Mooney M20J N5765N accident near West Glacier, Montana

Probable cause

The pilot’s inadequate performance planning and decision to continue the takeoff which, resulted in a runway overrun and collision with terrain.

NTSB analysis

The pilot reported that, he was departing to the south on a 2,500 ft long grass runway at a mountain airport with an estimated 5,000 ft mean sea level density altitude. The pilot calculated the airplane’s performance using the pilot’s operating handbook, which revealed a takeoff distance of 1,800 ft on grass. According to the pilot, during the takeoff run, the airplane lifted off the ground after traveling between 1,250 ft and 1,870 ft down the runway as the airplane reached 60 mph. However, the airplane touched back down to the runway surface near the end of the runway and impacted fallen timber before it came to rest. The airplane sustained substantial damage to the rudder and right wing. The pilot reported that there were no mechanical failures or malfunctions with the airplane that would have precluded normal operation.

The pilot stated that, before his takeoff run, he observed the windsock, which indicated winds from the east at 9 kts. However, wind data retrieved from a nearby station and sounding information indicated that winds may have been from the north at 5 kt, which would have resulted in a tailwind.

Text from the NTSB. Open the NTSB docket for WPR21LA239 for the full record.