United Airlines Flight 624
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 A DC-6 similar to UAL's ill-fated Flight 624 |
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| Summary | |
|---|---|
| Date | June 17, 1948 |
| Type | Inflight Fire |
| Site | Mount Carmel, Pennsylvania |
| Fatalities | 43 |
| Injuries | 0 |
| Aircraft | |
| Aircraft type | Douglas DC-6 |
| Operator | United Airlines |
| Tail number | NC37506 |
| Passengers | 39 |
| Crew | 4 |
| Survivors | 0 |
United Airlines Flight 624, a DC-6 (NC37506), originated in San Diego, California with stops in Los Angeles and Chicago enroute to LaGuardia Airport in New York City. The four-engine propeller-driven passenger airliner crashed at 1:41 P.M. Eastern Daylight Time on June 17, 1948 at Mount Carmel, Pennsylvania, killing all 4 crew members and 39 passengers on board.[1]
Contents |
[edit] Background
The Douglas DC-6 fleet had been grounded by Civil Aviation authorities for four months during the previous winter as a result of the fatal crash of United Airlines Flight 608 on October 24, 1947. It was determined that that crash had been caused by a design flaw that allowed vented fuel to be drawn into the heater air intake scoop that caused a fire in the cargo compartment. As a result, changes were made and a fire extinguisher system was installed on all DC-6 aircraft, including the accident aircraft.[citation needed]
[edit] Accident sequence
Flight 624 had just completed a routine initial descent as part of its approach into the New York area, when the forward cargo hold fire indicator light illuminated, leading the flight crew to believe there was a fire in that cargo hold. Although this later turned out to be a false alarm, the crew decided to discharge CO2 bottles into the forward cargo hold, to try to extinguish the possible fire. While proper operating procedure called for opening the cabin pressure relief valves prior to discharging the CO2 bottles, to allow for venting of the CO2 gas buildup in the cabin and cockpit, there was no evidence the crew opened the relief valves. Consequently, the released CO2 gas seeped back into the cockpit from the front cargo hold and apparently partially incapacitated the flight crew. The crew then put the aircraft into an emergency descent, and as it descended lower it hit a high voltage power line, bursting into flames, then smashing through the trees of a wooded hillside.[1]
[edit] Famous victims
Among the passengers were Broadway theatre impresario Earl Carroll, and his girlfriend, actress Beryl Wallace, Henry L. Jackson, men's fashion editor of Collier's Weekly magazine, and Venita Varden Oakie, the former wife of actor Jack Oakie.[citation needed]
[edit] Investigation and final report
The Civil Aeronautics Board investigated the crash and published a narrative describing the following sequence of events in its final report:[1]
The airplane, named "Mainliner Utah", arrived in Chicago at 09:52 en route from Los Angeles to New York. After a 52-minute turnaround, the DC-6 departed for New York. The airplane climbed en route to its planned altitude of 17,000 feet. At 12:23, and at 12:27 the crew made a routine acknowledgment of a clearance to descend en route to an altitude between 13,000 and 11,000 feet. A little later a fire warning led the crew to believe that a fire had erupted in the forward cargo hold. They then discharged at least one bank of the CO2 fire extinguisher bottles in the forward cargo hold. Because they did not follow the correct procedure, the cabin pressure relief valves were closed. This caused hazardous concentrations of the gas to enter into the cockpit. These concentrations reduced the pilots to a state of confused consciousness probably resulting in loss of consciousness. An emergency descent was initiated until it described a shallow left turn, heading towards constantly rising terrain. Five miles east of Shamokin the airplane, flying only 200 feet above the ground, entered a right climbing turn. As it passed to the north of Mt. Carmel, the climbing turning attitude increased sharply. The airplane then crashed in a power line clearing on wooded hillside at an elevation of 1,649 feet. The airplane struck a 66,000 volt transformer, severed power lines and burst into flames. Investigation revealed that the fire warning in the cargo compartment had been false.
The CAB concluded with the following probable cause for the accident: "The Board determines that the probable cause of this accident was the incapacitation of the crew by a concentration of CO2 gas in the cockpit."
[edit] Note
United now uses the 624 designation to refer to a Chicago-DC route.[citation needed]
