Air Safety, Tragedy at Teneriffe

While the airplanes were en route to Las Palmas, a bomb exploded in the airport passenger terminal. On account of this incident and a warning regarding a possible second bomb, the airport was closed. Therefore, KLM 4805 was diverted to Los Rodeos (Tenerife) Airport, arriving at 1338 z on March 27, 1977. For the same reason, PAA 1736 proceeded to the same airport – its alternate – landing at 1415.

At first the KLM passengers were not allowed to leave the airplane, but after about 20 minutes they were all transported to the terminal building by bus. On alighting from the bus, they received cards identifying them as passengers in transit on flight Kl 4805. Later, all the passengers boarded KLM 4805 except the HINT company guide, Miss Robina Guiseline Monique Van Lanschot, who remained in Tenerife.

When Las Palmas Airport was opened to traffic once more, the PAA 1736 crew prepared to proceed to Las Palmas, which was the flight’s planned destination.

When it attempted to taxi on the taxiway leading to Runway 12, where it had been parked with four other aeroplanes on account of the congestion caused by the number of flights diverted to Tenerife, they discovered that it was blocked by KLM Boeing 747, Flight 4805, which was located between PAA 1736 and the entrance to the active runway. The first officer and the flight engineer left the airplane and measured the clearance left by the KLM, reaching the conclusion that it was insufficient in order to let PAA 1736 pass by, obliging them to wait until the former had started to taxi.

The PAA 1736 passengers did not leave the airplane during the whole time that it remained in the airport.

KLM 4805 called the tower at 1656 requesting permission to taxi. It was authorised to do so and at 1658 requested to backtrack on Runway 12 for takeoff on Runway 30. “The tower controller first cleared the KLM to taxi to the holding position for Runway 30 by taxiing down the main runway and leaving it by the (third) taxiway to its left. ” KL M 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 make a backtrack.

The KLM confirmed that it had received the message, that it would make a 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 1. The tower replied in the negative and repeated that it should continue on to the end of the runway and there make a backtrack.

Finally, at 1659, KLM 4805 replied, “OK, Sir. ” At 1702, the PAA 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 the latter confirmed that at that moment they were passing by Taxiway C-4. The tower controller told KLM 4805, “OK, at the end of the runway make one eighty and report ready for ATC clearance. ”

In response to a query from KLM 4805, the tower controller advised both airplanes – KLM 4805 and PAA 1736 – that the runway centreline lights were out of service. The controller also reiterated to PAA 1736 that they were to leave the main runway via the third taxiway to their left and they should report leaving the runway.

At the times indicated, the following conversations took place between the tower and the KLM 4805 and PAA 1736 airplanes; with times taken from KLM CVR (cockpit voice recorder):

1705:44.6 KLM 4805 – The KLM four eight zero five is now ready for takeoff and we are waiting for our ATC clearance (1705:50.77).

1705:53. 41 Tower – KLM eight seven zero five you are cleared to the Papa Beacon, climb to and maintain flight level nine zero, right turn after takeoff, proceed with heading four zero until intercepting the three two five radial from Las Palmas VOR (1706:08. 09).

1706:09. 61 KLM 4805 – Ah – Roger Sir, we are cleared to the Papa Beacon, flight level nine zero until intercepting the three two five. We are now (at takeoff) (1706:17. 79).

1706:18. 19 Tower – OK . . . Stand by for takeoff, I will call you (1706:21. 79). Note: A squeal starts at 1706:19. 39. The squeal ends at 1706:22. 06.

1706:21. 92 PAA 1736 – Clipper one seven three six (1706:23. 39).

1706:25. 47 Tower – Ah – Papa Alpha one seven three six report the runway clear (1706:28. 89).

1706:29. 59 PAA 1736 – OK, will report when we’re clear (1706:30. 69).

1706:61. 69 Tower – Thank you.

Subsequently, KLM 4805, which had released its brakes to start the takeoff run 20 seconds before this communication took place, collided with the PAA. The control tower received no further communications from PAA 1736, nor from KLM 4805.

There were no eyewitnesses to the collision.

Place of accident. The accident took place on the runway of Tenerife Airport (Los Rodeos) at North 28deg 28min 30sec latitude and West 16deg 19min 50sec longitude. The field elevation is 2073ft (632 metres).

Date. The accident occurred on March 27, 1977, at 17hr 06min 50sec GMT.

Injuries to persons. KLM 4805 airplane – Fatal: crew, 14; passengers, 234.

PAA 1736 airplane – Fatal: crew, 9; passengers, 317. Non-fatal: crew, 7; passengers, 61; others, 2. Nine of these passengers subsequently died as a result of injuries received. The others were company employees, sitting on the cockpit jumpseats, who had boarded the plane in Tenerife.

Damage to the aircraft. Damage to the planes was 100 per cent due to the impact and post-impact fire.

