What happened
During an ILS approach, the N500AK, an aircraft type, encountered icing conditions while in flight. Radar monitoring indicated that the aircraft experienced a reduction in speed prior to reaching the outer marker, a pattern consistent with a loss or reduction of engine power. Following this deceleration, the aircraft entered a steep descent and crashed.
Post-accident investigations confirmed that the engines were not functioning at the time of impact and that the propellers had been feathered. There was no evidence of mechanical failure regarding the engines, propellers, or the anti-ice system prior to the crash. However, indicators for the engine inlet anti-ice system and the stability augmentation system (SAS) fault warning were illuminated during the impact.
Findings
Investigation into the engine manufacturer's data revealed that similar flameout events had been documented in other aircraft operating in icing conditions, occasionally occurring after descending into warmer air. The flight manual provided specific procedures for managing icing if the anti-ice system was inactive, including the use of continuous ignition and the sequential activation of engine and propeller heat. All four fatalities occurred during the accident.