1953 — Feb 14, National Air 470 structural failure, extreme turbulence, Gulf of MX off Mobile Bay, AL–46

–46 AirDisaster.com. Accident Database. “Accident Synopsis 02141953.”
–46 CAB AIR. National Airlines, Inc. – In Gulf of Mexico, February 14, 1953.
–46 Eckert. “Fatal commercial air transport crashes, 1924-1981.” AJFM&P, 3/1, Mar 1982, Table 1.

Narrative Information

Civil Aeronautics Board Accident Investigation Report:

“The Accident

“National Airlines’ Flight No. 470 of February 14, 1953, a DC-6, N 90893, was lost with all 46 persons aboard off Mobile Bay, Alabama, at about 1710. Seventeen bodies and light parts of the aircraft surfaced and were recovered the following day. It was not until May 20 that a part of the aircraft structure was recovered. Subsequently, approximately 75 per cent of the wreckage was located and raised.

“History of the Flight

“Flight 470 originated at Miami, Florida, for New Orleans, Louisiana, with one stop scheduled at Tampa, Florida. Captain Ernest Springer, First Officer C. T. Stettner, Flight Engineer Edward Campion and Stewardesses L. Blamseuser and B. Baucom comprised the crew.

“….. From Miami the flight was uneventful….with the Tampa landing at 1515….Seventeen passengers boarded at Tampa and there were 24 through passengers, making a total of 41, and five crew members.

“….Flight 470 departed Tampa at 1543. Its flight plan, filed previously at Miami, specified a cruising altitude of 14,500 feet according to Instrument Flight Rules and an estimated elapsed tune of two hours for the direct 498 statute miles to New Orleans. Included among the weather data attached to the captain’s copy of the flight plan was a forecast of thunder-storms attended by moderate to severe turbulence in the vicinity of New Orleans, the destination….

“….Flight 917 landed at New Orleans at 1612. It reached the ramp at 1617 and at 1624, its captain sent the following message to Miami flight Control and to all company stations between New Orleans and Jacksonville, Florida, including Pensacola, Florida: “Flight 917 advises extreme turbulence all altitudes just east of New Orleans.” At 1636, the captain sent the following message to the same stations: “Reference extreme conditions stop at present time severe turbulence No. 1. check (NA-1) to New Orleans weather looks better to west of New Orleans.”….

“At 1649, Flight 470 reported passing over NA-2 at 1645 at 14,500 feet, and estimated being over NA-1 at 1710. It also reported ‘Thunderstorms all quadrants…’ Pensacola radio received and acknowledged this message, and advised the flight of ‘severe turbulence’ between NA-1 and New Orleans as reported by Flight 917. Flight 470 acknowledged, asked what altitude Flight 917 reported turbulence, and was informed ‘severe turbulence at all altitudes.’ Again Flight 470 acknowledged.

“At 1654, the flight advised Pensacola that it was reducing power because of turbulence and five minutes later requested Air Route Traffic Control clearance to descend from 14,500 feet to 4,500 feet. This was granted within a minute or so, with the provision that descent between 10,000 feet and 8,000 feet be visual. At 1703, the Flight advised Pensacola of passing through 10,000 feet, and at 1712 (recorded), advised that it had reached 4,500 feet at 1710. Pensacola repeated this message back to the flight and gave it the 1648 New Orleans special weather. This was: measured 800, overcast, visibility 10 miles, wind north-northeast 25 m.p.h., with gusts to 34, the altimeter 29.61; barometer unsteady. The flight acknowledged and there were no further radio contacts.

“An attempt by New Orleans at 1718 to contact Flight 470 was unsuccessful, as were subsequent attempts by several other stations, and at 1840 the Coast Guard’s air-sea rescue service was alerted.

“Low clouds and heavy seas hampered the search both by air and sea. However, on the following day (February 15) floating debris and 17 bodies were recovered from a fairly localized area in the Gulf of Mexico at about 30 degrees 38′ North Latitude and 87 degrees 46′ West Longitude. This posit ion is approximately 38 miles to the right of the aircraft’s direct course and is about 20 miles southeast of Mobile Point at the easterly mouth of Mobile Bay. Two wrist watches on bodies were impact stopped at 5:10 (1710).

“Investigation – Part I – General

“The floating debris that was recovered the day following the accident was carefully examined. This material consisted of hand luggage, personal belongings, and numerous diversified broken and town fittings and furnishings from all sections of the cabin. Severe damage to many of these small articles, such as the extreme distortion of a lady’s metal compact within a leather purse, indicated that the impact forces must have been of great magnitude…. condition of the bodies told clearly that no one had survived, even briefly….

