B777-200
Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Confusion; Situational Awareness
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Procedure; Chart Or Publication; Human Factors; Manuals
While working B777-200 today; I noticed the Captain's seat front rail stops were not correctly positioned; and when I checked the forward limit switch; it was broken off. After noticing the discrepancy; I placarded on MEL 25-1a; the Captain's seat power functions inoperative. As said before; it appears the figures and explanations on seat installation are not clear enough. Evening; ETOPS Pre-Departure Check (PDC).
Reporter stated he was working a PDC Check on a B777-200 aircraft. Revisions to the Maintenance Manual Seat Installation Procedures and Figures (Diagrams) will be made soon to clarify the correct installation position of the Front Rail Stop Limit switch. Because the limit switch (micro-switch) on the lower frame of the Captain's seat had been installed upside down; the micro-switch could not ride up on the ramp on the seat rail stop fitting to interrupt electric power to the seat motor. As a result; the limit switch on the seat frame was literally cut in half and allowed the seat motor to continue driving the seat forward to the rail end stops. The limit switch is not a Line Replaceable Unit (LRU); the seat has to be replaced.Reporter stated there are eight different ways to install the stops while the limit switch is only installed on the inboard side of the seat frame facing outboard. The Maintenance Manual is being misinterpreted due to the unclear procedures and drawings Maintenance has to use for the installation.
A Line Aircraft Maintenance Technician noticed during a Pre-Departure Check on a B777-200 aircraft; the Captain's seat forward limit switch was broken off. The front rail stops were also not correctly positioned. Unclear procedures and drawings in the Aircraft Maintenance Manual allowed for misinterpretation of installation.