Page:CAB Accident Report, Pennsylvania-Central Airlines Flight 143.pdf/24

 a test was conducted to determine the effect of a single large obstruction in the cold air duct. A similar engine was run up at 28 inches of manifold pressure and 2150 r.p.m. with the propeller in the full-low pitch position, which were the power and the propeller setting used by Captain Wright when he ran up his engine at Charleston. In the test a board was placed across the cold air duct so that it blocked off approximately half of the air intake area. The area blocked off was then increased in stages of 10 per cent. No abnormal functioning of the engine was noticed until 95 per cent of the total air intake area had been blocked off, at which time the manifold pressure and engine r.p.m. dropped to 25 inches and 1800, respectively, but the engine then continued to operate normally at this manifold pressure and r.p.m. The possibility of carburetor icing was also considered. The engine lost power in a comparatively short time without the gradual loss of power which characterizes the presence of carburetor ice. Since the temperature was 81 and the dew point 49, and since the other engine functioned normally under the same conditions, the presence of carburetor ice is quite improbable.

On the basis of all of the evidence, the tear-down inspection of the engine, and the inspections and tests with respect to the fuel and air intake systems, the Board is unable to determine the reason for the stopping of the right engine of NC 13359.