Leonardo

27 march 1977: Aircraft collision Tenerife, Canary Islands

On the sunday afternoon of march, 27 1977, the KLM Boeing 747 Rijn is taking off without permission on the Los Rodeos airfield at the Canary Island of Tenerife. The airfield is covered in dense fog. On the only runway is PANAM's Boeing 747 Clipper Victor taxiing in the opposite direction. The two planes collide and explode in flames. Of all persons on board of both aircraft 583 people die, 46 people on board of the PANAM, including the cockpit crew, are severely wounded, but will survive. 15 PANAM passengers escape the inferno unhurt.

(nederlandse versie)

the prelude
the disaster
causes
lessons learned
strange?
sources

The prelude :

During that sunday march 27, 1977, it is getting busier and busier at the small airport of Los Rodeos Tenerife, one of the Canary Islands. The airport of nearby Las Palmas is closed due to a bomb-alert and all airtraffic is diverted to Los Rodeos. Los Rodeos has 1 runway. During that sunday, the apron and taxi-lanes are filled with parked aircraft.

former Los Rodeos, now Tenerife Norte (TFN)

The KLM Boeing-747 PH-BUF 'de Rijn' operates flight KL4805 with 235 holidaymakers and a crew of 14 to Las Palmas. Most people on board are Dutch, but there are also 2 Australians, 2 Americans and 4 Germans on board.
Captain of the KL4805 is the very experienced Jacob Veldhuyzen van Zanten. He is working for KLM since 1950, has 11700 flighthours and is the figurehead of the KLM flying corps. His picture is used in many KLM-publications, like the magazine in the back of the seats of this flight. Veldhuyzen van Zanten did not fly many operational hours anymore: For most of his time, he is working as chief-instructor for the 747, thereby spending many hours on the 747 flightsimulators. But since some weeks he has started to fly regular trips again.
The KLM Boeing lands at 13.38 hour on Tenerife and is parked outside the apron, on a parkingspace at the south-side of the apron. Captain Veldhuyzen van Zanten decides that his passengers can deplane and wait in the terminal.
Amongst them are 3 female travel guides , who have been trained in Amsterdam and are now flying back to their workplace, Tenerife. As the KLM would fly to Las Palmas, they should travel back to Tenerife later that sunday, but now they have unexpectedly arrived at their final destination. But KLM does not allow tem to get off the plane here at Tenerife. They must wait and fly to Las Palmas to collect their luggage. But one of them, Robina van Lanschot, decides to ignore the rules and asks her friends to collect her luggage in Las Palmas for her so she can stay in Tenerife. She will be the only surviver of flight KL4805.

KLM Boeing-747 PH-BUF de Rijn

The PANAM Boeing-747 N736PA 'Clipper Victor' arrives 30 minutes after the KLM-Boeing at Los Rodeos and is parked next to KLM.
Clipper Victor is not just any Boeing 747: It is the flagship of PANAM and the first commercial used 747, that made the first-ever 747 maidenflight on januari 21, 1970 from New York to Londen.
Flight PA736 has 16 crewmembers and will bring 380 Americans to their cruiseship for a cruise around the Meditteranean Sea.
Captain Victor Grubbs is - just like his KLM counterpart - very experienced with 21000 flighthours. If it had been up to him to him, Clipper Victor would not have landed at Los Rodeas at all, but would have flown a "holding pattern" untill the time that Las Palmas would re-open. But AirTraffic Control did not give him permission for that.
Grubbs cannot deplane his passengers, because the terminal building is fully occupied with passengers from the other waiting planes, and there is also lack of food and drinks to provide to his passengers.

PANAM Boeing 747 Clipper Victor

3 smaller aircraft are parked around the 2 enormous 747's. Meanwhile, the KLM-crew is worried because their maximum hours on duty in the cockpit may make it impossible to fly to Las Palmas and still be able to do the return flight to Amsterdam that same day. Captain Veldhuyzen van Zanten decides to load 55 tons of fuel while waiting at Los Rodeos, so that he can make a immediate return once he arrives in Las Palmas. Together with KLM-operations, they have calculated that they can make the returntrip to Amsterdam just in time.
Meantime, the weather detoriates. There is a light rain and the sea-fog is getting denser. The weather forecast is even worse: Soon, flight conditions will drop below the save takeoff limits and crew and passengers have to stay at Tenerife. The KLM crew is in a hurry.

