let you know how my test flight goes.

Fuel was running low because I was flying from PANC to NARITA Tokyo had a 20+ kt headwind. Fuel was close but all was well until I lost #2 engine and couldnt use the fuel in tank #2.

TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: Trapped fuel

Post by TreeTops »

Hey Cliff,
Have you managed to do this test flight and find out any issues?
Cheers
Trev

Cliff Wimberly
Airman
Posts: 42
Joined: 10 Jul 2015, 16:56

Re: Trapped fuel

Post by Cliff Wimberly »

I flew the test flight from Shannon to Tempelhoff. I did not shut down an engine but what I did told me what I needed to know.
I filled tanks 1,2,and 3 with insufficient fuel to make the flight. Tank #4 had fuel aplenty. During the flight I turned tank 4's selector to
engine to tank + manifold. I turned the selectors for tanks 1,2 and 3 to engine to manifold. Engines 1,2, and 3 were able to run off of the manifold fuel supplied by #4 tank. I ran all four engines in this configuration until the fuel in #4 tank had been burned down to about the same amount as was in tanks 1, 2 and 3 (note, no fuel was being used out of tanks 1, 2, and 3 while their selectors were turned to engine + manifold) . After fuel was equal in all tanks I switched all four selectors to engine to tank and completed the flight.

Had I chose to do the same flight and shut #4 down, I would have switched #4 tank selector to tank + manifold and engines 1, 2 and 3 would have been able to run off of the fuel supplied by tank #4. when tank #4 became empty switch 1, 2 and 3 selectors to engine to tank or engine to tank + manifold and complete the flight.

TreeTops
Master Sergeant
Posts: 1086
Joined: 07 Apr 2010, 06:13

Re: Trapped fuel

Post by TreeTops »

Seems like everything is working normally then.

I would imagine the limit of two engines taking fuel from the manifold maximum is a safety thing. I'm not a pilot but you can read about pilot's and their thoughts on changing fuel tanks in a single piston engine plane. The when's and why's born out of hard won lessons over the history of aviation.

Scenario : the B337 is 4 hours into an ocean crossing and another 4 hours to nearest landfall.
Changing fuel tank selectors becomes a bit more critical than turning a knob on our PC's. It is easy for us sim pilot's to just work our way along the row of selectors casually changing all 4 tanks at once because the manual tells us how things should be set. I would image the flight engineer would change one tank selector and wait for any problems to arise before changing another.
So imagine if 3 engines were taking fuel from the manifold,the FE was distracted and the tank ran dry. Suddenly the trip goes from 4 engines purring away to quickly losing 3. Now the situation is very dire and it happened in a heartbeat. These things should never happen of course but history tells us otherwise.

The whole fuel program for a long flight is designed such that 2 hours from landing all tanks should be equal and for the final 2 hours all engines are set to Tank to engine. It is to maximise safety during the critical landing phase.
Cheers
Trev

Cliff Wimberly
Airman
Posts: 42
Joined: 10 Jul 2015, 16:56

Re: Trapped fuel

Post by Cliff Wimberly »

Your are absolute correct. The beauty of flight sims is that they allow us to try things that one would be reluctant to try in a real live flight. Sims were used extensively during the investigation of "Sully's" ditching.
OBTW I shut down and feathered #3 over the Channel. The fuel system worked just as expected. Engines 1,2 and 4 were able to use the fuel in #3 tank # 3 selector switched to tank to manifold. 1,2, and 4 selectors were switched to engine to manifold until #3 fuel was almost empty then I switched them to tank to engine. I was able to land safely in Munich.
I tried being cute and attempted to restart #3 just prior to landing. No joy. I might try shutting down an engine and restarting another day.
My original problem must have been the result of a Sim hiccup.

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