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Aircraft accidents, when they happen, are high-profile events, often involving a large-scale loss of life and widespread devastation. And while they can’t be undone, the accident investigation process can help to ensure that the same things never happen again.
Today, flying is safer than it has ever been – 2017 was the safest year on record for commercial aviation, with zero deaths, while the fatal accident rate for large commercial passenger flights is 0.06 per million flights, or one fatal accident for every 16 million flights.
Much of this can be attributed to the advances in safety that have been made following fatal aircraft accidents. The accident investigation process ensures that lessons are learned and practices changed, to safeguard life in the future.
While there are countless examples that we could draw upon, here are five aircraft accidents that transformed aviation in the 20th century – in the most significant of ways.
1. Eastern Air Lines Flight 401
When: 29 December, 1972.
Where: Everglades, Florida.
Eastern Air Lines Flight 401 was a Lockheed L-1011-1 Tristar jet, which crashed into the Florida Everglades while the crew were focused on troubleshooting what later proved to be a faulty landing gear indicator light. Consequently, they failed to notice that the autopilot had been disconnected, causing the aircraft to lose altitude and crash.
The aircraft has been taking passengers from John F. Kennedy International Airport in New York to Miami International Airport in Florida and was under the command of 55-year-old Captain Robert Albin Loft, alongside 39-year-old first officer Albert John Stockstill and 51-year–old flight engineer Donald Louis Repo. The flight had been routine but problems arose as the Tristar began its descent into Miami.
After the landing gear had been lowered, Stockstill noticed that the landing gear indicator light had not illuminated green, to indicate that the landing gear had been locked in the down position. This was later discovered to be simply due to a burned-out lightbulb.
When the light failed to illuminate on repeated attempts, Loft requested to enter a holding pattern, climbing to 2,000 feet and holding west over the Everglades. The crew then proceeded to confirm whether the landing gear was down, with Repo descending into the forward avionics bay to carry out a visual inspection.
Once their assigned altitude had been reached, Loft instructed Stockstill to switch on the autopilot. However, over the next few minutes, the aircraft began to gradually descend at an almost imperceptible rate. By the time the pilots became aware of what was happening, it was too late.
Shortly after being cleared for a left turn back to Miami Airport, the aircraft impacted the ground at 227 miles per hour, continuing to move through the grass and water and break up as it did so.
The National Transportation Safety Board (NTSB) investigated the crash, finding that the autopilot had inadvertently been switched from altitude hold to control wheel steering (CWS) pitch mode – this had most likely been caused by Loft "bumping" the control column. The force required to achieve this was different for channels A and B – therefore, Stockstill may not have been aware of any change.
The NTSB concluded in their accident report that the crash was most likely due to "the failure of the flight crew to monitor the flight instruments during the final four minutes of flight, and to detect an unexpected descent soon enough to prevent with the ground".
Communication clearly broke down in the case of Eastern Air Lines Flight 401, as the crew became distracted by what was revealed to be a minor issue – with grave consequences. As a result of the crash (and other subsequent incidents), Crew Resource Management (CRM) training was developed and implemented across many airlines. These training procedures put the Captain in charge of ensuring that the monitoring of all indicators and warning systems is delegated among the crew, in order to avoid accidents caused by human error.
In general terms, the Civil Aviation Authority (CAA) describes CRM as "the training of the cognitive and social skills needed to support technical training in order to optimise safe and efficient aircraft operation".
2. The Tenerife Airport Disaster – KLM Flight 4805 and Pan Am Flight 1736
When: 27 March, 1977.
Where: Los Rodeos Airport, Tenerife (now Tenerife-North Airport).
Survivors: 61 (all were on board Pan Am Flight 1736).
The Tenerife Airport Disaster remains the deadliest accident in the history of aviation. KLM Flight 4805 and Pan Am Flight 1736, both Boeing 747s, collided on the runway at Los Rodeos Airport in Tenerife, resulting in 585 deaths.
The two aircraft had been diverted to the small, regional airport following a minor bomb explosion at Gran Canaria Airport; this event had led to congestion and meant that departing aircraft were having to taxi on the single runway. The runway was connected to a major taxiway via four short taxiways. Simultaneously, thick fog was shrouding the airport, preventing those in the control tower from having a clear view of aircraft on the ground.
At the controls of KLM 4805 was 50-year-old Captain Jacob Veldhuyzen Van Zanten, KLM’s top instructor pilot and the face of its magazine adverts. In the cockpit with him were 42-year-old first officer Klaas Meurs and 48-year-old flight engineer William Schreuder. Flying Pan Am 1736 was 56-year-old Captain Victor Grubbs, 39-year-old first officer Robert Bragg and 46-year-old flight engineer George Warns.
The Pan Am aircraft was ready to depart ahead of the KLM aircraft, but the latter was refuelling, thereby blocking access to the runway. Instead, the KLM aircraft was instructed to taxi down the runway, with the Pan Am to follow behind and take the third exit onto the taxiway. In the bad visibility, the Pan Am crew taxied past the third exit; meanwhile, KLM 4805 prepared for take off. Pam Am 1736 was still on the runway.
