Tenerife airport disaster

Tenerife disaster
(KLM 4805 & Pan Am 1736)

Occurrence
Date	March 27 1977
Summary	Runway collision
Site	Tenerife, Canary Islands, Spain
Aircraft type	Boeing 747-121
Aircraft name	Clipper Victor
Operator	Pan American World Airways
Registration	N736PAdisaster
Passengers	380
Crew	16
Fatalities	583
Injuries	61
Survivors	61

The Tenerife collision took place on March 27, 1977, at 17:06:56 local time (also GMT), when two Boeing 747 airliners collided at Los Rodeos (TCI) on the island of Tenerife, Canary Islands, Spain, killing 583 people. The accident has the highest number of fatalities (excluding ground fatalities) of any single accident in aviation history. It occurred as a result of an unfortunate synchronicity of a chain of events, any one of which having not transpired would have prevented the accident.

The aircraft involved were Pan American World Airways Flight 1736, named Clipper Victor, under the command of Captain Victor Grubbs, and KLM Royal Dutch Airlines Flight 4805, named Rijn (Rhine River), under the command of Captain Jacob Veldhuyzen van Zanten. KLM 4805, taking off on the only runway of the airport, crashed into the Pan Am aircraft which was taxiing on the same runway.

Tenerife North Airport (TFN) (then called Los Rodeos - TCI) is situated in the northern part of Tenerife, and is now used mainly for flights within the Canary Islands and flights from the Spanish mainland.

Bomb threat

Pan Am Flight 1736 had taken off from Los Angeles International Airport with an intermediate stop at New York's JFK International Airport. The aircraft was a Boeing 747-121, registration N736PA. KLM Flight 4805, a charter flight from the Netherlands, had taken off four hours before from Amsterdam Schiphol Airport. The destination of both planes was Las Palmas on Gran Canaria.

Upon contacting Gran Canaria International Airport, the Pan Am flight was told that the airport was temporarily closed due to a bomb attack supposedly by Canary Islands' separatists. A bomb had exploded in the airport concourse, injuring several people, and a threat of a second bomb had been received. Although the Pan Am crew indicated that they would prefer to circle until landing clearance was given, the plane was ordered to divert to Tenerife North Airport (Los Rodeos) on the nearby island of Tenerife, together with many other planes. The KLM aircraft was also given instructions to divert to 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. The diverted aircraft 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.

Chain of events leading to disaster

Refueling

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 refueling vehicle obstructed the way to the active runway. Captain van Zanten had decided to refuel at Los Rodeos instead of Las Palmas, apparently to save time. The refuelling was to take an estimated 35 minutes.

Taxiing and weather conditions

Following the tower's instructions, the KLM aircraft was cleared to backtaxi to the end of the only runway and make a 180 degree turn to put the aircraft in takeoff position (a difficult maneuver to perform with a 747 on the narrow 150' wide runway). While KLM 4805 was backtaxiing on the runway, 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 had limited the visual range to about 300 meters.

Shortly afterwards Pan Am 1736 was instructed to also backtaxi along the same runway and take the third exit on their left, leaving the main runway, and taxi via 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 using an airport diagram proceeded to identify the unmarked taxiways as they slowly reached them. Based on the chronology of the 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 (C-1) and second (C-2) taxiways but their discussion in the cockpit never indicated that they had identified the third (C-3) taxiway which they were instructed to use. The crew appeared to remain unsure of their position on the runway up until the collision which occurred near the intersection with the fourth taxiway (C-4).

Communication misunderstandings

Immediately after lining up, the KLM captain advanced the throttles slightly (a standard procedure known as spin-up to verify the engines are operating properly for takeoff) and the co-pilot 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 take-off" and "waiting for our ATC clearance". The KLM crew then received a clearance which specified the aircraft's departure route and gave instructions which stated what to do after take-off (the word take-off itself was part of the clearance); but not an explicit, distinct statement saying that they were cleared for take-off. The KLM co-pilot read the clearance back to the controller completing the readback with the statement "we're now at take-off" 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 take-off roll. The controller initially responded with "O.K." (terminology which, although commonly used, is nonstandard), which the KLM crew heard clearly and reinforced their misinterpretation that they indeed had explicit take-off clearance. The controller's response of "O.K." to the co-pilot's nonstandard statement that they were "now at take-off" was likely due to his misinterpretation that they were in take-off position, and ready to begin the roll when take-off clearance was received, but not actually in the process of take-off. The controller then immediately added "Stand by for take-off, I will call you", indicating that the controller had never intended the clearance to be interpreted as a take-off clearance. However, a simultaneous radio call from the Pan Am crew at that precise moment caused mutual interference on the radio frequency and all that was audible in the KLM cockpit was a heterodyne beat tone, making the crucial latter portion of the tower's response inaudible to the KLM pilots. The Pan Am crew's transmission, which was also critical, was reporting that they had not finished taxiing and were still on the runway. This message was also blocked by the heterodyne and inaudible to the KLM crew. Either message, if broadcast separately, would have been audible in the KLM cockpit and given the KLM crew time to abort its take-off.

