What happened
On January 30, 2015, a Bombardier DHC-8-400 operating within the Warsaw TMA (EPWA) experienced an altitude deviation during its approach to landing. The aircraft was cleared by air traffic control to descend to an altitude of 3,000 feet. However, after performing a turn to intercept the ILS 11 localizer, the aircraft descended to 2,500 feet, deviating from the authorized altitude by more than 300 feet.
Following this deviation, air traffic control issued instructions for the aircraft to climb back to 3,000 feet. Once the correct altitude was regained, the remainder of the approach proceeded normally following the ILS guidance.
The investigation
The PKBWL investigation focused on the sequence of events leading to the altitude excursion and the cockpit actions during the transition to the ILS intercept. The investigation examined the flight path and the crew's adherence to altitude constraints provided by the controller.
Findings
- The investigation established that the primary cause of the incident was the crew's failure to engage the ALT SEL (altitude select) button.
- This omission prevented the aircraft from capturing and maintaining the previously set target altitude of 3,000 feet during the maneuver.