tunturi - "gravity fuel feed...FL240...not high"

As a sideways flier I'm not too familiar with the info available in the modern electric jet QRH or aircrew manuals, but am a little surprised at the rather vague note about 'degraded performance at altitiude'. http://www.pprune.org/ubb/NonCGI/eek.gif

In the old bucket I am familiar with, advice is quite specific - "If fuel load blah1.. FL200", however - "If fuel load below blah2.. FL100".

Yep, FL100!!

The difference? - fuel at 'blah2' has further to travel, the engine driven pumps have to 'suck' harder, but it also does not have the benefit of the partial pressurisation created by the RAM effect in the tank vent system.

Think altitude, think bernoullies. http://www.pprune.org/ubb/NonCGI/cool.gif

Keep thinking mate. - its healthy.

PS. not in the QRH - "If fuel load below blah3.. (should never happen in theory)..Get out the ditching drills cause fuel won't flow uphill!!!) - so watch those bank angles. :)

[This message has been edited by OilCan (edited 04 July 2001).]

Greenarc -

That makes perfect sense. The FAA finds no significant value to CRM, so such things are destined to happen.

Towerdog: I bow to your superior knowledge..I would have put money on it being Eastern as I thought I was very up on it at the time,just as well I didn't then http://www.pprune.org/ubb/NonCGI/redface.gif
But it was as a direct result of QRH action on EEC failure. Yes I also remember the Tristar incident ...very very lucky boys.

Oilcan:
The Boeing QRH really is that vague, nothing like your very specific manuals. Basically the QRH drill I am referring to covers one or both booster tank pumps failing in one tank. It does not recommend opening crossfeed but simply warns against problems at "high altiude". Crossfeeding drill specifically states to open cross feed
valve(s)but of course that is because you definitely want to feed both engines from the same tank and not to prevent flameout due to lack of boost pressure as such.
As I said I had just never considered FL240 as being "high"..I don't know why but I just hadn't. Now I do, although I see this incident happened at FL290. Incidentally, it is very easy to depart with crossfeed valve(s) open as switches can look very "neat" on the panel in this condition. First you'll probably know in fuel imbalance warning soemtime later (due difference in individual pump design pressure tolerances).

Edited for spelling and note to Towerdog

[This message has been edited by tunturi (edited 05 July 2001).]

On the Eastern incident -

Eastern had some labor negotiations going on. The seals were left off all three engines.

The G-ARWE problem was caused when the check captain in the jump seat helpfully silenced the u/c warning horn when the No 2 thrust lever was closed during the engine failure drill. The f/e (I think) was reaching for the u/c horn cutoff switch, but as it was cancelled already he hit the fire bell cutoff which I think is close to the u/c horn cutoff on the panel. So, he never progressed to pulling the fire handle because the fire bell never rang (it was cancelled at the instant it would have started to ring) and the engine fire checklist was not read.


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Feathers

With fuel panels, alway do something good before you do something bad. Any change in fuel panel feed or switches should be coordinated with the other pilot.

Roadtrip,

Your post reminds me of something my old 727 FE instructor (yes, many years ago) drilled into our brains: turn something ON before you turn something OFF (Of course this doesn't ALWAYS apply, which is why the "do something GOOD" saying is probably more appropriate ... but you get the point)

The other one was: if you flip a switch, confirm the action i.e. make sure that the switch did what it was supposed to do.

No finger-pointing here ... just passing along two common-sense principles which can help prevent systems switching errors.

Tunturi

You may like to get your QRH out again if you are still on type. As someone else has mentioned earlier high trust settings are also a factor and climbing thru FL290 will be full rated climb thrust. Compound that with the nose up attitude and suction feeding is sounding marginal at best.

Subsequent to this Boeing issued a bulletin to instruct us not to crossfeed in any other situation than cruise. Going a bit far for a cover up I feel but I have been wrong before.

:)

Ttree Ttrimmer:
"Tunturi
You may like to get your QRH out again if you are still on type."

OK. I have done and I quote for Eicas "FUEL SYSTEM PRESURE" "Thrust from affected engine may deteriorate during climb at high altitude. If required thrust cannot be maintained open crossfeed valve" (or valves if two fitted.
This covers failure of two pumps in one tank or indeed all pumps failed and is nothing to do with crosfeeding as such but same principal would apply. Incidentally crossfeed is opened for a single centre tank pump failure but this is only to prevent imbalance building up in wing tanks. So what am I missing here? Don't see what's different from what I said. EXCEPT that I am looking at a 757 QRH, is the 767 that different? Even if it is it doesn't change my original comment on not believing FL240 was classed as particularly high in these circumstances and Boeing give no guidance at all on this except for the bulletin which you mention.(yes I now know the incident occurred at FL290.
:confused: