History of the Flight
On January 20, 2007, a Robinson R44 II helicopter (registration C-FGTN, serial number 10210), operated by The Helicopter Company Inc., was flown to Kitchener/Waterloo Regional Airport for a maintenance inspection. A small delamination was found on one main rotor blade, and replacement blades were installed. Following blade installation, the aircraft maintenance engineer (AME) conducted blade tracking on two previous flights, adjusting pitch links after each.
The occurrence flight departed at 1722 eastern standard time, with the pilot and AME intending to track blades and check rotor RPM during autorotation. This ad hoc procedure differed from the manufacturer's instructions. The helicopter climbed to 2400 feet above sea level (1400 feet agl) and entered autorotation over fields southwest of Cambridge. During the descent, the AME heard an exclamation from the pilot and observed the engine/rotor RPM gauge indicating approximately 80%. No low rotor horn or warning light was reported. The helicopter struck the snow-covered frozen field with the front of both skids, coming to rest on its left side. The emergency locator transmitter activated, and rescue services responded. Both occupants suffered serious injuries and were ejected when seat belt attachments failed. The aircraft was destroyed.
Personnel Information
The pilot held a commercial helicopter license with approximately 1300 total flight hours, including 1000 on rotary-wing aircraft and 300 hours on the R44 II. He completed R44 training in June 2006 and last conducted autorotation training in September 2006. The pilot was seated in the right seat and had previously flown maintenance check flights on the Bell 206 and R44. He did not remember the events of the occurrence flight.
Aircraft Information
The helicopter was manufactured in 2005 and had accumulated 1082 hours. The manufacturer's procedure for in-flight track and balance involves adjusting in a hover, then checking at increasing airspeeds, and finally checking autorotational RPM. The recovered worksheet indicated blade adjustments after hover flights, but no record of forward airspeed checks. The manufacturer's autorotation RPM check specifies a gross weight of 1900 pounds or less, but the helicopter weighed approximately 2279 pounds. The expected autorotation RPM at that weight was 110.5%, above the red line of 108%.
Accident Sequence
No mechanical malfunction was found. The helicopter was flown on a maintenance test flight to track blades and check autorotational RPM, but the manufacturer's procedures were not followed. Without a detailed preflight briefing, the pilot may not have been fully aware of the test parameters. During the autorotation, rotor RPM dropped to about 80%, and the pilot was unable to recover. Possible scenarios include incorrect entry technique or failure to monitor RPM. The low rotor warning may have activated briefly. The engineer's attention on blade tracking may have distracted from monitoring. With insufficient altitude and time, the descent could not be arrested.
The investigation concluded that the combination of conducting blade tracking during autorotation, exceeding the maximum weight for the RPM check, and the rotor RPM decay led to the impact.