What happened
On February 5, 2020, an AT-3 R100, registration SP-CLB, was conducting a flight training mission departing from Mielec (EPML) toward Dęblin (EPCD). The flight was part of a professional pilot training program operated by ATO PWSZ in Chełm.
During the taxi phase, the crew kept the engine cooling and oil radiator flaps closed to accelerate oil temperature rise. While waiting for takeoff clearance, the crew was preoccupied with continuous audio alerts regarding low oil temperature. Due to time pressure from the approaching sunset and the impending closure of the destination aerodrome, the crew performed an immediate takeoff after receiving clearance.
As the aircraft departed the traffic pattern, the instructor noticed audio warnings regarding coolant temperatures. Upon checking the engine monitor (MPV-50), the crew discovered the device was still displaying the "welcome" screen, which does not show cylinder head temperatures (CHT) or exhaust gas temperatures (EGT). Once the screen was switched to the operational page, the crew observed that the CHT had reached 154ºC, exceeding the allowable limit. Although the crew opened the cooling flaps, which stabilized the CHT, they noticed a steady drop in oil temperature despite the oil radiator flaps remaining closed. The crew subsequently decided to return to Mielec and landed safely without further incident.
The investigation
The investigation established that the crew failed to complete all items on the required pre-flight checklist. Specifically, the engine cooling air intake flaps were not moved to the open position before takeoff. Furthermore, the crew did not exit the engine monitor's startup screen, which deprived them of real-time CHT information during the initial climb.
The investigation also examined the cockpit environment, noting that the engine monitor's audio alert system frequently triggers both minor and critical warnings (such as low oil temperature during engine start) using the same sound. This high volume of non-critical alerts can lead to pilot desensitization and may obscure more critical information during high-workload phases of flight.
Findings
- Failure to perform all checklist items, specifically neglecting to open the engine cooling air intake flaps before takeoff.
- The engine monitor was left on the startup screen, preventing the crew from monitoring CHT and EGT.
- The presence of frequent, non-critical audio alerts contributed to a lack of situational awareness regarding the rising temperatures.
- Time pressure related to sunset and airport operating hours influenced the crew's decision-making during taxiing.