Page:CAB Accident Report, Northwest Airlines Flight 5.pdf/8



The fuselage of the airplane was completely burned back to the leading edge of the stabilizer and the wing butts were partially melted. The leading edge of the left wing and the de-icer boot were burned and melted and the fabric had been burned off the left aileron but the aileron hinges and controls appeared to be in operating condition. While the outboard section of the right wing had not been burned, the leading edge had been damaged from the wing tip section to a point about 6 feet in toward the fuselage (apparently caused by striking trees). The right aileron was intact and undamaged and the controls appeared to be in operating condition. The flaps were in the up position and the landing gear was retracted. The tail assembly was only slightly damaged.

While the fire had destroyed most of the cockpit instruments and controls, it was possible to determine the settings or indications of some of them. The throttles wore in closed position, the mixture controls at cruising position, the right propeller pitch control in the 2050 r.p.m. position, and the left in the 2450 r.p.m. position. The pilot's air-speed indicator showed 83 to 85 m.p.h. and the dial reading of the directional gyro was 220 degrees. Both cockpit clocks were damaged and burned but it was possible to determine that they both had stopped about 2:04 a.m. The propeller de-icer gauge and valve and the de-icer valve for the wings and stabilizer were completely burned and melted so that it was impossible to determine their settings.

The left engine rested on its nose in front of the engine mount with all cylinder heads in the rear bank completely destroyed by fire. The propeller was attached with one blade melted off about 8 inches from the hub, another blade was bent and the tip melted, and the third blade was bent in approximately a 75-degree curve and was twisted.

The right propeller and the nose section of the right engine had broken off and remained at the point at which the airplane had struck the bank of the ravine and at the time the airplane came to rest the remainder of the right engine apparently broke free from the engine mount and nacelle and rolled approximately 15 feet forward of the nose of the airplane.

After examination at the scene of the wreckage, the engines and propellers were removed to Northwest's shops at St. Paul, Minnesota, where they were disassembled and inspected by Mr. Earl L. Smith, Air Safety Investigator for the Civil Aeronautics Board, Mr. Ralph E. Geror, Superintendent of Maintenance for Northwest, Mr. R. Paul O'Neal, Service Representative for United Aircraft Service Corporation, and Mr. Chester M. Brown, Propeller Division Superintendent for Northwest. The examination and inspection revealed very little evidence which would indicate whether the engines were producing power at the time of impact, but nothing was found which would indicate any failure or malfunctioning of either engine prior to the accident. The left engine was so badly damaged by fire that it was impossible to determine whether it had been operating at the time of the accident. With respect to the right engine, the condition of the reduction gear splines and of the propeller governor, and a sheared generator, indicated that the propeller was rotating at the time of impact. Whether this rotation was under power, or merely windmilling, could not be determined from the inspection of the engine.

Damage to the gear segments, blade bushings and rotating cams of the propellers, and spider arms bent from 0.002" to 0.010" out of their planes, indicated that breakage had occurred as a result of sudden stoppage of rotation.