Due to the fog, the KLM crew was not able to see the Pan Am 747 taxiing 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.

While the KLM crew had started its take-off 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 if the Pan Am was not clear, however the captain, focused on the takeoff and under the impression that they had take-off clearance, replied yes emphatically and continued with the take-off.

Final radio & flight deck transmissions

These communications are taken from the cockpit voice recorders of both aircraft, as well as from the Tenerife control tower's tapes.

1705:22.0
PAN AM CAPTAIN That's two. [Captain Grubbs is identifying the second turn-off from the runway as the Pan Am continues to back-taxi]
1705:36.7
[KLM first officer completes pre-flight checklist. KLM 4805 is now at the end of the runway, in position for departure.]
1705:41.5
KLM FIRST OFFICER Wait a minute, we don't have an ATC clearance. [This statement is apparently a response to an advancing of the throttles in the KLM.]
KLM CAPTAIN Nee, dat weet ik, vraag maar. [No, I know that, ask for it.]
1705:44.8
KLM (RADIO) Uh, the KLM ... four eight zero five is now ready for take-off ... uh and we're waiting for our ATC clearance.
1705:53.4 - 1706:08.9
TENERIFE TOWER eight seven * zero five uh you are cleared to the Papa Beacon climb to and maintain flight level nine zero right turn after take-off proceed with heading zero four zero until intercepting the three two five radial from Las Palmas VOR.
1706:07.4
KLM CAPTAIN Yes.
1706:09.6 - 1706:17.8
KLM (RADIO) Ah roger, sir, we're cleared to the Papa Beacon flight level nine zero, right turn out zero four zero until intercepting the three two five and we're now (at take-off / uh..taking off).
1706:11.1
[KLM brakes released.]
1706:12.2
KLM CAPTAIN We gaan ... check thrust. [We're going ... check thrust].
1706:14.0
[Engine acceleration audible in KLM cockpit]
1706:18.19
TENERIFE TOWER OK.
1706:19.3
PAN AM (RADIO) No .. eh.[This message was not heard by the KLM crew due to a radio heterodyne.]
1706:20.08
TENERIFE TOWER Stand by for take-off, I will call you. [This message was not heard by the KLM crew due to a radio heterodyne.]
1706:20.3
PAN AM (RADIO) And we're still taxiing down the runway, the clipper one seven three six. [This message was not heard by the KLM crew due to a radio heterodyne.]
1706:19.39 - 1706:23.19
TENERIFE TOWER Roger alpha one seven three six report when runway clear.
1706:29.6
PAN AM (RADIO) OK, we'll report when we're clear.
1706:31.7
TENERIFE TOWER Thank you
1706:xx.x
PAN AM CAPTAIN Let's get the hell out of here.
1706:xx.x
PAN AM FIRST OFFICER Yeah, he's anxious, isn't he.
1706:xx.x
PAN AM FLT ENGR Yeah, after he held us for half an hour. Now he's in a rush.
1706:32.43
KLM FLT ENGR Is hij er niet af dan? [Is he not clear then?]
1706:34.1
KLM CAPTAIN Wat zeg je? [What do you say?]
1706:34.15
KLM UNKNOWN Yup.
1706:34.7
KLM FLT ENGR Is hij er niet af, die Pan American? [Is he not clear, that Pan American?]
1706:35.7
KLM CAPTAIN Jawel. [Oh yes. - emphatic]
1706:40.0
[Pan Am captain sees landing lights of KLM Boeing at approx. 700 m]
PAN AM CAPTAIN There he is ... look at him. Goddamn that son of a bitch is coming!
PAN AM FIRST OFFICER Get off! Get off! Get off!
1706:43.4
KLM FIRST OFFICER Vee-one.
1706:44.0
[PH-BUF (KLM 4805) started rotation.]
1706:47.4
KLM CAPTAIN [Exclamation/expletive]
1706:50
N736PA (Pan Am 1736) records sound of collision.

