Tenerife Airport DisasterKLM flight 4805 and Pan Am flight 1736

Bachelor’s of Aviation Management

What happened• The Tenerife airport disaster was a fatal

runway collision between two Boeing 747’s on Sunday, March 27, 1977, at Los Rodeos Airport.

• Killed 583 people• A bomb explosion at Gran Canaria Airport,

and the threat of a second bomb, caused many aircraft to be diverted to Los Rodeos Airport

• A dense fog developed at Tenerife, greatly reducing visibility.

• Result: • Destroyed both aircraft• Killing all 248 aboard the KLM flight• 335 passenger killed from the Pan Am flight. • Sixty-one people aboard the Pan Am flight,

including the pilots and flight engineer, survived.

How it happened• The civil aviation authorities had therefore closed the airport temporarily after the bomb

detonated and diverted all of its incoming flights to Los Rodeos.

• The official report from the Spanish authorities explains that the controller instructed the Pan Am aircraft to use the third taxiway because this was the earliest exit that they could take to reach the unobstructed section of the parallel taxiway.

• The Pan Am crew found themselves in poor and rapidly deteriorating visibility almost as soon as they entered the runway

• Misinterpretation that they were in takeoff position and ready to begin the roll when takeoff clearance was received, but not in the process of taking off.

• Both airplanes were destroyed. All 234 passengers and 14 crew members in the KLM plane died, as did 326 passengers and nine crew members aboard the Pan Am, primarily due to the fire and explosions resulting from the fuel spilled and ignited in the impact. The other 56 passengers and five crew members aboard the Pan Am aircraft survived, including the captain, first officer and flight engineer.

The 2 BoeingsPan America World Airways(747-121) KLM Royal Dutch Airlines(747-

206B)

Causes• Sudden fog greatly limited visibility. The

controller tower and the crews of both planes were unable to see each other.

• Simultaneous radio transmissions, with the result that neither message could be heard.

• Use of ambiguous non-standard phrases by the KLM co-pilot and the Tenerife control tower.

• The airport was forced to accommodate a great number of large aircraft, resulting in disruption of the normal use of taxiways.

a. Diversion of aircraft to Los Rodeos Bomb threat at Gran Canaria

International Airport by the separatist anti-Francoist Fuerzas Armadas Guanches.

The civil aviation authorities had therefore closed the airport temporarily after the bomb detonated and diverted all of its incoming flights to Los Rodeos

Five large aircraft were diverted to Los Rodeos, the airport is too small to accommodate all planes.

After the threat at Gran Canaria had been contained, authorities reopened that airport.

b. Taxiing and take-off preparations The KLM was cleared to taxi the full length of the

runway and make a 180° turn to get into takeoff position

The controller asked the flight crew to report when it was ready to copy the ATC clearance.

Afterward, the Pan Am was instructed to follow the KLM down the same runway, exit it by taking the third exit on their left and then use the parallel taxiway.

Initially, the crew was unclear as to whether the controller had told them to take the first or third exit.

There were no markings or signs to identify the runway exits and they were in conditions of poor visibility.

The Pan Am crew appeared to remain unsure of their position on the runway until the collision

c. Weather conditions at Los Rodeos Los Rodeos airport is at 633 metres (2,077

feet) above sea level, which accounts for cloud behavior that differs from that at most other airports.

Clouds at 600 m (2,000 ft) above ground level at the nearby coast, are at ground level at Los Rodeos/Tenerife North.

The Pan Am crew found themselves in poor and rapidly deteriorating visibility almost as soon as they entered the runway.

According to the ALPA report, as the Pan Am aircraft taxied to the runway, the visibility was about 500 m (1,600 ft).

Shortly after they turned onto the runway it decreased to less than 100 m (330 ft).

d. Communication misunderstandings Immediately after lining up, the KLM pilot advanced the throttles and the aircraft started to

move forward.

The co-pilot advised the captain that ATC clearance had not yet been given, and Captain Veldhuyzen van Zanten responded, "I know that. Go ahead, ask.“

The KLM crew then received instructions which specified the route that the aircraft was to follow after take off.

The instructions used the word "take off," but did not include an explicit statement that they were cleared for take off.

Meurs (co-pilot) read the flight clearance back to the controller, completing the read back with the statement: "We are now at take off.“ Captain Veldhuyzen van Zanten interrupted the co-pilot's read-back with the comment, "We're going.“

The controller, who could not see the runway due to the fog, initially responded with "OK" (terminology which is nonstandard), which reinforced the KLM captain's misinterpretation that they had take off clearance.

The controller's response of "OK" to the co-pilot's nonstandard statement that they were "now at take off" was likely due to his misinterpretation that they were in take off position and ready to begin the roll when take off clearance was received, but not in the process of taking off.

The controller then immediately added "stand by for take off, I will call you,“ indicating that he had not intended the clearance to be interpreted as a take off clearance.

A simultaneous radio call from the Pan Am crew caused mutual interference on the radio frequency, this caused the KLM crew to miss the crucial latter portion of the tower's response.

