NTSB Identification: DEN07IA027.
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Scheduled 14 CFR operation of FRONTIER AIRLINES INC
Incident occurred Monday, October 23, 2006 in Denver, CO
Probable Cause Approval Date: 06/27/2007
Aircraft: Airbus Industrie A319-111, registration: N924FR
Injuries: 136 Uninjured.
NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
During the landing flare approximately 10 feet above ground level, the aircraft pitched nose down while the captain applied aft sidestick force. The rate that the nose descended seemed to be commanded and extremely smooth. The first officer wondered if he could have accidentally bumped his sidestick, but he did not think that action occurred. The captain landed the airplane with the main landing gear touching down first, and the captain's sidestick was once again responsive. The entire event took no longer than 2 seconds. No electronic centralized aircraft monitor (ECAM) warnings or other indications were noticed by the flight crew. Review of the digital flight data recorder (DFDR) data revealed that the captain's sidestick (left) was inoperative for approximately 1 second during the landing flare. During that time, the first officer's sidestick (right) pitch was in the neutral position. Less than one second after the captain's sidestick went to inoperative, both sidestick pitch positions went to approximately 14-16 degrees aft. Pitch data revealed a decrease in pitch of approximately 2 degrees during the event. The airframe manufacturer provided the following analysis of the incident: "Captain was Pilot Flying (PF). First officer was Pilot Non Flying (PNF). Manual approach and flare input from the PF were nominal. But, it appeared that [the] PNF take-over and priority pushbutton was pushed inadvertently for approximately 1 to 2 seconds during flare. As a warning, white arrow pointing to the right was displayed in front of captain (PF) and F/O (first officer) green light was lit in front of F/O (PNF). With the F/O priority button pressed, EFCS (Electrical Flight Control System) disregarded the captain inputs to the benefit of the F/O one. During this time, as no order (neutral) was applied on F/O sidestick, aircraft elevators returned to neutral position, leading pitch attitude to be reduced by 1.5 degrees. EFCS switched back to captain sidestick when priority switch was released, and captain resumed flare and landing uneventfully." According to operator, the non-flying pilot's hand should not be on the sidestick during critical phases of flight, such as the landing flare; however, the non-flying pilot should be in a position to takeover control, if required.
The National Transportation Safety Board determines the probable cause(s) of this incident to be: The inadvertent activation of the priority pushbutton on the sidestick by the first officer resulting in a nose down pitch and loss of aircraft control during the landing flare. Full narrative available
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