Aircraft Accident/Incident Report

Apache Junction, Arizona 85220
Tuesady, December 14, 2004 22:37 MST

The emergency medical services helicopter crashed while attempting to land in a mall parking lot to pickup an accident victim. Witnesses reported that the helicopter overflew the landing zone in right turns, then approached from the northeast. During the final approach at 100 feet agl, the helicopter was observed to become unstable. It rolled right about 30 degrees, then left about the same, then right about 45 degrees, pitched nose up to the left, and then descended while spinning to the left. The helicopter impacted the parking lot in a nose down attitude on the left side. In an interview several days after the accident, the pilot said she was at about 100 feet agl, and had slowed to 20 - 25 knots when she felt the helicopter nose come up and to the right gently, but not as a yaw or a roll. She said she corrected left with the cyclic, and the helicopter responded with a significant and violent roll to the left. She remembered the helicopter starting to spin (at least once), and saw the buildings of the strip mall. She then put the cyclic to the full left to avoid the building. She said she saw the hydraulic caution light on, but did not hear the aural warning. She then grabbed the cyclic with both hands and pulled back and right, but it didn't move. The anti-torque pedals appeared to work and stopped the spin. The helicopter then impacted the ground. The engine continued to run after the ground impact, and a surviving passenger and multiple rescue personnel moved numerous switches in the cockpit in an attempt to shutdown the engine, hence all postimpact switch positions are unreliable. A guarded hydraulic system on/off toggle switch is mounted on the end of the collective control that allows the pilot to manually turn off the hydraulic system. The collective control and the switch guard were damaged in the impact sequence; the hydraulic switch was found in the OFF position. The systems control panel on the center pedestal has 36 back-lighted, mechanically latched push-on/push-off switches. The hydraulic test switch, which deactivates the hydraulic system for a preflight check of the accumulator pressures, is located diagonally next to the landing light switch. The pedestal switch positions were documented the morning after the accident, and the hydraulic test switch was in the OFF position (OFF is normal, ON turns the system off). In the 3 months prior to the accident, four discrepancies were written against the helicopter for various control system problems, including stiff flight controls, excessive control inputs required for normal flight, and nuisance hydraulic warning light and horn activations. The most recent write-up was 1 month prior to the accident. The company maintenance department's corrective actions included cleaning the control system bearings, replacing the left hand and collective hydraulic system actuators, and repairing damaged electrical wiring and cannon plugs. No evidence of preimpact failure or malfunction was found in examinations of the control system and functional testing of the hydraulic system components. The hydraulic system accumulators were found to still have an unquantified amount of pressure after the accident. After this accident, the operator installed guards over the hydraulic test switch to prevent inadvertent activation.

A loss of control during the final approach to land for undetermined reasons.