BM,
I make hundreds of touch and goes lately with my Tiger, a real crowd pleaser and so much fun to do.
But right from the beginning I bought the model, I noticed it, thereby correcting it "automatically".
Due to the number of roller landings, also made by my son who confirms the behaviour we can be 100% sure the effect is there and not caused by fingertrouble.
In the mean time I have consulted a befriended aerodynamics specialist plus some extremely well experienced model flyers.

The influence of the ground effect is a complex one, there are many interactions with terra firma during the last part of the flight. Normally having little effect on pitch, but obviously this plane does.

We considered the lifting of the tail as a factor. Take into account that the Practical Scale Tiger Moth has the tailplane set a 5 degr pitchup. That in itself is quite large, however biplanes have "strange" setups on this matter. But as I said, I notice the effect during touch and goes, aiming for for 2 point landings, the tail sits high and to my guessing outside the ground effect.

One of my experienced friends used to fly a Beech Staggerwing model, he now recalls it was a drag landing this model, as it just did not want to stop flying when landing, the opposite effect thus. As this Beech type, as the name already says, has its lower wing staggered or in front of the top one, it would confirm my thoughts of the lower wing influence.

Coming back on my original post I must say that the higher sinkrate is not only caused by the pitch down effect, but it looks like a general lift loss there, combined with some pitch down. of course the short time span in which it happens makes a precise judgement difficult.

My aerodynamics friend mentiones he had a collegue who spent 10 Years investigating ground effect and still ended up with more questions than answers...




The is not a clear conclusion to be made