View Single Post
  #4  
Old December 15th 03, 04:11 AM
Robert Bonomi
external usenet poster
 
Posts: n/a
Default

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.