Investigation Summary
The flight was operating a multi-leg route from Miami to New Orleans. During the leg from Tampa, the crew encountered a storm system of unexpected intensity. While the pilots were aware of thunderstorms, they had not been fully briefed on the development of a severe frontal wave. Another National Airlines flight (Flight 917) had landed shortly before and reported 'extreme turbulence at all altitudes,' a message relayed to Flight 470 while it was at 14,500 feet. In response, the crew reduced power and requested a descent to 4,500 feet to escape the worst conditions. The last radio contact occurred at 17:12 CST, reporting they had reached 4,500 feet at 17:10. Investigation of the wreckage, which was located months later in 50 feet of water, showed that the left wing had separated from the fuselage. The Civil Aeronautics Board (CAB) concluded that the combination of extreme vertical gusts and the pilot's efforts to maintain control in the storm created loads that caused the airframe to fail.
Final Conclusions
The CAB determined the probable cause was the loss of control followed by in-flight failure and separation of portions of the airframe structure. This occurred while traversing an intense frontal-wave storm of extremely severe turbulence. A significant contributing factor was that the pilot had not been fully informed of the storm's severity and exact location due to delays in weather advisory dissemination and the airline's lack of a dedicated meteorology department.
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Ernest Springer
First Officer
C. T. Stettner
Systems & Failure Modes
Airframe Structure
The Douglas DC-6 suffered a catastrophic failure of the left wing and other components due to gust loads exceeding design limits.
Weather Reporting
A breakdown in the relay of a 'Severe Weather Bulletin' meant the crew entered the storm without knowing its true intensity.
Interesting Facts
- 01Floating debris and the first 17 bodies were recovered 20 miles southeast of Mobile Point, approximately 38 miles off the intended course.
- 02The main wreckage was eventually located on the sea floor 3.8 miles offshore and about 52 miles to the right of the planned course.
- 03Wristwatches found on recovered bodies were stopped at 17:10, indicating the time of impact.
- 04The main wreckage was not located until May 20, 1953, over three months after the accident.
- 05The left wing was found 2,100 feet away from the main fuselage wreckage on the sea floor.
- 06National Airlines did not have its own meteorology department at the time, relying on U.S. Weather Bureau reports.
Safety Actions & Advisories
Weather Advisory Improvements
The investigation highlighted the need for faster dissemination of severe weather bulletins from the Weather Bureau to Air Route Traffic Control (ARTC) and subsequently to en route flights.