Peter Clark wrote:
snip

But that's not what I understand stab tanks are for. With MTOW and
lots of gas you are pretty heavy forward, and can be out of the
acceptable takeoff trim range, so having fuel in the back helps put
you back in the envelope (basically acting as ballast). As you fly
off the fuel in the main tanks, you replenish with the stab tanks by
pumping forward (range). They don't replace (or get used for)
elevator trim.

I believe the Concorde didn't have elevator trim due to the delta
wing, so the only way to make adjustments was to pump the fuel around
and physically shift the arm.

Yes Peter, I fully understand what you're talking about 'but this
ain't that'. I do understand that some a/c do have large CG
changes as fuel is burned off. The a/c that I'm probably most
familiar with is the CP107 Argus (4 engined ASW patrol aircraft).

They held 6640 Imperial gallons of high octane fuel and their CG
changed only slightly between full fuel and dry tanks. The CG
started off more or less in the middle of the allowable range,
slowly moved forward till down to 3/4 full then reversed and
moved rearward slowly ending up near the aft limits near dry
tanks. (an odd pattern indeed)

Anyway I'll keep looking for info on this 'drag reduction thing'.
--


-Gord.

"I'm trying to get as old as I can,
and it must be working 'cause I'm
the oldest now that I've ever been"