The flight instructor reported that the private pilot receiving instruction was flying a simulated engine failure approach to an airport in gusty crosswind conditions. When the airplane approached 50 feet above the ground on final, the flight instructor called "go-around." He reported that the instructed pilot "simultaneously pulled back and went full throttle." The flight instructor stated that the airspeed was about 80 knots, and "the airplane fell straight to the ground" short of the runway. After the impact, the airplane bounced forward onto the runway, the left main landing gear collapsed, and the airplane departed the runway to the left about 550 feet from the runway threshold. The flight instructor reported that he verified that the throttle was full forward before the impact. A postaccident examination revealed substantial damage to the right wing. The flight instructor reported there were no mechanical malfunctions or failures with the airplane that would have precluded normal operation. According to the Federal Aviation Administration (FAA) Airport Facility Directory, trees were listed as an obstacle for the runway used. About the time of the accident, 7 nautical miles southeast of the airport, an automated weather observing system reported wind from 190 true at 13 knots, gusting to 21 knots. The tree line was located upwind and parallel to the airplane's final approach. The FAA Pilot's Handbook of Aeronautical Knowledge describes effects of obstructions on wind. The handbook states, "It is especially important to be vigilant when flying in or out of airports that have large buildings or natural obstructions located near the runway." The handbook further states, "During the landing phase of flight, an aircraft may 'drop in' due to the turbulent air and be too low to clear obstacles during the approach."