Helio H-550A Stallion

The certificated airline transport pilot and a passenger were conducting a low level flight over mountainous terrain. The surface wind conditions were reported to be from the south at or above 20 knots. The pilot reported that he approached the mountain peak in a southerly direction and climbed the airplane to an altitude of 150 feet above the ground to clear the mountain. The airplane encountered downdraft conditions on the lee side of the mountain. The pilot failed to immediately correct for this condition and the airplane collided with the upsloping mountainous terrain when the pilot was executing a 180° turn.

The airplane collided with trees and power lines during takeoff from a 2,000 foot long open area with 10 parachutists aboard. The pilot said he experienced an unsolicited rollback in engine power prior to the collision. Reportedly, some power was regained. However, not in time to avoid the collision. But, the jump club chairman reported that no change in the engine's operation was observed throughout the mishap. Witnesses at the takeoff area reported that the winds were 12 knots out of the northeast, which would have given the flight a quartering tailwind component for the takeoff. According to the flight manual, the maximum demonstrated crosswind is 12 knots. The examination of the airplane failed to indicate any system malfunction or failure.

After dropping skydivers the pilot entered a descent to return to the airport for another load of jumpers. He was receiving radar advisories during the drop from a tracon controller. As the aircraft descended below 4,000 feet msl the controller terminated the radar advisory service. Immediately after the controller discontinued the service he asked the pilot to check for a stuck microphone switch. The aircraft continued its descent and collided with a camping trailer and building under construction in an extreme nose low attitude. The elevator trim was found in the full nose down position. No other malfunctions were found. The pilot, sole on board, was killed.

The airplane was descending to Trat when it crashed under unknown circumstances into the sea, killing all four occupants. Apparently, they escaped Cambodia.