[MaggieL]

Light airplanes parked outdoors are tied down to keep them from blowing around. Airplanes about to be flown are not, and unfastening tie-downs is ordinarily a part of preflight. But when hand-propping an airplane you're going to fly alone, procedure usually calls for the tail tiedown to be left in place until after the engine is started and safely running at idle. Ideally, an airplane being handpropped has a pilot at the controls, but this isn't always possible.

With a strong enough wind, any aircraft will "fly" in the sense of becoming airborne. "Strong enough" is defined by a characteristic airspeed called the "stalling speed" or V sub S, which on the airplane I fly is 54 knots...in a 54 knot wind straight on the nose, the wings will generate enough areodynamic lift to pick the airplane up off its wheels, and drag will start pushing it in the direction of the wind, since the wheels are no longer creating friction with the ground. An Aeronca Champ has a stall speed around 36 knots, 33 if the flaps are down.

With high enough winds and low enough stall speed, wierd stuff can happen. Some ultralights have *very* low stall speeds; when an aircraft's stall speed is less that the current wind speed, it can hover, or fly backwards. I've seen this done.

When you start getting ino the realm of heavy multienegine aircraft, stall speeds go up into the hundreds of knots; only wheel chocks are required to secure such airplanes unless there's a tornado or hurricaine.