Incident Description
During the landing flare at approximately 10 feet above ground level, the aircraft pitched nose down while the captain applied aft sidestick force. The rate of nose descent appeared commanded and extremely smooth. The first officer briefly considered whether he had accidentally bumped his sidestick but concluded that was unlikely. The captain completed the landing with the main landing gear touching down first, and the captain's sidestick was again responsive. The entire event lasted no longer than two seconds. No electronic centralized aircraft monitor (ECAM) warnings or other indications were observed by the flight crew.
Flight Data Recorder Analysis
Review of digital flight data recorder (DFDR) data revealed that the captain's (left) sidestick was inoperative for approximately one second during the landing flare. During that period, the first officer's (right) sidestick pitch was in the neutral position. Less than one second after the captain's sidestick became inoperative, both sidestick pitch positions moved to approximately 14–16 degrees aft. Pitch data showed a decrease of approximately 2 degrees during the event.
Manufacturer Analysis
According to the airframe manufacturer, the captain was the pilot flying (PF) and the first officer was the pilot non-flying (PNF). Manual approach and flare input from the PF were nominal. However, it appeared that the PNF take-over and priority pushbutton was pushed inadvertently for approximately one to two seconds during the flare. As a warning, a white arrow pointing to the right was displayed in front of the captain, and the first officer's green light was illuminated. With the first officer's priority button pressed, the Electrical Flight Control System (EFCS) disregarded the captain's inputs in favor of the first officer's. Since no order (neutral) was applied on the first officer's sidestick, the aircraft elevators returned to neutral, reducing pitch attitude by 1.5 degrees. When the priority switch was released, EFCS switched back to the captain's sidestick, and the captain resumed the flare and landing uneventfully.
Operator Policy
According to the 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 positioned to take over control if required.