Other damage. The runway was damaged in the area of impact by the impact itself and by subsequent fire. Costs of repairs thereof amounted to 16,005,464. 22 pesetas.

Medical and Pathological Information. On account of the magnitude of the disaster, the Spanish, Dutch and American medical authorities, as well as the Spanish Judicial Authority, agreed that the pathological teams should work together in the tasks of identification, embalming and possible autopsies.

It was not possible to perform autopsies on the members of the KLM crew on account of the state of the bodies.

Fire. Alarm and mobilisation of the firefighting team – The weather conditions, with fog patches at zero metres prevented the accident from being immediately and directly visible from the control tower, where they only heard one explosion followed by another, without being able to localise them or ascertain their cause.

Moments later, an aircraft located on the parking apron advised the tower that it had seen a fire, without specifying the exact place or its cause.

The tower immediately sounded the fire alarm for the fire service, informing them that there was a fire and that they should be prepared for an urgent departure. The tower had not yet been able to locate the fire.

Subsequently, a member of the CEPSA Co arrived at the fire station parking lot, where the firemen were all ready and prepared, and told them that there was a fire “to the left of the parking area. ”

This was the first, though vague, indication regarding the location of the fire. The firemen immediately communicated this information to the tower and set out at the greatest possible speed, which nevertheless was very low on account of the weather conditions which carried the serious risk of collision with persons, vehicles and airplanes, in view of the fact that they had to cross the very congested parking apron diagonally.

Finally, they saw a bright light through the fog and when they came closer, although they were as yet unable to see the flames, they suffered the effects of strong heat radiation.

When there was a slight clearing, they saw for the first time that there was an airplane totally enveloped in flames, the only visible part being the rudder.

After they had begun to fight the fire, a greater clearing in the fog took place and they saw a bright light farther away, which they thought at first was part of the same airplane which had broken off and was also burning.

They divided up the fire trucks and, on approaching what they thought was only a second focal point of the same fire, they discovered a second airplane on fire. They immediately concentrated their efforts on this second airplane because the first was totally irrecoverable.

As a result of this action, they were able – despite the tremendous range of the fire in this second airplane – to save the left side, from which between 15,000 and 20,000 kilos of fuel were subsequently removed.

Meanwhile, because of the dense clouds surrounding it, the tower was still unaware of the exact location of the fire, and whether one or two airplanes had been involved in the accident.

The impact, start of and extinguishing of the fire – There is no indication of a failure prior to the impact. The distance from the approach end o Runway 30 to the Pan Am wreckage was about 1385 metres. From here to the main KLM wreckage there was a distance of about 450 metres.

The Pan Am was at an angle of about 45deg relative to the centre of the run, ie, at about 75 deg magnetic. It is possible that it continued to move after the impact.

Apparently, the KLM No. 1 engine only grazed the tip of the Pan Am’s right side; the nose and front landing gear overshot the latter airplane and the main landing gear smashed against it in the area of its No. 3 engine.

The KLM was entirely airborne when the impact took place. Its tail drag had scraped the runway in an excessive rotation for a distance of 65ft; the tracks on the runway began about 300ft before the place of impact.

Some sections of the right side of the Pan Am were found near the KLM, indicating that indeed there was an impact there.

The KLM fuselage skidded over the Pan Am aft fuselage, destroying it and shearing off the empennage. The KLM continued in flight, hitting the ground about 150 metres farther on and sliding another 300 metres on the runway. It caught fire suddenly and violently.

Rescue and survival. There were no survivals in the KLM aircraft, even though the impact both against the Pan Am and against the ground could not have been excessively violent; however, an immediate and raging fire must have prevented adequate emergency operations because all the aircraft’s evacuation doors remained shut even though the fuselage was not deformed significantly.

In the Pan Am aircraft, the first-class lounge disappeared as a result of the impact, as well as nearly the whole of the top of the fuselage. The lounge floor gave way, which meant that the crew had to jump to the first-class section and get out through a hole in the left wall, behind the L1 exit. This hole was the main escape route for the passengers located in the forward part of the aircraft. None of those in the first-class lounge survived.

According to the survivors, the shock of impact was not excessively violent, leading them to believe that the cause was an explosion. They jumped to the ground through openings in the left side, or through door L2, which was duly opened, from a height of 20ft (6 metres). The left engines were still turning, and there was a fire under the wing at this side. A large number of passengers escaped off this wing, jumping from it to the grass. Explosions were already taking place, and the ambulances appeared almost immediately. At the centre and aft of the plane, the accumulation of wreckage and twisting of metal sheets of the fuselage must have been such that, apart from the fire which suddenly broke out, it formed a kind of trap, preventing forward exit of the passengers.

Total evacuation time is estimated to have been about one minute.

Socio-psychological causes:

• Limits on-duty time of Dutch crews.

Until a few years ago, the flight captain was able, at his own discretion, to extend the limit on his crew’s activity in order to complete the service. However, this was changed recently in the sense of imposing absolute rigidity with regard to the limit of activity. The captain is forbidden 10 exceed ii and, in case he should do so, may be prosecuted under the law.

