Event Details
A certificated flight instructor (CFI) and a student pilot were conducting landing practice at a grass airstrip. The student had successfully completed crosswind landings at the same airstrip earlier in the flight. The final approach was to runway 31 at the departure grass airstrip. The wind was reported from 360 degrees at 14 knots with gusts to 20 knots.
Sequence of Events
According to the CFI, when the airplane was about 30 feet above ground level, it encountered an "unexpected strong down flow of wind (wind shear)" coming over the tree line on the northeast side of the runway. This caused the airplane to hit the ground hard. The CFI reported that he took control of the airplane just before the hard touchdown. The airplane bounced, and the CFI attempted to recover, but stated he "didn't have time to explain to the student what was happening." Both pilots were on the controls when the airplane touched down a second time. The CFI reported that both brakes were "locked" and the airplane skidded for about 75 feet before nosing over. He noted that he could not counteract the student pilot's brake input.
Pilot Statements
The CFI provided the account of the event. No other statements were recorded.
Investigation
Neither the aircraft type, registration, nor any other identifying information was provided in the report. The occurrence took place at an unspecified grass airstrip.