Page:CAB Accident Report, United Air Lines Flight 823.pdf/7

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The aircraft was equipped with a Lockheed Aircraft Service model 109C flight recorder, serial No. 578. The recorder was installed in the electrical compartment below the cabin floor at fuselage station (FS) 389. The recorder shell was crushed to one-half its original diameter and had separated due to shear loads. The contents were exposed to fire which destroyed the aluminum recording tape. No usable information was available. This is the first instance of the destruction, by fire, of recording tape in a Lockheed recorder.

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The aircraft struck on a 45-degree, heavily wooded slope at an elevation of approximately 1,400 feet m.s.l. The heading on impact was 135 degrees, the nose was approximately 55 degrees below the horizon, and the bank angle was about 45 degrees left wing down. The wreckage, except the No. 9 emergency window and some small pieces from the cabin interior, was contained in an area 300 feet long and 200 feet wide.

A 1/2 to 3/4 mile wide ground search was conducted for 5-1/2 miles back along the flightpath from the impact site. The No. 9 emergency window, scraps of cloth from the cabin interior, an emergency exit placard, and parts of a window seal were located 2,320 feet, on a magnetic bearing of 035 degrees, from the primary wreckage site. The cabin material was scattered over an area which extended about 600 feet from the window. The free-fall victim was located 8,400 feet, on a magnetic bearing of 030 degrees, from the primary wreckage site. A cigarette lighter with a clear plastic fuel reservoir 7/8 full was found near the body. No other material from the aircraft was found along the flight path.

The aircraft wreckage was fragmented and severe ground fires burned for several hours after the accident. All major components were accounted for at the accident scene and there was no evidence of pre-impact structural failure. The landing gear and flaps were retracted. The primary flight control trim settings were: aileron, one degree right wing down; elevator, one degree nose down; and rudder, 3/4 degree, nose right.

The engines were rotating with the propeller blade angles in the flight range at the time of impact. The powerplants revealed no evidence to suggest failure or maloperation.

The hydraulic and electrical systems components, including lines and wiring respectively, were extensively damaged by impact and, in part, destroyed by fire. However, an examination of the pieces that were recovered did not reveal any evidence of system failure or malfunction. One electrically operated fuel boost pump and the NESA inverter showed rotational damage.

The flight control system utilizes push-pull rods beneath the cabin floor, located to the left of the fuselage centerline. Except for terminal ends and some steel sections, these rods are made of aluminum. Parts of the aluminum material were destroyed by fire.