1948 — June 17, United Air #624 CO2 in cockpit/crash ~Mount Carmel ~Shamokin, PA–43

Compiled by Wayne Blanchard Sep 24, 2023 for upload to: http://www.usdeadlyevents.com/

–43  Aviation Safety Network. Accident Description. United Air Lines Flight 624, 17 Jun 1948

–43  CAB. AIR. United Air Lines, Inc., Near Mt. Carmel, Pennsylvania, June 17, 1948.

–43  Eckert. “Fatal commercial air transport crashes, 1924-1981.” AJFM&P, 3/1, Mar 1982, p53.

–43  Haine, Edgar A. Disaster in the Air. New York: Cornwall Books, 2000, pp. 242-247.

–43  Nat. Fire Protection Assoc. “Large Loss Fires of 1948.” Quarterly, 42/3, Jan 1949, 196.[1]

–43  Pottstown Mercury, PA. “Boyertown Couple, 41 Others Die in Plane Crash.” 6-18-1948, 1

–43  Syracuse Herald Journal, NY. “Dead Listed In Air Crash.” 6-18-1948, p. 16.

Narrative Information

Civil Aeronautics Board Accident Investigation Report:

“The Accident

“United Air Lines Flight 624, a DC-6 airplane, NC-37506, en route from Chicago, Ill, to New York, N. Y., crashed three miles east-northeast of Mt. Carmel, Pa., at 1241, 1 June 17, 1948. All 43 occupants were killed and the air plane was destroyed.

“History of the Flight

“The airplane arrived in Chicago, Illinois, at 0952, June 17, 1948, en route from Los Angeles, California, to New York City…The flight departed for New York with a new crew at 1044. Aboard were 39 passengers, a crew of four….A routine report was made over Phillipsburg, Pennsylvania, approximately 500 miles east of Chicago, at 1223, and at 1227 the crew made a routine acknowledgment of a clearance to descent en route to an altitude between 13,000 and 11,000 feet. Four minutes later, at 1231, the company radio operator at LaGuardia Field heard a voice which did not identify itself calling loudly and urgently. Another United crew in a DC-3, flying over the same route behind Flight 624 and at a different altitude, heard what they termed screaming voices calling “New York.” Then, after an unintelligible transmission, This is an emergency descent.” Inasmuch as all other air carrier flights in the vicinity at this time were accounted for, this transmission undoubtedly emanated from Flight 624.

“The airplane was first observed by ground witnesses 31 miles northwest of the scene of the accident flying a southeasterly heading toward Shamokin, Pa. The airplane flew over the Sunbury Airport, Sunbury, Pa., at approximately 4,000 feet above the ground on a southeasterly heading. Immediately north of Shamokin the airplane, then only 500 to 1,000 feet above the ground, described a shallow left turn. The course was toward constantly rising terrain, the hills around Sunbury being 900 feet in elevation and the hills around Shamokin being approximately 1,600 feet in elevation. Five miles east or beyond 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 struck a hillside at an elevation of 1,649 feet. Within ten miles of the flight path and the scene of the crash there were areas on which an emergency landing could have been made.

“Investigation

“NC-37506 crashed approximately three miles east-northeast of Mt Carmel, Pa., in a power line clearing on wooded mountainous terrain. The airplane struck a 66,000 volt transformer and severed power lines. The time at which this occurred was automatically recorded at the Culpment, Pa. steam electric station at 1241.

“An explosion just after impact scattered the wreckage over an area 580 feet long and 175 feet wide. A flash fire followed, scorching and smudging parts of the wreckage throughout the entire area.

“A considerable number of the pieces of the airplane were identified The smoke detector and five of the six fire detectors installed in the forward baggage compartment were found. The inlet duct adapter (detector manifold) installed in the boiler room, which receives air from the smoke detector, was…found. Inspection of the fire detector units revealed no soot, smoke or evidence of burning, and smudge tests made on the interior of the smoke detector adapter showed no trace of smoke. The normal complement of six 15-pound CO₂ bottles was found in a damaged condition from the impact. The six CO₂ discharge valves were also accounted for; however, they had been broken from their respective bottles by impact, thus allowing the contents, if any, of the bottles to be released….Other pieces from all sections of the airplane were examined for indications of in-flight fire or smoke, and many of these were also subjected to laboratory tests for indications of gases or of smoke from various sources. On the basis of these tests and the testimony of the ground witnesses, we conclude that no fire had existed aboard the airplane prior to the time of impact.

