An inverted wing in extreme ground effect produces downforce with a static peak at h/c~10%. A sinusoidally heaving wing at reduced frequency of k=0.5 has less average downforce than the static mean. Dynamic downforce is approximated from analytical/state-space models based on static chordwise separation.*

An inverted single element was subjected to a sinusoidal heaving motion in both free flight and extreme ground effect, with the ground-effect simulations oscillating in various states of interaction with the peak lift ride height of the wing. Peak negative lift during the heaving cycle was greater than the static values at the same ground clearances, time, and ensemble averaging showed an overall reduction in the lift coefficient of 10–22%. An analytical model combining potential flow lift predictions and a new variation of the Goman–Khrabrov state-space model predicts the lift behavior of the wing-in-ground effect based on reduced frequency and ground clearance.