“All of the seventeen recovered bodies had numerous fractures and a few bore marks of discoloration. These marks were first and second degree burns and were scattered over various parts of anatomies with no apparent pattern. The cause of these burns could not be determined with finality but competent medical opinion is that they were not electrical (lightning) bur were possibly friction, or more likely, thermal as from exposure to a flash fire following impact.
….

“Investigation – Part II – Wreckage
….

“Investigation – Part III – Weather Experienced by National Flight No. 917

“The captain of flight 917 testified that when he was approaching New Orleans (between NA-1 and New Orleans) at his assigned cruising altitude of 4,500 feet, he experienced severe turbulence, coupled with heavy rain and heavy hail. He also testified that the aircraft’s instrument panel intermittently shook so violently that the flight instruments were difficult to read. Another indication of the severe and abnormal weather is found in his statement that the turbulence was not of the violent updraft and downdraft type usually associated with well-developed thunderstorms. Rather, the gusts seemed to be more lateral; the captain stated, “The rudder was forced back and forth without changing direction of flight.” He also stated that most of the passengers became airsick and “. . . we had more of a twisting whirling motion, too, which caused the airplane to shake and shudder from one side to another which is unusual in a normal thunderstorm.” There was very little lightning and altitude was controlled within 1,000 feet.

“This captain also testified that shortly before he reached the worst of the weather, he discovered by radio fix that he was approximately 40 miles to the right of his course, Extreme changes in heading were necessary to get back on the course, and subsequent computation shows that the unusual and unexpected wind that he encountered must have been from a general southerly direction and in the order of 100 miles per hour. This drift occurred in the vicinity of NA-1.

“Despite the highly unusual weather conditions as described by the captain of Flight 917, he reported to his company only ‘extreme’ turbulence, and later, ‘severe’ turbulence between NA-1 and New Orleans. The lost flight therefore received only the information that there was severe turbulence at all altitudes….

“Investigation – Part IV – Witnesses

“….A lighthouse keeper at the mouth of Mobile Bay, accustomed to reporting weather conditions, stated that the wind reached ‘whole gale force,’ which by definition could mean up to 75 miles per hour. There is some diversity of testimony as t wind direction but the majority opinion is that it changed from easterly to westerly at about 1710….

“One witness who was on…[a] tanker thought that the wind was about 100 miles per hour, and stated that the visibility was so poor that he could barely see half of the ship’s length (about 250 feet). This witness is one of the 10 who claim to have heard an airplane, and he believed it to be so low that he thought it might strike the vessel…..

“In reference to possible tornadoes, one witness, a commercial fisherman and therefore in all probability a fairly observant judge of weather who was at home about eight miles east-northeast of the crash site, stated that he looked out of the south window overlooking the Gulf and saw a tornado extending approximately half way down to the surface from the bottom of the cloud deck which he estimated to be 300 feet high. Another witness, a man of scientific background, believed that he heard the nose of a tornado (he had heard other tornadoes) but did not see it.

“There was scattered property damage throughout this general area near the mouth of Mobile Bay. Some trees were leveled and a few structures were damaged. At nearby Fort Morgan, Alabama, a U. S. Coast Guard lighthouse keeper reported their flag pole was bent over. This flag pole was of galvanized iron pipe three inches at base, tapering off to one and one-half inches at top, 45 feet above ground, and equipped with three 1/4-inch cable guy wires. Two of these wires broke and the pole was blown nearly down, bending at the base. The time was 1700 hours. It took 15 minutes from the time he first noticed the pole bending until it reached maximum deflection. He estimated the wind velocity to be 50 to 60 m.p.h. or greater….

“In this connection it may be pertinent to point out that the development of this storm was under radar surveillance at the Keesler Air Force Base, Mississippi, approximately 60 miles west-northwest of the recovered wreckage. The radar manifestation showed that the storm was generally southwest of Keesler Air Force Base and lay across the direct route between Tampa and New Orleans, and that it reached its peak development from 1600 to 1700. The observer on duty stated that the echo was the most intense encountered by him in nearly two years of weather observation on radar scopes at Keesler Air Force Base….

“Investigation – Part V – Weather Experienced by National Airlines’ Flight 470

“….The crest and center of a very energetic, open wave, extra-tropical cyclone was in the general area where the flight crashed at about the time of the crash. It had moved unexpectedly fast across the Gulf of Mexico from near Brownsville, Texas….

“The most severe weather of this system occurred in the vicinity and to the north of the apex of the wave. It was traveling east-northeastward between 50 and 60 miles per hour and appears to have not only been located at about the area of the crash but to have attained its most severe development during that period. Flight 470 must have encountered unusually severe turbulence in that area. Weather conditions in general were such that waterspouts and/or tornadoes might possibly have existed….