Collision

Simplified map of runway, taxiways, and aircraft. The red star is 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 C4. The Pan Am crew applied full power and took a sharp left turn onto 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 metres (65 ft). The lower fuselage of the KLM plane hit the upper fuselage of the Pan Am plane, ripping apart the center of the Pan Am jet nearly directly above the wing.

The KLM plane was briefly airborne, but the impact with the Pan Am had sheared off the #1 (rightmost) engine, and the #2 engine (inner starboard) had ingested significant amounts of shredded materials from the Pan Am. The KLM pilot quickly lost control, went into a stall, rolled sharply, and slammed into the ground belly-up at a point 150 m past the point of collision and slid a further 300 meters down the runway.

All 234 passengers and 14 crew members in the KLM plane were killed. 326 passengers and 9 crew members aboard the Pan Am flight perished, primarily due to the fire and explosions resulting from the fuel spilled in the impact. Fifty-six passengers and 5 crewmembers aboard the Pan Am aircraft survived, including the Captain, First Officer, and Flight Engineer. Most of the survivors on the Pan Am aircraft were able to walk out onto the left wing through holes in the fuselage structure. At least one passenger stated that the 747's engines were still running for a few minutes after the accident. Survivors waited for rescue, but it didn't 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 jumped to the ground below. The only member of the KLM passenger manifest to avoid the disaster was Robina van Lanschot, a travel guide who lived on Tenerife and, wanting to see her boyfriend that night, elected not to reboard the 747 when it was due to depart.

File:Tenerife collision.jpg

A computer generated image of the impact from the TV series Seconds From Disaster

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 take-off, while the Tenerife control tower was certain that the KLM 747 was stationary at the end of the runway and awaiting takeoff clearance.

Probable cause

While there is disagreement about their relative importance, the investigation concluded that the major causal factors of the accident were:

• KLM mistakenly took off without a take-off clearance.
• Pan Am mistakenly continued to exit 4 instead of exiting at number 3 as directed by ATC.
• Squelched radio messages (two calls between the planes and the control tower interfered with each other because they happened at precisely the same instant).
• Use of ambiguous non-standard phrases by the KLM co-pilot ("We're at take off") and the Tenerife control tower ("O.K.").
• The airport, designed to handle smaller aircraft like the Boeing 737, was (due to rerouting from the bomb threat) forced to accommodate a large number of larger aircraft, resulting in disruption of the normal use of taxiways.

Speculations

Experts speculated about other contributing factors:

• 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 further challenge van Zanten, possibly because van Zanten was not only senior in rank, but also one of the most able and experienced pilots working for the airline.
• The possibility that van Zanten was in a hurry to commence the delayed flight due to Dutch regulations on exceeding crew duty hours.
• The use of an unsafe procedure. An air traffic control clearance by a control tower issued under no-visibility conditions is not a safe procedure as such a clearance is based on visual contact. However, most authorities allow control to continue based entirely on reports from pilots, who do not have visual contact either. Although this practice still occurs in some countries, it is increasingly being abandoned and superseded by the installation of surface movement radar. It has also been revealed that some countries do not conform entirely with international standards concerning poor visibility conditions. Some tower units accept it under the strict condition that only one aircraft is operating on the runway, while taxiing to and from it is done by using a vehicle called a "follow-me car" moving slowly ahead of the plane, leading the pilot. The unsafe nature of the procedure that caused the accident in Tenerife was verified in a bitter way some 25 years later in two other accidents: the Singapore Airlines flight 006 accident at Taipei's international airport on October 24, 2000 and what became known as the Linate Airport disaster at Milano Linate International Airport on October 8, 2001. Flight SQ006, a Boeing 747-400 was cleared for take-off with extremely low visibility under tropical storm at Taipei after the flight crew reported to the tower that they were at runway 05L (which cannot be confirmed by the tower due to reduced visibility) where in fact the aircraft was at runway 05R which was closed with construction equipment stationed further down the runway (which again cannot be seen by the Singapore Airline flight crew because of reduced visibility). The Boeing attempted to take off when the crew spotted the equipment ahead of them but similar to the KLM in the Tenerife disaster, its belly clipped the eqiupment and the aircraft crashed into the runway, killing 83 out of 179 people on board. The Flight SK686, a McDonnell Douglas MD-87 airliner, was cleared for take-off during zero-visibility conditions that did not permit a visual survey of the runway by the tower. A German Cessna Citation pilot had followed an incorrect taxiway, and erroneously reported his aircraft to be clear of the runway. The MD-87 collided with the Cessna and came down on aerodrome buildings, resulting in the deaths of 118 people.

