The Worst Airline Disaster in History: Tenerife

The Tenerife Fire

The explosion and resulting fireball of the two planes at Tenerife
The explosion and resulting fireball of the two planes at Tenerife

The Tenerife Disaster

The worst disaster, in terms of human life on the airplanes involved, occurred on March 27, 1977.  It was a collision involving two 747 airplanes, both of them nearly fully loaded, at a small airport that has now become infamous among those who study airline disasters.  The airport was in Tenerife, a small island near the Canary Islands.  It took the lives of 583 people and remains the deadliest in the history of commercial aviation.  What makes the story of Tenerife so remarkable is how it was a succession of strange coincidences, activities and events that caused the accident.

The bombing

The first event that set things into motion involved the airport on the Canary Islands.  Inside the terminal of Gran Canaria International Airport a bomb exploded.  The bomb was planted by members of a separatist movement known as the Fuerzas Armadas Gaunches.  They had called ahead and given warning that they intended to plant the bomb.  It was 1:15 p.m. and there were dozens of planes in the air heading for the airport.

The two main airplanes that were ultimately involved in the fatal accident were Pan Am Flight 1736, a lane that had flown all night out of Los Angeles International Airport and KLM Flight 4805.  KML 4805 was a chartered plane from the Netherlands.  The Pan Am flight had 380 passengers and KML 4805 carried 235 passengers.

When the crew of the Pan Am flight were notified of the bombing at the airport they requested to circle the air field until the airport re-opened.  This request was denied.  Several heavy-loaded aircraft were diverted to Los Roderos Airport on the nearby island of Tenerife.  Los Roderos was a very small airport not used to handling huge aircraft like the 747s that were now headed for the single runway and single taxi-way that comprised the whole of Los Rederos’ airport.  

The planes land

There were at least five large planes on the ground at Los Roderos.  Most of the planes were sent off of the runway to wait on the taxi-way.  The airport was so small and so crowded that once the planes were lined up, they could not get around one another.  Also, the planes were packed in so tight that when the airport on the Canary Islands was re-opened most of the planes had to taxi down the runway, turn around, and then take off.

The small airport was completely unable to handle the large number of large planes.  The airport is located in a valley, surrounded by mountains.  The weather is subject to rapid and severe changes, with fog and low-lying clouds moving in and blanketing the runway quickly.  At the time of the accident, the control tower had no ground radar, thus if clouds rolled in, the controllers would be unable to see the planes on the runway or taxi-way.

KLM landed first and was directed to the taxiway to wait in line with other planes.  Pan Am then landed and was told to park behind the KLM plane.  Passengers from both planes were allowed to leave as it was unknown how long it would take to clear the airport and determine that there weren’t any other bombs.  From the KLM plane a Dutch tour guide decided to remain on Tenerife as she lived on the island and had a boyfriend who also lived there that she wanted to visit.

The airport is cleared and problems arise

After some time the airport on the Canary Islands was opened.  The planes sitting on the taxiway were cleared to take off.  Most of them had to do a maneuver known as back-taxiing where they had to taxi back down the runway in which they would take off.  Given the size of many of the airplanes this was a remarkably difficult operation to undertake.  

At this point a couple of things happened that would eventually make the accident almost inevitable.  The first was that the captain of the KLM plane, Jacob Veldhuyzen van Zanten, decided that he would refuel his plane while it was sitting on the taxiway.  Other planes, ahead of him, were allowed to go ahead.  However, the large KLM plane blocked the Pan Am plane.  By a mere twelve feet the Pan Am plane was unable to get around the KLM flight.  Thus, the Pan Am plane was forced to wait forty-five minutes as the KLM fligh was refueled.

It has been theorized that Captain Veldhuyzen van Zanten was trying to save time as KLM had strict rules against overtime.  However, the refueling not only delayed things dangerously, it also made the KLM plane extra-heavy with fuel, which would prove critical later.

At the same time, the weather began to change.  With the airport being located in a valley it was susceptible to low-lying clouds and fog.  When the planes were first allowed to take off, the runway and airfield was clear and air controllers in the tower could easily see the planes.  Now, low-lying clouds began rolling in as KLM began to refuel.  By the time the plane had completed the refueling the planes could not see the tower and, more critically, the tower could not see them.  With no ground radar, the planes were all but invisible, capable of communicating what was happening to the tower only video radio.

Things get worse

Once the KLM flight had refueled the tower instructed the crew and the plane to back-taxi along the runway and then make a 180 degree turn in order to get into takeoff position.  The controller in the tower requested that the crew of the plane inform him when they had reached that position and were ready to receive clearance for takeoff.  The crew was in the midst of performing their pre-flight checklist and took their time in acknowledging those instructions.  They did not radio the tower that they had received the instructions until they were already in takeoff position.

Just as the KLM plane reached the takeoff position the Pan Am flight was given instructions to back-taxi.  They were then told to take the third exit runway to the taxi-way and then run the remaining length of the taxi-way to then get into takeoff position at the end of the runway.  This is where more confusion came into being.

There were four exits from the runway to the taxiway.  At first, with the controller speaking in an accent, the crew did now know if they were instructed to take the first or the third exit.  When they asked for clarification they received the instructions, “the third one, sir; one, two, three; third, third one.”  The crew then began looking at a map they had of the runway and began attempting to count off the runway exits.  They were already past the first one and the one labeled with the number 3 was at such a severe angle that making the turn would have been all-but impossible for the large plane.  Thus, the crew assumed they meant the exit labeled with the number four, but the third one they would have come to since being issued the instruction.

Meanwhile, the KLM flight was waiting at the end of the runway.  Thus, the next phase that would lead to the disaster began.  The crews would begin trying to communicate with the tower, but the messages would become garbled, mixed and confusing.

