Air Canada Flight 621
| Air Canada Flight 621 | |
|---|---|
 An identical aircraft from the company |
|
| Accident summary | |
| Accident type | structural failure after engine stall |
| place | near Brampton (Ontario) |
| date | 5th July 1970 |
| Fatalities | 109 |
| Survivors | 0 |
| Aircraft | |
| Aircraft type | Douglas DC-8-63 |
| operator | Air Canada |
| Mark | CF-TIW |
| Departure airport |
 Montreal-Dorval Airport , Quebec , Canada
|
| Stopover |
Toronto International Airport , Ontario , Canada
|
| Destination airport |
 Los Angeles International Airport , United States
|
| Passengers | 100 |
| crew | 9 |
| Lists of aviation accidents | |
On July 5, 1970, a Douglas DC-8-63 crashed on Air Canada Flight 621 after several explosions tore open the fuel tanks in the right wing . This was preceded by a go - around maneuver at Toronto International Airport , where the plane landed so hard that an engine broke off and a wing tank leaked. All 109 inmates were killed in the accident.
Flight history
Air Canada's Douglas DC-8 ( registration number : CF-TIW), which was delivered on April 29, 1970 , was on a scheduled flight from Montreal-Dorval Airport via Toronto- International Airport to Los Angeles International Airport . Until shortly before the stopover in Toronto , the flight went without any special incidents.
The two pilots had already flown many times together and, at the captain's insistence, had got used to skipping the step “ unlocking spoilers ” prescribed in the landing checklist . Only when the aircraft passed the lights on runway 32 at a height of around 18 meters (60 feet ) did the captain request the co-pilot to unlock the spoilers. The co-pilot accidentally extended the flaps completely instead of simply unlocking them. The machine suddenly lost its lift. Although the master immediately initiated a go-around maneuver, he could not prevent the aircraft from sagging and the main landing gear from touching down very hard on the runway. The high angle of attack of the machine led to a tail strike . The impact occurred at a rate of descent of about six meters per second and exceeded the structural load limits of the aircraft, as a result of which the right outer engine (engine no. 4) and its suspension tore off the wing.
Only half a second later the plane took off again. The crew retracted the spoilers and landing gear and climbed to a height of almost 850 meters (3,100 feet). The pilot notified the air traffic control with that they are in a traffic pattern would tighten to execute a renewed approach to the runway 32nd The lower hull of the right reserve tank was damaged by the demolition of the engine pylon. The leaking kerosene probably ignited on the torn electrical cables. Eyewitnesses on the ground stated that the aircraft dragged a dark plume of smoke behind it during the climb and flames could be seen. About two and a half minutes after take-off, the outer section of the right wing was torn open by an explosion of the fuel gases in the reserve tank. A second explosion occurred eight seconds later in the main tank further to the fuselage, causing the right inner engine (engine no. 3) to break off. A further six and a half seconds later, a third explosion caused extensive damage to the wing structure, which led to the complete demolition of the outer third of the wing. The machine then rolled to the right around its longitudinal axis and went into an uncontrolled nosedive . The burning Douglas DC-8 hit a field around ten kilometers northwest of the airport, near the city of Brampton , at a speed of around 410 km / h (220 knots ).
Accident investigation
The Canadian final report does not meet the requirements of the ICAO and does not contain any explicit information on the “probable cause of the accident”. It is clear from the report, however, that the accident was caused by the captain's failure to comply with the binding checklist procedure, his unclear instructions and the resulting operating error on the part of the copilot.
According to the airline's aircraft operating manual, the spoilers should be unlocked when working through the landing checklist, so that they are set automatically after touchdown. The captain had got used to skipping the step “unlocking spoilers” , which is a binding step in the landing checklist , because he feared that the flaps could inadvertently deploy in the event of a malfunction. The master also asked his first officers to implement the deviating procedure. The co-pilot of this flight had initially spoken out clearly against the non-compliance with the regulations requested by the captain on previous joint flights and demanded that the spoilers should be operated as prescribed in the operations manual. This conflict was eventually resolved through a compromise between the two views. When the co- pilot was flying the machine (" pilot flying "), the captain (" pilot not flying ") unlocked the spoilers on call on the final approach . If, on the other hand, the captain steered the aircraft ("pilot flying"), the spoilers were not unlocked before landing, but instead were manually extended by the copilot immediately after touchdown. On the day of the accident, the crew deviated from their own chosen approach. The captain had announced that this time the flaps should be unlocked shortly before touching down on his call; When he gave the brief and non-standardized “OK” command a few minutes later , the copilot (“pilot not flying”) extended the flaps manually as usual. The copilot recognized his mistake immediately and apologized. At the same time, the captain increased the power of the engines to the maximum and pulled the aircraft nose up to take off. Before the engines reached their take-off capacity , the plane hit the runway hard.
There was no evidence that the pilots were aware of the severity of the damage the aircraft had sustained on touchdown. They only registered 107 seconds after take-off that engine no. 4 was no longer delivering power, but they probably assumed an engine failure and not a complete demolition of the engine. Likewise, the pilots did not notice that kerosene was leaking and the wing had caught fire. The crew did not mention any technical problems while speaking to air traffic control and announcing the traffic pattern. The conversations recorded by the cockpit voice recorder also did not indicate that the pilots assumed that there were serious problems until the first tank explosion.
According to the investigators, the consequences would not have been so devastating if the captain had decided against the go-around and in favor of continuing the landing. However, he was not accused of any wrongdoing because he wanted to prevent a collision with the runway with the maneuver and could hardly foresee the resulting consequences.
The accident resulted from failure to comply with the checklist procedure. The crew's approach, which deviated massively from the standard anyway, was fundamentally changed again during the flight involved in the accident and the fatal extension of the spoilers was triggered by the captain's highly ambiguous “OK” command . As a result, the co-pilot pulled the lever for the spoilers as usual into the lower position instead of the upper position and thus accidentally extended the flaps.
Neither in the operating manuals of the manufacturer Douglas nor those of Air Canada had it been documented that manual setting of the spoilers was even possible after the landing gear had been extended. The Air Canada training pilots were also not aware of this. The Canadian commission of inquiry criticized the fact that the manufacturer had failed to install a safety mechanism that prevented the spoilers from being unintentionally deployed on approach. After a Douglas DC-8-61 of the Icelandic airline Loftleidir was damaged on June 23, 1973 by a similar operating error of the spoilers during a landing at John F. Kennedy International Airport , the US Federal Aviation Administration (FAA) ordered an appropriate safety retrofitting of all aircraft of the DC-8-50 and DC-8-60 series.
Individual evidence
- ↑ a b c d e f g h Official final report of the Canadian commission of inquiry (PDF) ( Memento of May 29, 2005 in the Internet Archive )
- ^ A b Aviation Safety Network, July 5, 1970
- ^ Aircraft disasters , David Gero, Stuttgart 1994
Coordinates: 43 ° 46 ′ 47 " N , 79 ° 41 ′ 28" W.