"Tony" wrote:

I haven't found a decent reference for this -- can anyone help?

Here's an online reference, including some graphs:

http://www.se-technology.com/wig/htm...en=aero&code=0

There are also a number of real-life examples where ground effect was
beneficial.

One was the Ekranoplan ground effect vehicles that operated in the
Caspian Sea. You can search for that name or the "Caspian Sea Monster"
to learn more about them.

Fighter pilots during WWII would often take advantage of ground effect to
extend their endurance when returning from sorties.

There was also the story of the MATS C97 (military version of the
Stratocruiser) that had its #1 prop separate from the aircraft, and lost
both port engines just past the point-of-no-return on a flight to Hawaii.
Initial calculations by the flight engineer suggested that they would
have to ditch 30 minutes from their destination. The captain jettisoned
all excess weight, and flew in ground effect for six hours, with full
right trim, and having to stand on the right rudder pedal with both feet
for the duration of the flight. They eventually landed safely after a
missed approach with 30 minutes of fuel remaining.