A barrel roll, or displacement roll, is a one positive g maneuver, no harm there, except I hear in an Airbus inverted flight resets the computers. (I don’t fly the ‘bus so that is an unsubstantiated rumor.)
Transport category aircraft are not stressed for sustained negative g flight. Lots of bad things happen in a negative g environment; coffee spilling out of the pots, oil not reaching bearings, batteries leaking corrosive fluids, very limited maneuver margins, etc. Minimum maneuvering load factors are covered in 25.337 and specify only –1 g as the lower limit and +3.8 as the upper limit. It may be possible for short durations, but the stress on the engine pylons might be too much, there is a difference in pushing and pulling. Pylons designed for pushing might not hold up to pulling.
In the book Bravo Two Zero, Andy McNab writes that the transport they were on did a roll, also I have talked with sources that say the 727 does a fairly decent roll. Others would know more, but that’s my two cents.
[edited to correct homonyms, role = roll]
Last edited by '%MAC'; 22nd May 2002 at 14:34.