Tenerife airport disaster

Tenerife disaster
(KLM 4805 and Pan Am 1736)

CGI rendering of Pan Am 1736 about to be hit by KLM 4805. Some fog has been cleared to give a clearer perspective of the aircraft.
Accident
Date	March 27, 1977
Summary	Ground collision involving weather conditions, pilot error, technical limitations
Site	Los Rodeos Airport (now Tenerife North Airport) Tenerife, Canary Islands
Total fatalities	583
Total survivors	61
First aircraft
Type	Boeing 747-121
Name	Clipper Victor
Operator	Pan American World Airways
Registration	N736PAdisaster
Flight origin	Los Angeles International Airport
Stopover	John F. Kennedy International Airport, New York City, USA
Destination	Gran Canaria Airport
Passengers	380
Crew	16
Fatalities	335 (326 passengers, 9 crew members)
Survivors	61
Second aircraft
Type	Boeing 747-206B
Name	Rijn ("Rhine")
Operator	KLM Royal Dutch Airlines
Registration	PH-BUFdisaster
Flight origin	Schiphol Airport, Amsterdam, Netherlands
Destination	Gran Canaria Airport
Passengers	234
Crew	14
Fatalities	248 (all)
Survivors	None

The Tenerife airport disaster in 1977 was a collision involving two Boeing 747 airliners 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 583 fatalities, the crash remains the deadliest accident in aviation history. All 248 aboard the fully fuelled KLM flight were killed. There were also 335 fatalities and 61 survivors from the Pan Am flight, which was struck along its spine by the KLM's landing gear, under-belly and four engines. Rescue crews were unaware for over 20 minutes that the Pan Am aircraft was also involved in the accident, due to the heavy fog and the separation of the crippled aircraft following the collision.

The collision took place on 27 March 1977, at 17:06:56 local time. The aircraft were operating as Pan Am Flight 1736 (the Clipper Victor) under the command of Captain Victor Grubbs, and KLM Flight 4805 (the Rijn or Rhine in English) under the command of Captain Jacob Veldhuyzen van Zanten. Taking off in heavy fog on the airport's only runway, the KLM flight crashed into the top of the Pan Am aircraft backtaxiing in the opposite direction. The Pan Am had followed the backtaxiing of the KLM aircraft, under the direction of Air Traffic Control, and the KLM's flight crew had been aware of Pan Am backtaxiing behind them on the same runway. Despite lack of visual confirmation, due to the fog, the KLM captain thought that Pan Am had cleared the runway and so attempted to take off without further clearance to do so. Several other key factors contributed to the accident.

Flight details

For both planes, Tenerife was an unscheduled stop. Their destination was Gran Canaria International Airport (also known as Las Palmas airport), serving Las Palmas on the nearby island of Gran Canaria. Both are in the Canary Islands, an autonomous community of Spain located in the Atlantic Ocean off the west coast of Morocco.

Pan Am Flight 1736 had taken off from Los Angeles International Airport with an intermediate stop at New York's John F. Kennedy International Airport. The aircraft was a Boeing 747-121, registration N736PA. Of the 380 passengers, 14 had boarded in New York, where the crew was also changed. The new captain was Victor Grubbs, and the first officer ("co-pilot") was Robert Bragg; there were 14 other crew members. 61 people, including 5 crew members survived. The airplane was Pan Am's first Boeing 747 (ex Clipper Young America).

KLM Flight 4805, a charter flight for Holland International Travel Group from the Netherlands, had taken off four hours before from Amsterdam Airport Schiphol. Its captain was Jacob Veldhuyzen van Zanten and the first officer was Klaas Meurs. The aircraft was a Boeing 747-206B, registration PH-BUF. The KLM jet had 235 passengers and 14 crew members, including 48 children and three infants. Most of the KLM passengers were Dutch; four Germans, two Austrians, and two Americans were also on the plane. After the aircraft landed at Tenerife, a tour guide named Robina van Lanschot, who lived on the island in Puerto de la Cruz and wanted to see her boyfriend that night, elected not to re-board the 747, leaving 234 passengers on board.

Chain of events leading to disaster

Bombing at Las Palmas

Events on both planes had been routine until they approached the islands. Then, at 1:15 pm, a terrorist bomb (planted by separatist Fuerzas Armadas Guanches) exploded in the terminal of Gran Canaria International Airport. It had been preceded by a phone call warning of the bomb. The civil aviation authorities closed that airport after the bomb detonated and diverted all of its incoming flights to Los Rodeos, including the two Boeing 747 aircraft involved in the disaster. Upon contacting Gran Canaria airport, the Pan Am flight was informed of the temporary closure. Although the Pan Am crew indicated that they would prefer to circle in a holding pattern until landing clearance was given, the plane was ordered to divert to Los Rodeos, along with the KLM flight. This led to the critical cramped aircraft conditions within the smaller island's airport.

