On Mon, 02 Oct 2006 23:41:26 +0200, Mxsmanic
wrote:

RK Henry writes:

Of course you can put the airplane on the runway at 100 knots. It's
just bad practice. Tires and brakes are expensive. Excess stress on
the landing gear can cause expensive damage.

Stalling 20 feet above the runway can do lots of damage, too. I
suppose that a stall six inches above the runway is harmless, but if
it's only six inches, why bother? And it cuts things really close to
try to get a stall only within the last six inches above the runway,
no more and no less.

Do the math. Flying onto a runway at 100 knots as opposed to say, 60
knots, means that the airplane has to absorb a LOT more energy than
dropping it from just 20 feet.

E = 1/2 MV^2
vs.
E = MGH.

Admittedly, airplanes are better able to absorb energy along their
longitudinal axis than along their vertical axis, but a semi-stalled
airplane isn't going to just fall right down, so 20 feet won't be
quite so painful. A mercy for hapless students and the airplanes that
they rent. You can even mitigate an incipient stall from that height
with a little power, or even initiate a go around.

RK Henry