DRAGONFLY N346FL accident near Charlestown, New Hampshire

Probable cause

The passenger’s decision to continue an unstable approach while at low altitude and in proximity to a known obstacle, which resulted in a collision with power lines.

NTSB analysis

The pilot was in the airport’s traffic pattern receiving mentoring and airplane familiarization from the passenger in the rear seat, who had been a private pilot but had his airmen and medical certificates revoked about 4 years before the accident. The pilot reported that, during the third landing, the airplane was too high while on final approach and the passenger told the pilot to perform a go-around. A witness who saw the airplane on the subsequent downwind described the airplane as being “slower and lower” than normal.

Near the end of the downwind leg, at an estimated altitude of 400 ft above ground level, the passenger yelled “something about power” according to the pilot and assumed control of the airplane. When abeam the runway threshold, with an engine speed about 3,200 rpm which was about 300 rpm below normal cruise speed, the passenger turned onto the base leg. The pilot later reported that although the airplane’s altitude was “low,” it seemed sufficient to clear the power lines located several hundred feet to the west of and nearly parallel to the runway. The pilot reported that a partial loss of engine power occurred about the same time the passenger turned the airplane onto the base leg. The airplane banked “hard” to the left, pitched nose down, and descended into one of the power lines. After the airplane impacted the ground, the engine continued to operate until the pilot shut it down.

Because the previous pattern circuit was too high on final approach and resulted in a go-around maneuver, the pilot may have overcompensated and flown the accident pattern at too low of an altitude given the power line obstruction on the base leg. The passenger was likely concerned about the approach when he took over the controls. His subsequent turn to the base leg suggests that he intended to continue in the normal traffic pattern over the power lines. Given the low altitude at the time, this decision involved significantly greater risk than extending the downwind and correcting whatever condition(s) that caused the passenger to take control.

The pilot described a partial loss of engine power about the same time the passenger made the turn to base leg, which was followed by a sharp turn to the left and a nose-down attitude just before impact with the power lines. The investigation could not determine if the reduction in engine power was due to a failure or malfunction or was intentionally commanded by the passenger in an attempt to avoid the power lines. Postaccident examination of the engine did not reveal any anomalies that would have resulted in a partial loss of engine power.

Toxicology testing for the passenger, who was flying the airplane at the time of the collision with the power line, was positive for tetrahydrocannabinol (THC), the primary psychoactive chemical in cannabis and hashish and its metabolites. The levels detected may have been sufficient to cause significant impairing effects; however, they do not indicate the severity of THC-related impairment or whether such impairment contributed to the accident. Therefore, whether impairing effects of the passenger’s THC use contributed to the accident could not be determined.

Text from the NTSB. Open the NTSB docket for ERA21LA283 for the full record.