Congestion at Los Rodeos

In all, at least five large aircraft were diverted to Los Rodeos, a regional airport that could not easily accommodate them. The airport consisted of one runway and one major taxiway parallel to it, as well as several small taxiways connecting them. While waiting for Gran Canaria airport to reopen, the diverted aircraft took up so much space that they were parked on the long taxiway, meaning that it could not be used for taxiing. Instead, departing aircraft would have to taxi along the runway to position themselves for takeoff, a procedure known as a backtaxi. In this case, it was a deadly circumstance.

Refuelling

After the threat at Gran Canaria International Airport had been contained, authorities reopened the airport. The Pan Am aircraft was ready to depart, but the KLM plane and a refuelling vehicle obstructed the way to the active runway. Captain van Zanten had decided to fully refuel at Los Rodeos instead of Las Palmas, apparently to save time, but added extra weight, greatly retarding liftoff (and accident escape) ability, which proved fatal. The refuelling took an estimated 35 minutes. By a factor of just 12 feet of lack of maneuver clearance, due to KLM's refuelling, Pan Am was stuck behind it until KLM was finished, delaying its ability to fly out before the KLM flight. Airport conditions were tight and cramped.

Taxiing and weather conditions

Following the tower's instructions, the KLM aircraft was cleared to backtaxi the full length of runway 30 and make a 180° turn to put the aircraft in takeoff position — a difficult maneuver to perform with a 747 on a runway only 45 m (150 ft) wide. While KLM 4805 was backtaxiing on runway 30, the controller asked the flight crew to report when it was ready to copy the ATC clearance. Because the flight crew was performing the checklist, copying this clearance was postponed until the aircraft was in takeoff position on Runway 30. During taxiing, the weather deteriorated and low-lying clouds now limited the visual range to about 300 m (1,000 ft). Legal or stipulated threshold for take-off was 700 metres visibility, as noted in the Nova documentary and relayed by a surviving Pan Am pilot in an on camera interview. Pan Am pilots were thinking visibility conditions were not present for take-off. But weather changed by seconds and/or minutes.

Shortly afterward, Pan Am 1736 was instructed to also backtaxi, to follow the KLM aircraft down the same runway, to exit the runway by taking the "third exit" on their left and then using the parallel taxiway. Initially the crew was unclear as to whether the controller had told them to take the first or third exit. The crew asked for clarification and the controller responded emphatically by replying: "The third one, sir; one, two, three; third, third one". The crew began the taxi and proceeded to identify the unmarked taxiways using an airport diagram as they reached them.

Based on the chronology of the cockpit voice recorder (CVR) and the distances between the taxiways (and the location of the aircraft at the time of the collision), the crew successfully identified the first two taxiways (C-1 and C-2), but their discussion in the cockpit never indicated that they had sighted the third taxiway (C-3), which they had been instructed to use. There were no markings or signs to identify the runway exits. The Pan Am crew appeared to remain unsure of their position on the runway until the collision, which occurred near the intersection with the fourth taxiway (C-4). Pan Am's lack of visibility and runway exiting confusion probably contributed to its slow taxiing speed, another key factor in the accident.

The angle of the third taxiway would have required the plane to perform a turn of approximately 145°, which would lead counter-productively back toward the still-crowded main apron. At the end of C-3 another 145° turn would have to be made to continue taxiing towards the start of the runway. Taxiway C-4 would have required just two 35° turns. A study carried out by the Air Line Pilots Association after the accident concluded that making the second 145° turn at the end of taxiway C-3 would have been "a practical impossibility", although the Dutch report stated that such a maneuver "could reasonably be performed". The official report from the Spanish authorities did not explain why the controller had instructed the Pan Am aircraft to use the third taxiway, rather than the sensible and easier fourth taxiway.

Communication misunderstandings

Immediately after lining up, the KLM captain advanced the throttles (a standard procedure known as "spin-up", to possibly verify that the engines are operating properly for takeoff) and the co-pilot, surprised by the maneuver, quickly advised the captain that ATC clearance had not yet been given. The captain responded, "I know that. Go ahead, ask." The co-pilot then radioed the tower that they were "ready for takeoff" and "waiting for our ATC clearance". The KLM crew then received a clearance which specified the route that the aircraft was to follow after takeoff. The instructions used the word "takeoff", but did not include an explicit statement they were cleared for takeoff.

