Pan AM / KLM Collision at Tenerife

At 12.30PM a bomb explodes 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). Las Palmas Airport opened to traffic again at 15.00PM. Because the Pan Am passengers remained on aboard it was possible to leave Tenerife at once. The taxiways were congested by other aircraft however. This meant the PanAm crew had to backtrack on Runway 12 for take-off on Runway 30. The entrance to Runway 12 however, was blocked by the KLM Boeing. The Pan Am flight had to wait for almost 2 hours before all KLM passengers (except 1) had reboarded and refuelling had taken place. The KLM flight was then cleared to backtrack Runway 12 and make a 180deg. turn at the end. Three minutes later (at 17.02PM) Pan Am 1736 was cleared to follow the KLM aircraft and backtrack Runway 12. The Pan Am crew were told to leave the runway at the third taxiway and report leaving the runway. At 17.05:44h KLM 4805 reported ready for take-off and was given instructions for a Papa beacon departure. The KLM crew repeated the instructions and added "We are now at take-off". The brakes were released and KLM 4805 started the take-off roll. Tenerife tower, knowing that Pan Am 1736 was still taxying down the runway replied "OK ...... Stand by for take-off, I will call you." This message coincided with the PanAm crew's transmission "No ... uh we're stil 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.", were upon the Pan Am 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 Pan Am Boeing still taxiing down the runway. The crew tried to climb away and became airborne after a 65ft taildrag in an excessive rotation. The Pan Am crew immediately turned the aircraft to the right and applied full power. The KLM aircraft was airborne, but the fuselage skidded over the Pan Am's aircraft fuselage, destroying it and shearing off the tail. The KLM aircraft flew on and crashed out of control 150m further on, sliding another 300m 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."

Click to enlarge
The aircraft collided on the runway at Tenerife, Spain after the KLM crew started their takeoff roll without proper clearance. 583 died in this, the worst aviation accident in history.

The wreckage of KLM Boeing 747 PH-BUF.

01.29h (Mar.26) [times are in GMT] PanAm Flight 1736 took off from Los Angeles Airport for a flight to Las Palmas via New York. 06.17h PanAm 1736 lands at New York-JFK. 07.42h Flight 1736 takes off after a crew change and refuelling. 09.31h KLM Flight 4805 takes off from Amsterdam for a flight to Las Palmas. 12.30h A bomb explodes in the Las Palmas passenger terminal. Because of warnings of a possible second bomb, the airport was closed. 13.38h KLM 4805 diverts to Tenerife and lands at Los Rodeos Airport at 13.38h. c. 14.00h The KLM passengers are allowed to leave the plane 14.15h The PanAm flight also diverts to Tenerife. c. 15.00h Las Palmas Airport opened to traffic. Because the PanAm passengers remained on aboard it was possible to leave Tenerife at once. The taxiways were congested by other aircraft however (all diverted from Las Palmas). This meant the PanAm crew had to backtrack on Runway 12 for take-off on Runway 30. The entrance to Runway12 however, was blocked by the KLM Boeing. c. 16.15h All KLM passengers (except 1) started boarding the aircraft again and refuelling of the KLM aircraft took place. By refuelling at Tenerife the 16.45h Refuelling of the KLM aircraft was finished. 16.59h Clearance was given by the controller to KLM 4805 to backtrack Runway 12 and make a 180deg. turn. 17.02:08h 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. 17.04:24h PA 1736 passes taxiway C-1. 17.05:22h PA 1736 passes taxiway C-2. 17.05:44h KLM 4805 reported ready for take-off and was given instructions for a Papa beacon departure. 17.06:09h The KLM crew repeated the instructions and added "We are now at take-off". 17.06:11h The brakes were released and KLM 4805 started the take-off roll. 17.06:18h Tenerife tower replied "OK ...... Stand by for take-off, 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. 17.06:25h Tenerife tower replied: "Papa Alpha 1736 report runway clear.", wereupon the PanAm crew replied: "OK, will report when we're clear". 17.06:32h This caused some concerns with the KLM .......... asking the captain: "Is Source: Flight Safety Digest July 1995(1-10)/Flight Safety Foundation; ICAO Circular 153-AN/56

