Helicopteres Guimbal CABRI G2 N722TX accident near Beaumont, Texas

Probable cause

The flight instructor's low-altitude maneuvering, which exceeded the helicopter's performance capability in the high-density altitude conditions and resulted in a loss of control.

NTSB analysis

The student pilot was practicing basic hovering skills under the supervision of the flight instructor. Due to the high air temperature and minimal airflow over the engine, the engine oil temperature had increased beyond the approved limits. The flight instructor decided to fly a low-altitude circuit along the perimeter of the airport to increase the airflow and cool the engine. The low-altitude circuit was performed at an altitude of about 100 ft above ground level and at a speed of about 60 knots. About halfway around the circuit, the oil temperature had returned to normal, and all other engine indications were normal at that time. However, during the turn at the southwest corner of the airport, which was about three-quarters of the way around the circuit, the helicopter began to lose altitude and would not respond to the flight instructor's control inputs. The flight instructor was unable to regain control, and the helicopter subsequently impacted the ground.

Postaccident examination of the helicopter did not reveal any anomalies consistent with a preimpact failure or malfunction. In addition, the flight instructor stated that there were no issues with the helicopter before the accident. Impact marks showed that the main rotor blades struck the ground before the landing skids, which was consistent with a bank angle of at least 40° at the time of the accident.

According to information that the helicopter manufacturer provided, the engine power and helicopter performance required to maintain altitude while maneuvering exceeded the power and performance available with the elevated density altitude conditions at the time of the accident flight, which resulted in a loss of altitude and an impact with the ground.

Text from the NTSB. Open the NTSB docket for CEN17LA290 for the full record.