Date: 201403
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Eurocopter AS 350/355/EC130 - Astar/Twinstar/Ecureuil
Operator: Air Taxi
Operating under: Part 135
Mission: Passenger
Flight phase: Parked
Aircraft component: Tail Rotor Drive Gearbox
Reporter organization: Air Taxi
Reporter function: Inspector
Reporter qualification: Maintenance Inspection Authority
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural FAR
Detector: Person Maintenance
Result: General Maintenance Action
Contributing factors: Company Policy; Human Factors; Incorrect / Not Installed / Unavailable Part
Primary problem: Human Factors

Narrative: During a Record Review for a new Airworthiness Directive (A/D) (A/D 2014-05-07) compliance; it was found that the installed Tail Rotor Gearbox Part Number (P/N) was incorrectly presented on the aircraft (helicopter) Maintenance spreadsheet. The helicopter Manufacturer publishes a document; the Master Servicing Manual (MSM) which list all components approved for installation on that particular model helicopter; along with the applicable Service Life Limits and Overhaul requirements. I researched the installed [Tail Rotor] Gearbox Part Number (P/N) to see if it had a different Overhaul Time or Service Life Limit on the internal gears; but did not find that gearbox part number listed.On the Gearbox Historical Record Card; the gearbox had only been utilized on a Eurocopter AS350-B3 Helicopter. Going to the B3 MSM; the Gearbox Part Number (P/N) was there with the applicable Service Life Limits. I sent a message to the Manufacturer's Technical Representative (Tech Rep) questioning the installation model validity for the 'in question' gearbox. The Tech Rep replied that it was not authorized for use on the AS355-F2 series helicopters. I immediately contacted the Director of Maintenance (DOM) concerning this and he acknowledged the message and information. This was in March 2014; early morning. Upon arriving at work the following day; I sent the Director of Maintenance (DOM) the message I had received from Eurocopter's Tech Rep concerning the gearbox. He; (the DOM); verbally stated there was a replacement ordered for the next day. I did not pay much more attention to this until I witnessed the aircraft depart on a flight. Management had chosen to ignore the fact that an incorrect Tail Rotor Gearbox was installed and continued to utilize the aircraft. Solution: the aircraft should have been 'Grounded' until the correct part was installed. The current Airworthiness Certificate is invalid due to the aircraft not being maintained in accordance with (IAW) the Manufacturer's instructions.




Synopsis: A Quality Assurance Inspector reports a current Airworthiness Certificate for one of their AS355-F2 series helicopter was invalid due to the aircraft not being maintained in accordance with (IAW) the Manufacturer's instructions. He had reported to his Director of Maintenance (DOM) that an unauthorized Tail Rotor Gearbox had previously been installed on the AS355-F2; but the DOM chose to release the helicopter into service.