Re: Information needed

Date:         28 Aug 97 02:30:39 
From:         k_ish <kenish@ix.netcom..com>
Organization: Netcom
References:   1
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Marc Guimond wrote:

> I was just recently told by uncertain sources that airplanes in the Boeing
> 747-400 family where able to fly inverted.  I would like to know if it is
> truely possible both theoretically and practically for such a massive craft
> to do so.

>From the pure aerodynamics / physics perspective, any aircraft can fly
inverted.  There are two maneuvers which will do this.  One is a loop,
the other is a barrel roll.  In both cases, the aircraft is pulling
positive g's through the entire maneuver, so it couldn't care less which
way is "up", unless the maneuver is radical enough to overstress the
airframe.

If you are talking about *sustained* inverted flight, I doubt most
transport aircraft are capable of this.  All the blue water would pour
out of the toilets! ;-)

There have been instances where commercial transports have been upside
down.  The original Boeing 367-80 prototype was intentionally rolled by
the test pilot over Lake Washington.  There is a famous painting of
this.  Inadvertent incidents include a China Air 747 that had a
high-speed upset over the Pacific and rolled inverted.  The crew was
able to recover by extending the landing gear.  Recovery was at a
frighteningly low altitude, and they shed a lot of parts such as gear
doors.  Another was a China Eastern MD-11 over the Aleutians, and IIRC,
a 707 of NW that did a loop after an autopilot failure.

Legally, FAA regulations consider inverted flight as "aerobatic
flight".  Since airliners are certified to the Transport Category, and
not the Aerobatic Category, they cannot legally be flown inverted.

Ken Ishiguro