What happened
The flight began after the aircraft was deiced in a heated hangar, removing accumulated snow. Departure occurred during blowing snow conditions with a forecast for occasional moderate icing up to 20,000 feet. The pilot reported that the snowfall lasted only five to ten minutes and that only a trace of ice, less than one-sixteenth of an inch, accumulated during the first fifteen minutes of flight. No further ice accumulation was observed.
Approximately forty-five minutes after takeoff, while cruising in instrument meteorological conditions conducive to induction system icing, the engine suddenly lost power and would not restart. The pilot descended toward an airport in IMC to approximately 400 feet above ground level but executed a wheels-up landing because he could not see the airport.
The investigation
The pilot attributed the loss of power to blockage of the air induction filter. The induction system was equipped with a spring-loaded door intended to open automatically and allow heated alternate air to flow to the engine if the filter became blocked. Piper indicated that opening in icing conditions could cause ice to accumulate in the fuel injection system, resulting in loss of power.
Findings
Contributing factors included the Piper PA-24 operating in icing conditions and the design limitation of the automatic alternate air door. To address this issue, Piper Service Bulletin No: 861 was issued on May 4, 1987, for the installation of an improved manually operated alternate air system on fuel-injected PA-24-260 aircraft.
Safety message
Pilots operating fuel-injected aircraft in icing conditions should be aware that automatic induction heating systems may contribute to ice accumulation in the fuel injection system rather than preventing it. Adherence to manufacturer service bulletins regarding manual alternate air systems is critical for safety.