Cockpit voice recordings show that there was confusion and miscommunication between the KLM crew and the air traffic control tower as to whether KLM 4805 was cleared for take off. Due to the fog, neither the Pan Am 1736 nor KLM 4805 crew were able to see one another – and there was no ground radar at the airport.
As KLM 4805 set off down the runway, the disaster that was about to unfold became clear. As the Pan Am captain saw the other 747 emerging through the fog, he desperately tried to move his aircraft off the runway - but it was too late. Seeing the Pan Am aircraft up ahead, Van Zanten rotated his aircraft early in an attempt to clear the other aircraft, resulting in a severe tailstrike. The KLM aircraft struck the Pan Am aircraft broadside at more than 150mph, ripping through its centre and peeling off the top section; it stayed airborne briefly and then rolled sharply, hitting the ground 150 metres away from the collision and sliding down the runway for a further 300 metres. The KLM 747 was engulfed in flames and no one survived. 61 people manged to escape the Pan Am jet alive, including Captain Grubbs.
The disaster was investigated by Spanish, Dutch and American accident investigation teams, who concluded that the main cause of the accident was Captain Van Zanten taking off without clearance from ATC. The accident had far-reaching consequences for aviation safety, demonstrating in the most horrific way how a series of seemingly innocuous events can lead to death and destruction. The disaster impacted how aircraft and ATC communicate, with standard terminology being introduced to reduce the chance of confusion. Crew were also encouraged to challenge their captains if they thought something was wrong; first officer Meurs had voiced concerns to his captain as they prepared for take off but didn’t push the issue.
As with the Eastern Air Lines Flight 401 accident, the Tenerife Airport Disaster contributed to the development of CRM training.
3. British Airtours Flight 28M
When: 22 August, 1985.
Where: Manchester Airport, UK.
British Airtours Flight 28M was due to take 131 passengers and six crew from Manchester International Airport to Corfu International Airport, when take off was aborted due to what was subsequently identified as an uncontained engine failure. The pilot was 39-year-old Captain Peter Terrington, who was accompanied by 52-year-old first officer Brian Love.
As the Boeing 737 travelled down the runway, a loud thud was heard; initially thought to be a burst tyre, it was actually the result of a combustor can failure in the engine and uncontained shrapnel, which punctured the wing fuel tank. The aircraft was quickly brought to a halt and manoeuvred onto an adjacent taxiway, but smoke and flames had begun to engulf the cabin, leading to panic. Evacuation procedures were implemented, but difficulties soon arose. One of the front door exits was blocked, while the left overwing exit and rear exits were unusable, creating a bottleneck of passengers at the back of the aircraft. Nearly all of the victims died as a result of smoke inhalation.
This accident had a fundamental impact on the way that airlines deal with cabin configuration and evacuation procedures. The Air Accidents Investigation Branch (AAIB) released a report, which made a number of recommendations, including:
- Procedures should be developed to enable the crew to position an aircraft, when a ground fire emergency exists, with the fire downwind of the fuselage.
- Emergency equipment for use by cabin crew during an emergency evacuation should be stowed at the cabin crew stations.
- Operators should adopt a policy of distributing the most experienced cabin crew throughout the passenger cabin.
- A review of the cabin configuration should be conducted.
- A thorough review should be undertaken into techniques for extinguishing fires inside the passenger cabins of public transport aircraft, with a view to rectifying the current deficiencies in airfield firefighting capability when dealing with internal fires.
- Onboard water spray/mist fire extinguishing systems having the capability of operating both from on-board water and from tender-fed water should be developed as a matter of urgency and introduced at the earliest opportunity on all commercial passenger carrying aircraft.
One of the changes to be implemented was the expansion of the space between the seats and the exit row, to prevent obstructions during an emergency situation. It also became standard practice to ensure that the passengers sitting in those seats know how to, and are physically able to, operate the exit doors.
Many airlines also now have escape hatches that swing out and up, so that the hatch doesn't fall inside the cabin and block escape routes.
Subsequent occurrences have demonstrated the positive legacy created by this tragedy. On 2 August, 2005, 297 passengers and 12 crew were successfully evacuated from Air France Flight 358 after it overshot the runway at Toronto Pearson International Airport. And on 8 September, 2015, 157 passengers and 13 crew all survived when British Airways Flight 2276 caught fire during take off from Las Vegas-McCarran International Airport.
4. Delta Air Lines Flight 191
When: 2 August, 1985.
Where: Dallas/Fort Worth International Airport, USA.
Delta Airlines Flight 191 was a Lockheed L-1011 Tristar travelling from Fort Lauderdale, Florida to Los Angeles with a stopover at Dallas/Fort Worth International Airport, which crashed as it attempted to land during a thunderstorm at the latter.
At the controls were 57-year-old Captain Edward Connors, 42-year-old first officer Rudolph P. Price and 43-year-old flight engineer Nick Nassick. The flight had been routine until the aircraft encountered a thunderstorm just a few miles from the airport. Other aircraft had successfully landed shortly before and, despite spotting lightning ahead as they moved closer to the airport, the pilots continued their trajectory.
