First a disclaimer: I understand the security issues involved
in the following and would not encourage anyone to try this
at home, but I am interested in the theoretical side of it.

Imagine you get things wrong and are caught out low on final,
still a fair distance out, and it looks marginal whether you
are going to reach the runway or not.

One technique I have sometimes heard described is to dive for
the deck and complete the remaining distance in ground effect.
For the sake of the argument we can assume fairly flat ground,
free of obstacles, though not necessarily landable.

The advantages claimed are usually better glide performance in
ground effect and less headwind and absence of downdrafts close
to the ground.

On the other hand you'll be travelling at higher than optimal
airspeed for most of the distance.

I am wondering how much truth there actually is to this
technique. Would it significantly increase your range and
improve your chances of reaching the field or not ?

Would it perhaps work better against a strong wind gradient
(as I suspect it might), and maybe not help a lot in calm
conditions ?

I'd be interested in any hard data/analysis or otherwise
enlightening comments on this.

Please note though, that I am not talking about high-speed
competition finishes, rounded off with a beatup and a sharp
pullup and all the dangers and other issues involved in that.

Cheers CV


CV, a group of test pilot trainees at Edwards AFB did an exhaustive
test on ground effect versus distance as a project during their
course; it was reported in the Feb 1990 SOARING magazine. IIRC, they
found that one had to fly a very precise profile - 0.95g push followed
by 1.05g pull, to a precise height - to see any measurable effect, and
concluded that it was better for the casual flier to fly best
lift/drag speed instead... I think they used a G103. The notation
from the index is:
Hadfield, Chris; with Chuck Louie, Ken Green, Rick Husband and Nate
Jones Is Ground Effect Worth It? [Aerodynamics], February, page 33

Chris Hadfield was a Canadian mission specialist on the Shuttle; two
flights, two spacewalks; top test pilot of his class at Edwards; and
US Navy Test Pilot of the Year for a F/A-18 out of control recovery
test program; Rick Husband was the crew commander on Columbia which
was destroyed on re-entry in Feb 2003, his second shuttle flight.

It might be worth getting the article reprint if you're interested in
the theory, or e-mail Edwards Test Pilot School for the report; I bet
it's swimming in math! IF you do, let us know how good my memory held
up.
DD