A Mechanic and two Apprentice Mechanics he was training on the removal and installation of a B737-500 aft entry door slide assembly are informed they improperly pinned the removed slide that was sent to the shop.

Narrative

I was instructing apprentice mechanics on aircraft door slide removal and installation for aircraft B737-500 in which the unserviceable slide was returned to stores in an unsafe pinned condition. To start; I take full responsibility for the incorrect pinning of the slide. I had performed this task several times in the past and felt confident in instructing them on this task. Having the Maintenance Manual on hand and referring to figures 1-5 and also the new serviceable slide from stores; I was unable to find the front of the slide regulator assembly. After examining the slide several times front to back; and top to bottom; and applying a great deal of force trying to pull open the yellow cover to expose the regulator; I found what I thought was the correct pin out location that matched the serviceable slide; inserted the pin; boxed up the slide and returned the unserviceable slide back to stores. I feel that the only contributing factor for the incorrect pinning of the slide was me not being able to access the front of the regulator and not wanting to forcedly disassemble the potentially explosive slide further than what we had done to expose only part of the regulator. Supplemental information from ACN 820662: We had finished our plane and were asked if we wanted to R&R a door slide. Since we had not done one before; we said yes. So went to where I proceeded to remove the aft entry door slide. After removal; we took outside just in case it deployed while taking the slide out of its cover. We took the new slide and laid it next to the old slide. Then we removed the pin from the new slide and put it in the old one. After putting the pin in the old slide; we all thought that it was not pinned right and proceeded to turn the slide and opening the sides. We all were kind of worried about turning it so much and tearing into it too much for it could deploy. Finally; we looked at the new one and where it was pinned and pinned the old one in the same spot. We put the old slide in its box and I put the new slide back on the aircraft. On our first day back after our days off; we were told that we had pinned the slide wrong. When it was sent to the slide shop it was noticed during inspection. Callback conversation with Reporter ACN 820660 revealed the following information: Reporter stated some of their slide packs have the regulator more exposed; while others are very difficult to access for the safety pin holes. His carrier has developed a better and more realistic video to help mechanics recognize the different types of door slides they have on their aircraft and locate the safety pin holes.