Narrative:

Following a revenue flight in this aircraft; repositioned aircraft to ZZZ for heavy check. Upon arrival at ZZZ; accepted another aircraft (after heavy check completed) to reposition to home base for revenue operations the following day. After a 30 minute delay for current FMS database to be uploaded (resulting from an inability of crew to sync FMS1 and FMS2 during preflight due to differing secondary database dates); ca began outbound taxi to runway. Prior to taxiing; taxi checklist was completed in which the following v-speeds were confirmed: V1 117 vr 122 V2 132 and vt 173. Upon confirming runway heading; ca transferred controls to first officer.following ca's '80 knots' call; at approximately 95 knots as ca was scanning engine parameters; ca heard loud clacking sound; immediately looked to his right and saw first officer's seat slide to the full aft position as first officer simultaneously called out 'your controls'. Ca immediately took the aircraft controls as the aircraft departed right of the runway centerline. As ca assumed control of the aircraft and steered aircraft back to the centerline; he simultaneously scanned the airspeed indicator as airspeed was rapidly approaching 110 knots. In the limited time ca had to make his decision to reject or continue the takeoff; a rapidly approaching V1; company rejected takeoff criteria and his positive control of the aircraft resulted in his decision to continue the takeoff. Despite fos startling slide rearward; he immediately repositioned his seat; ensured it was in the locked position; assumed pm duties and called 'V1...rotate'; ca commenced rotation at approximately 130 knots as he literally 'caught up' to instantly becoming PF; evaluating the situation and making the go/no decision. While aircraft exceeded vt on initial climb by approximately 5 to 10 KIAS (due to a sub 55;000 pound takeoff weight and cas late rotation) no limitations were exceeded. Normal climb was subsequently completed with gear and flaps retracted on schedule.during climb; first officer tested his seat track lock numerous times to ensure it was not malfunctioning. As aircraft climbed thru 11;000 feet; autopilot was engaged and ca transferred controls back to first officer. As ca pushed slightly back on his seat; a brief clack sound occurred as the ca's seat slid back 'one notch' of seat adjustment. Ca then tested the seat track lock on his seat. No subsequent inadvertent movement of either crew seat occurred. Ca and first officer agreed the seat lock handle had not been fully engaged on the first officer's seat prior to commencing the takeoff roll and to a lesser extent the same occurred on the ca's seat. In his 17 years of flying the crj; ca had experienced similar aft sliding of a crew seat numerous times due to the seat lock handle not fully engaged; however this was the first time it had occurred during takeoff roll/climb or any other critical phase of flight. The first officer later informed the ca his seat slid full aft after he applied rudder during the takeoff roll.the following morning; the ca came to the conclusion (despite no repeat of the seats inadvertently sliding aft even after repeated attempts by ca and first officer to move the seats aft with the locks engaged and his prior experience with multiple non-critical phase of flight occurrence's) he should have reported the incident to maintenance. Ca contacted maintenance control that morning and spoke with a maintenance controller and requested to speak to a maintenance supervisor. Ca then provided maintenance supervisor with the details of the incident the night prior and requested that maintenance meet the aircraft and inspect the ca and first officer seat track locks. Ca inquired how many flights the aircraft had operated that day and was told it was returning on its third flight of the day. Maintenance advised ca he would have maintenance meet the aircraft upon its arrival at the maintenance base to have the inspection performed.ca credits the fos immediate action (transfer of controls to ca) and immediate reaction (assuming of pmduties) as the key factor in determining the successful outcome of the event. Due to the rapid acceleration of the aircraft under the existing takeoff conditions; both ca and first officer had limited time to react and appropriately did so. However; the crew was fortunate the ca's seat did not move in a similar manner once the ca assumed control of the aircraft. Going forward; ca will readopt a procedure he practiced at his prior employer when adjusting his seat prior to aircraft movement: ensure seat lock handle is fully engaged and test for aft movement by forcefully moving aft 2 to 3 times in seat once seat lock is confirmed fully engaged. Furthermore; ca should have immediately reported the event to maintenance via ACARS. The following day when discussing the event with a different first officer the ca was paired with; that first officer commented he had two similar events during takeoff as PF on crjs at his prior employer.

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Original NASA ASRS Text

Title: During the takeoff roll following a heavy check; a CRJ-900 First Officer's seat slid aft to its stops. The First Officer quickly transferred controls to the Captain. Several revenue flights later; an aircraft inspection was requested by the Captain.

