Narrative:

The left aft jumpseat had been MEL'd and was in-operative so we were informed to just take the right aft jump seat instead. When preparing to take the jump seat before takeoff the 'C' flight attendant and I tried adjust the seat belt straps on the right aft jump seat and were unable to do so. The straps were very stiff; we thought possibly from lack of use and they were covered in what seemed to be dirt and sodas/coffee/ back galley spills. I was unable to tighten the lap belt or arm belts at all leaving a huge possibility for me to slide right out or receive whiplash if the plane were to slam on the breaks while taxing or if anything should happen. The 'C' flight attendant was unable to loosen her left arm strap enough to even put her arm in it and her lap belt was also so lose that if anything were to happen we would be harmed. Both her and I discussed what we should do as to this was very unsafe for us and we decided since we were close to take off and the whole back row of seats where not filled; we ran up to the last row isle seat. The 'C' sat in the c seat and I sat in the d seat and we discussed if we needed to get to an exit; a plan of who would run first and how the process would go; we buckled up and the plane took off. Up at cruising altitude we informed the pilots of the situation and they said that both of the jump seats had been written up in the log book; so we felt that we made the safe decision for the fact that nobody told us. After our landing a mechanic came out and said that it was written up in the log book but showed as safe to sit in so it couldn't be labeled as in-operative. We asked him if there was anything he could do to make the straps adjust and he was able to help us try and adjust it enough to where we could get in and out somewhat easily and not slide around too much. We both still had to wear the straps very loose and when we were taking the jump seat each time that day the 'C' still had issues even getting that left shoulder in the strap. We felt that the whole jump seat was a very unsafe situation as both of us could have been seriously injured if there were and turbulence or emergency situations.

Related reports:

Google
 

Original NASA ASRS Text

Title: B737 Flight Attendants are instructed to use the right aft jumpseats due to the left aft jumpseats being MEL'd. Just prior to takeoff it is discovered that the right jumpseat seatbelts and shoulder straps cannot be adjusted and the Flight Attendants quickly move to open seats in the last row of passenger seats.

Narrative: The left aft jumpseat had been MEL'd and was in-operative so we were informed to just take the right aft jump seat instead. When preparing to take the jump seat before takeoff the 'C' Flight Attendant and I tried adjust the seat belt straps on the right aft jump seat and were unable to do so. The straps were very stiff; we thought possibly from lack of use and they were covered in what seemed to be dirt and sodas/coffee/ back galley spills. I was unable to tighten the lap belt or arm belts at all leaving a huge possibility for me to slide right out or receive whiplash if the plane were to slam on the breaks while taxing or if anything should happen. The 'C' Flight Attendant was unable to loosen her left arm strap enough to even put her arm in it and her lap belt was also so lose that if anything were to happen we would be harmed. Both her and I discussed what we should do as to this was very unsafe for us and we decided since we were close to take off and the whole back row of seats where not filled; we ran up to the last row isle seat. The 'C' sat in the c seat and I sat in the d seat and we discussed if we needed to get to an exit; a plan of who would run first and how the process would go; we buckled up and the plane took off. Up at cruising altitude we informed the pilots of the situation and they said that Both of the jump seats had been written up in the log book; so we felt that we made the safe decision for the fact that nobody told us. After our landing a mechanic came out and said that it was written up in the log book but showed as safe to sit in so it couldn't be labeled as in-operative. We asked him if there was anything he could do to make the straps adjust and he was able to help us try and adjust it enough to where we could get in and out somewhat easily and not slide around too much. We both still had to wear the straps very loose and when we were taking the jump seat each time that day the 'C' still had issues even getting that left shoulder IN the strap. We felt that the whole jump seat was a very unsafe situation as both of us could have been seriously injured if there were and turbulence or emergency situations.

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.