What happened
On 12 November 2020, a BN2T-4S Islander, registration G-CGTC, was conducting emergency services operations near City of Derry Airport. While climbing to 7,000 ft amsl, the aircraft entered cloud conditions. The pilot, who had previously decided to fly below the 0°C isotherm to avoid icing, noticed a reduction in propeller torque and airspeed. Shortly after, the left engine flamed out, followed by the right engine.
Following the dual engine failure, the pilot established a glide descent toward Eglinton. During the descent, the right engine was successfully restarted at approximately 2,100 ft amsl. The left engine required multiple attempts before it also restarted at roughly 800 ft agl. Despite the loss of primary electrical services and navigation displays, the crew used an iPad to navigate toward the closed airfield. The aircraft performed a powered landing on the unlit runway at Eglinton with no injuries to the crew or passengers.
The investigation
The AAIB examined the aircraft's engines, fuel systems, and anti-ice components. Forensic analysis of the fuel and filters showed no contamination. While the engines showed typical wear and minor corrosion, no mechanical defects were found that could have caused the flameout. The investigation also reviewed the pilot's recent flying experience, the meteorological conditions, and the operator's safety protocols.
Findings
- The primary cause of the engine failures was likely ice accumulation in the engine intake ducts, which choked the airflow to the engines.
- It is probable that the engine anti-icing system was not activated before the aircraft entered the cloud.
- The pilot's recent experience in icing conditions was limited, which may have contributed to the oversight.
- Personal stressors and disrupted sleep patterns related to the pilot's contractual situation may have impacted performance.
- The aircraft's terrain awareness database was significantly out of date.
Safety action
- The operator implemented standardized icing condition briefings and checklists.
- New procedures were introduced for communicating altitude and temperature changes during flight.
- The operator enhanced communications regarding mental wellbeing and access to aviation-focused peer support programs.
- Funding was secured to update the TAWS database for the aircraft.