The KLM co-pilot read the flight clearance back to the controller, completing the readback with the statement "we're now at takeoff" or "we're now, uh, taking off" (the exact wording of his statement was not clear), indicating to the controller that they were beginning their takeoff roll. The captain interrupted the co-pilot's readback with the comment "We're going". As noted in the Nova documentary, the subordinate co-pilot this time chose not to embarrass his superior a second time and state they still did not have the proper clearance to take-off.

The Spanish controller, who could not see the runway due to the fog, initially responded with "OK" (terminology which is nonstandard), which reinforced the KLM crew's or captain's misinterpretation that they had takeoff clearance. The controller's response of "OK" to the co-pilot's nonstandard statement that they were "now at takeoff" was likely due to his misinterpretation that they were in takeoff position and ready to begin the roll when takeoff clearance was received, but not actually in the process of taking off. The controller then immediately added "Stand by for takeoff, I will call you", indicating that he had not intended the clearance to be interpreted as a takeoff clearance. He probably had not heard the captain's announcement that they were "going", since van Zanten had said this to his fellow crew members and not transmitted it on the radio himself.

However, a simultaneous radio call from the Pan Am crew caused mutual interference on the radio frequency, which was audible in the KLM cockpit as a whistling sound (or heterodyne). This made the crucial latter portion of the tower's response audible only with difficulty by the KLM crew. The Pan Am crew's transmission, which was also critical, was reporting that "We're still taxiing down the runway, the Clipper 1736!" This message was also blocked by the heterodyne and inaudible to the KLM crew. Either message, if heard in the KLM cockpit, would have given the KLM crew time to abort its second takeoff attempt.

Due to the fog, neither crew was able to see the other plane on the runway ahead of them. In addition, neither of the aircraft could be seen from the control tower, and the airport was not equipped with ground radar.

After the KLM plane had started its takeoff roll, the tower instructed the Pan Am crew to "report when runway clear". The crew replied: "OK, we'll report when we're clear". On hearing this, the KLM flight engineer expressed his concern about the Pan Am not being clear of the runway by asking the pilots, "Is he not clear, that Pan American?". However, the captain emphatically replied "Oh, yes" and continued with the takeoff.

Collision

Simplified map of runway, taxiways, and aircraft. The red star indicates the location of impact.

According to the CVR, Captain Grubbs, captain of the Pan Am plane, spotted the KLM's landing lights just as the plane approached exit C-4, exclaiming, "Goddamn, that son-of-a-bitch is coming!" with the co-pilot Robert Bragg yelling, "Get off! Get off! Get off!". The Pan Am crew applied full power and took a sharp left turn towards the exit to avoid a collision. KLM Captain van Zanten attempted to avoid a collision by climbing away, scraping the tail of the plane along the runway for 20 m (70 ft). The lower fuselage of the KLM plane hit the upper right side of the Pan Am's fuselage at approximately 140 knots (160 mph), ripping apart the center of the Pan Am jet nearly directly above the wing, and KLM's right engines totally took out Pan Am's upper-deck passenger cabin on the 747.

The KLM plane was briefly airborne, 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, went into a stall, rolled sharply, slammed into the ground at a point 150 m (500 ft) past the point of collision and slid a further 300 m down the runway. Being fully fuelled, a deadly inferno ensued.

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."

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 also killed, primarily due to the fire and explosions resulting from the fuel spilled in the impact. The other 56 passengers and 5 crew members aboard the Pan Am aircraft survived, including the captain, first officer, 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. After a short time running at full power the Pan-Am's engines began to disintegrate, throwing engine parts at high speed that killed at least one 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 and the airline's preferred pilot for publicity such as magazine advertisements. As such, KLM attempted to contact him to give public statements regarding the disaster, before learning that he was the captain involved. Veldhuyzen van Zanten had given Klaas Meurs, the first officer on the ill-fated flight, his Boeing 747 qualification check about two months before the accident.

Investigation

About 70 crash investigators from Spain, the Netherlands, the United States, and the two airline companies were involved in the investigation. Facts showed that there had been misinterpretations and false assumptions. Analysis of the CVR transcript showed that the KLM pilot was convinced that he had been cleared for takeoff, while the Tenerife control tower was certain that the KLM 747 was stationary at the end of the runway and awaiting takeoff clearance. It appears KLM's co-pilot was not as certain about take-off clearance as the captain.

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.

Probable cause

The investigation concluded that the fundamental cause of the accident was that the KLM captain took off without a 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 each other.
• 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").
• Pan Am mistakenly continued to exit C-4 instead of exiting at C-3 as directed.
• 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.

