Use of helicopter for spraying caused rotor damage

A helicopter being used for agricultural flying, for which it was not designed, was the reason a crack appeared in its main rotor blade, an inquiry has found.

The Transport Accident Investigation Commission (TAIC) has published a final report on the incident at Waikaia in January 2015.

While spraying, the pilot of a Robinson R44 helicopter felt an unusual and significant vibration, landed immediately, and found a crack in a main rotor blade.

The new report replaces an earlier one, released in 2018, though the findings are substantively the same, with some technical changes.

TAIC found the crack started in a fatigued section of the metal blade, and that the crack was not the result of any manufacturing defects in the materials or in the construction of the blade.

It also found that the helicopter had been operated primarily for agricultural flying, with the engine power likely to have exceeded the allowable limit at times.

The types of turn used by the operator during spraying operations, especially when the helicopter was close to the maximum permitted all-up weight, likely subjected the main rotor blades to additional stresses not envisaged by the manufacturer.

The helicopter was not designed specifically for agricultural flying.

The manufacturer had therefore not been required to consider the increased loads and cycles of agricultural flying when calculating the service life of the rotor blades.

TAIC was satisifed in April 2018 the CAA had found a new way to issue supplemental type certificates and a way to consider whether modifications could result in changes in operational use, which had been the TAIC's recommendation.