On August 6, 1966, a BAc 111 (registration N1553) operated by Braniff Airways was involved in an aviation accident near Falls City, United States of America in flight. 42 people were killed. Investigators recorded the probable cause as: In-flight structural failure caused by extreme turbulence during operation of the aircraft in an area of avoidable hazardous weather. This summary draws on records from the Bureau of Aircraft Accidents Archives (B3A).
Braniff Flight 250 crashed in Nebraska after encountering extreme turbulence near a squall line. All 42 occupants were killed in the in-flight structural failure.
Flight Details and Route Overview<br><br>Braniff International Airways Flight 250 was a scheduled domestic passenger and cargo service operating from New Orleans, Louisiana, to Minneapolis, Minnesota. The flight included intermediate stops at Shreveport, Louisiana; Fort Smith, Arkansas; Tulsa, Oklahoma; Kansas City, Missouri; and Omaha, Nebraska. The aircraft departed New Orleans at 1835 hours Central Standard Time and reached Kansas City without any reported incidents.<br><br>## Departure from Kansas City and Air Traffic Control Communications<br><br>At 2255 hours, the flight departed Kansas City under an Instrument Flight Rules (IFR) clearance to Omaha via Jet Route 41 at Flight Level 200. Prior to takeoff, the flight was restricted to 5,000 feet due to conflicting traffic. Approximately 12 miles north of Kansas City, control was transferred to the Kansas City Air Route Traffic Control Center (ARTCC). Radar contact was confirmed, and the flight was cleared to climb to and maintain FL 200.<br><br>Following discussions regarding weather conditions, the flight crew requested to maintain 5,000 feet to Omaha. They reported being at 6,000 feet, and the ARTCC cleared them to maintain that altitude until 5,000 feet became available. At 2303 hours, the Kansas City ARTCC began transferring control to the Chicago ARTCC. Before the transfer was completed, the flight requested and received permission to deviate to the left of course. At 2306 hours, the Kansas City controller cleared the flight to descend to and maintain 5,000 feet and to contact the Chicago ARTCC.<br><br>## Final Communications and Weather Encounter<br><br>During discussions about weather displayed on the Chicago controller's radar, the flight was advised that Braniff Flight 255 was on the same frequency at 10,000 feet, climbing to 17,000 feet after departing Omaha. The crews exchanged weather information, with Flight 255 reporting light to moderate turbulence from about 15 miles southeast of Omaha, which they expected to exit within another 10 miles. Flight 250 ended this conversation at approximately 2308:30 hours, which was the last transmission received from the flight.<br><br>## Crash and Casualties<br><br>Ground witnesses reported seeing the aircraft approach and either fly into or over a shelf of clouds preceding a line of thunderstorms approaching from the north and northwest. Shortly after, they observed an explosion in the sky followed by a fireball falling from the clouds. The aircraft crashed at approximately 2312 hours, 7.6 statute miles on a true bearing of 024.50 from Falls City, Nebraska, at an elevation of 1,078 feet above mean sea level. All 42 occupants were killed.<br><br>## Probable Cause and Findings<br><br>The official investigation determined that the probable cause was an in-flight structural failure caused by extreme turbulence during operation in an area of avoidable hazardous weather. The aircraft encountered a severe squall line oriented across its intended route, which was adequately forecast and reported by the Weather Bureau. However, the company forecast was somewhat inaccurate regarding the number and intensity of thunderstorms and associated turbulence.<br><br>The crew was aware of the forecast weather and that the system could have been circumnavigated to the west, a suggestion made by the co-pilot. The company dispatcher did not take action to delay or reroute the flight because the company forecast did not predict a solid line of thunderstorms, nor did the dispatcher relay information that might have persuaded the pilot-in-command to avoid the storm system. Despite apparent concern about the en-route weather and knowledge that the squall line was quite solid, the pilot-in-command elected to penetrate the line using airborne weather radar to select a light area.<br><br>Flight 250 never reached the main squall line. Instead, the aircraft broke up in a roll cloud approximately 5 miles from the nearest radar weather echo. At the time, the aircraft was at the proper configuration and airspeed for flight in turbulence, and the autopilot was engaged. The aircraft encountered extreme turbulence generated by strong horizontal and vertical wind shears associated with the outflow of cold air from the approaching squall line. This turbulence probably caused a large angled gust of very short duration with components in the lateral, vertical, and longitudinal planes. The resulting forces and accelerations caused the fin and right tailplane to reach their ultimate loads, with near-simultaneous failures. The aircraft then pitched downward until the right wing reached its negative ultimate load. The loss of these components rendered the aircraft uncontrollable, and it probably began a random tumbling motion that stabilized into a flat-spinning attitude before impact.