The history of aircraft development is marked by technological breakthroughs – from more fuel-efficient engines to the use of carbon-fibre materials – that have spurred the creation of better, safer aircraft. However, fatal accidents have also forced design changes that have improved subsequent aircraft and prevented further loss of life. Here are some examples.
BOAC flight 781
10 January 1954
A De Havilland Comet operated by British Overseas Airways Corporation crashed after suffering a catastrophic decompression in mid-flight. The Comet fell into the sea near Elba, off the Italian coast: all 35 people on board died.
It was the second in a series of three Comet accidents in less than a year, all from similar causes. Investigators found that structural cracking had started in the roof of the cabin: a window had become detached and struck control structures at the back of the aircraft, and the rear fuselage had then torn away.
The cause was metal fatigue, arising from the constant pressurisation and depressurisation of the aircraft’s fuselage during everyday use. Also, supports around the windows had been riveted, not glued, in a process which is thought to have caused cracks.
The fuselage was also experiencing considerably higher stresses than had been anticipated, particularly around the sharp corners of the Comet’s square windows. As a result, future jetliners would feature windows with rounded corners.
Delta Air Lines flight 191
2 August 1985
The Lockheed TriStar operated by US carrier Delta encountered a thunderstorm while approaching Dallas-Fort Worth to land. The aircraft struck the ground far short of the runway and disintegrated, killing 137 people and injuring 28 others. Investigators found that the crash had resulted from the flight crew’s decision to fly through a thunderstorm; the lack of procedures or training to cope with “microbursts” (small but intense downdraughts that occur in storms); and the lack of advance warning on the sharp changes in wind speed or direction known as wind shear.
After the investigation, an onboard weather radar was developed by Nasa. The resultant airborne detection and alert system was installed on many airliners after the US regulator insisted all commercial aircraft must have onboard means of detecting wind shear.
British Airtours flight 28M
22 August 1985
A Boeing 737 caught fire before takeoff at Manchester airport, with the loss of 55 lives. It was on its way to Corfu, in Greece. Before takeoff, one of the engines failed, causing the fire, and the captain instructed the crew to evacuate the plane. There were 82 survivors: most of the deaths were caused by smoke inhalation.
The accident brought about industry-wide action on plane design, including changes to the seating layout near exits; fire-resistant seat covers; floor-level emergency lighting; fire-resistant wall and ceiling panels; increased numbers of extinguishers; and clearer rules on evacuation procedures.
Aeroméxico flight 498
31 August 1986
Two planes collided in mid-air over the Los Angeles suburb of Cerritos. The tail of Aeroméxico flight 498, a McDonnell Douglas DC-9, was hit by a small private plane – a Piper PA-28-181 Archer – while descending towards Los Angeles International Airport. All 67 people on both aircraft were killed, as well as an additional 15 on the ground.
After that, all jets in US airspace were required to carry air avoidance collision systems. Another mid-air crash near New Delhi in 1996 – between a Boeing 747 and a Soviet-designed Ilyushin Il-76 – killed 349 people: that triggered the implementation of crash avoidance systems around the world.
USAir flight 427
8 September 1994
A Boeing 737 flying from Chicago crashed while approaching Pittsburgh International Airport. Investigators said the probable cause was that the aircraft’s rudder had malfunctioned and turned hard in the direction opposite to that commanded by the pilot, causing a loss of control from which the flight crew could not recover. All 132 people on board were killed.
Boeing subsequently agreed to design and pay for a new rudder control system for the entire worldwide 737 fleet.
Air France flight 447
1 June 2009
The crash of AF 447 raised concerns about the level of automation in aircraft, and those fears have been exacerbated by the 737 Max crashes in Indonesia and Ethiopia. The Airbus A330, operated by Air France and on its way from Rio de Janeiro to Paris, stalled and did not recover, crashing into the Atlantic with the loss of all 228 passengers and crew.
The initial investigation concluded that the aircraft crashed after the airspeed sensors iced over, causing the autopilot to disconnect in the middle of stormy weather. This sparked an unexpected handover of control to the pilots, one of whom was not used to hand-flying at altitude and who reacted incorrectly by pulling the nose of the aircraft upwards.
The pilot errors ultimately caused the aircraft to enter an aerodynamic stall – where the plane’s weight is no longer supported by the air flowing under the wings – and drop from the sky catastrophically at 11,000 feet per minute.
Following the disaster, regulators urged airlines to encourage more hand-flying to prevent the erosion of basic piloting skills.
