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**Bertie the Bunyip[_25_]** · June 12th 08, 08:57 PM posted to rec.aviation.student,rec.aviation.piloting

Tina wrote in news:54595019-a2b0-413e-aea8-
:

Yes, the time my son spent with canard aircraft brought out all sorts
of interesting information about canards and the history of trying to
scale up Rutan's original concept Beech Starship. The smaller true
canards like the Long-eze are pretty good aircraft. However there is
a reason why we don't see large (six plus passenger) true canards.
It's the relationship between CG, fuel load, payload and range.
Apparently in the scale up process there is a point where it is no
longer practical.

Ron Kelley

Would it not also be true that passive stability is not as important
in larger modern airplanes? I would guess (again, I admit being
ignorant of the realities) that adding a 10% aerodynamically induced
increased load on bigger aircraft would be avoided for efficiency
reasons? It might be better to have enough fly by wire and computer
induced stability instead. I don't know enough about this stuff to
even find the back of an envelope, let alone do a calculation there.

Yeah, that's one of the main reasons they're going for FBW. An aft cg also
improves buffet margins and allows a higher cruise altitude because of
that. Some airplanes pump fuel aft after takeoff to bring the CG well aft.
Even ones that aren't FBW. you have to have the autopilot engaged to
utilise this feature though.

Bertie