B737-700
Fatigue; Situational Awareness
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Human Factors; Procedure
I was performing a Post Dock General Walk around Safety Inspection on an aircraft. In the left wheel well I failed to see the presence of the Standby Leading Edge Shutoff lock out tool still attached to the valve; rendering the leading edge devices inoperative in the standby mode. It was not discovered until the aircraft flew to another station where the crew found it on preflight walk around before the next flight. I believe one of the contributing factors was the color of the lock-out tool. It is a dull red color which I believe blends into the surrounding components. Another contributing factor is the Maintenance Task Card for the Post Dock Intermediate Check- General Walk Around Safety Inspection. There is not a block that specifically states to remove this locking tool. It refers you to three different Maintenance procedures for the activation of the leading edge flaps and slats. Also; if I had paid more attention to the inspection of that component in the left wheel well; I believe this would have been prevented.
I was assigned to an aircraft for cabin visit. After all maintenance was completed; I did post dock inspection. I looked over the plane to make sure (all) panels were installed and no tools were left behind. I looked in wheel wells and everything looked normal. The leading edge lock out pin was removed and safety wired. I didn't notice any flags hanging down. After all paperwork was done; I bought off post dock. The following day I heard that a standby hydraulic valve lock was found installed after plane landed from flight. I don't know how I could have missed (seeing the) lock installed. It was pretty windy that night; the streamer must have blown up in wheel well to a spot where the mechanic and I didn't see it on post dock walk around.
After maintenance was performed on a B737-700; both an Inspector and a Maintenance Technician missed seeing that a standby leading edge shutoff lock tool was still installed while performing a final walk around.