On February 27, 1999, an Enstrom F-28F (registration N5700C) was involved in an aviation accident near San Jose, CA. Investigators recorded the probable cause as: The loss of aircraft control due to the pilot's sudden application of collective combined with excessive cyclic inputs. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter rolled onto its right side after the main rotor blades struck the ground during a postmaintenance test flight. The pilot, who had not flown in 90 days, reported possible cyclic mispositioning.
Incident Overview
A helicopter experienced a rollover during a postmaintenance test flight. The flight followed the tracking of the main rotor blades. A previous test flight had been completed with no discrepancies.
Events During the Flight
According to the pilot, as he pulled the collective, the helicopter suddenly rose to a 4-foot hover. The fuselage began swinging side to side and fore and aft beneath the main rotor. The pilot attempted to recover, but the aircraft pitched forward, causing the main rotor blades to strike the ground. The helicopter then rolled onto its right side.
Pilot Comments
The pilot stated that he thought he might have mispositioned the cyclic before raising the collective. He was trying to comply with a mechanic's request to "pull off before vibration became a problem." The pilot noted that the controls "felt" different than he had expected.
Post-Incident Inspection
A detailed inspection of the control system found no evidence of preexisting discrepancies.