Narrative: Following a revenue flight in this aircraft; repositioned aircraft to ZZZ for heavy check. Upon arrival at ZZZ; accepted another aircraft (after heavy check completed) to reposition to home base for revenue operations the following day. After a 30 minute delay for current FMS database to be uploaded (resulting from an inability of crew to SYNC FMS1 and FMS2 during preflight due to differing secondary database dates); CA began outbound taxi to runway. Prior to taxiing; taxi checklist was completed in which the following v-speeds were confirmed: V1 117 Vr 122 V2 132 and Vt 173. Upon confirming runway heading; CA transferred controls to FO.Following CA's '80 knots' call; at approximately 95 knots as CA was scanning engine parameters; CA heard loud clacking sound; immediately looked to his right and saw FO's seat slide to the full aft position as FO simultaneously called out 'your controls'. CA immediately took the aircraft controls as the aircraft departed right of the runway centerline. As CA assumed control of the aircraft and steered aircraft back to the centerline; he simultaneously scanned the airspeed indicator as airspeed was rapidly approaching 110 knots. In the limited time CA had to make his decision to reject or continue the takeoff; a rapidly approaching V1; Company rejected takeoff criteria and his positive control of the aircraft resulted in his decision to continue the takeoff. Despite FOs startling slide rearward; he immediately repositioned his seat; ensured it was in the locked position; assumed PM duties and called 'V1...rotate'; CA commenced rotation at approximately 130 knots as he literally 'caught up' to instantly becoming PF; evaluating the situation and making the go/no decision. While aircraft exceeded Vt on initial climb by approximately 5 to 10 KIAS (due to a sub 55;000 pound takeoff weight and CAs late rotation) no limitations were exceeded. Normal climb was subsequently completed with gear and flaps retracted on schedule.During climb; FO tested his seat track lock numerous times to ensure it was not malfunctioning. As aircraft climbed thru 11;000 feet; autopilot was engaged and CA transferred controls back to FO. As CA pushed slightly back on his seat; a brief clack sound occurred as the CA's seat slid back 'one notch' of seat adjustment. CA then tested the seat track lock on his seat. No subsequent inadvertent movement of either crew seat occurred. CA and FO agreed the seat lock handle had not been fully engaged on the FO's seat prior to commencing the takeoff roll and to a lesser extent the same occurred on the CA's seat. In his 17 years of flying the CRJ; CA had experienced similar aft sliding of a crew seat numerous times due to the seat lock handle not fully engaged; however this was the first time it had occurred during takeoff roll/climb or any other critical phase of flight. The FO later informed the CA his seat slid full aft after he applied rudder during the takeoff roll.The following morning; the CA came to the conclusion (despite no repeat of the seats inadvertently sliding aft even after repeated attempts by CA and FO to move the seats aft with the locks engaged and his prior experience with multiple non-critical phase of flight occurrence's) he should have reported the incident to maintenance. CA contacted maintenance control that morning and spoke with a maintenance controller and requested to speak to a maintenance supervisor. CA then provided maintenance supervisor with the details of the incident the night prior and requested that maintenance meet the aircraft and inspect the CA and FO seat track locks. CA inquired how many flights the aircraft had operated that day and was told it was returning on its third flight of the day. Maintenance advised CA he would have maintenance meet the aircraft upon its arrival at the maintenance base to have the inspection performed.CA credits the FOs immediate action (transfer of controls to CA) and immediate reaction (assuming of PMduties) as the key factor in determining the successful outcome of the event. Due to the rapid acceleration of the aircraft under the existing takeoff conditions; both CA and FO had limited time to react and appropriately did so. However; the crew was fortunate the CA's seat did not move in a similar manner once the CA assumed control of the aircraft. Going forward; CA will readopt a procedure he practiced at his prior employer when adjusting his seat prior to aircraft movement: ensure seat lock handle is fully engaged and test for aft movement by forcefully moving aft 2 to 3 times in seat once seat lock is confirmed fully engaged. Furthermore; CA should have immediately reported the event to maintenance via ACARS. The following day when discussing the event with a different FO the CA was paired with; that FO commented he had two similar events during takeoff as PF on CRJs at his prior employer.

Data retrieved from NASA's ASRS site 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.