Moreover, until December 1976, it was very easy to fix said limit of activity by taking only a few factors into account, but this calculation has now been made enormously complicated and in practice it is not possible to determine it in the cockpit; for this reason, it is strongly reco’:1m1:nded that the company should be contacted in order to determine It.

This was the situation in Tenerife, and for this reason, Capt Veldhuyzen spoke by HF (radio) to his company’s operations office in Amsterdam. There they told him that if he was able to take off before a certain time it would seem that there would be no problems, but that if there was any risk of exceeding the limit they would send a Telex to Las Palmas.

This uncertainty of the crew at not being able to determine their time limit exactly must have constituted an important psychological factor.

• Those who serviced the KLM airplane in Tenerife stated that the crew appeared calm and friendly; nevertheless, they perhaps felt a certain subconscious – though exteriorly repressed – irritation caused by the fact that the service was turning out so badly, with the possible suspension of the Las Palmas-Amsterdam flight and the resulting alteration of each person’s plans, which would be aggravated by the existence of other possible sources of lateness such as A TC delays, traffic congestion in Las Palmas, etc.
• Behaviour:

Care – This can be divided into voluntary and involuntary, or subconscious. The increase in one brings with it a decrease in the other.

Visibility both before and during the accident was very variable.

It changed from 1500 to 300 metres or less in very short periods of time. This undoubtedly caused an increase in subconscious care to the detriment of conscious care, part of which was already directed toward takeoff preparation (completing checklists, taxiing with reduced visibility, the decision to take off or to leave the runway clear and execute a difficult 180deg turn with a 747 on a 45metre runway, in fog).

Fixation – Two kinds: a fixation on what is seen, with a diminished capacity to assimilate what is heard, and another on trying to overcome the threat posed by a further reduction of precarious visibility.

Faced with this threat, the way to meet it was either by taking off as soon as possible or by testing the visibility once again and possibly refraining from taking off (a possibility which certainly must have been considered by the KLM captain).

Relaxation – After having executed the difficult 180deg turn, which must have coincided with a momentary improvement in visibility (as proved by the CVR, because shortly before arriving at the runway approach they turned off the windscreen wipers), the crew must have felt a sudden feeling of relief which increased their desire to finally overcome the ground problems: the desire to be airborne.

• Possible biometrical factors: felt.

Fatigue – Although within reasonable limits, fatigue began to be Overload – Problems were accumulating for the captain to a degree far greater than that of a normal flight. Likewise for the copilot, who did not have much experience in 747s.

Low-frequency electromagnetic waves – According to certain studies, these have a deleterious effect on man’s intellectual performance.

Noise and vibration – Their level is quite high in a 747 cockpit.

• Other Possible causes:

Route and pilot-instruction experience – Although the captain had flown for many years on European and intercontinental routes he had been an instructor for more than 10 years, which relatively diminished his familiarity with route flying. Moreover, on simulated flights, which are so customary in flying instruction, the training pilot normally assumes the role of controller – that is, he issues takeoff clearances. In many cases, no communications whatsoever are used in simulated flights, and for this reason, takeoff takes place without clearance.

Authority in the cockpit – Although nothing abnormal can be deduced from the CVR, the fact exists that a copilot not very experienced with 747s was flying with one of the pilots of greatest prestige in the company who was, moreover, KLM’s chief flying instructor and who had certified him fit to be a crew member for this type of airplane. In case of doubt, these circumstances could have induced the copilot not to ask any questions, assuming that this captain was always right.

Analysis and Conclusions

Analysis On March 27, 1977, a bomb exploded in the terminal building of Las Palmas Airport (Canary Islands), and for this reason, the passenger terminal was evacuated. As there had been a threat of a second explosion, much of the traffic arriving at Las Palmas Airport was diverted to that of Los Rodeos on Tenerife Island. For this reason, the parking area at the latter airport was saturated with planes.

The KLM Boeing 747, PH-BUF, arrived at Los Rodeos Airport at 13:38 and was parked at the end of the taxi runway next to a Braathens Boeing 737 (SAFE). Subsequently, a Sterling Boeing 727, a SATA DC-8 and the Pan American 747, N1736, were parked in the same area.

The Pan Am Boeing 747 which arrived at Los Rodeos Airport at approximately 14:15 was parked on the taxi runway next to the above-mentioned Braathens Boeing 737, Sterling Boeing 727, SA TA DC-8 and the KLM Boeing 747, PH-BUF, which had arrived at Los Rodeos Airport at 13:38.

Once the Las Palmas Airport had been reopened, the Pan Am plane, N1736, called the tower requesting permission to start up its engines; in reply, it was told that there was no ATC delay, but that they could have problems taxiing on account of the KLM plane which was ahead of it, and that taxiing on the taxiway would not be possible on account of the aircraft congestion on the main apron.