“Although the recording of the crew’s last transmission to New York at 1231 is intelligible only in part, it is clear from the recording that one or both pilots were reporting that fire extinguisher had been released in the forward cargo pit (the forward underfloor baggage compartment), and that the flight was making an emergency descent. Inasmuch as this report indicated the possibility of fire, it is pertinent to note in evaluating this fact that from January 1, 1948, through June 30, 1948, 22 false warnings of fire detectors in fuselage compartments, and 285 false warnings of smoke detectors were reported on air carrier airplanes….

“Although the recording of the crew’s last transmission to New York at 1231 is intelligible only in part, it is clear from the recording that one or both pilots were reporting that fire extinguisher had been released in the forward cargo pit (the forward underfloor baggage compartment), and that the flight was making an emergency descent. Inasmuch as this report indicated the possibility of fire it is pertinent to note in evaluating this fact that from January 1, 1948 through June 30, 1948, 22 false warnings of fire detectors in fuselage compartments, and 285 false warnings of smoke detectors were reported on air carrier airplanes….

“When the DC-6 airplane is pressurized, air escapes from one fuselage compartment to another since all pressurized compartments are not air tight. Consequently, when C02 gas is discharged into an under-floor fuselage compartment to extinguish fire, some of the gas will escape  into the cockpit and cabin….

“The Air Line Pilots Association on March 3, 1948, recommended to the Civil Aeronautics Administration and the Civil Aeronautics Board that ‘smoke masks type oxygen equipment be required available for all members of the crew on transport aircraft.’ The reason for the recommendation was to ‘assure that the crew would be able to carry on their work of landing the aircraft safely in spite of possible smoke interference in case of an aircraft fire.’….that agency considered that the additional protection of a smoke mask was unnecessary at that time. The CAA received a second letter, dated April 13, 1948, from the Pilot’s Association relative to the need for smoke masks, which letter also mentioned for the first time the CO2 hazard. Following receipt of this second letter the CAA instituted a medical study of the effect of smoke and noxious gases on flight crews. This study was not completed until after the Mt. Carmel accident….

“…..Since CO2, physiologically, displaces oxygen rapidly, it is possible for the subject to lose consciousness and recover without being aware of it. Although medical specialists differ regarding human tolerance to CO2, and further research is necessary, one fact is well established: C)2, in addition to reducing the oxygen content of the air, produces a positive, anesthetic effect on the central nervous system….

“Analysis

“The Crew’s transmission reported the release of the fire extinguisher in the forward cargo pit (the forward underfloor baggage compartment). There can be little doubt that this discharge of CO2 was due to the pilot’s belief that a fire actually existed in an under-floor fuselage compartment. Yet examination conducted during the course of the investigation showed that no in-flight fire had actually existed in any of the fuselage compartments.

“Ten minutes elapsed between the crew’s last call announcing an emergency and the time of the accident. This period of silence, coupled with the fact that the airplane while descending passed over visible emergency landing areas, including Sunbury Airport, and flew toward mountainous terrain where safe landing could not be accomplished, admits of only one explanation that the pilots were physically unable to perform their flight duties. Since the crew reported releasing CO2 in the forward baggage compartment, and since it was established that the cabin pressure relief valves were closed, it is reasonable to conclude that a dangerous concentration of CO2 existed in the cockpit. According to the expert medical testimony, a six percent concentration for three minutes would have reduced the pilots to a state of confused consciousness and a higher concentration or a greater time of exposure would have resulted in loss of consciousness.