Mixed messages

The KLM began to throttle up its engines which apparently caused the co-pilot to become confused.  He quickly reminded the captain that they had not yet been given what is known as ATC clearance to take off.  The Captain rather rudely responded that he was aware of this and that the co-pilot should ask for the clearance.  The co-pilot radioed the tower and stated they were “ready for takeoff” and then also stated they were “waiting for our ATC clearance.”  The tower responded by telling the crew what route they were to take after takeoff and, in doing so, used the word “takeoff.”  They did not directly indicate that takeoff clearance had been given, but the use of the word seemed to confuse the Dutch crew.

The co-pilot acknowledged the message and then repeated it to the control tower.  During this communication with the tower he said something to the effect of “we’re now at takeoff.”  Apparently he took this to mean that the plane was already starting forward and getting ready to take off.  However, the tower apparently took it to mean that the plane was sitting at the end of the runway awaiting clearance for takeoff.  

The co-pilot attempted, again, to explain their situation to the control tower.  However, during his communication the pilot interrupted him with the coarse, short, statement of “we’re going.”  This statement was heard by the control tower who responded with the non-standard response of “OK” thus, again, adding to the confusion that the plane was now cleared for takeoff.

At the time all of this was happening, the Pan Am flight was taxiing back down the runway.  They had passed the exit that was marked as number 3 and were heading to the number 4 exit.  When they heard that the KLM flight was getting ready to take off they attempted to radio the tower to inform everyone that they were still taxiing down the runway.  However, it was at the same time the KLM captain indicated that they were “going.”  The two simultaneous radio signals cancelled each other out and resulted in a blast of static and noise in the ears of the radio control tower.  As such, the control tower attendant was still unaware of what was about to happen right in front of them.  Fog and clouds covered the field.  The KLM pilot was getting ready to take off.  The Pan Am flight was on the runway, half-turned onto the number four exit, and no one was aware of what was happening.

The radio tower attempted to tell the KLM flight to stop.  The controller transmitted that the pilot was to “stand by for take off, I will call you.”  This was not acknowledged by the KLM crew, however.

Disaster of epic proportions

The KLM plane began moving forward.  Just as they began moving forward the crew overhead the radio tower contact the Pan Am plane and ask that they “report when runway clear” and then the Pan Am flight replied “OK, we’ll report when clear.”  The flight engineer on the KLM flight realized, with alarm, that the Pan Am flight was not clear of the runway. He was overheard in the cockpit recordings asking, “Is he not clear, that Pan American?”  The captain, however, seemed to dismiss him and said, “Oh, yes.”  The flight engineer was apparently afraid to be more forceful with the respected captain and he remained silent.

The Pan Am flight was now sideways against the oncoming KLM plane.  They were attempting to get on the number 4 exit.  The captain of the Pan Am flight looked out his window and saw, with growing alarm, the landing lights of the KLM flight.  He notified his crew and all of them stared as, through the fog, the huge plane approached them.  

Co-pilot Rober Bragg is heard on the cockpit voice recorder yelling “Goddamn, that son-of-a-bitch is coming straight at us!” and then he yelled “Get off!  Get off!  Get off!”  The crew went to full power to try to get the plane moving and off the runway.

Inside the cockpit of the KLM flight Captain van Zanten saw what was about to happen.  He brought the plane to full power and attempted to take off, over the Pan Am flight.  However, his plane was heavy with passengers, luggage, and fuel.  The front of the plane was able to take off, the back of the plane scraped across the runway for 20 meters.  The nose gear of the KLM plane cleared the plane, but the rear end of the plane hit the Pan Am flight in the middle.  

The Pan Am plane was ripped apart about halfway down the fuselage.  The KLM plane managed to lift into the air for a bit but the collision had ripped off two engines and then remaining engines had then sucked debris from the destroyed engines into their intake.  The plane quickly lost altitude and crashed and exploded into a ball of flame.  Jet fuel had sprayed everywhere.  Soon, both planes were in flames.

Everyone aboard the KLM flight was killed when the plane came down and exploded.  On the Pan Am flight 326 passengers and nine of the crew were killed when the flames enveloped the plane.  The flight crew and 56 passengers did survive by crawling out through open holes in the fuselage and onto the wing.  When the tower realized what was happening they thought only the KLM flight had crashed and survivors stood on the wings of the burning airplane as the fire crews raced to the KLM plane.  Many surivors jumped and injured themselves.  A total of 583 people had lost their lives.

A tragedy of errors

Investigations showed that a number of strange things had occurred to conspire against the two planes.  First, of course, was the bombing.  Had that not happened, the accident never would have happened.  Second, if the Pan Am flight had been allowed to keep circling instead of landing at the smaller airport, the accident never would have happened.  Had the KLM flight not refueled or had the Pan Am flight been able to get around the KLM flight the accident would never have happened.  Had the flight engineer on the KLM flight been more forceful and willing to cross the captain, it might not have happened.  Had the crew of the Pan Am flight been able to understand and make the turn off of the runway easier, the planes would not have collided.  Had the tower been able to see the runway and planes, it could have been avoided.  Had the controllers and KLM crew not used non-standard wording when communicating, they might have understood what was happening and avoided the collision.  Had the Pan Am flight not radioed at the same time as the KLM captain and negated each other with noise, again, the accident might not have occurred.

Since the accident a standard of wording is to be used with flight crews and control towers for each takeoff and landing.  Safeguards have been put in place in planes and on runways to prevent accidents like it.  Thus, and perhaps for all time, the Tenerife disaster may remain the deadliest accident in airline history.

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