Indeed, when the time came to taxi, the Pan Am was forced, on account of the position of the KLM, which was blocking its way, to wait for the latter’s departure. The three other planes parked there had already departed.

Approximately 1 hour later, KLM 4805 requested an estimated departure time. They said that they needed to refuel and that this would take approximately 30 minutes. They filled up with 55,500 I. while the passengers remained on board. Later, the KLM requested permission to start up its engines, and then clearance to taxi.

• It was cleared to taxi toward the holding position of Runway 12 and to change its surface frequency of 118. 7 to the approach frequency of 119. 7.
• A few minutes later, Pan Am called again in order to request clearance to start up its engines, and was cleared to do so.

If we keep in mind that the Tenerife-Las Palmas flight is one of about 25min duration, the taking on of 55,500 I of fuel leads us to suppose that the KLM captain thereby wished to avoid the difficulties of refuelling in Las Palmas, with the resulting delay, because a great number of airplanes diverted from Tenerife would be going there later. The aircraft could, in fact, have returned to Amsterdam with the fuel it had without refuelling in Las Palmas.

The conversations that took place between KLM 4805 and the control tower until the plane started to taxi on the main runway were as follows: The times are those taken from the KLM CVR.

1658:14.8 – KLM 4805 – Approach KLM four eight zero five on the ground in Tenerife.

1658:21.5 – APP – KLM – ah – four eight zero five roger.

1658:25.7 – KLM 4805 – We require a back-track on one two for takeoff runway three zero.

1658:30.4 – APP – OK four eight zero five . . . taxi . . . to the holding position runway three zero taxi into the runway and – ah – leave runway (third) to your left.

1658:47.4 – KLM 4805 – Roger sir, (entering) the runway at this time and the first (taxiway) we, we go off the runway again for the beginning of runway three zero.

1658:55.3 – APP – OK KLM eight zero – ah – correction, four eight zero five taxi straight ahead – ah – for the runway and – ah – make – ah – backtrack.

1659:04.5 – KLM 4805 – Roger, make a “backtrack”.

1659:10.0 – KLM 4805 – KLM four eight zero five is now on the runway.

1659:15.9 – APP – Four eight zero five roger.

1659:28.4 – KLM 4805 – Approach, you want us to turn left at Charlie One, taxiway charlie one? 1659:32. 28 – APP – Negative, negative, taxi straight – ah – up to the end of the runway and make “backtrack”.

1659:39.9 – KLM 4805 – OK, sir.

At 1703:14.4, KLM 4805 asked the tower controller if the runway centre lights were in service because, as the weather conditions were becoming worse, he wished to have this information in connection with the minimum required takeoff conditions.

At 1704:58.7, the tower controller, after having checked, replied that the runway centre lights were out of service, and he also passed on this information to the PAA Clipper 1736.

At 1705:27.08, KLM 48()5, which was already at the approach end of Runway 30, completed the turn in order to face the direction of takeoff.

From this point on, the KLM 4805 and the Clipper 1736 CVR tapes, as well as the data obtained from the KLM 4805 DFDR (are used) during the last 88 seconds.

At 1705:27.98, the engine braking begins and lasts for 2. 54sec.

At 1705:36.7, the copilot finishes the takeoff checklist and at 1705:41. 22 (67. 81sec before the impact), a slight forward movement due to opening of the throttle is observed (an increase of continued EPR in the four engines). At 1705:41. 5 the copilot says: “Wait a minute, we don’t have an ATC clearance. ” To which the captain replies, “No, I know that, go ahead, ask. ” At 1705:44. 6, KLM 4805 tells the control tower: “Ah – the KLM four eight zero five is now ready for takeoff, and we’re waiting for our ATC clearance. ” This message ended at 1705:50. 77.

This communication was heard in the PAA 1736 cockpit.

At 1705:53.41, the controller gave KLM the following ATC instructions: “KLM eight seven zero five – uh – you are cleared at the Papa beacon climb to and maintain flight level nine zero . . . right turn after takeoff proceed with heading zero four zero until intercepting the three two five radial from Las Palmas VOR. ” The message ended at 1706:08. 9. At the 1706:07. 33, before the message ended, the aircraft captain said, “Yes”, and 44. 31sec before the impact the No. 3 engine and the No. 4 engine slightly increased their EPR.

At 1706:09.61, the copilot repeated the ATC instructions given by the tower controller, at the following times and as follows: 1706:09. 61 – KLM 4805 (RD 2) – Ah – roger sir, we are cleared to the Papa beacon flight level nine zero, right turn out zero four zero until intercepting the three two five. We are now at takeoff.

At 1706:17.79, the copilot’s repetition of the ATC instructions ended.

At 1706:11.08, the brakes in the KLM 4805 were released.

At 1706:12.25, the aircraft captain said, “Let’s go . . . check thrust,” ending this sentence at 1706:16. 11.

