Narrative:

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.

Related reports:

Google
 

Original NASA ASRS Text

Title: 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.

Narrative: 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.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.