United Airlines Flight 823

United Airlines Flight 823 was a scheduled flight from Philadelphia International Airport, Pennsylvania to Huntsville International Airport, Alabama with 39 on board. On July 9, 1964 at approximately 18:15 EST, the aircraft, a Vickers Viscount 745D, registration N7405,[2] crashed 2.25 mi (3.62 km) northeast of Parrottsville, Tennessee after experiencing an uncontrollable fire on board, killing all 39.[1]^:3 The fire of unknown origin occurred in the passenger cabin.[1]^:14-15 One passenger abandoned the aircraft through the No.4 escape window prior to impact but did not survive the free-fall. "The Board is unable to identify the source of fuel, the ignition point of the fire, or the cause of the final manoeuvre."[1]^:15 The Probable Cause finding was "The Board determines that the probable cause of this accident was an uncontrollable in-flight fire, of undetermined origin, in the fuselage, which resulted in a loss of control of the aircraft."[1]^:15

United Airlines Flight 823

The aircraft involved, at Chicago O'Hare International Airport in 1963
Accident
Date	July 9, 1964 (1964-07-09)
Summary	In-flight fire for reasons unknown, loss of control
Site	Cocke County, near Parrottsville, Tennessee, United States 36°1′36.51″N 83°3′41.19″W
Aircraft
Aircraft type	Vickers Viscount 745D
Operator	United Airlines
Registration	N7405[1]
Flight origin	Philadelphia International Airport
Stopover	Washington-National Airport
Last stopover	Knoxville-McGhee Tyson Airport
Destination	Huntsville International Airport
Occupants	39
Passengers	35
Crew	4
Fatalities	39
Survivors	0

Approximately 33,000 lbs. of the 40,000 lb. (empty weight) airliner were recovered, with much of the missing weight attributable to cabin furnishings that were destroyed by fire. The wreckage was transported to the Naval Laboratory in Washington, D.C. where the Vickers was reconstructed by the Civil Aeronautics Board .[3]

The accident triggered an investigation of the Lockheed L-109C Flight Data Recorder which resulted in modifications of that device and revision of the standards for all recorders. Also addressed were potential problems with the Pyrene Duo Head Model DCD-10 for the underfloor baggage and heater compartments. There was an Airworthiness Directive issued. Revisions were made to the Pilot's Manual, Viscount Maintenance and Instruction, and Accessories Manuals.[1]^{:(Attachments 1-2)}

United used the Flight 823 designation on its Washington-Dulles to Mexico City, Mexico route.