There was some disagreement between the various investigative bodies, with the Dutch investigators accusing the Spaniards of listening to a football game and accusing the Americans of being at fault for staying on the runway. However, both the Spanish and American investigations pointed the finger mostly at the KLM crew.

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 take-off. The FAA equivalent is "taxi into position and hold". Air traffic instruction should not be acknowledged solely with a colloquial phrase such as "OK" or even "Roger", but with a read back of the key parts of the instruction, to show mutual understanding. Additionally the phrase "take-off" is only spoken when the actual take-off 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 crewmembers were played down. More emphasis was placed on decision-making by mutual agreement. This is known in the industry as Crew Resource Management, and is now standard training in all major airlines.

In 1978 a second airport was inaugurated on the South of 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 have installed a ground radar at Tenerife North following the accident.

Memorials

A memorial and final resting place for the victims of the KLM plane is located in Amsterdam, at Westgaarde cemetery. There is also a memorial in Westminster, California.

A memorial was dedicated at Tenerife North airport (TFN) on March 27, 2007. The 30th anniversary marks the first time that Dutch and American next of kin have joined in a ceremony.

Miscellaneous

Captain Jacob van Zanten in KLM magazine ads

• Captain van Zanten was the preferred pilot for KLM publicity, such as magazine ads. As such, KLM attempted to contact him to give public statements regarding the disaster before learning that he was the captain involved.
• Van Zanten had given the first officer on the accident flight, Klaas Meurs, his Boeing 747 qualification check about 2 months before the accident at Tenerife.
• First officer Robert Bragg, who was responsible for handling the Pan Am's radio communications, has 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 Air Crash Investigation), he stated that he was convinced that the Tower controller had intended for them to take the fourth exit C-4 because the controller delivered the message to take "the third one, sir, one; two, three, third, third one" when the Pan Am's position on the runway was between C-1 and C-2 (making the third exit counting from their current position C-4). However the CVR clearly shows that they received this message well before they unequivocally identified C-1, with the position of the aircraft somewhere between the entrance and C-1. Also, in a Time magazine 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 disaster features in many TV shows. They include Air Crash Investigation: Crash of the Century, Seconds From Disaster: Season 1: Collision on the Runway, the Discovery Channel TV series Most Deadly and others.
• Clipper Victor (ex-Clipper Mayflower and Clipper Young America), N736PA, was the first 747 to carry fare-paying passengers, replacing the original Clipper Young America, N733PA, at the last minute due to the latter's engine problems, on Pan Am's maiden 747 passenger flight from New York to London on January 22, 1970.

• Well-known people who were killed in the disaster were:
  • 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.

See also

• List of accidents and incidents on commercial airliners grouped by year
• The 2005 Logan Airport runway incursion, where there was almost a similar disaster

References

• Report from Pan Am site
• Coverage from Air Safety Network site (Pan Am 1736)
• Coverage from Air Safety Network site (KLM 4805)
• AirDisaster.com Accident Database (Pan Am 1736)
• AirDisaster.com Accident Database (KLM 4805)
• ICAO document mentioning phrasing used in the accident
• Air Line Pilot, August 2000, page 18

External links

• ASN Pan Am N736PA Accident Description
• ASN KLM PH-BUF Accident Description
• Historic BBC news report
• Historic Time magazine article
• Comprehensive account of collision
• 1001 Crash - A complete story of the Tenerife disaster : This story includes CVR transcriptions and pictures.
• Airmanship Online - A detailed account of the tragedy
• NOVA "The Deadliest Plane Crash" - Homepage to the NOVA TV episode
• Tenerife Memorial
• Project Tenerife
• PlaneCrashInfo.Com - Tenerife Disaster
• Ask the Pilot on the Tenerife disaster Patrick Smith, Salon.com

28.48165°N 16.3384°W / 28.48165; -16.3384