Eurocopter AS 350 B2 N747CH accident near Fort Worth, Texas

Probable cause

The pilot’s loss of control due to his not maintaining adequate airspeed and altitude during a simulated hydraulic flight control failure. Contributing to the accident was the flight instructor’s inadequate supervision and delayed remedial response.

NTSB analysis

The pilot had recently purchased the helicopter and was receiving flight training from a certified flight instructor (CFI). During practice traffic pattern work, the helicopter’s hydraulic system was turned off to simulate hydraulic failure on the flight control system. During the approach, the airport’s ground controller reported that they were on the wrong radio frequency, so the CFI changed the radio to the correct frequency. The helicopter’s airspeed slowed and the helicopter entered an uncommanded left yaw. The CFI tried to regain control by adding right pedal, trying to gain for forward airspeed, and reducing power. The helicopter did not respond to the CFI’s control inputs. Subsequently, the helicopter impacted the ground, rolled on to its side, and a postcrash fire ensued. A postaccident examination of the helicopter revealed no preimpact mechanical malfunctions or failures that would have precluded normal operations. A review of the helicopter’s flight manual reveals the note: “Caution, Do not attempt to carry out hover flight or any low speed maneuver without hydraulic pressure assistance. The intensity and direction of the control feedback forces will change rapidly. This will result in excessive pilot workload, poor aircraft control, and possible loss of control." Additionally, one or both pilots may have been distracted by the incorrect radio frequency.

Text from the NTSB. Open the NTSB docket for CEN11FA359 for the full record.