Robinson R44, VH-AIC

The Robinson R44 helicopter departed from Shipwreck Bay, QLD at about 1245 Eastern Standard Time on the final leg of a charter flight to Mareeba aerodrome. The pilot intended to track directly to Mareeba aerodrome under the Visual Flight Rules, with an expected enroute flight time of about 45 minutes. The pilot did not submit a flight plan to Airservices Australia, nor was a flight plan required, but the company retained a flight notification form for search and rescue purposes.

At about 1 NM to the south of Mareeba township, at a cruise altitude of 1,000 ft and an indicated airspeed of about 95 kts, the pilot heard an unusual noise associated with the main rotor blades. The pilot reported that the noise sounded as though a potato chip packet had been caught in the blades and a violent vibration occurred in conjunction with the unusual noise.

The pilot was unable to identify or read the aircraft instruments because of the vibration and was unable to adequately control main rotor RPM after the onset of that vibration.

The violent vibration necessitated a landing. The pilot entered autorotation and selected a paddock for the forced landing. He reported that the helicopter was difficult to control during the descent. In particular, he was unable to turn the helicopter with left and right cyclic inputs. In particular, while cyclic inputs altered the attitude of the helicopter left and right it would not turn in the selected direction. The pilot also reported that it was difficult to control main rotor RPM during the autorotative descent and he relied upon the low rotor RPM horn and light as an indication of rotor RPM. The horn and light activated intermittently during the descent.

During the descent, the helicopter struck powerlines and was substantially damaged. The pilot reported that he was unable to avoid the powerlines because of the ineffective cyclic inputs. The pilot and passenger, the only occupants, suffered minor injuries.

A report from the accident site indicated significant main rotor blade skin disbonding 60 mm from the tip and extending 1070 mm inboard on one blade and the beginning of skin disbonding on the other blade. The ATSB conducted a preliminary investigation and it was apparent that the problem was a continuing airworthiness matter. ATSB released the main rotor blades to the Civil Aviation Safety Authority (CASA) for further examination as part of an airworthiness investigation.