S01E12 Collision on the Runway: Tenerife airport disaster

January 15, 2013 | By | Comments More

On March 27, 1977, on the island of Tenerife in the Canary Islands, two 747 jumbo jets collided on a fog-shrouded runway, killing 583 people in what is still the deadliest crash in aviation history. Because the actions of both the flight crews of the two aircraft and Los Rodeos Airport’s air traffic controllers directly contributed to the disaster, the log of conversations between the two planes and the tower in the minutes leading up to the collision was investigators’ key tool for ultimately piecing together the events. Here, read an annotated transcript of the two planes’ communications with the tower.

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The Tenerife airport disaster occurred on Sunday, March 27, 1977, when two Boeing 747 passenger aircraft collided on the runway of Los Rodeos Airport (now known as Tenerife North Airport) on the Spanish island of Tenerife, one of the Canary Islands. With a total of 583 fatalities, the crash is the deadliest accident in aviation history.

After a bomb exploded at Gran Canaria Airport, many aircraft were diverted to Tenerife. Among them were KLM Flight 4805 and Pan Am Flight 1736 – the aircraft involved in the accident. The threat of a second bomb forced the authorities to close the airport while a search was conducted, resulting in many airplanes being diverted to the smaller Tenerife airport where air traffic controllers were forced to park many of the airplanes on the taxiway, thereby blocking it. Further complicating the situation, while authorities waited to reopen Gran Canaria, a dense fog developed at Tenerife, greatly reducing visibility. When Gran Canaria reopened, the parked aircraft blocking the taxiway at Tenerife required both of the 747s to taxi on the only runway in order to get in position for takeoff. Due to the fog, neither aircraft could see the other, nor could the controller in the tower see the runway or the two 747s on it. As the airport did not have ground radar, the only means for the controller to identify the location of each airplane was via voice reports over the radio. As a result of several misunderstandings in the ensuing communication, the KLM flight attempted to take off while the Pan Am flight was still on the runway. The resulting collision destroyed both aircraft, killing all 248 aboard the KLM flight and 335 of 396 aboard the Pan Am flight. Sixty-one people aboard the Pan Am flight, including the pilots and flight engineer, survived the disaster. 

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As the accident occurred in Spanish territory, that nation was responsible for investigating the accident. Investigators from the Netherlands and the United States also participated. The investigation revealed that the primary cause of the accident was the captain of the KLM flight taking off without clearance from Air Traffic Control (ATC). The investigation specified that the captain did not intentionally take off without clearance; rather he fully believed he had clearance to take off due to misunderstandings between his flight crew and ATC. Dutch investigators placed a greater emphasis on this than their American and Spanish counterparts, but ultimately KLM admitted their crew was responsible for the accident, and the airline financially compensated the victims.

The accident had a lasting influence on the industry, particularly in the area of communication. An increased emphasis was placed on using standardized phraseology in ATC communication by both controllers and pilots alike, thereby reducing the chance for misunderstandings. As part of these changes, the word “takeoff” was removed from general usage, and is only spoken by ATC when actually clearing an aircraft to take off. Less experienced flight crew members were encouraged to challenge their captains when they believed something was not correct, and captains were instructed to listen to their crew and evaluate all decisions in light of crew concerns. This concept would later be expanded into what is known today as Crew Resource Management. CRM training is now mandatory for all airline pilots.

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According to the CVR, Captain Grubbs, captain of the Pan Am plane, said, “There he is.” when he spotted the KLM’s landing lights through the fog just as his plane approached exit C-4. When it became clear that the KLM was coming towards them at takeoff speed, Grubbs exclaimed, “Goddamn, that son-of-a-bitch is coming straight at us!” while the co-pilot Robert Bragg yelled, “Get off! Get off! Get off!”. The Pan Am crew applied full power to the throttles and took a sharp left turn towards the grass in an attempt to avoid a collision. By the time Captain Veldhuyzen van Zanten noticed the Pan Am on the runway ahead, his aircraft was already traveling too fast to stop. In desperation he prematurely rotated his aircraft and attempted to clear the Pan Am by climbing away, causing a tailstrike for 20 m (66 ft).

The KLM was within 100m of the Pan Am when it left the ground. As it did so, its excessively steep angle of attack allowed the nose gear to clear the Pan Am but the engines, lower fuselage and aft landing gears struck the upper right side of the Pan Am’s fuselage at approximately 140 knots (260 km/h; 160 mph), ripping apart the center of the Pan Am jet almost directly above the wing. The right side engines crashed through the Pan Am’s upper deck immediately behind the cockpit.

The KLM plane remained briefly airborne following the collision, but the impact with the Pan Am had sheared off the #1 (outer left) engine, and the #2 (inner left) engine had ingested significant amounts of shredded materials from the Pan Am. The KLM pilot quickly lost control, and the 747 went into a stall, rolled sharply, and hit the ground at a point 150 m (500 ft) past the collision, sliding a further 300m down the runway. The full load of fuel, which had caused the earlier delay, ignited immediately.

A survivor of the Pan Am flight, John Coombs of Haleiwa, Hawaii, said that sitting in the nose of the plane probably saved his life: “We all settled back, and the next thing an explosion took place and the whole port side, left side of the plane, was just torn wide open.”

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Both airplanes were destroyed. All 234 passengers and 14 crew members in the KLM plane died, while 326 passengers and 9 crew members aboard the Pan Am flight were killed, primarily due to the fire and explosions resulting from the fuel spilled and ignited in the impact. The other 56 passengers and 5 crew members aboard the Pan Am aircraft survived, including the pilots and flight engineer. Most of the survivors on the Pan Am aircraft walked out onto the left wing, the side away from the collision, through holes in the fuselage structure. The Pan Am’s engines were still running at takeoff power for a few minutes after the accident despite First Officer Bragg’s intention to turn them off. The top part of the cockpit, where the engine switches were located, had been destroyed in the collision, and all control lines were severed, leaving no method for the flight crew to control the aircraft’s systems. After a short time running at full power, the Pan-Am’s engines began to disintegrate, throwing engine parts at high speed that killed a flight attendant who had escaped the burning plane. Survivors waited for rescue, but it did not come promptly, as the firefighters were initially unaware that there were two aircraft involved and were concentrating on the KLM wreck some distance away in the thick fog. Eventually, most of the survivors on the wings dropped to the ground below.

Captain Veldhuyzen van Zanten was KLM’s chief of flight training. His photograph was used for publicity materials such as magazine advertisements, including the inflight magazine on board PH-BUF. As such, KLM attempted to contact him to give public statements regarding the disaster, before learning that he was the captain involved. He had given the co-pilot on the ill-fated flight his Boeing 747 qualification check about two months before the accident.

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Category: Aircraft Disaster, Latest Episodes, Season 1

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