Burkhart Grob Flugzeugbau G109 N909G accident near Emigrant Gap, California

Probable cause

The pilot's inappropriate decision to continue the flight into higher elevation under high-density altitude conditions, which degraded the glider's climb performance and resulted in impact with trees short of the intended runway.

NTSB analysis

The pilot of a powered glider reported that while en-route to his planned destination, he became concerned about the glider's capability, even with the engine operating, to clear rising terrain ahead. The pilot further reported that he was advised by air traffic control that the nearest airport was about 5 nautical miles (NM) ahead and along his route. The pilot decided to continue to this airport, even though lower terrain was available behind him. During the diversion into the higher elevation, the pilot reported that the glider was "low over the terrain" and he determined that he had to make an off-airport landing. Subsequently, the pilot landed the glider into trees about ½ NM from the diversion airport.

The right wing and fuselage sustained substantial damage.

The pilot reported no preaccident mechanical malfunctions or failures with the powered glider that would have precluded normal operation.

About the time of the accident, at the diversion airport, an automated weather observing system reported the wind at 240 degrees true at 7 knots, a temperature of 80 degrees Fahrenheit (27 Celsius), and a dew point of 43 degrees Fahrenheit (6 Celsius). The airport's elevation was 5,283 feet above mean sea level (MSL) and the density altitude was 7,563 feet above MSL.

According to the Federal Aviation Administration Koch Chart, the powered glider would have experienced a 62% decrease to the normal rate of climb. The high density altitude likely contributed to the glider's inability to clear the trees en-route to the diversion airport.

Text from the NTSB. Open the NTSB docket for GAA16CA489 for the full record.