“Investigation – Part VI – Dispatching

“National Airlines does not maintain its own meteorological service; rather it depends on the U.S. Weather Bureau for weather information. The National dispatchers were properly certificated, and the examination for that certificate demands some knowledge of basic meteorology. None of the dispatchers on duty at Miami on the day of the accident had taken any extensive courses in meteorology. However, company records disclose that both had been serving as flight dispatchers for a number of years, including the dispatching of flights over the route involved. Airline pilots such as this crew had had long experience in practical meteorology and thus were able to evaluate weather data as it pertains to flight. It therefore appears that the dispatchers’ working knowledge of meteorology, together with the crew’s practical knowledge, should have insured a proper evaluation of the weather data then available….

“Analysis – Part I – Weather

“The development of open wave extra-tropical cyclones on quasi-stationary cold fronts in the Gulf of Mexico area is rather a common occurrence during the winter and spring months. However, in connection with the storm of February 14, 1953, an unusual complication of meteorological factors simultaneously affected the northern Gulf area which resulted in a storm of remarkable severity including turbulence aloft….

“Instead of the large updrafts and downdrafts that are frequently associated with thunderstorms and squall lines, the turbulence in this storm seems to have been in the nature of rapid, very sharp gusts of a chaotic nature. “[A] Navy pilot at 4,000 feet, just west of Mobile and north of the crash site, estimated the gusts at 2½ to 3G’s. There are indications that even more severe weather existed along the coast and offshore just south of Mobile….

“….It appears that between 1530 and 1630 errors in the movement and development of the storm were becoming apparent and that even though current forecasts included ‘severe turbulence,’ revised forecasts should have been issued by the Weather Bureau at New Orleans and Miami, particularly after the Severe Weather Bulletin had been received. Certainly the movement of the storm was not adequately covered by the current forecast at that time. A special advisory would have drawn attention to that development. Particularly, it appears that Flight Advisory Weather Service should have issued information to ARTC to be passed on to flights; on June 5, 1953, Weather Bureau offices were instructed by their Washington, D.C., headquarters to highlight such information.

“In this situation pilot could have contributed much. It appears that the first pilot information that reached the Weather Bureau indicating unusually severe turbulence aloft was after Flight 470 had crashed. The captain of Flight 917 did not give a full report of his difficulties….

“Although Flight 470 was dispatched in accordance with approved company procedures, a review of the company’s dispatching policy would indicate that a closer monitoring of en route flights would provide both the dispatchers and the crew with better current weather information whereby each could counsel with the other and arrive at a joint decision as to any change in plan affecting the safe conduct of flights.

“Analysis – Part II – Structure

“In studying the evidence, one is immediately impressed with the suddenness of the accident. It is apparent that whatever difficulty manifested itself, occurred rapidly and was of such a nature that the crew did not have an opportunity to communicate their predicament to ground personnel. Any probable cause arrived at must of necessity be consistent with this basic fact….

“In-flight structural failure was thought to be a likely possibility, and a detailed study of all available evidence was made in an attempt to substantiate or disprove its probability. While a number of puzzling, unexplainable points will probably remain, the Board is on the opinion that the preponderance of evidence indicates a structural breakup in flight prior to the initial water impact.

“A number of significant factors lead to the conclusion that an in-flight structural failure occurred. First of all, it is difficult, if not impossible, to explain the relatively great distance between the two wreckage areas unless it is theorized that the aircraft broke up in flight….

“….the Board is inclined to believe that…the aircraft was upset by a sharp unsymmetrical gust and that in the recovery (or attempted recovery) gust loads combined with maneuvering loads exceeded the strength of thee left wing and caused it to fail downward….

“Probable Cause

“The Board determines that the probable cause of this accident was the loss of control followed by the in-flight failure and separation of portions of the airframe structure while the aircraft was traversing an intense frontal-wave type storm of extremely severe turbulence, the severity and location of which the pilot had not been fully informed.” (CAB. Aircraft Accident Report. National Airlines, Inc. – In Gulf of Mexico, February 14, 1953 (File No. 1-0013). May 27, 1954.)

Sources

AirDisaster.com. Accident Database. Accident Synopsis 02141953. Accessed at: http://www.airdisaster.com/cgi-bin/view_details.cgi?date=02141953&reg=N90893&airline

Civil Aeronautics Board. Aircraft Accident Report. National Airlines, Inc. – In Gulf of Mexico, February 14, 1953 (File No. 1-0013). Washington, DC: CAB, May 27, 1954, 23 pages. At: http://dotlibrary1.specialcollection.net/scripts/ws.dll?file&fn=8&name=*S%3A%5CDOT_56GB%5Cairplane%20accidents%5Cwebsearch%5C021453.pdf [Not operable 5-23-2023]
Also accessed 5-23-2023 at:
https://www.baaa-acro.com/sites/default/files/import/uploads/2017/03/N90893.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.