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'.
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.
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).]