"KLM 4805 called the tower at 1656 requesting permission to taxi. It was authorized to do so and at 1658 requested to backtrack on runway 12 for take-off on runway 30. The tower controller first cleared the KLM flight to taxi in the holding Position for runway 30 by taxiing down the main runway and leaving it by the (third) taxiway to its left. KLM 4805 acknowledged receipt of this message from the tower, stating that it was at that moment taxiing on the runway, which it would leave by the first taxiway in order to proceed to the approach end of runway 30. The tower controller immediately issued an amended clearance, instructing it to continue to taxi to the end of the runway, where it should proceed to backtrack. The KLM flight confirmed that it had received the message, that it would backtrack, and that it was taxiing down the main runway. The tower signalled its approval, whereupon KLM 4805 immediately asked the tower again if what they had asked it to do was to turn left on taxiway one. The tower replied in the negative and repeated that it should continue on to the end of the runway and then backtrack. Finally, at 1659, KLM 4805 replied, "O.K., sir." At 1702, the PA aircraft called the tower to request confirmation that it should taxi down the runway. The tower controller confirmed this, also adding that they should leave the runway by the third taxiway to their left. At 1703:00, in reply to the tower controller's query to KLM 4805 as to how many runway exits they had passed, t he latter confirmed that at that moment they were passing by taxiway C-4. The tower controller told KLM 4805, "O.K., at the end of the runway make one eighty and report ready for ATC clearance..."

Click to enlarge

Overall
The Canary Islands, situated off the coast of Morocco, are a popular tourist site, but Los Rodeos airport, on the island of Tenerife was particular busy on the day of March 27, 1977. Las Palmas airport, located in the Canary Islands capitol had been rocked by a bomb early in the afternoon and inbound traffic had been diverted to Los Rodeos. The airport on Tenerife did not have near the capacity of Las Palmas, so aircraft were squeezed in on it's ramp. Among those diverted to Los Rodeos that day were Pan Am 1736 and KLM 4805, both Boeing 747s. The Pan Am flight had arrived after KLM and parked behind it on the apron, just short of the departure end of runway 12. On the flight deck of the KLM aircraft, it's Captain, Jacob van Zanten, a highly regarded training captain, was anxious to get back in the air as his duty hours for his crew were running low. When the tower called to inform crews that Las Palmas had re-opened, van Zanten decided that, instead of refueling at Las Palmas which would undoubtedly be busy with the re-opening, he would refuel while waiting on the ramp at Los Rodeos. It was now Pan Am's turn to depart, but the only to reach the departure end of the active runway, runway 30, was to enter runway 12 and backtrack. Unfortunately, KLM had only just begun refueling and there was no way 1736 could taxi around it with the limited space at Los Rodeos. Pan Am's First Officer Bragg called the KLM crew, asking how long it would take to refuel to which they replied "About 35 minutes." There was nothing the crew of 1736 could do but wait. While 4805 was refueling, fog was moving onto the airport and by the time they had finished, visibility had decreased to as little as 900ft in some areas. The KLM crew finally started their engines and prepared to takeoff. As they taxied to the beginning of runway 12, the tower instructed 4805 to "...taxi straight ahead...ah...for the runway...make...ah...backtrack." At this point, 1736 had also started it's engines and was holding short of the runway. The visibility now prevented the tower from being able to see neither the runway nor the two aircraft. Bragg then called the tower for instructions and 1736 was told to "...taxi into the runway and...ah...leave the runway third...third to your left." Apparently the pronunciation was unclear to Captain Grubbs who said "I think he said first" to which Bragg replied "I'll ask him again." Meanwhile the tower called 4805, instructing them "...at the end of the runway make one eighty and report...ah...ready for ATC clearance." After this communication, Bragg called back and said "Would...you confirm that you want us to turn left at the third intersection?" The tower replied "The third one, Sir...one two three...third one." The crew of 1736 was still having difficulty sorting out the taxiways as they rolled down the runway. At this point, 4805 had reached the end of the runway and was making it's 180 degree turn. As the aircraft finished the turn, van Zanten opened the throttle and the plane began to move forward. First Officer Meurs said "Wait a minute...we don't have an ATC clearance." to which van Zanten said "No, I know that. Go ahead and ask" as he held the brakes. Meurs called for the clearance and as he was reading it back, van Zanten again opened the throttles, saying "Let's go, check thrust." After repeating the clearance, Meur, in an attempt to let the controller know what was happening, said "We are now at takeoff." The tower controller apparently took this to mean they were ready for takeoff, saying "OK...standby for takeoff...I will call you." On the flight deck of 1736, the crew was obviously anxious about the implications of the transmission from 4805, Braggs saying "We are still taxiing down the runway!" to which the tower replied "Roger, Pan Am 1736, report the runway clear." Unfortunately, this first transmission blocked the tower's transmission to 4805 so all the KLM crew heard was "OK." The transmission from 1736 troubled 4805's Flight Engineer Schreuder, prompting him to say "Did he not clear the runway then?" van Zanten, now focusing on the takeoff replied with only "What did you say?" Schreuder repeated himself, saying "Did he not clear the runway then, that Pan American?" to which both van Zanten and Meurs replied "Yes, he did." 1736 was still creeping down the runway, trying to find the proper turnoff, but obviously now concerned about KLM's transmissions. Grubbs said "Let's get the hell right out of here" to which Bragg replied "Yeah...he's anxious isn't he?" A few seconds later, Grubbs spotted the lights of 4805 coming at them through the fog and said "There he is...look at him! Goddamn...that son-of-a-bitch is coming!" He opened all four throttles in an attempt to swing the aircraft off the runway as Bragg yelled "Get off! Get off! Get off!" van Zanten saw 1736 still in the runway and pulled back, attempting to climb off the runway before impacting the aircraft. The nose gear managed to clear 1736, but the rest of the aircraft slammed into the Pan Am plane's starboard side. 4805 remained airborne for a few more seconds before slamming into the ground and exploding. 1736 was crushed and quickly caught fire as well. Everyone on board 4805 was killed. The flight crew of 1736 all survived uninjured, having just missed being hit by 4805's engine. Amazingly, 66 others survived from the Pan Am aircraft. Unfortunately, 583 people died that day on Tenerife in what is still today the worst aviation accident in history. The biggest question on the minds of investigators was why van Zanten, a highly experienced training captain, would begin a takeoff without a takeoff clearance from the tower. Meurs was still copying the en route clearance when van Zanten began advancing the throttles. It seems clear that van Zanten was aware that the clearance hadn't been received when Meurs checked him and he replied "No, I know that. Go ahead and ask." It is likely that van Zanten was in a rush to get to Las Palmas because of the delay on the ground and his crew's lack of extra duty hours. However, even after the en route clearance was given, the tower instructed 4805 to "standby for takeoff" which the crew failed to hear as well as the clear indications that 1763 was still on the runway. In addition, Meurs did nothing to further enlighten van Zanten that they were not cleared for takeoff after his initial comment. It is possible that Meurs was not comfortable challenging van Zanten due to his experience level. The efforts of the crew of 1736 were hampered by the low visibility. They had only a small diagram of the airport and the third taxiway led backwards from their intended taxi direction, a turn of 135 degrees which would be extremely challenging in a 747. They apparently believed that the fourth taxiway, which was at a 45 degree angle in the proper direction was the one the tower intended for them to use, so the proceeded past taxiway three. None of the taxiways at Los Rodeos were marked. A final consideration was the difficulty with English of the tower controller and the 4805 crew. With the weather as bad as it was, relying solely on radio communications was already a dangerous practice, but the non-standard communications of both parties lead to the breakdown of situational awareness. The Dutch investigation team placed the blame firmly on the controllers at Los Rodeos while the American investigation team found the actions of Captain van Zanten to be the primary cause of the accident.

