What happened
An emergency medical services helicopter was attempting to land in a mall parking lot to pick up an accident victim. Witnesses observed the aircraft performing right turns over the landing zone before approaching from the northeast. During the final approach at approximately 100 feet above ground level, the aircraft became unstable. The helicopter rolled right about 30 degrees, then left, followed by a right roll of approximately 45 degrees. The aircraft pitched nose up to the left and descended while spinning to the left, ultimately impacting the parking lot in a nose-down attitude on its left side.
The pilot reported that while flying at 100 feet above ground level and slowed to 20–25 knots, she felt the nose rise gently to the right. Upon attempting to correct with the cyclic, the helicopter responded with a violent roll to the left. The pilot noted that the hydraulic caution light was illuminated, though no aural warning was heard. During the descent, she applied full left cyclic to avoid nearby buildings. Following the impact, the engine continued to run. Because a surviving passenger and rescue personnel moved various cockpit switches in an attempt to shut down the engine, post-impact switch positions were considered unreliable.
The investigation
The investigation focused on the hydraulic system and recent maintenance history. Investigators examined the hydraulic system's guarded on/off toggle switch located on the end of the collective control. While this switch was found in the OFF position, it was noted that the collective and its guard were damaged during the impact. Additionally, the hydraulic test switch on the center pedestal was found in the OFF position during documentation the following morning.
Records indicated that in the three months preceding the accident, four discrepancies had been reported regarding control system issues, including stiff flight controls, excessive control inputs, and nuisance hydraulic warnings. Recent maintenance actions included cleaning control system bearings, replacing left-hand and collective hydraulic actuators, and repairing electrical wiring. However, examinations of the control system and functional testing of the hydraulic components revealed no evidence of preimpact failure or malfunction. The hydraulic system accumulators retained an unquantified amount of pressure after the accident.
Findings
- The aircraft experienced a significant roll and spin during the final approach phase.
- Recent maintenance had addressed several control system and hydraulic warning issues.
- Post-impact switch positions were unreliable due to intervention by passengers and rescuers.
- Following the accident, the operator installed guards over the hydraulic test switch to prevent accidental activation.