Robinson Helicopter Co 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.