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August 2, 1985 brought thunderstorms to the Dallas-Ft. Worth area. Delta flight 191 was approaching Dallas-Ft. Worth International Airport on a stopover between Ft. Lauderdale and Los Angeles. 156 passengers and eleven crew members were on board the Lockheed L-1011 as it began to execute an ILS approach to runway 17L with the First Officer flying the aircraft. The crew observed a thunderstorm cell lying along the approach path which was producing rain, prompting the First Officer to say "We're gonna get our airplane washed." He also made remarks about lightning ahead near the storm cell.

Nevertheless, the crew continued the approach. At a height of approximately 800ft, the aircraft deviated from the glideslope and, with gear extended, touched down in a field some 6,000ft short of the runway and slightly to the left of centreline. It bounced and then impacted again, crushing a car on the highway. It then continued to slide, bouncing off one water tank and slamming into another. The aircraft then exploded into a fireball which was partially extinguished by water pouring from the tank. 137 people were killed in the accident as well as the driver of the car on the highway.

......Recovery of the aircraft's FDR and CVR proved instrumental in determining the cause of the crash. It was clear that the crew was aware of the thunderstorm lying along the approach path. Ten minutes before the crash, ATC transmitted a message saying "There's a rain shower just north of the airport.." Readout of the FDR showed that 191 encountered increasing headwinds as it entered the area of the thunderstorm. After encountering downdrafts, the First Officer applied nose-up inputs, but a sharp updraft followed, increasing the angle-of-attack to near a stall. Forward pressure was applied, but a downdraft then pushed the aircraft below the glideslope. At this point, the aircraft was emerging from the backside of the thunderstorm, encountering tailwinds of nearly 50kts. The Captain then called for "TOGA", or takeoff/go-around, power to be applied.

The manoeuvre was begun too late however to prevent the aircraft from crashing. Clearly 191 encountered a strong microburst, a product of the thunderstorm, but the question remained as to why the continued the approach. Although the crew had visually identified the cell, two aircraft just ahead of 191 on the approach landed safely and reported no difficulties. Several other flight crews in the area saw lightning and even a funnel cloud, but none of the crews reported any of the sightings to the tower. The thunderstorm which developed over the approach path developed rapidly. The meteorologist at Dallas-Ft. Worth reported seeing no weather echoes within 10nm of the airport some 40 minutes prior to the accident. He left for his dinner break, returning just after 191 crashed.

Upon returning, he found a level 4 thunderstorm in the area. No warning was given from the airport's LLWAS until after the accident either. Because of the speed of the buildup, no SIGMET or severe weather watch was issued. Nevertheless, the NTSB ruled that the crew had adequate visual clues to determine the severity of the storm. They also ruled that the weather radar on the aircraft lacked the definition to display an adequate picture of the storm. Subsequent to the accident, a more sophisticated LLWAS was developed to increase the level of safety at airports prone to thunderstorms.