NTSB Factual Report

On May 28, 2006, about 1700 mountain standard time, a Diamond Aircraft Industries HK 36 TTC single engine motorized glider, N637TT, experienced a partial loss of engine power during takeoff from runway 24 at Payson Airport (PAN), Payson, Arizona. The airplane drug a wing tip while the pilot maneuvered toward a landing spot. The pilot/owner operated the glider under the provisions of 14 CFR Part 91 as a personal local area flight. The glider sustained substantial damage. The private glider pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed for the flight, and no flight plan had been filed. The flight departed PAN about 1640.

In the pilot's written statement, he reported that he had decided to do an orientation flight before traveling back home. He completed a walk around utilizing the Federal Aviation Administration (FAA) approved checklist with no discrepancies noted. He received weather from AWOS, took off, and headed north for about 10 nm climbing to an altitude of 8,300 feet msl. He let the engine cool down for about a minute prior to shutting it off, and then started to glide back to the airport. As he got closer to the airport he decided to do a straight in approach. As he approached runway 24 for landing, he started the engine following the checklist. The engine started without any problems. The pilot reported that he was "very high" over the pattern and decided to do a go around, and then follow the pattern for an engine ON landing.

The pilot stated that he continued in the pattern with the power at idle. About midfield, and on upwind, he advanced the throttle to apply power and climb back to pattern altitude; however, there was no corresponding power increase even though the engine continued to run. The pilot moved the throttle back and forth without any results. He switched the auxiliary fuel pump OFF and reported that there was no change. He looked at the gauges but could not recall if they were all in the "green." He stated that at that point the glider was at the end of the runway and there was no place to land. The glider was traveling towards a residential area, so he decided to attempt a 180-degree turn back to the runway. The pilot stated that he made a steep bank turn and about 3/4 of the way through the turn, the glider lost altitude and the left wing tip contacted the ground. The glider spun around and the tail impacted the ground before the glider came to a complete stop upright. The pilot turned off the fuel valve and shut down the engine.

In the RECOMMENDATION section NTSB Form 6120.1/2 (Pilot/Operator Report), the pilot stated that if had done the power check at altitude before he needed the power, he would have been able to perform a safe emergency landing.

An FAA airworthiness inspector conducted an engine examination. She reported that after the left wing tip contacted the ground, the glider cartwheeled until it came to rest upright. Due to the damage to the engine, a ground run was not conducted. She reported that there were 10 gallons of fuel on board the glider. The crankshaft moved freely when rotated and compression was obtained at all cylinders. The spark plugs were visually examined with uniform normal operating signatures noted. She verified continuity of the engine and propeller controls. The fuel pump was operated normally. The FAA inspector further noted that the electronic ignition harness exhibited no obvious breaks. There were no mechanical discrepancies noted.

The National Transportation Safety Board investigator-in-charge (IIC) interviewed the pilot. At the time of the accident he noted the conditions as visual flight rules, with winds down the runway at 5 knots, and a temperature of 81 degrees Fahrenheit. He also reported that the glider had 7 gallons of fuel on board.

NTSB Probable Cause

partial loss of engine power for undetermined reasons.