Date: 201308
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: A330
Operator: Air Carrier
Operating under: Part 121
Flight phase: Parked
Aircraft component: Powerplant Mounting
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Powerplant; Maintenance Airframe
Human factors: Situational Awareness; Training / Qualification; Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural FAR
Detector: Person Maintenance
When detected: Other During Maintenance
Result: General Maintenance Action
Contributing factors: Company Policy; Human Factors
Primary problem: Human Factors

Narrative: My name is Mechanic X and I am a Machinist in ZZZ. I went to ZZZ1 to work on an A330 Right Engine mount problem on August 2013. The airplane was parked in the Maintenance Hangar. The write-up addressed corrosion in and around the previously machined spot faced areas on the top of the [pylon where the engine's] four forward mount bolts [would be located]. I was told that this work was done in ZZZ2 by our Heavy Maintenance Contract Repair Station vendor. In my opinion; the repair was not within the Structural Repair Manual (SRM) repair limits and should not have been flying at all. It is also my opinion that it was an accident waiting to happen. The original repair called out for the bottom of the spot face to be machined with an .080' thousandths of an inch radius. The bottom of their spot face was sharp and looked to be no more than .005' thousandths of an inch. The larger radius is in place to prevent cracking conditions. Out of all the places on that airplane that you do not want cracks to form; that to me is the most important area. Also; there is about a one inch thick wall mount structure located between the bores. When they machined the spot face they went into the sides of this wall. After three days of intense discussion between the Engineer; Inspection; Management; and the Aircraft Manufacturer; they made the decision to fly the A330 to the [same] Repair Station and change the pylon. Myself and my co-worker machinists did not want to touch it because it would have made matters much worse than they already were. I personally would not have felt safe flying on that airplane. I am filing this report to bring to light the Contract Repair Station's shoddy maintenance practices and to hopefully ensure this does not happen again!!! It was quite obvious that the repair was not done correctly just by looking at it. We also found out that the original machined spot face depth was already below limits. They may have had authorization to machine to this depth. In order for us to accomplish the .080' thousandths of an inch radius; we would have had to increase the depth by at least .080' thousandths to achieve the correct radius. The Aircraft Manufacturer did not want to do that; since the Contract Vendor did not machine the correct radius in the first place; this is why our repair would have required us to machine much deeper to accomplish the repair. Otherwise; with the correct cutter and light corrosion; a 'skim' cut would have probably solved the problem. That would have solved the problem of the radius of the spot face depth; but another problem was also in play here. The Contract Vendor [had also] cut into the structure wall of the engine mount. I would be surprised if the Aircraft Manufacturer would even allow a repair after all of this. The Contract Vendor not only created a potentially catastrophic flying situation; the total maintenance costs incurred were absolutely staggering!!! Our Contract Repair Station Vendor in ZZZ2 did very poor work that was totally unacceptable and unsafe! I believe our Machine Shop should do the work; especially in critical areas such as this. The engine mount cannot be sold separately. It is sold as an entire assembly; pylon and all.

Callback: Reporter stated he has an Airframe and Powerplant (A/P) license and has been working as a Machinist out of his Air Carrier's Machine Shop for fifteen years. Their Mechanics had pulled the Right Engine off of the A330 for other problems and found corrosion on the pylon's forward mount where the engine mount bolts attach. Company Engineering wanted to Cadmium Plate (Cad-Plate) the area; but the corrosion removal became an issue due to the improper spot-facing of the hole radius and additional improper machining damage that was done by the Contract Repair Station to the wall mount structure located between the engine mount bore holes. Reporter stated if someone makes a straight cut; without a adequate radius cut; then the bore area is subject to cracks that could migrate and the engine mount failing and most likely causing an engine to separate in flight or during takeoff. He believes the Heavy Maintenance Contract Repair Station's Quality Assurance is not adequate and neither is his Air Carrier's oversight of the same Repair Station. He believes his Air Carrier is asking for more trouble by sending the A330 aircraft back to have the entire pylon removed and replaced by the same Repair Station that had damaged and made the engine pylon not only unrepairable; but unsafe for flight.



Synopsis: A Machinist Technician describes the extent of damage he noticed that had been caused by a Heavy Maintenance Contract Repair Station vendor's improper machining of four forward mount bore holes on the Right Engine pylon of an A330 aircraft. The entire pylon required replacement due to the unrepairable damage and potential for an in flight failure of the pylon engine mount.