Dutch response

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 football game 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 message "We are still taxiing down the runway, the Clipper 1736!" indicated that the Captain Bragg had recognised the ambiguity;
• if the Pan Am aircraft had not taxied beyond the third exit, the collision would not have occurred.

Speculations

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. He may have suffered from "training syndrome", having been in charge of everything at the simulator (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.
  • After having studied the cockpit voice recorder, some investigators say 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 before he had adequate airspeed. The sharp lifting angle caused the KLM jet to drag its tail on the runway, thereby reducing its speed even further. The plane had, however, exceeded its V1 speed.

Responsibility

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.

Safety response

As a consequence of the accident, there were sweeping changes made to international airline regulations and to aircraft. Aviation authorities around the world introduced requirements for standard phrases and a greater emphasis on English as a common working language. For example, ICAO calls for the phrase "line up and wait" as an instruction to an aircraft moving into position but not cleared for takeoff. The FAA equivalent is "position and hold". Also several national air safety boards began penalizing pilots for disobeying air traffic controller's orders. Air traffic instruction should not be acknowledged solely with a colloquial phrase such as "OK" or even "Roger", but with a readback of the key parts of the instruction, to show mutual understanding. Additionally, the phrase "takeoff" is only spoken when the actual takeoff clearance is given. Up until that point both aircrew and controllers should use the phrase "departure" in its place (e.g. "ready for departure"). Cockpit procedures were also changed. Hierarchical relations among crew members were played down. More emphasis was placed on team decision-making by mutual agreement. This is known in the industry as Crew Resource Management.

In 1978 a second airport was inaugurated on the island: the new Tenerife South Airport (TFS). This airport now serves the majority of international tourist flights. Los Rodeos, renamed to Tenerife North Airport (TFN), was then used only for domestic and inter-island flights, but in 2002 a new terminal was opened and it carries international traffic once again, including budget airlines. The Spanish authorities installed a ground radar at Tenerife North following the accident.

Memorials

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Monument in Westgaarde Cemetery, Amsterdam

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File:Monumento Conmemmorativo Internacional 27 de Marzo de 1977.jpg

International Tenerife Memorial, Mount Mesa Mota, Tenerife, Canary Islands

|}A Dutch national memorial and final resting place for the victims of the KLM plane is located in Amsterdam, at Westgaarde cemetery. There is also a memorial at the Westminster Memorial Park and Mortuary in Westminster, California.

The 30th anniversary marked the first time that Dutch and American next of kin, and aid helpers from Tenerife, joined in international commemoration service held at the Auditorio de Tenerife in Santa Cruz; the International Tenerife Memorial was inaugurated at the Mesa Mota March 27, 2007. The monument was designed by Dutch sculptor Rudi van de Wint. A special 50-page commemorative booklet including a DVD in English, Dutch, and Spanish was published a year later, on March 27, 2008.

Notable people killed in the disaster

• Eve Meyer, a pin-up model, film actress and producer and former wife of Russ Meyer.
• A. P. Hamann, the former city manager of San Jose, California, and his wife Frances Hamann.

The crash in popular culture

The disaster has featured in many TV shows and documentaries. These include Survival in the Sky, Black Box, Seconds From Disaster: Season 1: Collision on the Runway, Cineflix's Crash of the Century and the Discovery Channel TV series Most Deadly and Destroyed In Seconds. It featured in PBS's NOVA episode "The Deadliest Plane Crash" in 2006.

See also

• Linate Airport disaster (October 2001)
• List of accidents and incidents on commercial airliners grouped by year
• National Geographic Seconds From Disaster episodes

External links

• "Ask a Pilot: A look back at the catastrophic chain of events that caused history's deadliest plane crash 30 years ago." by Patrick Smith, Salon.com, April 6, 2007
• Accident description for Pan Am Flight 1736 at the Aviation Safety Network
• Accident description for KLM Flight 4805 at the Aviation Safety Network
• AirDisaster.com Accident Database (Pan Am 1736)
• AirDisaster.com Accident Database (KLM 4805)
• ICAO document mentioning phrasing used in the accident
• Tenerife – a survivor’s tale, by Robert L. Bragg (Capt., Pan Am and United, Ret.)
• Secret Tenerife: On This Day in 1977: Runway Collision Kills 583, March 27, 2004
• Historic BBC news report
• PBS's: NOVA "The Deadliest Plane Crash" (2006) - Homepage to the NOVA TV episode 3 of season 34
• International Tenerife Memorial
• Project Tenerife
• List of passengers on the Pan Am
• List of passengers on the KLM
• PlaneCrashInfo.Com - Tenerife Disaster
• Airliners.net photos:
  • PH-BUF (KLM 4805)
  • N736PA (Pan Am 1736)