Boeing 747-206B – PH-BUF

Incident Overview

Date: Sunday 27 March 1977

Aircraft Type: Boeing 747-206B

Owner/operator: KLM Royal Dutch Airlines

Registration Number: PH-BUF

Location: Tenerife-Los Rodeos International Airport (TCI) – ÿ Spain

Phase of Flight: Take off

Status: Destroyed, written off

Casualties: Fatalities: 248 / Occupants: 248

Component Affected: KLM Flight KL4805, Pan Am Flight PA1736, KLM Boeing, Pan Am BoeingKLM Flight KL4805, Pan Am Flight PA1736, KLM Boeing, Pan Am Boeing

Investigating Agency: CIAIACCIAIAC

Category: Accident

On March 27, 1977, at 12:30 local time, a bomb explosion in the Las Palmas passenger terminal triggered a chain of events leading to a catastrophic collision between KLM Flight KL4805 and Pan Am Flight PA1736. KLM Flight 4805, carrying 248 passengers and crew, collided with Pan Am Flight 1736, resulting in the deaths of all 248 passengers on KLM and 335 on Pan Am. The airport was closed due to a large number of diverted flights, and the Pan Am crew, having remained on board, was able to immediately leave the area. However, the congested taxiways caused a significant delay and a near-collision between the aircraft. KLM Flight 4805 was cleared to backtrack, and a 180-degree turn was executed, but the KLM Boeing was blocked by the Pan Am. The Pan Am crew was instructed to leave the runway at the third taxiway and report, and the KLM crew repeated the instructions, adding ‘We are now at takeoff’. After a 3-minute delay, the Pan Am flight cleared to follow the KLM, and the KLM crew began the takeoff roll. The KLM aircraft subsequently reported ready for takeoff and began the Papa beacon departure. During this time, the PanAm crew transmitted ‘No… uh we’re still taxiing down the runway, the Clipper 1736’. This led to a shrill noise, and Tenerife tower responded, ‘Papa Alpha 1736 report runway clear.’ The KLM crew then climbed away, resulting in a 65-foot tail drag and a subsequent crash. The KLM aircraft crashed further down the runway, sliding 300 meters, and subsequently catching fire. The probable cause was a misjudgment between the tower and the KLM crew regarding the clearance, leading to a collision with the Pan Am aircraft due to the latter’s remaining on the runway.On March 27, 1977, at 12:30 local time, a bomb explosion in the Las Palmas passenger terminal triggered a chain of events leading to a catastrophic collision between KLM Flight KL4805 and Pan Am Flight PA1736. KLM Flight 4805, carrying 248 passengers and crew, collided with Pan Am Flight 1736, resulting in the deaths of all 248 passengers on KLM and 335 on Pan Am. The airport was closed due to a large number of diverted flights, and the Pan Am crew, having remained on board, was able to immediately leave the area. However, the congested taxiways caused a significant delay and a near-collision between the aircraft. KLM Flight 4805 was cleared to backtrack, and a 180-degree turn was executed, but the KLM Boeing was blocked by the Pan Am. The Pan Am crew was instructed to leave the runway at the third taxiway and report, and the KLM crew repeated the instructions, adding ‘We are now at takeoff’. After a 3-minute delay, the Pan Am flight cleared to follow the KLM, and the KLM crew began the takeoff roll. The KLM aircraft subsequently reported ready for takeoff and began the Papa beacon departure. During this time, the PanAm crew transmitted ‘No… uh we’re still taxiing down the runway, the Clipper 1736’. This led to a shrill noise, and Tenerife tower responded, ‘Papa Alpha 1736 report runway clear.’ The KLM crew then climbed away, resulting in a 65-foot tail drag and a subsequent crash. The KLM aircraft crashed further down the runway, sliding 300 meters, and subsequently catching fire. The probable cause was a misjudgment between the tower and the KLM crew regarding the clearance, leading to a collision with the Pan Am aircraft due to the latter’s remaining on the runway.

Description

KLM flight KL4805, a Boeing 747-200, and Pan Am flight PA1736, a Boeing 747-100, collided on the runway at Tenerife-Los Rodeos International Airport, killing all 248 occupants on the KLM aircraft and 335 occupants on the Pan Am flight. On March 27, 1977, at 12:30 local time a bomb exploded in the Las Palmas passenger terminal. Because of warnings of a possible second bomb, the airport was closed. A large number of flights were diverted to Tenerife, a.o. KLM Flight 4805 from Amsterdam and PanAm Flight 1736 (coming from Los Angeles and New York). Both aircraft were parked on a crowded apron until Las Palmas Airport opened to traffic again at 15:00. Because the PanAm passengers had remained on aboard, it was possible to leave Tenerife immediately. However, the taxiways were congested by other aircraft. This meant the PanAm crew had to backtrack on runway 12 for takeoff on runway 30. The entrance to runway 12 however, was blocked by the KLM Boeing. The PanAm flight had to wait for almost two hours before all KLM passengers (except 1) had reboarded and refueling had taken place. The KLM flight was then cleared to backtrack runway 12 and make a 180 degree turn at the end. Three minutes later (at 17:02) Pan Am 1736 was cleared to follow the KLM aircraft and backtrack runway 12. The PanAm crew were told to leave the runway at the third taxiway and report leaving the runway. At 17:05:44 KLM 4805 reported ready for takeoff and was given instructions for a Papa beacon departure. The KLM crew repeated the instructions and added “We are now at takeoff”. The brakes were released and KLM 4805 started the takeoff roll. Tenerife tower, knowing that Pan Am 1736 was still taxiing down the runway replied “OK …… Stand by for takeoff, I will call you.” This message coincided with the PanAm crew’s transmission “No … uh we’re still taxiing down the runway, the Clipper 1736”. These communications caused a shrill noise in the KLM cockpit, lasting approx. 3.74 seconds. Tenerife tower replied: “Papa Alpha 1736 report runway clear.”, whereupon the PanAm crew replied: “OK, will report when we’re clear”. This caused some concerns with the KLM flight engineer asking the captain: “Is he not clear then?” After repeating his question the captain answers emphatically: “Oh, yes”. A number of second before impact the KLM crew saw the PanAm Boeing still taxiing down the runway. The crew tried to climb away and became airborne after a 65 feet tail drag in an excessive rotation. The PanAm crew immediately turned the aircraft to the left and applied full power. The KLM aircraft was airborne, but the fuselage skidded over the PanAm’s aft fuselage, destroying it and shearing off the tail. The KLM aircraft flew on and crashed out of control 150 m further on, sliding another 300 m while bursting into flames. PROBABLE CAUSE: “The KLM aircraft had taken off without take-off clearance, in the absolute conviction that this clearance had been obtained, which was the result of a misunderstanding between the tower and the KLM aircraft. This misunderstanding had arisen from the mutual use of usual terminology which, however, gave rise to misinterpretation. In combination with a number of other coinciding circumstances, the premature take-off of the KLM aircraft resulted in a collision with the Pan Am aircraft, because the latter was still on the runway since it had missed the correct intersection.”

Source of Information

http://www.project-tenerife.comhttp://www.project-tenerife.com

Primary Cause

A misjudgment between the tower and the KLM aircraft regarding the clearance, resulting in a misinterpretation of the standard terminology and a premature takeoff, which caused the collision.A misjudgment between the tower and the KLM aircraft regarding the clearance, resulting in a misinterpretation of the standard terminology and a premature takeoff, which caused the collision.

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