B737-700
Situational Awareness; Communication Breakdown
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Object
Procedure; Human Factors; Environment - Non Weather Related; Aircraft
I was asked by my Co-worker assigned with me to lower flaps for visual inspection and post dock inspection. I verified with the engine change Crew (also assigned to the aircraft) that it was okay to do so. They confirmed. I looked quickly under both wings for people and obstructions. There was a wing stand under the left wing. It was not used for our operation. It looked to be in a safe position; however I was mistaken. I completed the reactivation of hydraulics by removing the hydraulic pump switch guard. I yelled out to the engine change Crew and my Co-worker thru the R-1 door 'Hydraulics coming on; Flaps coming down'. My Co-worker echoed 'Hydraulics - Flaps'. I heard this and thought I was clear to lower flaps; because I heard no other alarms from my Co-worker after he announced. I pushed the ground call button as a final warning and turned on hydraulics. I proceeded to lower flaps. As the flaps were lowering I was observing; from the L1 and R1 doors; the progress. From my view things looked okay. As the flaps approached near full extension @ approximately 30; I heard and felt a crunching sound. I immediately turned off hydraulics. I went down to investigate what happened. The left wing outboard flap fairing tail cone had crushed into the wing stand. I felt that my Co-worker was observing the overall flap deployment operation. I was wrong. I should have made sure that he was aware of all things around the aircraft before I operated the flaps. We are normally very careful of these things in the hangar.
[Another AMT] and I were on the MV-2 together. [Maintenance Inspector] said lowering the flaps would not interfere with the engine change. I needed the flaps (lowered) to complete the MV-2 check. I told [Another AMT] that we should lower the slat and flaps. [Another AMT] went up to the cockpit; I went over to the engine change Crew; asked them if it was ok for hydraulics and to lower slats and flaps; and they said it was ok. The anti-collision light came on. I did not clear [Another AMT] to lower flaps. I cleared the area around the right wing flaps then went to the E&E compartment to verify that the hydraulic CBs had been reset. They had not been reset; so I reset them. When I came out of the E&E compartment I was told of the aircraft damage. I never had the opportunity to clear the left side of the aircraft.
When lowering the flaps during maintenance on a B737-700 the mechanic was unaware of a wing stand under the flap fairing. The left wing outboard flap fairing tail cone crushed into the wing stand.