There is no mystery as to how an aeroplane can fly upside down (Letters, 4 April). The amount of lift generated (and the direction in which it acts) depends primarily on the direction from which the air approaches the wing, as well as on its cross-sectional shape and other matters. When flying inverted, the pilot holds the nose of the aircraft much further from the ground than the tail (by pushing forward on the control column). Significant lift is then generated, but at the cost of very much more drag than in normal flight. If the plane has a powerful enough engine which will keep running, inverted flight may be maintained, otherwise the plane will slow down until some recovery action has to be taken. I know it works, I've done it.
Michael Webber Portishead, Bristol
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