Wing in Ground Effect?

In article ,
Kyle Boatright wrote:

"Robert Bonomi" wrote in message
servers.com...
In article ,
BllFs6 wrote:

[[.. munch ..]]

2.....question.....as you approach the ground VERY closely (lets assume
your
landing gear are up AND you somehow maintain a constant forward speed AND
you
maintain the same angle of attack) does the drag GO down or does the lift
go
up?

Both, "more-or-less". You get a 'cushion' of higher-pressure air that is
'trapped' under the wing. Lift is due to the pressure difference between
the top and bottom of the wing. _Either_ a decrease in upper-surface
air pressure, or an increase in lower-surface pressure will result in
increased lift.

The trapped air-cushion also acts like a nearly 'frictionless bearing',
reducing drag.

I've seen a Cherokee 6 use up more than 12,000 ft of runway, due to
ground-
effect. Full flaps, the stall warning sounding, and aimed right at the
'numbers', get to about 2' above touch-down, and the PIC *cuts* the
engine.
Not to idle, but _off_. We follow the stationary prop for more than two
miles *without* touching down -- then he kicks the engine, throttles up,
and
goes around for another attempt. He -had- been cleared by the tower for
touch-and-go practice. This one was logged as a "missed touch-and-go".

It was amazing how -little- speed we lost during that two mile 'float'
down
the runawy. Only shed about 5 kts.

Obviously, this Cherokee 6 had the "eternal motion" upgrade.

A Cherokee 6 is a fairly draggy airframe. Assuming no odd circumstances (
i.e. moving from a large tailwind to a large headwind or a severely downhill
runway), I'd pay $50 to anyone who could float a Cherokee 6 over 1000' down
the runway if the excercise was started with the flaps down, the engine
stopped, and the aircraft a 2' of altitude and within 10 knots of stall
speed.

Agreed, about the airframe, but that big slab of a low wing makes for an
impressive air-cushion. *No* odd circumstances, per your list. Main
runway at DSM, summer 1975. PIC was check-pilot from the FBO there -- I'm
drawing blank on the FBO name, "{mumble} Aviation" I think. Check-flight
prior to an XC rental.

His entire point of the exercise was the ground-effect issue. 2nd time
around, he shows the 'effective' landing technique. Leaves the engine on,
settles into ground effect, whereupon he reaches down for the flaps lever,
_up_ flaps, and 'thump' onto the wheels.