Aircraft accidents are not the most common in the transport industry, but their incidence is not to be ignored. Every year, hundreds of people lose their lives and property worth millions of dollars is destroyed in aircraft accidents. There have been numerous passenger aircraft accidents in the U.S. aviation history, with some claiming up to three hundred lives. One factor that stands out in most aircraft accidents is the contribution made by weather conditions in most of these accidents. After a crash of Delta Air flight 191 on the 2nd of August 1985, investigations highlighted weather to be the major contributing factor though pilot error also played a significant role. The drafts of air associated with microbursts is a significant threat to planes as the crash of Delta Air flight 191 at the Dallas/Fort Worth International Airport reveals.
Caracena, Ortiz, and Augustine (1986) report that on August 2nd, 1985, 1805 hours Central daylight, a passenger plane belonging to Delta Airlines crashed during landing at the Dallas/Fort Worth International Airport. This flight was a regular flight between California and Florida with an en-route stop at Dallas, Texas. It departed from Fort Lauderdale at 1510 hours Eastern Time on that fateful day with 152 passengers and 11 crew members on board, and with Los Angeles as the final destination. The flight was expected to be normal, though a weather forecast report had suggested a high possibility of the plane facing a storm with scattered rain shower. Rain showers and thunderstorms are considered to be common occurrences in aviation, and with stipulated procedures on how they are to be dealt with, the forecast given was not much of an impediment to this flight.
As Caracena et al. (1986) further write, a thunderstorm formed directly on the aircraft’s path while flying over Louisiana. The pilots decided to cautiously execute standard descent procedures with a slight alteration of the flight path. This change enabled the plane to navigate and successfully achieve the planned descent over Louisiana and approach Fort Worth International Airport for final descent. However, weather at the airport was also poor and an isolated thunderstorm formed in the plane’s path during final descent into the designated runway. Captain Connors and his co-pilot, first Officer Price, decided to continue descent through a thunderstorm that had formed in the airport’s vicinity. Unfortunately, the plane was caught in a microburst at an altitude of 1500 feet (460m). The remaining part of the descent into the designated runway was turbulent and ended with a fatal crash of the Delta Air flight 191.
According to the U.S. Department of Commerce (2005) report, the initial touchdown of the plane was some 1900 meters from the north end of runway 17L. The impact of this touchdown bounced the plane back into the air, and during the second touchdown, while crossing state Highway 114, the plane collided with a car and hit a light pole. This ignited its side wing fuel tank and triggered an explosion. The plane then skidded into the airfield where after hitting two water tanks it burst into flames. Though the emergency response was prompt, the number of fatalities was high with 136 passengers succumbing to injuries. Crash investigations by various agencies including the National Transportation Safety Board (NTSB) began immediately.
Findings of the Investigations
The primary focus of accident investigations is the determination of the causes of an accident. Results of an accidents investigation create the basis for prevention of similar accidents in the future. Determination the probable causes of aviation accidents enables aviation authorities to take steps towards the improvement of aviation safety. On page 80 of the Aircraft Accident Report NTSB/AAR-86/05, the probable cause of the Delta Flight 191 crash is given. The report details this cause as the decision taken by the pilot to execute a descent procedure through a cumulonimbus cloud where they had observed lightning, coupled with the air crew’s lack of adequate training on how to avoid and escape low-altitude wind shear. This culminated in the aircraft encountering a microburst-induced wind shear at low altitude and crashing shortly after (U.S. Department of Commerce, 2005). Simply put, the wind shear resulting from the storm microburst is the primary cause of the plane crash.
A downburst occurs in an area of significantly rain-cooled descending air. When this rapidly descending cold air hits the ground, it gets displaced in all directions, producing relatively strong winds (Golding, 2005). When a downburst affects an area of 4 kilometers or less, it is then referred to as a microburst. Golding (2005) further states that when a cumulonimbus cloud becomes mature, there is an occurrence of strong downdrafts which are related to precipitation in the form of hail or rain. At times these microbursts become too powerful with vertical wind speeds of up to 6,000 feet per minute (Golding, 2005). When a microburst hits the surface, the wind is displaced outwards mostly in a horizontal manner. This causes a considerable change in pressure that can be lethal to a plane at low altitude.
Downbursts (microbursts) are a hazard to low flying aircraft. They have caused numerous plane crashes during landing and takeoff. As an aircraft approaches a downburst, it will encounter a strong headwind that will lead to its increase in speed. At this point, the pilots are tempted to reduce engine power (Golding, 2005). As indicated on page 70 of the Aircraft Accident Report, when Flight 191 encountered the cumulonimbus cloud its speeds initially increased drastically from 150-173 KIAS, and the pilot was forced to retract the throttles (U.S. Department of Commerce, 2005). This is a dangerous move for as the plane maneuvers through the downburst the wind it encounters lowers its airspeed and lift.
A significant downward force and loss of speed can push a plane to the ground or cause massive instability. As indicated on page 71 of the Aircraft Accident Report, while cutting through the cloud, the plane experienced a fall in speed from 173 KIAS to 133 KIAS (U.S. Department of Commerce, 2005). It resulted in the loss of performance and height, and the pilot was forced to suddenly lift the plane’s nose to avoid a crash. The plane also experienced a sudden sideward gush that made it unstable. Survivors described the final seconds of the flight as turbulent and violent. Eventually, the pilots lost control of the plane, and a crash was inevitable (U.S. Department of Commerce, 2005).
Implications of the Crash
The crash of Flight 191 and the ensuing investigations had several impacts. The main effect was the development and incorporation of a system to detect and report wind shear in subsequent plane models. The investigation revealed that in the period between 1970 and 1985 alone, wind shear had resulted in a total of 18 aircraft accidents. Also, the communication protocol between air traffic control, air service, and pilots was enhanced. Communication between air control and other external institutions such as disaster preparedness units was also improved (U.S. Department of Commerce, 2005).
In conclusion, Delta Air Flight 191 crashed in the Dallas/Fort Worth International Airport on the 2nd of August 1985 due to an encounter with a microburst. Microbursts cause wind shear that disrupts the normal performance of planes. The pilot in charge of the aircraft and his co-pilot acknowledged facing conditions that characterize a microburst. The rapid and intended gain and loss of speed by the plane as well as the sideward thrust are characteristic of the pressure changes that result from a microburst. The accident influenced the improvement of aviation communications systems, airport safety as well as plane safety. Subsequent planes were built to include a system to detect and alert pilots of wind shears.
Caracena, F., Ortiz, R., & Augustine, J. A. (1986). The crash of Delta Flight 191 at Dallas-Fort Worth International Airport on 2 August 1985: Multiscale analysis of weather conditions. Washington, DC: U.S. Department Of Commerce.
Golding, W. (2005). Low-level windshear and its impact on airlines. Journal of Aviation/Aerospace Education & Research, 14(2), 35-45.
U.S. Department of Commerce. (2005). Aircraft accident report: Delta Airlines Lines Inc., Lockheed L-1011-385-1, N726DA Dallas/Fort Worth -International Airport, Texas August 2, 1985. Washington, DC: National Transportation Safety Board