Accident at Parrottsville, Tennessee, 9 Jul 1964

Accident narrative

On July 9, 1964, United Air Lines Flight 823, a Vickers Viscount 745D, crashed approximately 2-1/4 miles northeast of Parrottsville, Tennessee, at 1815 e.s.t. All 34 passengers and four crewmembers aboard the aircraft at the time of the crash were killed. One additional passenger died of impact injuries following a free fall from the aircraft before the crash. The aircraft was destroyed by impact and fire.

**The flight** Flight 823 was a regularly scheduled domestic flight from Philadelphia, Pennsylvania, to Huntsville, Alabama, with intermediate stops at Washington, D.C., and Knoxville, Tennessee. The flight departed Washington at 1636 with 35 passengers and a crew of four. The crew consisted of Captain Oliver E. Sabatke, First Officer Charles L. Young, and Stewardesses Carole L. Berndt and Virginia K. Vollmer.

The aircraft had no known discrepancies when it departed Washington, and the flight operated without reported difficulties during its initial segment.

**The sequence of events** At 1758:35, the crew reported to the Atlanta Air Route Traffic Control Center that they were passing the Holston Mountain VOR. Approximately one minute later, the crew requested a clearance to descend to the lowest available altitude and were cleared to 8,000 feet. At 1802:45, the crew canceled their Instrument Flight Rules (IFR) clearance. The controller offered to pass control of the flight to Knoxville Approach Control when they were closer, and at 1802:55 the crew responded "OK." This was the last known transmission from the aircraft.

Radar contact was lost at 1813:30. Ground witnesses observed the aircraft flying at an estimated 200 to 500 feet above the ground, generally parallel to but south of its airway. A witness about 11 miles northeast of the crash site noted a violet red light burning on the fuselage. Further along the flightpath, witnesses saw smoke of varying density coming from the aircraft.

About two miles from the crash site, witnesses observed black smoke coming from the fuselage near the wings. A large black object, later identified as a passenger, was seen falling away from the aircraft, followed by dense black smoke. A short time later, a bright object, later identified as the left No. 9 emergency cabin window, fell from the aircraft. The aircraft was then observed to nose up, the left wing went down, and the aircraft dived into a rocky wooded hillside, where it exploded and burned.

**What the investigation found** The main wreckage was contained in an area 300 feet long and 200 feet wide. However, a ground search back along the flightpath located the No. 9 emergency window, scraps of cabin interior cloth, and an emergency exit placard 2,320 feet from the primary wreckage site. The free-fall victim was located 8,400 feet from the main site.

The aircraft's flight recorder was recovered, but the recording tape was destroyed by fire. The Board noted this was the first recorded instance of the destruction by fire of recording tape in a Lockheed recorder.

Examination of the wreckage revealed no evidence of pre-impact structural failure, and the powerplants showed no evidence of failure or maloperation. The landing gear and flaps were retracted.

The Board found conclusive evidence of an inflight fire in the passenger cabin. The free-fall victim had received burns before death, and his clothing was impregnated with soot. Fire-damaged passenger cabin material was found remotely from the primary impact area. The investigation noted evidence that firefighting and smoke evacuation procedures had been carried out by the crew. One cabin carbon dioxide fire extinguisher had been discharged, a cabin water extinguisher had been prepared for discharge, and a flight crew walk-around oxygen bottle was found with its valve open. The cabin outflow valves were in the manually depressurized position, and the supercharger spill valve actuators were set to dump air overboard.

Extensive fire damage was also found in the electrical bay beneath the cabin floor, but the Board could not establish this as the origin of the fire. Tests on carbon deposits from the free-fall items and underfloor wreckage identified the soot as the product of incomplete combustion of saturated aliphatic hydrocarbons, such as kerosene, hydraulic fluid, or lighter fluid. Kerosene engine fuel and hydraulic fluid were aboard in quantity, but the Board was unable to identify the source of the fuel or the ignition point.

The Board noted that the final maneuver and crash indicated the aircraft was not under the crew's control. The Board advanced several hypotheses for this loss of control—including pilot distraction, failure of flight control rods due to fire damage, pilot incapacitation by heat or smoke, a load shift from passengers moving aft, or an overt act—but found no probative evidence to determine the cause of the final maneuver.

**Probable cause** The Board determined that "the probable cause of this accident was an uncontrollable inflight fire of undetermined origin, in the fuselage, which resulted in a loss of control of the aircraft."