CHI96FA052

According to a rear seat passenger, the airplane was flying through heavy snow, when both engines lost power. The loss of power occurred as the airplane was flying in instrument conditions at night. Subsequently, the airplane descended and was destroyed, when it collided with trees. During an examination of the airplane on December 13, 1995, ice was found in the air induction system of both engines. No other airplane or engine malfunction was found during the examination. The pilot's operating handbook stated that alternate air should be placed in the full 'on' position prior to entering known or expected icing conditions.

On December 11, 1995, at 1820 central standard time (cst), a Piper PA-23-250, N54791 was destroyed when it collided with trees and terrain. The pilot reported a loss of power on both engines to Chicago Center, prior to impact. Instrument meteorological conditions prevailed at the time of the accident. The personal 14 CFR Part 91 flight was operating on a IFR flight plan. The pilot and two passengers sustained serious injuries. One passenger received minor injuries. The flight departed from Wausau, Wisconsin en route to Tulsa, Oklahoma at 1740 cst.

The 400 foot wreckage path followed a magnetic heading of 160 degrees. All airplane components were found along the wreckage path. Due to the weather forecast for six inches of snow the evening of December 12, 1995, the airplane wreckage and cockpit were documented, and then moved from the accident location to a unheated airplane hanger. Photographs 1-4 show the wreckage as documented on December 12, 1995.

During the airplane inspection on December 13, 1995, ice was found in the air induction system of both engines. No other airplane or engine malfunction was found on December 13, 1995.

Photographs 5-8 show the air box, air filter box and air filter as removed from the right engine on December 13, 1995. Numerous pieces of ice were found in the right air box, beyond the air filter. Photographs 9 and ten show the fuel control unit and air filter for the left engine as photographed on December 13, 1995. All four impact tubes in the left fuel control unit were completely covered with ice. With the impact tubes blocked by ice, the diaphragm in the fuel control unit would not supply any fuel to the left engine's cylinders.

Both alternate air controls were found in the off position as documented on December 12, 1995, at the accident site. Both left and right air valves were found in the filtered air position on December 13, 1995. Both alternate air cockpit controls could be moved on December 13, 1995.

In a personal interview with the investigator in charge (IIC) a rear seat passenger said the airplane was flying through heavy snow, prior to the loss of power on both engines. The passenger also said that it was a very short time period between the loss of power on the left engine and the loss of power on the right engine.

The pilot's operating handbook was reviewed by the IIC and states that "On the control pedestal are two manual alternate air controls which may be used by the pilot to select alternate air if the automatic feature should fail. These should be placed in the FULL "ON" position prior to entering known or expected icing conditions."