At 15.00 hr, the Las Palmas airport re-opens. The queue of waiting aircrafts on Los Rodeos is starting to move. First, the smaller aircrafts around the 2 jumbo's are leaving and then the PANAM can start. The KLM is still loading fuel and have to wait.
The only runway of Los Rodeos is used in the direction 30. To get from the parking position at the south-side to the take-off position, the planes have to taxi southward along the apron and the taxi-way or initially orthbound via the apron, the taxiway and the in a southerly heading via the runway itself. The Boeing 747's have no choice: They are too big to get around the waiting aircraft on the apron. They have to "backtrack" over the runway to the take-off position at the beginning of runway 30.
To get to the runway, the PANAM has to maneuver around the KLM, but there is not enough space: The PANAM must wait for the KLM to finish it's re-fuelling. The behaviour of the KLM crew is annoying the PANAM crew. Meanwhile, the fog is getting thicker and the visibility is reaching the takeoff limit of 700 meter.

PANAM waiting next to the KLM on the parkinglot of Los Rodeos

The disaster:

At 16.58 hr, the KLM is ready to depart ands starts rolling on the runway to the take-off position. The PANAM follows at 17.02 uur.
While the 2 Boeings are taxiing on the runway, they cannot see eachother in the fog. The tower controller cannot see the planes either. There is no groundradar and the air traffic controllers must rely on their radio communication to track the planes. No follow-me truck is guiding the cockpit crews during their taxi-ride on the runway.
The tower first asks the KLM to leave the runway at exit 3 and take the taxiway to the take-off position. Some moments later, the controller changed his mind and asked the KLM to backtrack and make a 180 degree turn at the takeoff position.
The KLM captain is not charmed by the efficiëncy of the tower and gets annoyed.

The PANAM is also asked to leave the runway at exit 3. In the first instance, the crew did not catch if the tower said "first" or"third". At 17.03 the PANAM asks the tower to confirm exit 3. The tower confirms, counts from one to three, but does not mention an exit number.
In the fog, the PANAM crew does not know exactly where they are on the runway. They try to locate the exits on the map of the airfield. Meanwhile, they are executing the pre-takeoff checklist. While doing this, they have passed exit C2 without noticing it. The exits don't carry signs.
Looking at the map, they believe the tower could not have had the intention to get the big 747 exiting at C3, which is in a 135 degree angle opposite the direction of the PANAM's taxiroute. The Boeing would have to make two very difficult turns to get to the taxiway. Shorly after C3 is exit C4, in a 45 degree angle, and easy to take. The crew believes the tower has another way of counting the exits: "maybe he counts these (are) three" .
To see where they are in the fog, the PANAM slows down. It is 17.05.30 as the PANAM crew, not knowing their exact position, passes exit C3 on their way to exit C4.

At 17.05.41 hr, the KLM-Boeing has turned 180 degrees at the take-off point of runway 30 and is ready for departure. The captain releases the breaks and the Boeing starts rolling when the co-pilot reminds his captain that there is no permission for the flight (the Air Traffic Control Clearance). "No, I know, ask for it", said captain Veldhuyzen van Zanten. He applies the breaks again.
The PANAM is still on the runway near exit C3, invisible to the KLM crew in the fog.

At 17.05.44 the co-pilot of the KLM-Boeing reports to the tower "ready for takeoff and wait for ATC Clearance".
At 17.05.53 he receives the Air Traffic Control Clearance for the flight to Las Palmas, but no permission to take off:
"KLM eight seven zero five (*) you are cleared to the Papa beacon, climb to and maintain
flight level niner zero, right turn after take-off, proceed with heading zero
four zero until intercepting the three two five radial from Las Palmas VOR".

(* According to the transscript of the radio traffic, a wrong callsign is used. KLM was flight 4807, not 8705)

The KLM-copilot reads back the Air Traffic Control Clearance:
"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..."
but while he reads back the clearance, his captain says: "We are going".
It is 17.06.13. when the captain releases the breaks for the second time and opens the throttles.
The co-pilot finishes the read-back of the ATC clearance with the remark:
"...and we are now at takeoff".

It is 17.06.18. The airtraffic controller thinks that the KLM is waiting at the take-off point at the far-end of runway 30, and confirms the read-back of the ATC clearance with:
"OK, standby for takeoff".
At 17.06.20, the PANAM crew is not happy with their situation and what they hear on the radio. The visibility is 300 meters, both crews cannot see eachother. To be sure, the PANAM crew passes the message to the tower that they are still on the runway. But this transmission disturbs the "Standby for takeoff" part of the message for the KLM. The KLM crew only hears a whistle-tone after the "OK" from the airtraffic controller.
The KLM captain interpretes this "OK" as the Take-Off Clearance and proceeds with the take off. But at that moment, the aircraft is already 6 seconds on its way to take off, picking up speed for the "rotate", the point where the aircraft will get airborne.

