The flight instructor reported that during a soft field takeoff on a private 1,800-foot turf airstrip, with 10 degrees of flaps, the airplane wheels lifted off the ground so he relaxed back pressure on the yoke, and the airplane settled back onto the ground. He further reported that after the airplane lifted off and settled back onto the ground a second time, he decided to abort the takeoff by reducing the power to idle, but the airplane lifted off the ground momentarily and settled onto the ground for a third time. The pilot firmly applied the brakes, but the airplane overran the runway.

The airplane sustained substantial damage to the firewall.

The flight instructor reported that there were no preaccident mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.

The flight instructor further reported that he admits that he was late in deciding to abort the takeoff.

The Federal Aviation Administration has published the Airplane Flying Handbook FAA-H-8083-3B (2016). This handbook discusses pilot actions after liftoff during soft field takeoffs and states in part:

After the airplane becomes airborne, the pilot should gently lower the nose with the wheels clear of the surface to allow the airplane to accelerate to VY, or VX if obstacles must be cleared. Immediately after the airplane becomes airborne and while it accelerates, the pilot should be aware that, while transitioning out of the ground effect area, the airplane will have a tendency to settle back onto the surface. An attempt to climb prematurely or too steeply may cause the airplane to settle back to the surface as a result of the loss of ground effect. During the transition out of the ground effect area, the pilot should not attempt to climb out of ground effect before reaching the sufficient climb airspeed, as this may result in the airplane being unable to climb further, even with full power applied. Therefore, it is essential that the airplane remain in ground effect until at least VX is reached. This requires a good understanding of the control pressures, aircraft responses, visual clues, and acceleration characteristics of that particular airplane.