lordy lord....but I am going to say that this is a dificult one to measure scientifically and I dont know that I can help much.
I know that I once made good use of Ground Effect whilst overwater with a 212 that had lost a stove on rotation off the deck. When we levelled off (at I guesstimate about 5 feet) the Nr was veeeery low but we had airspeed and we did not want to swim so flew for what seemed a couple miles coaxing the airspeed and Nr back up to acceptable levels (sort of like flying a 47G after over pitching) before climbing out back to the beach (Bombay actually)
I really push using the ground effect when doing OEI training with the S76 to get the IAS/Nr combination back up.
Anyhow...try this for lateral thinking...if anyone knows about GROUND EFFECT , it is the boys who are playing with various "In Ground Effect Vehicles". The Russians called them "iraknoplanes" (or something similiar....not sure of spelling) and built some reall monsters ....like the size of a DC-10
interesting subject...