At 17.06.25, the tower controller asks the PANAM to report when they have left the runway. The KLM flight engineer, less occupied with the take-of procedure, picks up that message and is questioning the position of the PANAM. He asks his captain twice: "He has left the runway, the PANAM ?". The first time, the captain does not react. The second time he replies uninterested: "Yes, he has".
On board of the PANAM, the crew is very worried about the radio traffic between the KLM and the tower. "Lets get the hell right out of here" says captain Grubbs and tries to steer his heavy Boeing off the runway onto exit C4, that is showing up in his windows at that moment.

Shortly before 17.06.50 uur both crews see each other. "There he is! Look at him! Goddamn ... that son-of-a-bitch is coming!" shouts Grubbs as he sees the lights of the KLM showing up fast. "Get off, get off" shouts his co-pilot. Grubbs applies full throttle and steers the Jumbo onto the grass left of the runway.
The KLM captain pulls back the steering column to get the 747 off the ground. The tail of the Boeing scrapes along the runway surface over 22 meters. The KLM is actually flying over the PANAM, but hits the tail and the top of the PANAM. The KLM crashes 150 meters further on the runway. The PANAM comes to a standstill in the field near the runway.

upfront is the wreckage of the KLM and exit C3,
behind is the remains of the PANAM and exit C4

The KLM glides 450 meter over the runway and is immediately engulfed in flames. The PANAM is badly damaged at the top and rightside, where the fueltanks are ruptured. The PANAM catches fire as well. At the front leftside, some passengers can jump several meters to the ground from the wing. The PANAM crew can leave the wreckage through a hole in the body.

There are no witnessess to the crash, but an aircraft flying nearby sees the glow of the flames and asked the tower if there is fire on the runway. The tower cannot see what has happend, but can hear the explosions. They call the airport firebrigade, who starts searching through the dense fog for the crashsite. First, they find the burning KLM, that is beyond rescue. After a while, they also find the burning PANAM.
Only then the scale of the carnage is becoming clear. Rescue teams from all over the small island are rushing to Los Rodeos. Some the PANAM survivers are standing and laying in the grass, covered with burns and broken bones. The firebrigade manages to keep the left wing, full of fuel, out of the fire. The wounded are quickly transported to the hospital of Santa Cruz by ambulances and taxi's. The remains of the KLM are burning until the next day. The recovery and identification of the bodies takes weeks.

All 248 souls on board of the KLM Boeing and 317 souls on board of the PANAM are dead. 55 people from the PANAM are badly wounded. 9 of them will die later in the hospital. 15 people have escaped the PANAM unhurt. Of the 16 crewmembers of the PANAM, 7 survived, including the cockpit crew.

the burning PANAM

the remains of the KLM

Most Dutch casulties are buried together on the 'Tenerife-field' on the Westgaarde cimentary in Amsterdam.

Tenerife Monument Westgaarde Amsterdam

On march, 27 2007 a monument was erected on the Mesa Mota mountain.

The causes:

The air traffic controllers and cockpit crews were stressed due to the overcrowdedness of the small airport, the delays and the upcoming fog. Furthermore, the tower was rumoured to have a radio or TV playing with a footbalmatch on it. Visibility from the tower to the runway was zero due to the fog and there was no ground radar available. The controllers were totally dependant on their radio equipment to provide them with information regarding the position and intentions of all aircraft on the airport. Radio communication was hampered by blocking of signal when 2 transmissions would take place at the same time.
Los Rodeos was not equipped to host so many airplanes, especially large airplanes like the Boeing 747's of PANAM and KLM. There was no maouevering space, so the runway was the only option to get the big planes onto their take off position. The take- offs had to continue as the upcoming fog would cause further delays.

The airtraffic controller was unclear in way he counts the runway exits. Although the maps clearly showed exit numbers, the tower did not use those numbers and literly counted them out for the PANAM crew. There were no signs at the exits.
Both KLM- and PANAM got the instruction to leave the runway at the third exit. The KLM was later redirected to "backtrack" the runway. The PANAM crew got the instruction to take exit 3 three times. The third exit, counted from the beginning of the runway at the 12 position, was exit C3. C3 is in a 135 degree angle to the runway. To get from C3 to the taxiway, another 135 degree turnm would be needed. It is difficult and rather unlogic to have the big Boeings make these turns, especially as shortly after C3 is exit C4 in a easy-to-take 45 degree angle.
The airtraffic controllers at Los Rodeos had no experience with Boeing 747's and might have overlooked the complexicity of such turns. The PANAM crew had the impression that the controller had the intention to use C4 but used a different way of counting them (17.05.40: "maybe he counts these (are) three").
The PANAM crew did not asked again if they had to take C4, but drove - unaware of their exact position on the runway, and thinking that they were just passing C2 - beyond C3 on their way to C4.

