What happened
On July 8, 2015, during the takeoff roll at EPPO airport, the crew of a Bombardier DHC-8-400 operated by PLL LOT observed several warning indications, specifically PITCH TRIM, ELEVATOR FEEL, and PROP DEICE. The crew immediately aborted the takeoff during the initial phase of the roll. The pilot suspected that the malfunctions might have been caused by atmospheric discharges from a nighttime thunderstorm occurring over the airport, which potentially impacted the Air Data System (ADS).
Following the incident, maintenance personnel drained the moisture from the Primary Pitot/Static Line and performed operational tests on the ADS. When these actions failed to resolve the issue, the decision was made to ferry the aircraft to EPWA. During a subsequent maintenance flight on July 9, 2015, the crew noted discrepancies in airspeed and altitude readings between PFD1 and PFD2, prompting another return to EPPO.
The investigation
The investigation focused on the repeated failures of the aircraft's flight instrumentation and the effectiveness of the maintenance interventions. After the second incident, technicians replaced the left pitot probe and conducted further ADS operational tests. The aircraft was then ferried to EPWA. Upon arrival at EPWA, maintenance crews performed leak tests on the static pressure system, which revealed a leak in the number 2 static system. This leak was subsequently repaired by sealing the left static pressure probe.
Findings
- The primary cause of the initial incident was a malfunction of the left pitot probe (LH PITOT PROBE).
- A secondary contributing factor was a leak identified within the Air Data System (ADS) static pressure lines.