dgliderguy

Guys,

This question was posed years ago in Frances Reynolds superb (and sorely missed) technical basics column in Model Builder magazine. He proposed it as a small rubber-powered jobbie let loose inside the Space Shuttle, IIRC.

The answer is that the plane in zero gravity and 1 atmosphere pressure would do endless loops right in front of your face. If you look at the plane as a free-body diagram, the CG is ahead of the CP, and the tailplane provides a down force to counter the lift-weight couple. The wing has a positive incidence in relation to the tailplane, which is sometimes referred to as longitudinal dihedral, more commonly 'decalage'. It is this decalage that causes the airplane in zero gravity to do endless loops, since the absence of gravity means there is no more lift-weight couple for the decalage to balance out. Only if you remove the decalage will the airplane 'climb' in a straight line along the resultant of the lifting force vector and the thrust vector.

P.S. Thanks, Ollie, for that excellent explanation of how a wing produces lift.