The fact that the PANAM missed exit C3 itself is not be a crucial cause of the disaster. The PANAM crew clearly indicated to the tower that they were still un the runway, and the tower asked them explicitly to report when them would have left the runway. The tower had obvious the intention to hold the waiting KLM at the take off position untill the PANAM had left the runway, and did not give the take off clearance to the KLM.
Investigations showed later that the disaster would not have happened if the PANAM would have left the runway at C3, and that such turn was possible with a 747.

The KLM crew had no visibility on the total runway and was unaware of the exact position of the PANAM, but the crew knew that the PANAM was taxiing rolling behind them on the runway. This can be read from the reaction of the KLM mechanic: "Hasn't he left the runway, the PANAM ?"

The PANAM crew was very busy finding out were they where and what exit to take. But the crew was also concerned that the tower and the KLM might have missed the fact that they were still at the runway and radio'd that to the tower.

The tower, knowing that the PANAM was still on the runway, did not give the Take-Off Clearance to the KLM. The KLM co-piloot knew that they did not got a Take-Off Clearance yet, but hesitated to overrule his boss when the captain started to roll with the words: "We are going".
Instead , he ended the read-back of the ATC-Clearance with the unsual words: "..we are now at take-off".
The tower did not recognize - maybe due to insufficient knowledge of the English language - the subtle truth of the "we are now at take-off" message, assuming instead that the KLM aircraft was in fact in the the take-off position. Ths explains the subsequent message by the tower controller:
"OK, standby for takeoff" .

At that crucial moment, the radio transmissions dealing with messages from PANAM, KLM and tower at the same time, created a noise that blocked the crucial part of the "OK, standby for take-off " message from the tower to the KLM. Only the word "OK" was heard in the KLM cockpit, which was interpreted by the captain as the long awaited approval to take off. He continued his take off, that he had in fact initiated some 6 seconds earlier.

The tower asked the PANAM to report when they had left the runway, and this was noticed by the KLM flight-engineer. He was doubtful of the position of the PANAM and asked the captain twice: "Is he not off, then, that PANAM ?".
The first time, the captain does not react. The second time he replies decided but uninterested: "Yes, he is". The flight-engineer did not raise the question again.

The flight conditions at Los Rodeos are detoriating at the moment the two Boeing 747's started their take off procedures

• Visibility - 300 meters during taxiïng - dropped under the take-off limit of 700 meters. Moments later, when the KLM was ready for take-off, there was a minor improvement, which was probably just enough to take off. The actual visibility at the moment of takeoff by the KLM aircraft has not been verified.

• The simultaneous use of the runway for take-offs and taxiïng is a dangerous thing to do, even when visibility is good. It should never be done in dense fog, when both the aircraft and the tower cannot see each other, and without any follow-me truck to guide them

• The radio traffic was often disturbed and the Spanish air traffic controllers were not expressing themselves in a clear and understandable way to the cockpit crews.

In these difficult and dangerous conditions, none of the parties showed much prudence:
The air traffic controller, having no clue were his planes where on the runway, did not asked their positions frequently and gave them unclear commands, without checking if they were well understood and executed.
The PANAM captain, knowing that the KLM was ahead of them and ready for take off, but uncertain about their exact position and in doubt which exit to take, decide to opt for exit C4, without checking this explicitly with the air traffic controller.
The KLM captain, assuming a take off clearance based on often disrupted radio traffic, and knowing that the PANAM was somewhere outthere in thick fog on the runway, did not doublechecked the position of the PANAM, either from the tower of from the PANAM itself.
Even when his mechanic shows hid doubts about this, he continued the take off.

However, the main cause of the Tenerife airdisaster are the cockpit-relations of the KLM crew.
Capatin Veldhuyzen van Zanten was very experienced and the absolute boss in the cokpit. He was a instructor on the KLM's 747 flight simulators, were he also practiced the role of air traffic controller. Only recently he went back to active flight operations.
The KLM captain was stressed because his crew was getting to their flighttime limits for that day. He was ancious about the divertion to Tenerife, the delays and the poor air traffic control, who changed thier minds about the taxi procedure a couple of times.
As soon as the 747 had made the 180 degree turn and was in take-off position, he released the brakes. The captain had not even a flight clearance at the time, and his co-pilot hastely stepped in to get that arranged. But for the second time, the captain lost his patience, released the brakes and pushed the throttles forwards.
The "OK" that he had picked up in the radio traffic, was enough for him to continue his take-off, that he had initiated 6 seconds earlier. He totally ignored the doubst that his mechanic had about the where-abouts of the PANAM. For one reason or another, the KLM captain was absolutely sure that he could take-off.

