Narrative:

I was working inside the routine overnight (ron) hanger on 3rd shift. I alone was given a work task on an APU filter remove/replace (right/right) with workcard. When I accessed the APU compartment; I realized that there was very little room for me to accomplish the required task (due to the fact of air conditioning duct routing and my body size). I removed the duct at four connection points (three points for air flow and one point for hard-mounting to structure). In the process of removing the duct; I noticed difficulty in the removal because there were three cannon plugs still connected on the outboard side; which was not easily visible. I disconnected the cannon plugs and I filled out a discrepancy form for the removal of the duct. I then proceeded with my job task until completion (2-3 hours). I proceeded to reinstall the duct assembly; reconnecting the four contact points. The lack of room made it difficult to reinstall and frustrating. I took a second look for area safety and closed the access door. Signed-off my paperwork and went home as my shift ended. I was having trouble sleeping [later] that day and when I woke up that evening I was startled with the thought of the cannon plugs not being installed. I remembered that I had not connected the cannon plugs. The APU compartment is a small confined area and not well lit. I often work in that compartment with a headlight on and a flashlight as a backup. I've performed the APU filter workcard on several aircraft in the past and never had an issue with ducts being in my way. This was the 1st time that I've come across this situation; let alone take off that duct for any reason (I believe it may have been because it was a -300 series aircraft and the air conditioning system is different than a -100 series). I was unfamiliar that it even had cannon plugs attached. And the fact of reconnecting the cannon plugs was not in my thoughts whatsoever; even after the installation. The cannon plugs were not even visible due to the fact that they were behind the duct out of the way and [poor] visibility. The positioning of the duct and access was again limited for viewing access. I immediately called up the company and notified the supervisor on duty of the event; and notified the supervisor that when I showed up for work three and a half hours later; I would fill out a report. I have thought about this a lot. Other than a block on certain workcards at the very end; reminding the person performing the work to acknowledge any cannon plugs removed; were reinstalled. Or an inspector block at the end of the APU fuel filter workcard to verify if duct assemblies are removed for access; to verify complete duct installation as a second set of eyes. Streamers probably wouldn't work so well in this case.

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Original NASA ASRS Text

Title: While at home; a Mechanic reports waking-up and remembering he did not reconnect three electrical canon plugs to an air conditioning duct after completing an APU Fuel Filter change Task Card on a DHC-8-300 aircraft.

Narrative: I was working inside the Routine Overnight (RON) hanger on 3rd shift. I alone was given a work task on an APU filter Remove/Replace (R/R) with workcard. When I accessed the APU compartment; I realized that there was very little room for me to accomplish the required task (due to the fact of air conditioning duct routing and my body size). I removed the duct at four connection points (three points for air flow and one point for hard-mounting to structure). In the process of removing the duct; I noticed difficulty in the removal because there were three cannon plugs still connected on the outboard side; which was not easily visible. I disconnected the cannon plugs and I filled out a discrepancy form for the removal of the duct. I then proceeded with my job task until completion (2-3 hours). I proceeded to reinstall the duct assembly; reconnecting the four contact points. The lack of room made it difficult to reinstall and frustrating. I took a second look for area safety and closed the access door. Signed-off my paperwork and went home as my shift ended. I was having trouble sleeping [later] that day and when I woke up that evening I was startled with the thought of the cannon plugs not being installed. I remembered that I had not connected the cannon plugs. The APU compartment is a small confined area and not well lit. I often work in that compartment with a headlight on and a flashlight as a backup. I've performed the APU Filter Workcard on several aircraft in the past and never had an issue with ducts being in my way. This was the 1st time that I've come across this situation; let alone take off that duct for any reason (I believe it may have been because it was a -300 series aircraft and the Air Conditioning System is different than a -100 series). I was unfamiliar that it even had cannon plugs attached. And the fact of reconnecting the cannon plugs was not in my thoughts whatsoever; even after the installation. The cannon plugs were not even visible due to the fact that they were behind the duct out of the way and [poor] visibility. The positioning of the duct and access was again limited for viewing access. I immediately called up the company and notified the Supervisor on duty of the event; and notified the Supervisor that when I showed up for work three and a half hours later; I would fill out a report. I have thought about this a lot. Other than a block on certain workcards at the very end; reminding the person performing the work to acknowledge any cannon plugs removed; were reinstalled. Or an Inspector block at the end of the APU Fuel Filter Workcard to verify if duct assemblies are removed for access; to verify complete duct installation as a second set of eyes. Streamers probably wouldn't work so well in this case.

Data retrieved from NASA's ASRS site as of April 2012 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.