Overview
On 29 November 2015, a Bombardier DHC-8-Q400 aircraft experienced an incident during takeoff at Warsaw Chopin Airport (EPWA). The crew rejected the takeoff after receiving a 'PITCH TRIM' message. The aircraft was carrying 43 occupants, none of whom were injured. This was the fourth such event reported via an Air Safety Report (ASR); three previous incidents occurred on 23 October (two events) and 24 October 2015.
Event Details
During the takeoff roll, at a speed of 70 knots, the 'PITCH TRIM' caution message appeared. The crew immediately rejected the takeoff and returned to the parking stand. The flying pilot (first officer) did not confirm use of the trim during the takeoff, suggesting inadvertent activation. The captain also reported no irregularities. The crew's decision to abort the takeoff was deemed correct.
Investigation
After the event, maintenance personnel performed an inspection and necessary checks according to task cards. No mechanical fault was found. An analysis of the flight data indicated that at the time the caution activated, the control wheel was deflected to the left, but the pilots did not confirm any need for a crosswind takeoff technique. The onboard computer error codes were read and revealed that the cause was activation of one half of the elevator trim switch on the control wheel. Technical faults with the Air Data Computer (ADC), Flight Control and Engine Computer (FCECU), or the trim actuator were ruled out.
Cause
The investigation determined the probable cause to be the use of one half of the elevator trim switch on the control wheel.
Preventive Measures
Following the earlier incidents, a bulletin article was published in Issue No. 7 of the Q400 fleet bulletin. Additionally, instructors were advised to remind pilots during pre-simulator briefings to pay attention to elevator trim position and the potential for inadvertent activation of the warning when one half of the switch is moved. The investigation committee did not issue any safety recommendations.