The co-pilot had only recently received his certification for a 747 and had only 95 flying hours on this type. Captain Veldhuyzen van Zanten was his instructor and examinator.
The first time when the captain started to roll the 747 without ATC-Clearance, he took action, but when the captain started rolling for the second time, while the co-pilot was still busy reading back the ATC-Clearance, he stepped back. Not knowing what to do, he finished the read-back with the unusual "We are now at take-off".

The behaviour of the KLM-crew was analysed thoroughly after the crash.
Due to the stress, the captain was exposed to 5 psyhical effects:

• Less attention and lower observation power
• Not capable of dealing with rapidly changing situations
• Tunnelvision
• Fallback to known routines
• Transfer of responsibility to someone else•less attention and lower observation power

The captain had a desired vision of the situation and reacted accordingly. He was not open to influences from outside. He fell back to well known procedures in the flight simulator, where he was playing the role of air traffic controller. He was not able to deal with other options and factors. He was unable to take notice of them and effectively, ignored them.

In the KLM cockpit a strong hierarchy and a steep authority gradient was present, which caused 3 other psyhical effects:

• The desire of the less experienced to keep trust in the - most experienced - leader.
• The approval of the superior behaviour of the most experienced in the group
• The desire of the lower ranked to maintain the cohesion in the group.

The co-pilot did not want to discuss the take-off decision of his boss. He was confident that the most experienced person would take the best possible decision, and although noticeable surprised about the start without Take-Off Clearance, he did not initiate any action.
The flight-engineer was - after he made some comments about the position of the PANAM - answered condescendingly by the captain and had no intentions to convince him.

Lessons learned

There are more incidents known in which the hierarchy in the cockpit was blocking the prevention of a disaster. In one case, the captain had died, not being noticed by the co-pilot, while he did not want to ask his captain why he made such a steep decend.

The role of the captain as the allmighty boss in the cockpit was under discussion after the crash. Instead of being the boss, he was now coach of a team. Modern management techniques were applied to the relation of the teammembers, so that everyones voice was being heard. While the captain remains responsible for everyone and everything on board, there was no "overruling authority" anymore.

Aircraft- and vehicle movements on the apron are factors concerning risks and threats. Ground radar systems, movement sensors and strict adherence to runway entry procedures will form a barrier into unwanted runway incursions.

Discrepencies in Investigation Results ?

3 investigations were started, by the Spanish, American and Dutch aviation authorities, but the results of these 3 investigations were not in line with eachother.
All reports mentioned 6 main causes to the disaster, but every report gave another view on the responsibility for it :

• The inadequate airtraffic control and airfield facilities at Tenerife
• The fog.
• The PANAM missing the indicated exit C3.
• The disturbed radio-communication on a critical moment during the clearance of the KLM.
• The KLM taking off without Take-Off Clearance.
• The KLM-captain ignoring alerts from his flight engineer

The most significant cause to the crash was the decision of the KLM-captain to take-off without approval from the tower, while not acting upon signals of his crew questioning the position of the PANAM.
This issue was hardly mentioned in the Dutch investigation; The RijksLuchtvaartDienst pointed out that the KLM-captain was allowed to consider the ATC-clearance as an implicit Take-Off Clearance. But to international rules, that is only true when the ATC-clearance includes an explicit Take-Off Clearance (".. and cleared for take-off runway...), which was not the case.
The RijksLuchtvaartDienst puts all the blame at the Spanish airtraffic controllers and the PANAM crew.
The RijksLuchtvaartDienst (on paper an independant government organisation) owned its "reason for being" to KLM. Without the important role that KLM plays in the aviation industry, the RijksLuchtvaartDienst would be playing a small role behing the scenes, while now they were entitled to play the big game with major players like their American counterpart FAA and industryleaders like Boeing. So the RijksLuchtvaartDienst had reasons to defend KLM's imago as reliable airline. The captain was the face of the KLM, with his picture appearing all kinds of KLM publications. It was not good for KLM's imago that a man like that made such big mistakes. Also, Veldhuyzen van Zanten, as the most important 747-instructor in the Netherlands, was wellknown inside the RijksLuchtvaartDienst.

The spanish investigation report tried to mask the inadequate airtraffic control and airfield facilities and focussed mainly on the errors of the two captains.

Unsurprisingly, the USA-report came to the conclusion that PANAM crew did all possible to avoid the crash and puts alle the blame to the KLM captain and the spanish airport authorities.