Narrative:

While performing removal and replacement of the left overwing slide; job card references you to aircraft maintenance manual 25-65-00-2 disarming of the off-wing slide escape system. These tasks were complied with per aircraft maintenance manual. The slide pack was then removed and replaced per operation. The next step is to check rigging of the inflation bottle -- this checked good. Next; the bellcrank dimensions checked good. At this point; no inspection will be required. Step 6 of the operation is arming of the off-wing escape system; which references you to aircraft maintenance manual 25-65-00-2. I got to step 4 connecting the emergency light batteries. At this time the right overwing slide deployed. After reviewing the situation; the only actions taken not specifically called out in the aircraft maintenance manual were to disarm the disable handle on the right-hand side escape hatches. The reason I moved the disable handle on the right side was due to the fact the aircraft maintenance manual calls out to disconnect the right and left side battery packs; which I believe correspond with the escape hatches. The operation or maintenance manual should have you pin both inflation bottles; which would then only allow the squibs to be discharged but would not allow the slide to deploy. This is not called out in the operation or aircraft maintenance manual. Callback conversation with reporter revealed the following information: reporter stated adding another action item to the job card procedure to also install a safety pin in the slide inflation bottle on the slide not being replaced; would at least prevent inadvertent release of the slide bottle pressure. Reporter stated after the slide deployed; more experienced mechanics on the following shift noticed one of the safe switches near the right overwing hatch appeared to be sticking and not releasing to the disarm position. That would account for the right slide deploying when he connected the emergency light batteries after installing the left overwing slide. The emergency batteries are cross connected to make sure at least one set of batteries will provide current to fire the squibs for the inflation bottle to inflate the slide. Reporter stated he noticed; during an over-wing hatch window change a few weeks earlier; the procedure required the mechanic to install safety pins in the left and right overwing inflation bottles; even though only one side was being changed. Since his incident; his carrier has added language to install safety pins in both slide inflation bottles whenever the overwing hatches are removed; or maintenance on the slide system occurs.

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Original NASA ASRS Text

Title: After the left overwing slide was replaced; a mechanic reports the right overwing slide on a B767-300 deployed while connecting the emergency light batteries during the rearming procedures.

Narrative: While performing removal and replacement of the left overwing slide; Job Card references you to Aircraft Maintenance Manual 25-65-00-2 disarming of the off-wing slide escape system. These tasks were complied with per Aircraft Maintenance Manual. The slide pack was then removed and replaced per Operation. The next step is to check rigging of the inflation bottle -- this checked good. Next; the bellcrank dimensions checked good. At this point; no inspection will be required. Step 6 of the Operation is arming of the off-wing escape system; which references you to Aircraft Maintenance Manual 25-65-00-2. I got to Step 4 connecting the emergency light batteries. At this time the right overwing slide deployed. After reviewing the situation; the only actions taken not specifically called out in the Aircraft Maintenance Manual were to disarm the disable handle on the right-hand side escape hatches. The reason I moved the disable handle on the right side was due to the fact the Aircraft Maintenance Manual calls out to disconnect the right and left side battery packs; which I believe correspond with the escape hatches. The Operation or Maintenance Manual should have you pin both inflation bottles; which would then only allow the squibs to be discharged but would not allow the slide to deploy. This is not called out in the Operation or Aircraft Maintenance Manual. Callback conversation with Reporter revealed the following information: Reporter stated adding another action item to the job card procedure to also install a safety pin in the slide inflation bottle on the slide not being replaced; would at least prevent inadvertent release of the slide bottle pressure. Reporter stated after the slide deployed; more experienced mechanics on the following shift noticed one of the safe switches near the right overwing hatch appeared to be sticking and not releasing to the disarm position. That would account for the right slide deploying when he connected the emergency light batteries after installing the left overwing slide. The emergency batteries are cross connected to make sure at least one set of batteries will provide current to fire the squibs for the inflation bottle to inflate the slide. Reporter stated he noticed; during an over-wing hatch window change a few weeks earlier; the procedure required the mechanic to install safety pins in the left and right overwing inflation bottles; even though only one side was being changed. Since his incident; his carrier has added language to install safety pins in both slide inflation bottles whenever the overwing hatches are removed; or maintenance on the slide system occurs.

Data retrieved from NASA's ASRS site as of May 2009 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.