The following was ascertained from the DFDR data: 1706:11. 70 (37. 33sec before impact): it was deduced from the LONG that the airplane began to move with longitudinal acceleration.

1706:13.99 (35.04sec before impact): the EPRs have risen above the figures for idling (1. 12-1. 12-1. 14-1. 14).

1706:14.94 (34.09sec before impact): the start of a change of course was observed from the HEAD.

1706:17.17 (31.86sec before impact): from the VANE it can be ascertained that life had begun. The value reached was 6. 8deg. Airspeed was increasing (46. 41). Direction straightened out.

From everything that happened during this time, it is seen that while the first officer was repeating the ATC instructions given by the controller, KLM 4805 had already started its ground run, while at 1706:14. 00, moreover, the sound of engines starting to accelerate is observed.

At 1706:18.19, the controller replied to the read-back of his ATC clearance in the following way: “OK,” and at 1706:20,08, ie; 1. 89sec later, added: “and by tor take toll. . . I will call you,” ending said message at 1706:21. 79.

During this time, at 1706:19.35, the KLM 4805 takeoff had already been reached and stabilised (1. 39 to 1. 42).

Simultaneously, in the Pan Am cockpit, on hearing this conversation, the pilot says “No, uh”, and the copilot says, “And we are still taxiing down the runway, the Clipper one seven three six”.

This communication caused a shrill noise in the KLM cockpit, which started at 1706:19. 39 and ended at 1706:22. 06.

At 1706:25.47, the tower controller confirmed the reception of the Pan Am message in the following way: “Papa Alpha one seven three six report runway clear. ” This was audible in the KLM cockpit.

The message ended at 1706:28. 89.

At 1706:29.59, the PAA replied: “OK, will report when we’re clear. ” This reply was audible in the KLM cockpit.

The control tower replied, “Thank you,” and then the following sentences were spoken in the KLM cockpit.

1706:32.43 – C3 – Is he not clear, then?

1706:34. 10 – Cl – What do you say?

1706:34,15 – PA – Yup.

1706:34.70 – CJ – Is he not clear that Pan American?

1706:35.70 – Cl – Oh, yes (emphatic)

At 1706:43. 49, the copilot intoned the V’ and subsequently on the DFDR PCC the following were observed: a pulling of the control column, with the aeroplane nose pointing up, 16 per cent of the way back from a 44 per cent forward position and from Pitch 2, airplane nose pointing up.

At 1706:46.04, ie; 2. 99sec before impact, increased direction toward the right is observed in the HEAD; 0. 46sec later, a curving of the airplane to the left is seen in the Roll parameter (ROLL) and 1. 54sec before impact, a roll to the right is observed in the Roll Control Wheel Position parameter (RCW).

At 1706:47.44, the captain utters an exclamation -the impact takes place shortly afterwards.

On listening to the PAA CVR, it may be deduced that its crew saw the KLM 9. 5sec before the impact.

From the actions of the Tenerife Control Tower, it may be inferred that their ordering the KLM to leave the runway by the third taxiway was so that they should leave the main runway as soon as possible and then proceed along the parallel taxiway. This third taxiway was the first by which it was possible to take the airplane off the main runway because access to the parallel taxiway by C-1 and C-2 was not possible on account of the aircraft congestion on the parking apron.

Later, in order to make the manoeuvre easier, the controller chose to order this airplane to continue down the right side of the main runway and at the end . . . make a 180deg turn.

Likewise, he indicated to the PAA that they should leave by the third taxiway. At first, there was some confusion regarding the words “first” and “third”. But this was finally dispelled because the controller made the following clarification: “The third one Sir, one, two, three, third one. ”

The situation deteriorated further when low-lying clouds reduced visibility to the point at which neither airplane taxiing on the main runway, nor some of those located in the parking area, were visible from the tower.

It transpires from careful listening to the KLM CVR that although cockpit operation was correct and the checklists were adequately kept, there was some feeling of anxiety regarding a series of factors, which were: the time margin remaining to them, to the point of straining the allowable limit of their duty time; the poor and changing visibility which, especially as runway centrelights were not operative, might prevent the possibility of takeoff within the weather limits required by the company; the inconvenience for the passengers, etc. It is also observed that, as the time for takeoff approached, the captain -perhaps on account of all these worries – seemed a little absent from all that was heard in the cockpit. He inquired several times, and after the copilot confirmed the order to backtrack, he asked the tower if he should leave the runway by C-1, and subsequently asked his copilot if he should do so by C-4. On arriving at the end of the runway, and making a 180-degree turn in order to place himself in takeoff position, he was advised by the copilot that he should wait as they still did not have an ATC clearance. The captain asked him to request it, which he did, but while the copilot was still repeating the clearance, the captain opened the throttles and started to take off. Then the copilot, instead of requesting takeoff clearance or advising that they did not yet have it, added to his readback, “We are now at takeoff. ” The tower, which was not expecting the aircraft to take off as it had not given clearance, interpreted the sentence as, “We are now at the takeoff position. ” (When the Spanish, American and Dutch investigating teams heard the tower recording together and for the first time, no one, or hardly anyone, understood that this transmission meant that they were taking off). The controller replied: “OK, . . . stand by for takeoff . . . I will call you. ” Nor did the Pan Am, on hearing the “We are now at takeoff,” interpret it as an unequivocal indication of takeoff. However, in order to make their own position clear, they said, “We are still taxiing down the runway. ” This transmission coincided with the “Stand by for takeoff . . . I will call you,” causing a whistling sound in the tower transmission and making its reception in the KLM cockpit not as clear as it should have been, even though it did not thereby become unintelligible.

