What happened
On March 10, 2018, a Learjet 60XR, registration SP-CEZ, was conducting a line training flight from Nuremberg, Germany, to Minsk, Belarus. The crew, consisting of an instructor pilot and a trainee pilot, was operating under IFR at night within the Minsk Flight Information Region (UMMV FIR).
While cruising at FL 330, the crew received instructions to descend to FL 220. As the instructor pilot initiated the descent, the trainee pilot was responsible for updating the descent parameters in the second Flight Management System (FMS2). During this process, the aircraft's speed began to decrease and the altitude increased, reaching nearly FL 350.
An Air Traffic Control Officer (ATCO) observed the deviation via S-mode transponder data and noted that the aircraft's vertical speed information had disappeared for approximately 40 seconds. The ATCO intervened to address the 300-foot altitude deviation and verified that the crew understood the original descent instruction. Following the intervention, the instructor aborted the climb and resumed the descent to FL 220, at which point vertical speed data reappeared on radar.
The investigation
The investigation focused on the discrepancy between the commanded descent and the actual climb. Air Traffic Control and the Belarusian Air Navigation Service Provider (ANSP) reviewed the radar data, initially considering whether the deviation was caused by a momentary transponder malfunction. However, an internal analysis by the aircraft operator specifically reviewed the trainee pilot's performance during the flight.
Findings
- The primary cause of the deviation was the incorrect setting of the aircraft vertical speed value in the FMS, where the trainee pilot entered a climb command instead of a descent command.
- A contributing factor was the inappropriate supervision of the trainee pilot's actions by the instructor during the FMS programming phase.
Safety action
Following the incident, the operator's Director of Flight Operations conducted a review of the event with the involved crew members.