Due to the fog, neither crew was able to see the other plane on the runway ahead of them.

In addition, neither of the aircraft could be seen from the control tower, and the airport was not equipped with ground radar.

InvestigatorAbout 70 crash investigators from Spain, the Netherlands, the

United States, and the two airline companies were involved in the investigation.

Facts showed that there had been misinterpretations and false assumptions.

Analysis of the CVR transcript showed that the KLM pilot was convinced that he had been cleared for take off, while the Tenerife control tower was certain that the KLM 747 was stationary at the end of the runway and awaiting take off clearance.

It appears KLM's co-pilot was not as certain about take-off clearance as the captain.

The four overarching categories in the Swiss Cheese Model are:

• Organizational Influences• Unsafe Supervision• Preconditions for Unsafe

Acts• Unsafe Acts

Type of model used by the investigators

• Explosion at Gran Canaria Airport• Size & Characteristics of Los Rodeos Airport (Tenerife)• Dense Fog in Tenerife• Absence of Ground Radar• KLM 4805 Fully Refuels at Los Rodeos Airport• Pan Am 1736 Misses Turn• Personality Traits of Key Personnel

The Analysis Made by the Investigators.

The words “take off” should never be used in an ATC clearance.

A redundant means should be provided to confirm take off clearance at all airports.

Recommendations

All aeronautical communications should be conducted with precise standardised terminology. Rigid standards should be applied to ensure that all personnel involved in commercial aeronautical communications are fluent in English and speak with minimal accent.

Ground radar should be installed at all air carrier airports.

Recommendations

Means should be taken to avoid confusion of an ATC clearance with take off clearance. This may involve changing the name “ATC clearance” so that it is clearly understood to be nothing more than a description of the route to be flown.

Commercial aircraft should not taxi at any airport in visibility conditions below 150 meters unless suitable taxi lighting or other visual aids and airport ground radar are operational.

Landing lights should be on, if practicable, whenever an aircraft is moving.

Strobe anti-collision lights should be installed on all air carrier aircraft, and operated whenever practicable.

Recommendations

Lessons Learned

Technical Related

Clearances to move about an airport, especially clearances to take off or land, should be clear and unambiguous, and compliance should be

exact.

“Upon receiving a departure clearance, the KLM flight misunderstood this as a take-off clearance and began their take-off roll with Pan Am still on the runway. Had the KLM crew questioned the clearance, or queried the control tower as to the location of the Pan Am flight, the accident may have been avoided.”

Lessons Learned

Flight crew communications regarding airplane safety readiness should be open and effective. Each crew member must clearly give and receive communication in such a way that the flight safety decisions represent the best product of this open, two-way communication.

“The flight engineer then asked the KLM captain, "Is he not clear, then?" The KLM captain replied, "What do you say?" and the flight engineer reiterated, "Is he not clear, that Pan American?" The captain responded with an emphatic "Oh, yes" and continued the take-off.”

Lessons Learned

Common Theme Related

Deviations from operations or procedures that are considered normal, or routine, increase the risks for human errors of all kinds. When it is necessary to deviate from normal operations, extra vigilance and strict adherence to proper procedures should be emphasized.

“A bombing at the Las Palmas airport, the intended destination of both the KLM and Pan Am flights, as well as many others, caused a diversion to and an unusual situation at the Tenerife airport. Everyone involved, from each flight to the air traffic controllers, were forced to compensate for the unusual circumstances.”

Lessons Learned

Regulatory standards should be sufficiently flexible to allow deviation in special circumstances, without compromising safety. Application of an appropriate alternative can result in the level of safety intended by the regulation.

“A revised Dutch regulation, imposing new limitations on crew duty time, was discussed in the accident report and was concluded to have had an influence on the decision-making of the KLM captain. Previous duty time regulations allowed a captain some flexibility in extending the crew's duty time. The new law, enacted in December 1976, was inflexible, and compliance was difficult.”

Conclusions1. Aircraft crews are highly structured, mechanistic groups known to

be capable of failures of communication and decision-making. The Tenerife air disaster is a clear example of that. Mechanistic groups typically perform very well as long as the tasks are fairly predictable and routine. However, during crisis situations, these trained responses tend to break down. Nowhere is this more evident than in the air transportation industry.

2. Accidents due to equipment failures are now thought to constitute just three to five percent of all airline accidents. The remaining accidents are attributable solely to human error. Of the accidents attributed to human error, nearly three quarters of them are due to poor human communication.

3. Authorities at the U.S.A, National Aeronautics and Space Administration’s Ames Aerospace Human Factors Research Division also reports that up to 80 percent of all aircraft accidents are due to a lack of adequate coordination or utilization of available resources (Cate, 1990).

4. We must continue looking for ways to reduce subjective decisions on the part of pilots. We can’t take the human factor out unless we want a system that is completely rigid and inflexible. Research, study of lessons learned, and application of the knowledge gained will help reduce the chances of another Tenerife disaster in the future.