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 Post subject: Oil Pump switch issue
PostPosted: Mon Jul 11, 2011 9:40 am 
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The oil switch to pump oil into the engines in the fwd position works ok but for some odd reason the switch in the aft position is also adding oil from the central tank into the selected engine. I was under the impression the switch in the aft position would pump oil from the selected engine back into the central tank?

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PostPosted: Mon Jul 11, 2011 9:45 am 
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This is actually the way it is supposed to work. You can only pump oil TO the engine, and cannot take it. This is why engineer's let the oil get pretty low before pumping in, in the event there was a failure, all that oil isn't lost.

FWD and AFT refers not to oil pumping direction but FWD pump and AFT pump.

Scott.

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PostPosted: Mon Jul 11, 2011 9:58 am 
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Thanks for clearing that up. I must have read something that confused me :)

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PostPosted: Mon Jul 11, 2011 6:29 pm 
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I'm glad this came up. I read that it was only possible to pump oil TO an engine, so couldn't understand why there were forward & aft options on the switch. I hadn't remembered to try it out though to see what happened, but now I know :D


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PostPosted: Sun Jun 10, 2012 5:36 pm 
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This was confusing me, as prior to COTS the switch could add but also remove oil from the engine.

So how did:

Quote:
The captain then decided to cut off the oil supply to the engine

prior to the PAA Flight 6 ditching?

See: http://en.wikipedia.org/wiki/Pan_Am_Fli ... nt_details

I had always thought he used the oil switch back position to transfer the engine oil back to
"Oil Central" :-)

Anyone?

Cheers,

- jahman.


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PostPosted: Sun Jun 10, 2012 5:50 pm 
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When they say the captain cut-off oil to the engine, it means he flipped the cutoff switches on the overhead. These drive closed valves on the firewall for the fuel and oil supply lines. The oil transfer pump only works in one direction - central tank to engine tanks as Scott said. You cannot move oil from the engine tanks to the central oil tank or between the engine tanks. I believe before the first update it could do this until the guys realized the error and then fixed it, but it's been that way for quite some time. The central oil tank has 2 pumps (forward and aft) for both redundancy, and to ensure that all of the oil can be taken from the tank as depending on pitch, one of the two pumps will become uncovered as the oil level gets low in the tank. Had Boeing not placed 2 pumps in the tank, it is possible that 10-15 gallons of oil could be trapped in the tank and unusable. This was not acceptable with the distances that they were planning to fly.

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PostPosted: Mon Jun 11, 2012 2:34 am 
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Many thanks for the clarifications. Blimey, I should have thought of the firewall oil cutoff switch!

Makes sense to have fore and aft oil pumps, but a single switch means the system is not fail-operational. I'm surprised the folks at the Boeing Department of Redundancy Department let that one sneak by. Also the fuel tangs don't have fore and aft pumps...

Oh, well, I'll miss the entertainment of moving oil back and forth between the engines and Oil Central.

Cheers,

- jahman.


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PostPosted: Mon Jun 11, 2012 2:45 am 
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jahman wrote:
-SNIP-
Oh, well, I'll miss the entertainment of moving oil back and forth between the engines and Oil Central.

Cheers,

- jahman.


hehehe....I find more than enough 'entertainment' in just keeping oil in my old, worn
engines on long hops!

On one flight from the SF Bay Area to Honolulu my concern was not the possibility of
running out of fuel. Instead it was the possibility of running out of oil! :)

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PostPosted: Mon Jun 11, 2012 2:56 am 
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Yes, I understand that could happen with worn engines! I am amazed at the amount of oil those engines go through.

I would love a mod that allows jury-rigging a spare 55 gallon oil drum in the cargo hold to refill Oil Central via a hand pump (1 quart per mouse click!)

Cheers,

- jahman.


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