Applies Only To Aircraft With Air Comm Corporation (Air Comm) Air Conditioning Kit

The FAA has issued an Emergency AD for Airbus Helicopters Model EC120B helicopters that have an Air Comm Corporation (Air Comm) air conditioning kit installed in accordance with Supplemental Type Certificate No. SR00491DE.

This action was prompted by a report that the operator of an Airbus Helicopters Model EC120B heard an abnormal noise during flight that gradually became more pronounced resulting in a precautionary landing. While applying power to land, the helicopter yawed left. Application of the right pedal did not correct the rotation requiring the pilot to perform a hovering
auto rotation.

A preliminary investigation showed that the mating splines of the air conditioner system’s pulley and the tail rotor output pinion had worn away allowing the pulley to rotate freely on the output pinion. Failure of the drive pulley and tail rotor output pinion during flight may result in the loss of tail rotor drive and subsequent loss of directional control.

After this incident, Air Comm issued Service Bulletin SB-EC120-111815, Revision A, dated November 20, 2015, prompting an inspection of another Model EC120B helicopter that also showed severe wear in the mating splines of the air conditioner system’s pulley and the tail rotor output pinion. The wear was not detected until after the tail rotor drive was disassembled to allow the removal of the Air Comm pulley drive. No play was detected between the air conditioner system’s pulley and the tail rotor output pinion prior to disassembly and the pilot had not reported any concerns.

The root cause of this condition has not been determined and the investigation is on-going.

The Emergency AD requires, before further flight, and at intervals not to exceed 25 hours time-in-service, partially disassembling the tail rotor drive system to allow for the removal of the air conditioner compressor drive pulley.

With the drive system disassembled and the compressor drive pulley in its normal installed position on the tail rotor output pinion shaft, this Emergency AD requires applying clockwise and counter-clockwise, up-and-down, and left-and-right force by hand to the pulley while holding the rotor brake disc stationary. If any movement exists between the pulley and tail rotor output pinion (play), this Emergency AD requires replacing the pulley and tail rotor output pinion before further flight. If no play exists, this Emergency AD requires removing the pulley and visually inspecting the pulley and output pinion splines for wear. If any splines are not straight, contain any inconsistent cross-sections end-to-end, contain any localized material deformation, or any material loss, this Emergency AD requires replacing the pulley and tail rotor output pinion before further flight.

Within 10 days after completing the initial inspection, this Emergency AD also requires reporting certain information to the FAA.

(Image from file)

FMI: EAD