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A37575
1st Apr 2010, 12:31
When conducting a B737 Classic single engine approach with fuel imbalance procedures still applied (crossfeed selector open and two main tank fuel pumps off), is there any FCOM or FCTM requirement that normal fuel feed procedures (crossfeed selector off, all main tank pumps switches on) must be re-instated before landing? If so, in what Boeing document is this stated?

CaptainSandL
1st Apr 2010, 12:48
No – or not that I know of!

The FCTM has a section discussing fuel balancing at pages 8.18-19. Amongst it is written:

“Fuel Balancing Considerations

during critical phases of flight, fuel balancing should be delayed until workload permits. This reduces the possibility crew errors and allows crew attention to be focused on flight path control”

This suggests to me to return all the fuel pumps and crossfeed back to their normal position for landing (and possible go-around). I use the one engine inop landing checklist as my trigger point to do this.

S&L

Tee Emm
1st Apr 2010, 13:45
Fuel Balancing Considerations

during critical phases of flight, fuel balancing should be delayed until workload permits. This reduces the possibility crew errors and allows crew attention to be focused on flight path control”I can understand that statement with regard to engine failure after take off even though the high fuel flow on the operating engine will cause significant imbalance possibly beyond the limit soon after the aircraft is cleaned up. But supposing by the time a holding pattern or radar vectors has the aircraft ready for final but with significant imbalance still in place, what are the operational considerations if the crew continue to land with crossfeed open and both fuel pumps off on the low side? Would a go-around be affected? Perhaps the absence of advice by Boeing in the FCTM in this regard can be taken that it doesn't really matter either way?

Some regulators require risk assessment considerations to be addressed before ops departments direct operational changes from manufacturer's FCOM recommendations. That being so, perhaps fingers could be pointed by flight ops inspectors who might say there is no pressing reason before landing to configure back to crossfeed off and all pumps on as normal?

flyburg
1st Apr 2010, 14:14
Strange,

My FCOM states Fuel crossfeed valve must be closed before TO and LDG in the limitations section.

I wonder if there is a difference in this with different companies?

Greetings

King on a Wing
1st Apr 2010, 18:11
flyburg....
that should read "crossfeed valve should be closed for takeoff and landing except during NNC's"
That's what I understood when I last flew that thing some decades ago...

flyburg
2nd Apr 2010, 07:04
That is interesting, I wonder if we could get some more input from people what the wording is in their FCOM's regarding this.

Thanks

rudderrudderrat
2nd Apr 2010, 09:23
Hi,

My recollection was that the 707, 737-200 & L1011 had a note in the Limitations Section of the Flying Manual, that the fuel cross feed must be closed for Approach and Landing. I think the classic B747 had the same limitation.

The B747-400, 737-NG and A320 series don't have such a limitation i.e. they may have the fuel cross feed open for approach and landing.

So it depends on which variant you are flying and what the Limitations section of the FCOM says.

It's a mystery to me why it was a restriction in the first place. I can only guess it was originally due to something with VMCA demonstration flight on the GA and flying with up to 5 degs bank into the live engine(s) and fuel transfer from the high wing to the engine(s) on the low through the open cross feed and fuel imbalance could go out of limits.

It looks like the problem has been designed out in modern aircraft.

mustafagander
2nd Apr 2010, 09:46
In my copies of the B747 and B744 limitations both types require at least one cross feed valve open for T/O and landing.

Think about the number of tanks and it makes sense to have a "hot spare" available in the event of pump failure but still avoid the possibility of all engines feeding off the one set of boost pumps.

capt. solipsist
2nd Apr 2010, 14:42
737-400 FCOM dated 4 Dec 2009 makes no mention of cross-feed valve being required to be closed on approach.

in the hick town where i'm from, we crossfeed till the difference reaches max (453 kgs), then crossfeed to the other side till max again. that way, we actually manipulate the valve only every 900kgs or so, approach phase or otherwise.