Collision on the Runway is the 12th episode of Seconds from Disaster and finds the cause of the worst air accident in aviation history.
KLM Flight 4805 and Pan Am Flight 1736 collide and explode on the runway at Los Rodeos Airport in the Canary Islands, killing 583 people.
CauseEditAbout 70 crash investigators from Spain, the Netherlands, the United States, and the two airline companies were
Subsequent to the crash, first officer Robert Bragg, who was responsible for handling the Pan Am's radio communications, made public statements which conflict with statements made by the Pan Am crew in the official transcript of the CVR. In the documentary Crash Of The Century (produced by the makers of Mayday), he stated he was convinced the tower controller had intended they take the fourth exit C-4 because the controller delivered the message to take "the third one, sir; one, two, three; third, third one" after the Pan Am's had already passed C-1 (making C-4 the third exit counting from there). The CVR shows unequivocally that they received this message before they identified C-1, with the position of the aircraft somewhere between the entrance and C-1. Also, in a Time article, Bragg stated that he made the statement "What's he doing? He'll kill us all!" which does not appear in the CVR transcript.
The investigation concluded that the fundamental cause of the accident was that Captain Van Zanten took off without takeoff clearance. The investigators suggested the reason for his mistake might have been a desire to leave as soon as possible in order to comply with KLM's duty-time regulations, and before the weather deteriorated further.
Other major factors contributing to the accident were:
- The sudden fog greatly limited visibility. The control tower and the crews of both planes were unable to see one another.
- Simultaneous radio transmissions, with the result that neither message could be heard.
The following factors were considered contributing but not critical:
- Use of ambiguous non-standard phrases by the KLM co-pilot ("We're at take off") and the Tenerife control tower ("OK").
- The Pan Am aircraft had not exited the runway at C-3.
- The airport was (due to rerouting from the bomb threat) forced to accommodate a great number of large aircraft, resulting in disruption of the normal use of taxiways.
The Dutch authorities were reluctant to accept the Spanish report blaming the KLM captain for the accident. The Netherlands Department of Civil Aviation published a response that, whilst accepting that the KLM aircraft had taken off "prematurely", argued that he alone should not be blamed for the "mutual misunderstanding" that occurred between the controller and the KLM crew, and that limitations of using radio as a means of communication should have been given greater consideration.
In particular, the Dutch response pointed out that
- the crowded airport had placed additional pressure on all parties, KLM, Pan Am, and the controller;
- sounds on the CVR suggested that during the incident the Spanish control tower crew had been listening to a soccer match on the radio and may have been distracted.
- the transmission from the tower in which the controller passed KLM their ATC clearance was ambiguous and could have been interpreted as also giving take-off clearance. In support of this part of their response, the Dutch investigators pointed out that Pan Am's messages "No! Eh?" and "We are still taxiing down the runway, the Clipper 1736!" indicated that Captain Grubbs and First Officer Bragg had recognised the ambiguity;
- if the Pan Am aircraft had not taxied beyond the third exit, the collision would not have occurred.
Speculation regarding other contributing factors includes:
- Captain Van Zanten's failure to confirm instructions from the tower. The flight was one of his first after spending six months training new pilots on a flight simulator, where he had been in charge of everything (including simulated ATC), and having been away from the real world of flying for extended periods.
- The flight engineer's apparent hesitation to challenge Van Zanten further, possibly because Captain Van Zanten was not only senior in rank, but also one of the most able and experienced pilots working for the airline.
- A study group put together by the Air Line Pilots Association found that not only the captain, but the first officer as well dismissed the flight engineer's question. In that case, the flight engineer might have been either reassured or even less inclined to press the question further.
- The reason only the flight engineer reacted to the radio transmission "Alpha one seven three six report when runway clear" might lie in the fact that this was the first and only time the Pan Am was referred to by that name. Before that, the plane was called "Clipper one seven three six". The flight engineer, having completed his pre-flight checks, might have recognized the numbers but his colleagues, preparing themselves for take-off, might have subconsciously been tuned in to "Clipper".
- The extra fuel the KLM plane took on added several factors:
- it delayed takeoff an extra 35 minutes, which gave time for the fog to settle in;
- it added over forty tons of weight to the plane, which made it more difficult to clear the Pan Am when taking off;
- it increased the size of the fire from the crash that ultimately killed everyone on board.
- Captain Van Zanten's reaction, once he spotted the Pan Am plane, was to attempt to take off. Although the plane had exceeded its V1 speed, it did not yet have adequate airspeed. The sharp lifting angle caused the KLM jet to drag its tail on the runway, thereby reducing its speed even further.
Although the Dutch authorities were initially reluctant to blame Captain Van Zanten and his crew, the airline ultimately accepted responsibility for the accident. KLM paid the victims or their families compensation ranging between $58,000 and $600,000. As reported in a March 25, 1980, Washington Post article the sum of settlements for property and damages was $110 million (an average of $189,000 per victim, due to limitations imposed by European Compensation Conventions in effect at the time).