The communication from the tower to the PAA requested the latter to report when it left the runway clear. In the cockpit of the KLM, which was taking off, nobody at first confirmed receiving these communications until the Pan Am responded to the tower’s request that it should report leaving the runway with an “OK, we’ll report when we’re clear. ” On hearing this, the KLM flight engineer asked: “Is he not clear then?” The captain didn’t understand him and he repeated: “Is he not clear that Pan American?” The Captain replied with an emphatic “Yes” and, perhaps influenced by his great prestige, making it difficult to imagine an error of this magnitude on the part of such an expert pilot, both the copilot and flight engineer made no further objections. The impact took place about 13 seconds later.

From that moment until the next call to the airplanes, the tower took care of the 18-185 and the BX-387 and awaited the communication from the Pan Am 1736 reporting the “runway clear. ” It also received information coming from two airplanes located in the parking area that there was a fire in an undetermined place on the field, sounded the alarm, informed the Firefighting and Health Services, and broadcast the news of the emergency situation; it then called the two airplanes on the runway, not receiving any reply.

The conversations took place in the Pan Am cockpit and between the airplanes and the control tower from 1702:03. 6 were as follows (times taken from the PAA CVR):

1702:03. 6 – RD0-2 – Ah -We were instructed to contact you and also to taxi down the runway, is that correct?(1702:07. 4).

1702:08.4 -APP – Affirmative, taxi into the runway and -ah – leave the runway third, third to your left (background conversation in the tower).

1702:16.4 -RD0-2 -Third to the left, OK (1702:18. 3).

1702:18.4 – CAM-3 – Third he said.

CAM-? -Three.

1702:20.6 -APP – -ird one to your left.

1702:21.9 – CAM-1 – I think he said first.

1702:26.4 -CAM-2 – I’ll ask him again.

1702:32.2 -CAM-2 -left turn.

1702:33.1 -CAM-1 -I don’t think they have takeoff minimums anywhere right now.

1702:39.2 -CAM-1 -What really happened over there today? 1702:41. 6 – CAM-4 – They put a bomb (in) the terminal sir, right where the check-in counters are.

1702:46.6 -CAM-1 – Well we asked them if we could hold and -uh -I guess you got the word, we landed here.

1702:49.8 -APP -KLM four eight zero five how many taxiway – ah – did you pass? 1702:55. 6 -KLM – I think we just passed charlie four now.

1702:59.6 -APP -OK . . . at the end of the runway make one eighty and report – ah – ready – ah – for ATC clearance (background conversation in the tower).

1703:09-3 -CAM-2 -The first one is a 90deg turn.

1703:11.0 -CAM-1 -Yeah, OK.

1703:12.1 -CAM-2 -Must be the third . . . I’ll ask him again.

1703:14.2 -CAM-1 -OK.

1703:16.6 – CAM-1 -We could probably go in it’s ah . . .

1703:19.1 -CAM-2 – You gotta make a 90deg turn.

1703:21.6 -CAM-1 -Yeah, uh.

1703:21.6 -CAM-2– 90deg turn to get around this . . . this one down here it’s a 45.

1703:29.3 – RD0-2 -Would you confirm that you want the clipper one seven three six to turn left at the third intersection? (1703:35. 4). (PAA: “third” drawn out and emphasised).

1703:35.1 – CAM-1 -One, two.

1703:36.4 -APP -The third one sir, one, two, three, third third one (1703:38. 3).

1703:38.3 -CAM-l – One two (four).

1703:39.0 – CAM-1 -Good.

1703:39.2 -RD0-2 -Very good, thank you (1703:40. 4).

1703:40.1 -CAM-1 -That’s what we need right, the third one.

1703:42.9 -CAM-3 -Uno, dos, tres.

1703:44.0 -CAM-1 -Uno, dos, tres.

1703:44.9 -CAM-3 -Tres -uh -si.

1703:46.5 -CAM-1 -Right.

1703:47.6 -CAM-3 – We’ll make it yet.

1703:47.6 – APP -. . . er seven one three six report leaving the runway.

1703:49.1 -CAM-2 – Wing flaps? 1703:50. 2 -CAM-1 -Ten, indicate ten, leading edge lights are green.

1703:54.1 -CAM-l -Get that.