Additional Information:
The Pan Am plane was captained by veteran pilot of the 2nd world war, Victor Grubbs. The KLM charter plane was captained by KLM's chief training pilot for 747's Jacob van Zanten, who had been flying with KLM for over 25 years - he had not flown recently but had instead been instructing. Indeed his co-pilot was a former pupil of his.

Dorothy Kelly who was a purser on the Pan AM saved Captain Victor Grubbs and some other passengers.

234 passengers and 14 crew members aboard the KLM plane died. 335 of those aboard the PamAm jet died although miraculously 61 PanAm passengers and crew survived. This gives a total of 583 fatalities.

The investigation into the tragedy was a joint one involving the Spanish, the NSTB, Pan-Am, Boeing the engine manufacturer, KLM and the Dutch government.



COCKPIT VOICE RECORDER compiled by R.Benetti


Accident Description

Date: 27-03-1977
Time: 17:06PM
Type: Boeing 747-121
Operator: Pan American World Airways
Registration: N736PA
C/n: 19643/11
Year built: 1969
Total airframe hrs: 25725 hours
Cycles: 7195 cycles
Crew: 9 fatalities / 16 on board
Passengers: 326 fatalities / 380 on board
Total: 335 fatalities / 396 on board
Location: Tenerife (Spain)
Phase: Taxiing
Nature: Non Scheduled Passenger
Flight: Tenerife-Norte Los Rodeos - Las Palmas (Flightnumber 1736)

Date: 27-03-1977
Time: 17:06PM
Type: Boeing 747-206B
Operator: KLM Royal Dutch Airlines
Registration: PH-BUF
C/n: 20400/157
Year built: 1971
Total airframe hrs: 21195 hours
Cycles: 5202 cycles
Crew: 14 fatalities / 14 on board
Passengers: 234 fatalities / 234 on board
Total: 248 fatalities / 248 on board
Location: Tenerife (Spain)
Phase: Take-off
Nature: Non Scheduled Passenger
Flight: Tenerife-Norte Los Rodeos - Las Palmas (Flightnumber 4805)

Sources:-
- Aviation Safety Network
- Air Disaster


Last Updated: Saturday, February 22, 2002 - 19:45 PM
1997-2003 Flightline Malta (Roberto Benetti). All rights reserved.