Page:CAB Accident Report, Western Air Lines Flight 221.pdf/8

 Initial propeller slash marks from the No. 2 engine were found on the runway starting at a point 5,489 feet beyond the displaced threshold, or approximately 59 feet beyond the tire marks left by the left main landing gear. These slash marks continued for a distance of 48-1/2 feet. The impact point of the No. 2 engine propeller and nose case was approximately 11 feet beyond the last slash mark made by this propeller. These components were found on the runway 850 feet beyond this point.

Propeller slash marks from the No. 1 engine started from a point 5,522 feet beyond the displaced threshold and continued for approximately 114-1/2 feet.

There was no evidence that any part of the aircraft other than the Nos. 1 and 2 propellers and both main landing gears made contact with the runway.

The aircraft's ground speed at impact was computed from the measured distance between propeller slash marks. To preclude any error due to the possible slowing of the propeller r.p.m. between the first and last propeller marks, only the measured distance between the first three clash marks of each propeller was used. Ground speed obtained from the computations taken from the No. 2 propeller slash marks was 126.3 knots. The No. 1 propeller marks indicate a ground speed of 127.4 knots.

The aircraft's longitudinal attitude at impact could not be determined, However, with minimum contact of the No. 2 engine propeller on the runway, the geometrical dimensions of the DC-68 aircraft are such that a maximum noseup attitude of approximately five degrees could be obtained without the tail skid making contact with the runway. Propeller contact with the runway as occurred could not have been obtained with the main landing gear in the fully extended and locked position without prior structural damage to the gear.

A lateral attitude at impact of approximately six degrees left wing down, was computed by comparing the relationship between the propeller tip path planes of the No. 1 and 2 propellers, with respect to the seven-degree dihedral of the wing.

The computed landing gross weight of the aircraft at Los Angeles was 79,993 pounds with a c.g. of 21.9 percent Mean Aerodynamic Chord. Both within operating limitations.

Aircraft performance, as outlined in the DC-6B performance curve, was examined by the Board to determine the climb characteristics of the DC-6B in a similar configuration to N93131 at the time of the go-around. It was shown that at a gross weight of 80,000 pounds at sea-level on a standard day, flaps extender 50 degrees, landing gear down, takeoff power on all four engines (2700 r.p.m. 200 BMEP), and an indicated airspeed of 100 knots, a 725 feet/minute rate of climb could be expected.

Testimony concerning the DC-6B performance and acceleration characteristics in various configurations was obtained from the chief pilot of the Douglas Aircraft Corporation. It was stated that with takeoff power and the aircraft in a go-around configuration, as outlined above, the level flight acceleration would