1703:55.0 -RD0-2 -Clipper one seven three six (1703:56. 4).

1703:56.5 – CAM-2 -Yaw damp and instrument?
1703:58.6 – CAM-1 -Ah -Bob we’ll get a left one.
1703:59.3 – CAM-2 – I got a left.
1704:00.6 – CAM-1 – Did you?
1704:00.9 -CAM-2 – And – ah -need a right.
1704:02.6 – CAM-1 – I’ll give you a little.
1704:03.8 – CAM-2 -Put a little aileron in this thing.
1704:05.0 -CAM-1 -OK here’s a left and I’ll give you a right one right here.
1704:09.7 -CAM-1 – OK, right turn right and left yaw.
1704:11.4 – CAM-2 -Left yaw checks.
1704:12.4 -CAM-1 – OK, here’s the rudders.
1704:13.6 -CAM-1 – Here’s two left, centre, two right centre.
1704:17.8 -CAM-2 -Checks.
1704:19.2 -CAM-2 -Controls.
1704:19.6 -CAM-1 – Haven’t seen any yeti
1704:20.3 -CAM-2 – I haven’t either.
1704:21.7 -CAM-1 -They’re free, the indicators are checked.
1704:24.6 -CAM-2 -There’s one.
1704:25.8 -CAM-1 -There’s one.
1704:26.4 -CAM-1 -That’s the ninety degree.
1704:28.5 – CAM-l -OK.
1704:37.7 – CAM-1 – (Sounds similar to stabiliser trim) (1704:44.8). half.
1704:34.5 -CAM-2 -Weight and balance finals?
1704:37.2 -CAM-1 -We were gonna put that on four and a
1704:39.8 -CAM-3 -We got four and a half and we weigh five thirty four (sound of stabiliser trim).
1704:44.6 – CAM-2 – Four and a half on the right.
1704:46.8 – CAM-2 – Engineer’s taxi check.
1704:48.4 – CAM-3 – Taxi check is complete.
1704:50.5 – CAM-2 – Takeoff and departure briefing?
1704:52.1 – CAM-1 – OK, it’ll be standard we gonna go straight out there till we get 3500ft then we’re gonna make that reversal and go back out to (unintelligible) fourteen.
1704:58.2 – APP – Eight seven zero five and clipper one seven … three six, for your information, the centreline lighting is out of service. (APP: transmission is readable but slightly broken).
1705:05.8 – KLM – I copied that.
1705:07.7 – RDO-2 – Clipper one seven three six.
1705:09.6 – CAM-1 – We got centreline markings (only) (could be “don’t we”) they count the same thing as … we need 800 metres if you don’t have that centreline … I read that on the back (of this) just a while ago.
1705:22.0 – CAM-1 – That’s two.
1705:23.5 – CAM-3 – Yeh, that’s forty-five there.
1705:25.7 – CAM-1 – Yeh.
1705:26.5 – CAM-2 – That’s this one right here.
1705:27.2 – CAM-1 – (Yeh) I know.
1705:28.1 – CAM-3 – OK.
1705:28.5 – CAM-3 – Next one is almost a forty-five, huh yeh.
1705:30.6 – CAM-1 – But it goes …
1705:32.4 – CAM-1 – Yeh, but it goes … ahead, I think (it’s) gonna put us on (the) taxiway.
1705:35.9 – CAM-3 – Yeah, just a little bit yeh.
1705:39.8 – CAM-1 – OK, for sure.
1705:40.0 – CAM-2 – Maybe he, maybe he counts these (are) three.
CAM-1 – Huh.

1705:44. 8 – CAM-1 – I like this.

1705:44. 8 – KLM – Uh, the KLM . . . four eight zero five is now ready for takeoff . . . we’re waiting for our ATC clearance.

1705:53. 4 – APP – KLM eight seven zero five uh you are cleared to the Papa Beacon climb to and maintain flight level nine zero . . .

right turn after takeoff proceed with heading zero four zero until intercepting the three two five radial from Las Palmas VOR (1706:08. 2).

1706:09. 6 – KLM – 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 takeoff). (1706:17. 9).

From the foregoing it may be inferred that the Pan Am crew at first had difficulty in understanding “third”, thinking that it was “first. ” In any case, the copilot asked again, and this doubt was dispelled at 1703:36. 4 as the tower controller told him: “The third sir, one, two, three, the third, third,” and the copilot confirmed this at 1703:39. 2. As a result of the poor visibility, the crew had difficulty in localising the exits from the runway whose position they were following on the little map that they had with them. Nevertheless, at 1704: 26. 4 the captain identified C-1 (which is the 90deg exit). At 1705:2 2. 0, they also identified C- 2. Then, perhaps through error, or thinking that C-4 was an easier exit than C-3, they overshot the exit ordered by the tower.

