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CIVIL AERONAUTICS BOARD
WASHINGTON, D C
Honorable N E Halaby
Administrator
Federal Aviation Agency
Washington 25, D C
Dear Mr Halaby
After investigating the accident involving Seaboard and Western Airlines L-1049D, N6503C, at Idlewild Airport on November 10, 1958, the Board recommended requirement of a mechanical low pitch stop in the Curtiss electric propeller to prevent any inadvertent reversal. Enclosed is a copy of the pertinent letter to the Director of Flight Operations and Airworthiness, dated December 19, 1958. At this time Curtiss-Wright had available a power unit assembly which provided this safety device. Subsequent correspondence from the Bureau of Flight Standards, dated February 20, 1959, indicated that an appropriate proposed airworthiness directive, which pertained to a mechanical low pitch stop, would be submitted to the industry for coordination This action did not result in an official requirement of this feature.
On May 28, 1963, Standard Airways L-1049G, N189S, crashed during approach at Manhattan, Kansas Investigation of the aircraft indicated that the No. 3 Curtiss electric propeller was inadvertently in the reverse range at one degree blade setting, the low pitch setting is 23.8 degrees. Ground inspection of the power unit revealed that the brake cage was not locked to the brake solenoid and had backed off several revolutions. Since this propeller installation did not incorporate a mechanical low pitch stop, the brake was ineffective in fixing the blades at low pitch and preventing blade angles in the reverse range. Although the aircraft burned after crashing, fortunately no fatalities were incurred by the 65 passengers; however, the potential catastrophe is readily apparent.
Several days later on June 3, 1963, Standard Airways L-1049G, N9742Z, feathered the No. 2 propeller after severe surging during cruise over Elkins, West Virginia. After safely landing at Philadelphia subsequent ground operation of the No. 2 powerplant revealed that the propeller would go into the reverse range without throttle selection. Examination of the propeller power unit disclosed that the brake cage
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