Beech A36TC N3803J accident near Stevensville, Montana

Probable cause

The pilot's decision to conduct a takeoff with a tailwind on an upsloping runway in an overweight airplane, which resulted in the airplane having insufficient energy to climb out of ground effect.

NTSB analysis

The pilot reported that before takeoff from his home airport for the personal flight, he noted the midfield windsock at the airport and believed that he would have a straight crosswind with gusts coming from both directions.

The pilot reported that the airplane lifted off about 80 knots. However, the airplane would not climb or accelerate, and the pilot felt that there was a rapid decrease in power. He ensured that the engine controls were in their appropriate positions for full takeoff power, but the airplane still would not climb. The airplane struck level terrain adjoining the right side of the runway and came to rest upright, about 300 ft from the runway centerline.

A witness reported that the airplane's engine sounded "strong and loud." The airplane lifted off about 2,400 ft from the runway threshold and attained an altitude of about 50 ft above ground level when the airplane began a steep right descending turn.

Although the pilot reported that he referenced the windsock and believed that he would be taking off with a direct crosswind, the airport's automated weather observation system indicated a tailwind component of about 8.5 to 11.2 knots for the takeoff runway at the time.

The accident runway was 3,800 ft long. Review of the airplane manufacturer's performance data indicated that a takeoff with maximum allowable gross weight and no flaps from a level runway with a 10-knot tailwind would have required a ground roll of about 2,109 ft and required about 3,385 ft to clear a 50-ft obstacle. The airplane manufacturer's published performance data did not account for tailwind components above 10 knots. The runway had a 1.94% uphill slope in the takeoff direction, but the performance data did not account for runway slope. Calculations indicated that the airplane was about 220 lbs above the maximum allowable takeoff weight. Each of these three factors would increase the takeoff distance and decrease the airplane climb performance, but there were no means for the pilot or investigators to quantify their individual or collective effects.

Examination of the airplane and engine did not reveal any preimpact mechanical malfunctions or failures that would have precluded normal operation and performance. However, it is likely that the overweight condition of the airplane, the significant tailwind, and the uphill runway slope combined to affect the takeoff so that the airplane had insufficient energy to climb out of ground effect.

Text from the NTSB. Open the NTSB docket for WPR17LA064 for the full record.