crossfeed valve check
Thread Starter
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From: Russia
Please, craig freier, may be you remember some references to any ETOPS manuals or so... In our TLB beside the "ETOPS flight performed" column there is the "Cross-feed valve check peformed" gap and my colleagues argue about it. I could find too little information, we don't have the company regulations concerned. I read one statement that in case of two valves installed the check was not required.
Joined: Jul 2007
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From: Germany
BOAC that is straight out of our OM, which is Boeing procedure based. The idea is not to let a pump run dry. The master caution logic will only trigger if both are dry, thus the procedure of switching one off so you get a master caution warning. Minimum quantities are 2300kg for takeoff, 950 for climb and cruise and 1400 for descent.
But I am always keen to learn. How do you do it? Comparing notes like this is one of the main benefits of Pprune for me.
But I am always keen to learn. How do you do it? Comparing notes like this is one of the main benefits of Pprune for me.
Per Ardua ad Astraeus
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From: UK
leder - we just used 2300/500 as per the AD (NB Not 930- where does that come from?) and 1400kg. BOTH Pumps off if below those figures, and allow scavenge to start to empty the tank in the cruise/descent phase. No crossfeed used (unless for balance). It seems to me that your procedure (as you wrote it) runs a main pump dry? We just turned off both while they were still 'fuel cooled'..........
You also MAKE an imbalance.
From the AD, with my bolding
Both center tank fuel pump switches must be selected OFF when center tank fuel quantity reaches approximately 1,000 pounds (500 kilograms) during climb and cruise or 3,000 pounds (1,400 kilograms) during descent and landing.
You also MAKE an imbalance.From the AD, with my bolding
Both center tank fuel pump switches must be selected OFF when center tank fuel quantity reaches approximately 1,000 pounds (500 kilograms) during climb and cruise or 3,000 pounds (1,400 kilograms) during descent and landing.
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From: Germany
Works a treat I promise you and the wording is straight from the OM, 950 not 930 was what I wrote, but that is by the by. Just goes to show there is many a way to skin a cat. I think the disadvantage of your procedure is that on the NG the scavenge pump only kicks in just below half tanks. We have been flying the NG from the beginning and I am confident we know what we are doing.
Per Ardua ad Astraeus
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From: UK
The problem as I see it is that your 'procedure' is contrary to the AD? I still read that you are running a pump dry? That is a no-no if the tanks are pre-mod. Unless you have a modified AD, where does 950 come from?
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From: OZ
Yury,
I think the AD you refer to in post #19 is superseded by the two xfeed valve installation.
Switching off one CWT pump almost guarantees an imbalance on the B767. As I recall it, the left pump feeds the left engine and the right pump the right engine. Each CWT pump only runs when its engine is above 50% N1.
I think the AD you refer to in post #19 is superseded by the two xfeed valve installation.
Switching off one CWT pump almost guarantees an imbalance on the B767. As I recall it, the left pump feeds the left engine and the right pump the right engine. Each CWT pump only runs when its engine is above 50% N1.
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From: deepest darkest recess of your mind
Lederhosen is correct, as there are alternative methods of compliance with the requirement. We use the same method, but are now allowed to use centre tank fuel on one pump and crossfeed for descent until the Master Caution lights up. Didn't used to do that. Also, the same figures apply for us, ie, 2300/950 kg.
Per Ardua ad Astraeus
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From: UK
PM - Leder has taken this off thread by PM since it is 'off topic', but for you - of course if it is in the company manual it is 'correct' for a company pilot to do it. However, I have often heard pilots describe the (500kg) fuel remaining in the centre tank (following AD2002-19-52) as 'unuseable' - which it is not. The confusion I have is:
1) It seems to apply to post-mod a/c
2) If so, why not just run the tank normally? What does fiddling around with single-pump ops achieve? I can see no advantage and would be interested in the logic.
Do you have an AD ref for this procedure?
Perhaps a new thread is required or you can join the PM trail?
1) It seems to apply to post-mod a/c
2) If so, why not just run the tank normally? What does fiddling around with single-pump ops achieve? I can see no advantage and would be interested in the logic.
Do you have an AD ref for this procedure?
Perhaps a new thread is required or you can join the PM trail?
Joined: Apr 2008
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From: Cheshire
To come back to the 737;
BOAC, do you have a reference for the AD you are discussing? And what is the mod? And what effect does it have?
Presumably the point of fiddling with cross-feed and single centre tank pump operations is to ensure a Master Caution is generated when that pump runs dry; if both pumps are on then one may run dry for a considerable period, with no MC until the other does too.
But flying the Classic we only have restrictions on operating the centre tank fuel pumps on the ground.??
BOAC, do you have a reference for the AD you are discussing? And what is the mod? And what effect does it have?
Presumably the point of fiddling with cross-feed and single centre tank pump operations is to ensure a Master Caution is generated when that pump runs dry; if both pumps are on then one may run dry for a considerable period, with no MC until the other does too.
But flying the Classic we only have restrictions on operating the centre tank fuel pumps on the ground.??
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From: Germany
In our OM it is listed as AMOC to AD 2002-24-51. It also states 'During the last hour of cruise on ETOPS flights do a Fuel Crossfeed Valve Check.' So I am actually back on the original topic! I would be happy to discuss the 737 fuel system on another thread as it is self evidently not without its complications.
Thread Starter
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From: Russia
Best regards to everybody for discussion. I clarify at last the situation for myself. B767 FCTM states:
"...during the last hour of ETOPS cruise, the FAA currently requires that a fuel crossfeed valve check be performed on airplanes with a single crossfeed valve. This verifies that the crossfeed valve is operating so that on the subsequent flight, if an engine fails, fuel feed is available from both main tanks through the crossfeed valve."
Thanks...
Thanks...
