Bombardier Inc CL-600-2B19 N261PS incident near Bowman, Georgia

Probable cause

the captain's inappropriate climb speed, his failure to monitor airspeed during the level off, and his inappropriate response to multiple stall warnings.

NTSB analysis

The flight had a normal takeoff and initial climb and then the was cleared by ATC to climb to flight level (FL) 340. The captain set an unsustainable vertical speed command in the autopilot during climb and intentionally allowed the airspeed to decrease well below the recommended climb speed. He did not check the minimum buffet boundary speed applicable to the flight and was not aware of company guidance cautioning against allowing the speed to decay during climbs to high altitude. He failed to monitor airspeed during level off at FL 340 and allowed it to fall to stick shaker speed.

According to the performance study, after the stick shaker activated the crew moved the column forward but then pulled back again while the shaker was still active. The shaker stopped for about one second as the crew continued to pull back. The stick shaker reactivated followed about one second later by the stick pusher, which pitched the aircraft down. The crew then pulled back increasing the angle of attack (AOA) and reactivating the shaker and pusher, which began a cycle of stick pusher dynamics. The airplane performance study shows the crew applied back pressure, or "pulls," seven times in response to sick pusher activation before relaxing back pressure and allowing the airplane to descend. The captain's actions were contrary to the manufacturer's and company's stall recovery procedures, and the airplane regained stable flight only after AOA was reduced by allowing the airplane to descend.

Text from the NTSB. Open the NTSB docket for DCA13IA058 for the full record.