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The height of the glide slope is 222.4 feet above field elevation at the middle marker, and 109.3 feet at the initial impact point.
The first ground contact was with the left wing tip and No. 1 propeller at a point 350 feet left of the conterline and approximately 1,900 feet from the thresold center of runway 28R. The aircraft slid an additional 800 feet where it came to rest on the east side of runway 1R and to the south edge of runway 28L. Ground impact damage to the fuselage was confined to the underside from the node aft to about fuselage station 1000.
Orange paint smears, similar in color to that appearing on the approach light structure, were present in a puncture area at the mispan of the right horizontal stabilizer and on the nose gear shock strut.
The investigation revealed no evidence of failure in the propellers or engin. The propeller impact blade angles were a minimum of 15 degrees positive on Nos. 1, 2, and 3 propellers. The No. 4 propeller had a minimum impact blade angle of 21 degrees positive. The Nos. 1, 2, 3, and 4 propeller governors had engine r.p.m. : settings of 2393, 2507, 2375, and 2364, respectively. The flight engineer's testimony reflected normal operation of the propellers and engines prior to initial impact with the approach light structure.
The nose gear assembly was found in the down and locked position, but the entire assembly had been forced rearward, as a unit, into the fuselage. The upper drag struts were found penetrating the flight deck flooring near the flight engineer's station. Flight control, trim tab, and engins control cables in this area were found either severed or pinched. Hydraulic lines in the same area were seveby the penetration, and evidence of intense areing was found at the nose gear well-electrical junction box. Both tires of the nose gear assembly were out and torn. The nose gear sliding door was located in the water at the base of the No. 3 approach light station, which is 270 feet from the runway threshold.
The entire left main landing gear assembly was found separated from the aircraft. However, the tires remained inflated and received no extensive cutting. The right main landing gear assembly had collapsed rearward, causing the tires to protrude through the upper wing surface. Impact damage was confined to the tires which were coverely gashed. Both main gear downlock mechanisms indicated the gear were extended and locked at initial impact.
The flaps were found in the approach or 66 percent setting with no indication of an asymmetrical condition.
The flight engineer testified that during the approach, he heard the copilot tell the pilot that "... he was right on." He also recalled the copilot saying that lights were in sight to the right and that he believed the captain made a slight correction to the right as a result of the statement. The flight engineer stated further that the throttles were retarded and he thought the airplane was in good position to land just bedore he felt the initial impact.
The San Francisco International Airport was below landing weather minimums several hours prior to the accident because of ground fog. The first approach talk 28R was commenced at 1140 following weather improvement. The aircraft, a Lockheed Electra, abandoned its approach to runway 28R at 1152 due to fog, circled the field