“The investigation disclosed the cabin pressure relief valves were closed prior to the accident, indicating that the pilot and co-pilot had not followed the approved emergency procedure when discharging CO2 gas into the forward baggage compartment. As previously noted, the extensive breakage of the airplane did not permit a determination as to the position of the flaps at the time of impact. However, the retracted position of the landing gear would indicate that the crew had elected to descend at the 300-mile per hour configuration. Had the crew followed the emergency procedure on such a descent configuration it appears that the accident would have been avoided. Although the retracted position of the landing gear points toward a descent configuration of 300 miles per hour, we recognize the possibility that had the crew elected to make a descent at 160 miles per hour, with flaps and gear extended, according to the Douglas tests performed after the accident, a hazardous concentration of CO2 gas would have existed in the cockpit even though the pilots had adhered strictly to the approved emergency procedure.

“Findings

….

3. The aircraft, after descending to a low altitude, assumed an erratic course in the direction of constantly rising terrain and finally crashed into a transformer in a power line clearing on wooded mountainous terrain approximately three miles east-northeast of Mt. Carmel., Pa.

….

“Probable Cause

“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.

….

“A fire in flight permits little opportunity for the exercise of detached and thoughtful consideration of emergency procedure. Immediate action is required if a fire is to be controlled. Too little consideration has been given to the psychological and physical limitations of crew members in time of stress and danger as related to the complexity of emergency fire procedure. It is not safe to assume that the pilot and co-pilot, under emergency pressure, will always adhere rigidly to the sequence of steps outlined in the CAA Approved Airplane Operating Manual.

“The possibility of human error under great mental stress is well documented in air transport experience and the design of aircraft controls, especially those of an emergency character, should take into consideration the natural limitations of human nature. These limitations argue against involved procedures applicable in emergencies. In harmony with this objective, the Douglas Aircraft Company has designed and is testing a modified fire extinguishing system which will permit all necessary steps to be executed by the movement of one control. An additional vent is also being designed to reduce CO2 concentration in the cockpit. Seven days after the Mt Carmel accident, the Director of Aviation Safety of the CAA directed telegrams to all CAA regional administrators calling attention to his telegram of June 10, 1948, referred to above, and advising that further investigation had disclosed the existence of the CO2 concentration condition found in Constellation aircraft by the Chillicothe tests in other makes of aircraft. The telegram concluded “Hence, flight crews of all aircraft should be advised to wear oxygen masks and utilize emergency cockpit smoke clearance procedures when carbon dioxide is released into any fuselage compartment from other than portable extinguishers. All scheduled U S air carriers operating DC-6s have equipped the airplanes with demand type full face oxygen masks for the use of the crew.”  (CAB. United Air Lines, Inc., Near Mt. Carmel, Pennsylvania, June 17, 1948.)

Newspapers:

June 17: “Mr. Carmel. June 17 (AP) – There is no such thing as a whole body in the desolation left by the crash of a United Airlines plane in this little mining community. Legs, arms, fingers, heads were strewn about leaving a hopeless task for Coroner John Evans. A shocked Rev. P. J. Phelan of nearby Centralia, walked among the victims – or what was left of them – trying to find enough over which to administer final rites. Scattered about the flaming area of more than an acre of scrub land were articles that only minutes earlier adorned the personages of living people.  Watches, rings, bracelets, articles of clothing were gathered up by somber awe stricken spectators. Visibly shaken were the 80 workers who came close to death when the stricken plane barely missed crashing into a colliery breaker in which they were working. Capt. George Warner, Jr. pilot of the ill-fated plane crashed after veering away from the breaker which extended 265 feet into the air.

“George Bolich Sr., 47, of Wilburton, was operating a mine locomotive with Jack Bradley of Catawissa, when he saw the plane coming in about 100 feet from the ground. ‘I sure was afraid when he winged over my head. After he hit it was quiet except for the licking of flames. That was just about the worst thing I ever saw.’ ‘It shook the whole colliery office building,’ said Clerk John D. Carey, of Lost Creek. ‘Some of our men ran up the bank but everything was burning in a wide area.’ He said….” (Pottstown Mercury, PA. “Boyertown Couple, 41 Others Die in Plane Crash.” 6-18-1948, 1.)