From the time correlation between the conversations taking place with the tower and inside the KLM 4805 and Clipper 1736 cockpits, as well as the data obtained from the KLM 4805 DFDR during the last 88sec before impact, the following may be ascertained: When at 1706:17. 9, KLM 4805 finished reading back the ATC clearance given by the control tower and added, “We are now (at takeoff)” and before the controller finished the sentence “OK . . .

stand by for takeoff, I will call you”, only ” . . . k” is heard in the Pan Am cockpit. The pilot says: “No uh . . . ” and the copilot says “And we’re still taxiing down the runway the Clipper one seven three six . . . ” (1706:23. 6). These communications caused a shrill noise in the KLM cockpit, which lasted approximately 3. 74sec.

During this time the KLM takeoff EPR was reached and stabilised (1. 39 to 1. 4 2).

At 1706:25. 6 the tower controller gave Pan Am confirmation: “Roger alpha one seven three six reports the runway clear”- to which the Pan Am replied at 1706: 29. 6, “OK, we’ll report when we’re clear. ” The tower replied, “Thank you,” but the KLM had already started its takeoff run. The Pan Am crew saw the KLM airplane approximately 8. 50sec before impact. Amidst logical exclamations of alarm, they accelerated to try to get off the runway, but the collision was already inevitable.

Conclusions

From all of this, it may be ascertained that the KLM 4805 captain, as soon as he heard the ATC clearance, decided to take off.

The fundamental cause of this incident was the fact that the KLM captain:

• Did not interrupt takeoff on learning that the Pan Am was still on the runway.
• In reply to the flight engineer’s query as to whether the Pan Am had already left the runway, replied emphatically in the affirmative.

Now, how is it possible that a pilot with the technical capacity and experience of Capt Veldhuyzen Van Zanten, whose state of mind during the stopover at Tenerife seemed perfectly normal and correct, was able, a few minutes later to commit a basic error in spite of all the warnings repeatedly addressed to him? An explanation may be found in a series of factors which possibly contributed to the occurrence of the accident.

• A growing feeling of tension as the problems for the captain continued to accumulate. He knew that, on account of the strictness in the Netherlands regarding the application of rules on the limitation of duty time, if he did not take off within a relatively short space of time he might have to interrupt the flight – with the consequent upset for his company and inconvenience for the passengers.

Moreover, the weather conditions in the airport were getting rapidly worse, which meant that he would either have to take off under his minimum or else wait for better conditions and run the risk of exceeding the aforementioned duty-time limit.

The special weather conditions in Tenerife must also be considered a factor in themselves. What frequently makes visibility difficult is not actually fog, whose density and therefore the visibility it allows can be fairly accurately measured, but rather layers of low-lying clouds that are blown by the wind and therefore cause sudden and radical changes in visibility. The latter can be zero metres at certain moments and change to 500 metres or 1km in a short space of time, only to revert to practically zero a few moments later. These conditions undoubtedly make a pilot’s decisions regarding takeoff and landing operations much more difficult.

• The fact that two transmissions took place at the same time. The “stand by for takeoff . . . I will call you” from the tower coincided with Pan Am’s are still taxiing down the runway,” which meant that the transmission was not received with all the clarity that might have been desired. The whistling sound which interfered with the communication lasted for about 3 seconds.

The following must also be considered factors that contributed to the accident:

• Inadequate language. When the KLM co-pilot repeated the ATC clearance, he ended with the words, “we are now at takeoff. ” The controller, who had not been asked for takeoff clearance, and who consequently had not granted it, did not understand that they were taking off. The OK from the tower, which preceded the “stand by for takeoff” was likewise incorrect – although irrelevant in this case because takeoff had already started about six and a half seconds before.
• The fact that the Pan Am had not left the runway at the third intersection. This airplane should, in fact, have consulted with the tower to find out whether the third intersection referred to was C-3 or C-4, if it had any doubts, and this it did not do. However, this was not very relevant either since Pan Am never reported the runway clear but, to the contrary, twice advised that it was taxiing on it.
• Unusual traffic congestion obliged the tower to carry out taxiing manoeuvres which, although statutory, as in the case of having airplanes taxi on an active runway, are not standard and can be potentially dangerous.

Although contributing to the accident, the following occurrences must not be considered direct factors in it: the bomb incident in Las Palmas, the KLM refuelling, the latter’s takeoff at reduced power etc.

Recommendations:

• Placing of great emphasis on the importance of exact compliance with instructions and clearances.
• Use of standard, concise and unequivocal aeronautical language.
• Avoidance of the word “takeoff” in the ATC clearance and adequate time separation between the ATC clearance and the takeoff 1704:44. 6 – 1704:46. 8 – 1704:48. 4 – 1704:50. 5 – CAM-2 – Four and a half on the right.

NEXT ISSUE: On December 28, 1978, a United Airlines DC-8-61 crash lands in a residential area of Portland, Oregon. The primary cause for the crash was lack of fuel; read how an experienced crew made a series of simple errors monitoring the fuel state culminating in a forced landing.