As Delta Air Lines Flight 191 approached the runway, the aircraft encountered a microburst, one of the deadliest and at, at the time, misunderstood weather phenomena. The microburst caused windshear – that is, a change in wind direction and/or speed in a short distance in the atmosphere. 800 feet above the ground, the aircraft was accelerated forward by strong winds, before rapidly losing speed and altitude. The pilots attempted to push the throttles to full power but it was too late. The Tristar hit the ground a mile short of the runway, before striking a car and colliding with two water tanks, whereupon it burst into flames.
The NTSB concluded that the accident had occurred because of the pilots’ decision to fly through a thunderstorm, as well as the lack of procedures and training on how to avoid or escape microbursts and the lack of information about windshear hazards.
Speaking to the Dallas News, FAA spokesperson Lyn Lunsford said: "This was the watershed accident that helped really galvanise the aviation industry to get a broad range of improvements in weather prediction."
Following the accident, the Federal Aviation Administration (FAA) rushed to develop technology that would detect microbursts. While aircraft had the ability to detect rain showers and thunderstorms, windshear was outside of their capabilities. As a result, commercial aircraft are now fitted with such radar, while, on the ground, airports are equipped with precision forecasting instruments. Pilots are also routinely trained in how to deal with windshear.
5. Aloha Airlines Flight 243
When: 28 April, 1988.
Where: Kahului, Hawaii.
Aloha Airlines Flight 243 was a Boeing 737-297 that was travelling between Hilo and Honolulu in Hawaii when it suffered an explosive decompression during flight. Although the aircraft was later able to land safely, a flight attendant lost her life, the majority of passengers suffered injuries, and the incident had a fundamental impact on the aviation industry.
The flight was operated by 44-year-old Captain Robert Schornstheimer, along with 36-year-old first officer Madeline Tompkins. The aircraft had been flying throughout the day with no problems reported. However, as the 737 reached its cruising altitude of 24,000 feet over the Pacific, a small section of the left side of the roof ruptured with a "whooshing" sound, leading to an explosive decompression that tore off a large section of the roof, from just behind the cockpit to the forewing area.
58-year-old flight attendant Clarabelle Lansing was sucked out of the aircraft; her body was never found. Tompkins had been flying the aircraft but, at this point, Schornstheimer took over the controls, diverting the aircraft to the airport on Maui Island. The aircraft made an emergency landing 13 minutes later.
The NTSB concluded that the destruction was caused by metal fatigue, which had been made worse by crevice corrosion. Having been in operation for 19 years, the 737 was continuously exposed to salt and humidity in Hawaii’s climate while operating short, "island-hopping" flights. A passenger, Gayle Yamamoto, later told investigators that she had noticed a crack in the fuselage when she had boarded the aircraft but had not said anything to the crew.
The accident investigation showed that the aircraft had not been inspected to sufficient standards and that maintenance programmes were deficient. Often, the fuselage was inspected at night, making it difficult to detect any issues.
In their report, the NTSB stated: "The probable cause of this accident was the failure of the Aloha Airlines maintenance programme to detect the presence of significant disbonding and fatigue damage which ultimately led to failure of the lap joint at S-10L and the separation of the fuselage upper lobe. Contributing to the accident were the failure of Aloha Airlines management to supervise properly its maintenance force; the failure of the FAA to evaluate properly the Aloha Airlines maintenance programme and to assess the airline’s inspection and quality control deficiencies; the failure of the FAA to require Airworthiness Directive 87-21-08 inspection of all the lap joints proposed by Boeing Alert Service Bulletin SB 737-53A1039; and the lack of a complete terminating action (neither generated by Boeing nor required by the FAA) after the discovery of early production difficulties in the B-737 cold bond lap joint which resulted in low bond durability, corrosion, and premature fatigue cracking."
Its recommendations included:
- Provide specific guidance and proper engineering support to principal maintenance inspectors to evaluate modifications of airline maintenance programmes and operations specifications which propose segmenting major maintenance inspections.
- Require formal certification and recurrent training of aviation maintenance inspectors performing non-destructive inspection functions.
- Issue an Airworthiness Directive for B-737 airplanes equipped with carbon steel engine control cables to periodically inspect the cables for evidence, to accomplish the actions set forth in Boeing Service Letter 737-SL-76-2-A.
- Issue an Air Carrier Operations Bulletin for all air carrier flight training departments to review the accident scenario and reiterate the need to assess airplane airworthiness as stated in the operators manual before taking action that may cause further damage or breakup of a damaged airframe.
Subsequently, the FAA developed the National Aging Aircraft Research Programme (NAARP), to ensure the continued airworthiness of high-time, high-cycle aircraft. Today, airworthiness is of the utmost importance across the aviation industry.
The aviation industry is no stranger to death and tragedy. However, the dedication to safety and learning from the mistakes of the past means that getting on an aircraft today is largely a safe endeavour. As Professor Graham Brathwaite, Head of the Safety and Accident Investigation Centre at Cranfield University, says in an article for The Conversation: "The fact we’re able to draw useful lessons from such destruction is testament to the efforts of air accident investigators worldwide."