June 18: “Chicago (AP)–The passengers aboard the United Airlines plane which crashed in Pennsylvania yesterday, killing all aboard were:

Earl Carroll, Hollywood producer.
Mrs. Jack Oakie, Hollywood , divorced wife of the motion picture actor.
Beryl Wallace, star of Carroll’s theater restaurant show.
E. George Von Sebo, New York City, official of Devoe & Reynolds, Inc., paint firm.
Parker W. Silzer, 48, Metuchen, N. J…son of…late former Gov. George S. Silzer of NJ.
Mrs. Alta Gwinn Saunders, professor of business English…Univ. of Illinois, Urbana.
Hugh McCloskey, the Texas Company, New York City.
Lt. Com. C. S. Avery, San Francisco.
Nathan Berke, Berke Bakeries, Brooklyn.
Ernest Winckoff, Berke Bakeries, Brooklyn.
Rowland Brown, auditor, Brown Brothers, Harriman and Company, New York City.
Arthur B. Smith, department head, Brown Brothers, Harriman and Co., New York City.
Frank Campi, San Jose, Calif.
H. Jackson, Crowell & Collier Company, publishers, New York City.
W. A. Kendall, Scarsdale, N. Y.
D. Marcus, Chicago.
Mrs. D. Marcus, same address.
The Marcus Infant.
Mrs. L. O. Weiser, Chicago.
The Weiser Infant.
A. S. Angus, the Texas Company, New York City.
A. G. Devito, Brooklyn.
Hans Joachim, San Francisco.
R. Harvey, Recotron Corp., New York City.
H. L. Slater, New York City.
Miss Kay Thorpe, NBC announcer in Chicago.
E. Hinchliff, Bursen Knitting Mills, Rockford, Ill.
G. W. Rogers, Lamond Corliss Company, New York City.
Y. Lecorre, Paris, France.
T. J. Gallagher, Bryn Mawr, Pa.
L. Dleringer, Comstock Electric Co., New York City.
R. B. Stewart, Comstock Electric Co., New York City.
N. V. Pessin, Los Angeles.
Mr. and Mrs. G. Harries, Boyertown, Pa.
Remo Bufano, nationally famous marionette producer, New York City.
William Casmer, New York City.
Albert W. Stempel, Stratford, Conn.
Paul March, 32, Sacramento, Calif.

Members of the airliner’s crew:
Capt. George Warner Jr., Westmont, Ill., pilot.
Richard Schember, 26, Elgin, Ill., first officer.
Nancy L. Brown, 23, R. D., Fort Meyers, Fla., stewardess.
Lorena R. Berg, 28, Woodstock, Ill., stewardess.”

(Syracuse Herald Journal, NY. “Dead Listed In Air Crash.” 6-18-1948, p. 16.)

Sources

Aviation Safety Network. Accident Description. United Air Lines Flight 624, 17 Jun 1948.  Accessed 2/8/2009 at: http://aviation-safety.net/database/record.php?id=19480617-0

 Civil Aeronautics Board. Accident Investigation Report. United Air Lines, Inc., Near Mt. Carmel, Pennsylvania, June 17, 1948. Washington, DC: CAB, August 2, 1949. Accessed 9-24-2023 at: https://reports.aviation-safety.net/1948/19480617-0_DC6_NC37506.pdf

 Eckert, William G. “Fatal commercial air transport crashes, 1924-1981.” American Journal of Forensic Medicine and Pathology, Vol. 3, No. 1, March 1982, Table 1.

Haine, Edgar A. Disaster in the Air. New York: Cornwall Books, 2000, 394 pages.

 National Fire Protection Association. “Large Loss Fires of 1948.” Quarterly of the National Fire Protection Association, Vol. 42, No. 3, January, 1949, pp. 137-183.

 Pottstown Mercury, PA. “Boyertown Couple, 41 Others Die in Plane Crash.” 6-18-1948, p. 1. Accessed at:  http://www.newspaperarchive.com/FullPagePdfViewer.aspx?img=7539146

 Syracuse Herald Journal, NY.  “Dead Listed In Air Crash [United 624, Mt. Carmel, PA].” 6-18-1948, p. 16. At: http://www.newspaperarchive.com/FullPagePdfViewer.aspx?img=27442564

[1] Incorrectly dates the crash as July 17, 1948.

Text content