Narrative:

We were doing our preflight duties for an early morning east coast departure and maintenance was trying to get us out in a hurry. I got up to get some water and heard a knock at the door. I thought maintenance had shut the door so I went to open it back up; the lights had been turned off so it was dark. I checked the strap and it was not across the handle. Thinking that they had closed and shut the door I lifted the latch. Well; you know what happens when you lift the handle when the door is still armed. I saw the light but it happened so fast I could not stop in time. I held the door as much as I could so it would not open all the way. The slide did not drop and inflate but the door assist bottle did discharge.I think that this happened because maintenance was in a hurry; we were up early home domicile time and communication was a little off. I should have checked all door safety latches but I took it for granted that the strap was not on that the door was not armed; it is ultimately my fault but the first officer took it upon himself to shut and arm doors without telling me. It is not my practice to arm doors for reposition flights with no one on the aircraft but the crew. The first officer was under the impression that doors had to be armed for ferry flights. Any time the door is shut and armed it should be communicated to the other crew members.

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Original NASA ASRS Text

Title: An air carrier Captain preparing for an early morning ferry flight inadvertently opened the main cabin door which he was not aware had been armed by the First Officer upon returning from his preflight.

Narrative: We were doing our preflight duties for an early morning East Coast departure and Maintenance was trying to get us out in a hurry. I got up to get some water and heard a knock at the door. I thought Maintenance had shut the door so I went to open it back up; the lights had been turned off so it was dark. I checked the strap and it was not across the handle. Thinking that they had closed and shut the door I lifted the latch. Well; you know what happens when you lift the handle when the door is still armed. I saw the light but it happened so fast I could not stop in time. I held the door as much as I could so it would not open all the way. The slide did not drop and inflate but the door assist bottle did discharge.I think that this happened because Maintenance was in a hurry; we were up early home domicile time and communication was a little off. I should have checked all door safety latches but I took it for granted that the strap was not on that the door was not armed; it is ultimately my fault but the First Officer took it upon himself to shut and arm doors without telling me. It is not my practice to arm doors for reposition flights with no one on the aircraft but the crew. The First Officer was under the impression that doors had to be armed for ferry flights. Any time the door is shut and armed it should be communicated to the other crew members.

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.