AN EMBRAER 135 ON TAKEOFF ROLL WITH FO FLYING AT V1 MINUS 10 KTS SEAT SLID BACK TO STOPS. CAPT SEIZED YOKE TO CONTINUE TAKEOFF. FO EXPERIENCED DIFFICULTY TO REPOSITION AND LOCK SEAT.

Narrative

THE FO SEAT SLID BACK ON TAKEOFF FROM RWY 27 IN BOS. THIS OCCURRED AT V1 MINUS 10 KTS. IT SEEMS AS IF THE SEAT LOCKING MECHANISM WAS FUNCTIONING IMPROPERLY. IT WAS VERY DIFFICULT TO GET THE PINS TO RE-ENGAGE AFTER THIS OCCURRED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THIS IS THE THIRD INCIDENT OF THE SEAT RELEASING WHEN OPERATING THE ACFT AND ALL OCCURRED WITH THE FO THE PLT IN CONTROL. THE RPTR SAID THE FIRST WAS AT ROTATION THE SEAT SLID BACK TO THE STOPS; SECOND EVENT WAS DURING TAXI THE SEAT UNLOCKED AND MOVED AFT; BUT DID NOT HIT THE STOPS AND THE THIRD IS THIS INCIDENT AT V1 SPEED MINUS 10 KTS. THE RPTR STATED ALL OF THE INCIDENTS WERE LOGGED FOR MAINT ACTION WHICH IS MOSTLY SPRAYING THE TRACK AND LOCK PIN WITH LUBRICANT. THE RPTR SAID THE PROB SEEMS TO BE AGGRAVATED BY SAND AND DIRT GATHERING ON THE FLOOR UNDER THE SEAT AND STICKING TO THE LUBRICANT. THE RPTR STATED WHEN FIRST SITTING IN THE SEAT HE WILL 'ROCK' THE SEAT AND CHK FOR LOCKING; BUT THIS DOES NOT ENSURE 'POSITIVE' LOCKING. THE RPTR SAID THE CARRIER ISSUED A FLT HANDBOOK REVISION THAT ADVISES 'TO CHK SEAT FOR LOCKING.'