Date: 201202
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B767-300 and 300 ER
Operator: Air Carrier
Operating under: Part 121
Mission: Cargo / Freight / Delivery
Flight phase: Parked
Aircraft component: Fan Reverser
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Powerplant; Maintenance Airframe
Human factors: Workload; Time Pressure; Situational Awareness; Communication Breakdown; Confusion
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Maintenance
When detected: Other Through aircraft records Audit
Result: General Maintenance Action
Contributing factors: Aircraft; Chart Or Publication; Company Policy; Equipment / Tooling; Human Factors; Incorrect / Not Installed / Unavailable Part; Logbook Entry; Manuals; Procedure; Staffing
Primary problem: Company Policy

Narrative: Parts were shipped to me for an Engineering Order. Both parts were -001's and had a large piece of heat shrink tubing installed with the words in large bold print; left-hand ONLY. They were for an Engineering Order to be accomplished on the left Engine Thrust Reverser. The Engineering Order was to verify the Part Numbers installed and replacing the [Fan Reverser] flex shafts as required. I replaced the left engine thrust reverser outboard shaft first; with no issues. I then proceeded on to the left engine thrust reverser inboard flex shaft. The Engineering Order does specify the correct part number to be installed as a -002. But; there is confusion with the Caution Note that is in bold print. The caution note states: FLEX SHAFTS ARE NOT INTERCHANGEABLE BETWEEN THE RH AND LH TRUST REVERSERS; FLEX SHAFTS ARE LABELED WITH 'RH ONLY' OR 'LH ONLY' INDICATING THE CORRECT THRUST REVERSER ON WHICH IT CAN BE INSTALLED. This leads one to believe left-hand ONLY is for left engine thrust reverser and right-hand ONLY is for right engine thrust reverser. This is not the case. The Engineering Order is referring to each engine thrust reverser as a whole; to have a left thrust reverser and a right thrust reverser. Not the way we usually refer to them. The Engineering Order doesn't require an annotation of Part Number and Serial Numbers. This was an opportunity lost as a check of installed part numbers. The Engineering Order was/is assigned by a printout with an assigned Task Number. Here the job is assigned and signed-off accomplished as a matter of an extended logbook. The assigned Task Number doesn't require any part number or serial number annotation either. The Parts Tag lends itself to installing the incorrect part. The -001 description is CABLE; FLEXIBLE DRIVE (LEFT-HAND). In our Maintenance program; the parts are classified by price and whether of not they are repairable. These shafts are Expendable/ Inspectable items which don't require any removed part number or serial number information to be entered. Just basic information like; who; where and when. Working the Engineering Order alone may have helped contribute to the error. A 'Second Set of Eyes' reviewing parts and paperwork could be of help to catch the error. Lastly; a heavy weekend work load was another contributing factor. There is a lot of pressure to produce as much work as possible over the weekend with as few mechanics as possible. We have had many paperwork errors due to this type of work environment. This has been brought to the Employer's attention for many years. Ultimately; this was my error; not verifying the Part Number listed on the Engineering Order prior to install. I assumed the labeling to be correct and; the parts I had for the job to be correct for the engine [the flex shafts would] be installed on. I was working on the left engine thrust reverser and; had parts labeled with Part Tags noting CABLE; FLEXIBLE DRIVE (LEFT-HAND). In closing; the Engineering Order could be better written and have Inspection 'Buy-Off' of the installed part number. The part tags and the part itself could be better labeled to differentiate engine thrust reverser; and position to be installed in/on.

Callback: Reporter stated their Maintenance Planners at their home base have a web page with all the maintenance tasks and will print out what is actually assigned to be accomplished. He was informed two and a half months after he had installed the left Engine Reverser Flex shafts; that a Quality Assurance Audit had compared the Flex Shaft Parts Tag with the Engineering Order assigned Part Number printout and noticed a discrepancy with the numbers.Reporter stated he believes the number one contributing factor was the Parts Department had sent out two reverser flex shafts with the same Part Number (P/N)-001; which was for the outboard reverser half on # 1 Engine. He had installed the same part number flex shaft on the right reverser half of # 1 Engine and did not have any difficulties with the installation or reverser Operational Check. He believes the only difference between the left and right flex shafts is the clockwise; or counter-clockwise; directional winding of the flexible cable shaft inside the Teflon lined steel casing to account for the left or right position of the reverser half. There were no operational flight incidents; but the correct flex shafts were later installed.



Synopsis: A Line Mechanic working a B767-300 aircraft reports he inadvertently installed two Fan Reverser Flex Shafts with the same Part Numbers at the left and right reverser half positions on # 1 Engine. The Part Number for the flex shafts was only for the left reverser half position.