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.