案例分析 CO426

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Pre-incident



On August 7, 1975, at Stapleton International Airport in Denver, Colorado, USA, a Boeing 727-200 belonging to Continental Airlines was preparing for passenger boarding and take-off, and the aircraft was scheduled to carry out flight CO426 from Stapleton International Airport to Continental Airport in Wichita, Kansas. By the deadline of 15:50 local time, a total of 75 male passengers, 49 female passengers and 3 minor children had boarded the aircraft, a total of 127 people, who were served by four female flight attendants, including flight attendant Juliana Shepard.

The boarding process was pleasant, because Juliana Shepard, then 24, was the youngest daughter of Alan Bartlett Shepard, Jr., the first American astronaut to go into space at the time, and it was obviously very pleasant to be on the same plane with the relatives of the hero who was almost a household name in the United States at the time.



On May 5, 1961, at the age of 37, Alan Shepard flew the Mercury spacecraft Freedom 7 on a suborbital flight, flying at an altitude of 116 miles from the Earth, splashing down in the Atlantic Ocean 15.5 minutes later, becoming the first American astronaut to go into space and the second astronaut in human history after Yuri Alekseevich Gagarin. Ten years later, in 1971, at the age of 47, Shepard took part in the Apollo 14 moon landing program, becoming the fifth man to walk on the moon.



Air Crash Consequences



The captain of flight CO642 was 38-year-old Robert Brown. E. Price, who was an excellent pilot with 11,465 hours of flying experience, but he had only just begun training as a captain of a Boeing 727 in early 1974, so he had only 483 hours of flight time on the Boeing 727.

The co-pilot was Robert J. Brown, then 33 years old. W. Shelton, who flew 6,555 hours, began co-pilot training on a Boeing 727 in 1971 and accumulated 998 hours of flight time on a Boeing 727. The flight engineer was 33-year-old William Brown. R. Kokal, who was a U.S. Air Force pilot before joining Continental Airlines, amassed 1,148 hours of flight time as a pilot and another 3,335 hours as a flight engineer, including 545 hours as a flight engineer for a Boeing 727.

This Boeing 727-200 passenger aircraft registration number is N88777, first flight on July 16, 1968, delivered to Continental Airlines on August 1 of the same year, to the day of the aircraft age of nearly 7 years, a total flight time of 23,850 hours, 9,846 takeoffs and landings, is a general use intensity of "middle-aged aircraft".



Analysis Process

1	At 16:10 local time in Denver, flight CO426 slowly taxied to the starting point of runway 35L at Stapleton International Airport and asked the tower for permission to take off. At that time, the co-pilot of Sheldon was in charge of piloting the plane, Captain Price was in charge of monitoring the instruments and ground contact, and Engineer Kokar was in charge of controlling the throttle. After the captain communicated with the tower normally, he was ready to take off as usual, and as the joystick was pulled up, the nose of the aircraft was lifted in response, and the nose wheels were lifted off the ground. But as soon as the landing gear was retracted, the plane vibrated and it felt like it was hard to climb. A stall warning sounded in the cabin, and the joystick shook because of the stall warning, and the plane eventually crashed.
2	Just 11.6 seconds after the plane left the ground, the Boeing 727-200 passenger plane No. N88777 of Continental Airlines flight CO426 made its first touch with a belly "prostate landing" attitude 387 feet south of the extension line at the take-off end of runway 35L, 106 feet away from the right side of the runway centerline, and then the fuselage was bounced up, and then flew forward for another 153 feet before touching the ground for the second time. The fuselage at the air intake of Engine 3 on the centerline snapped, and then the lower part of the nose was torn due to ground friction, and finally the plane taxied forward for more than 1,100 feet before stopping, and the final stop position was 1,600 feet south of the take-off extension of runway 35L, 160 feet to the right of the runway centerline extension.
3	After the plane came to a standstill, Captain Price confirmed that no one was killed on the plane, but more than a dozen wounded people immediately ordered the cabin to evacuate, and at the same time called the airport tower to immediately send fire engines and ambulances. In fact, he did this redundantly, because the plane fell to the ground almost under the nose of the tower controller, who realized that the plane was about to crash when he noticed that the plane was falling in altitude, and immediately notified the fire engine and ambulance at the airport to dispatch immediately. Shortly after the plane hit the ground, the shrill sirens of fire engines and ambulances sounded in the distance. Due to the rain, the plane leaked fuel but did not cause a fire, so the entire cabin evacuation process was relatively smooth, and all 127 passengers left the plane safely. During the evacuation, Alan Shepard's daughter Juliana Shepard stuck to her post when the purser was injured and unable to move, and she herself was also slightly injured, organized the orderly evacuation of passengers, and then inspected the cabin on behalf of the purser and reported to the captain that "the cabin evacuation is complete" before leaving the plane. In the aftermath, Robert, then chairman and CEO of Continental Airlines, praised Juliana for her bravery in the accident.
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Cause of Accident



The accident was investigated by the National Transportation Safety Board (NTSC), and after ruling out possible causes such as mechanical failures in the aircraft itself, fuel quality, crew errors, and passenger baggage violations, the investigation focused on the weather at the airport at the time.

According to the meteorological records of the day, the weather in Denver was bad that day, with thundershowers, and when the CO426 flight took off, there was a cluster of cumulonimbus clouds with strong convection up and down in the north of the airport. Judging from the sudden loss of altitude and speed in the final part of the CO426 flight, it is likely that the cumulonimbus cloud encountered a slight downburst and most likely encountered wind shear at the same time.

On the other hand, because Denver Airport was not equipped with weather radar at that time, it could only obtain meteorological data from the local meteorological station, and could not provide real-time meteorological data for the crew, which was also the reason for the release of the CO426 flight under such bad weather conditions. This situation was not alleviated until the mid-80s, when weather radars were installed at airports in the United States and real-time weather information was provided. Until then, there will be a number of flights that fall victim to micro-downbursts and windshear because they do not know the real-time weather conditions at the airport and the exact location of the severe convective air mass.

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