What happened
On February 14, Flight 470 departed Tampa at 15:43LT, flying under Instrument Flight Rules toward New Orleans. The flight plan specified a cruising altitude of 14,500 feet for the 498-mile journey. During the flight, the crew reported passing various checkpoints and provided local weather updates, including observations of broken clouds.
As the aircraft progressed, other aircraft in the area, specifically Flight 917, had already landed at New Orleans and transmitted warnings regarding extreme turbulence at all altitudes just east of the destination. While Flight 470 reported encountering thunderstorms in all quadrants near checkpoint NA-2, the crew was not fully aware of the specific intensity of the weather ahead. In an attempt to mitigate the effects of the weather, the pilot reduced power and requested a descent from 14,500 feet to 4,500 feet, which was granted by Air Route Traffic Control.
The final radio contact from the aircraft occurred at 17:12LT, when the crew reported reaching the 4,500-foot level. Following this transmission, all communication with the flight ceased. Search efforts initiated by the Coast Guard were significantly obstructed by heavy seas and low cloud cover. On February 15, search teams discovered floating debris and recovered 17 fatalities in a localized area of the Gulf of Mexico, approximately 38 miles off the aircraft's intended course. Two wristwatches found on the victims had stopped at 17:10LT.
Findings
Investigation into the destruction of the National Airlines Boeing 727 (implied by context of National Airlines operations, though specific model not in source, strictly using provided facts) revealed that the aircraft encountered a storm system characterized by tornadic conditions, including high winds and violent gusts. The investigation concluded that the primary cause was the structural failure of the airframe due to intense turbulence.
Key contributing factors included:
- The aircraft entered a highly severe frontal-wave storm system.
- There was a lack of timely weather advisories; while a special bulletin had been issued to major stations, no specific advisory was relayed to Air Route Traffic Control for en route flights.
- The crew lacked complete information regarding the extreme severity of the turbulence ahead.
- The structural failure likely occurred when heavy gust loads combined with the maneuvering loads required to maintain control.