Crash of a Swearingen SA227TT Merlin IIIC in Bristol: 4 killed

N500AK encountered icing in flight before start of ILS approach. Radar data showed that before reaching outer marker, it slowed in a manner that was consistent with a power reduction (or partial loss of power), then it entered a steep descent and crashed. Examination revealed engines were not operating at impact and that propellers had been feathered. No preimpact part failure or malfunction of engines, propellers or anti-ice system was found. There was evidence that engine inlet anti-ice annunciator lights and stability augmentation system (SAS) fault warning light were illuminated during impact. The engine manufacturer reported that flameouts had occurred in other aircraft, during or following operation in icing conditions, sometimes after descent into warmer air. Flight manual noted that if icing was encountered with anti-ice system off, select continuous ignition and then select engine and propeller heat (1 engine at a time, ensuring first engine was operating satisfactorily before selecting second engine) and engage sas heat. All four occupants were killed.