Los Rodeos, Tenerife's North airport is, unfortunately, famous for the fateful accident which occurred on March 27, 1977, in which 583 people died when KLM and Pan Am 747s collided on a crowded, foggy runway in Tenerife, Canary Islands. The incident remains the world's worst aviation accident in history.
*Probable Cause
The Subsecretaria de Aviacion Civil Report gave the probable cause of this accident:
The KLM aircraft had taken off without take-off clearance, in the absolute conviction that this clearance had been obtained, which was the result of a misunderstanding between the tower and the KLM aircraft. This misunderstanding had arisen from the mutual use of usual terminology which, however, gave rise to misinterpretation. In combination with a number of other coinciding circumstances, the premature take-off of the KLM aircraft resulted in a collision with the Pan Am aircraft, because the latter was still on the runway since it had missed the correct intersection
*Contributing Factors
“Considered factors” which contributed to the accident were (1) inadequate language, i.e., nonstandard phraseology from the KLM first officer and tower controller, (2) the Pan Am flight crew missing the correct taxiway, and (3) unusual traffic congestion, which required back-taxi operations on the active runway.
*Background
Both flights were rerouted from their original destination of Las Palmas, Canary Island, as a result of a terrorist bombing at the Las Palmas terminal. Local police had no alternative but to close the airport while they conducted a thorough search.
*Weather
On the day of the accident, light rain and patch low clouds covered the Los Rodeos Airport most of the early afternoon, which the KLM and Pan Am flights arrived. Fog and light rain persisted over the runway for the 30 minutes prior to the accident.
*History of Flights
KLM Flight 4805 was a chartered flight that originated from Amsterdam’s Schiphol Airport on the morning of the accident. The flight carried 234 holiday passengers, most of whom were Dutch, bound for the Las Palmas Airport, Grand Canary Island. The flight from Amsterdam to Las Palmas was four hours.
Pan Am Flight 1736 was a chartered flight that originated in Los Angeles, on the afternoon of 26 March. There were 364 passengers, mostly retires, boarded for the first leg of their trip to Las Palmas. From Grand Canary, they were to embark on a 12-day Mediterranean cruise.
KLM Flight 4805 was one of the first diverted flights that landed at Los Rodeos. The parking area and main taxiway were already full with airplanes that had been previously diverted by the time Flight 4805 cleared the runway.
The captain of Pan Am asked the Las Palmas controller if, instead of diverting to Los Rodeos, they could continue holding over Las Palmas. The controller refused the captain’s request and diverted the flight to Los Rodeos. Pan Am landed at 1345 and was instructed to park directly behind KLM Flight 4805.
*Pilot Experience
The KLM Captain had a total of 11,700 flight hours, 1545 in the Boeing 747. He was KLM’s chief training captain for the 747 and was featured in company advertisements, including those in in-flight magazines. The captain had spent recent years in the 747 training facility and did not typically fly much on scheduled flights.
*Language Barrier
The Spanish controllers at Los Rodeos had difficulty communicating in English. This was evident from the numerous misunderstandings and communication breakdowns between them and the KLM and Pan Am flight crews. Furthermore, the Dutch first officer, who was communicating on behalf of the KLM flight, used nonstandard ATC phraseology, some of which were most likely linked to his speaking English as a second language.
*Analyses – Flight Crew Judgment and Decision Making
Because of instances in previous years in which pilot fatigue seriously jeopardized the safety of a number of flights, the Dutch civil aviation authority required flight crews to observe rigid duty times, without exception.
From cockpit conversations, the KLM captain was worried about these restrictions and wanted to avoid the burden of remaining overnight with hundreds of passengers. He contacted the operations office in Amsterdam and was told that he had until 1830 to arrive back to Amsterdam. Shortly thereafter, ATC notified the waiting aircraft that Las Palmas Airport had just reopened.
The Captain’s worries were still not over. He needed to refuel prior to the flight into Amsterdam and with the dozens of aircraft soon arriving at Las Palmas, many presumably requiring refueling, the captain decided to refuel before departing Los Rodeos.
The Pan Am flight crew prepared to taxi but was told by the tower controller that while there was no delay in obtaining a departure clearance, the only way to the active runway was to maneuver around the KLM, which by that time had begun refueling. Undoubtedly frustrated, the Pan Am first officer radioed the KLM flight crew and asked how long the refueling would take. They were abruptly told, “About 35 minutes.” The first officer and second officer climbed down to the ground to determine if there was enough room to clear the KLM jet, but soon realized that the KLM had them blocked in and they would have to wait for the KLM to finish refueling.
Meanwhile, the weather at Los Rodeos began to deteriorate with poor surface visibility and light rain, adding to the stress already mounting for both flight crews. Moreover, the flight crews were most assuredly feeling tired – the Pan Am flight crew had been on duty for over 9 hours and the KLM flight crew for over 11 hours.
By 1625, the KLM jet was refueled and the flight crew was directed to back-taxi on runway 12 in preparation for departure on runway 30. As the KLM proceeded to move out of the congested area, the Pan Am crew received clearance to taxi a similar route as the KLM. When the Pan Am reached the holding point for runway 12, the foggy conditions had worsened over the runway.
The Pan Am crew, taxiing in the fog and a some distance from the KLM, was having difficulty understanding their taxi instructions. Reviewing the airport diagram, much like a road map, they continued their back-taxi on runway 12. The last taxiway (C4) was a high-speed taxiway for runway 12 – an easy 45-degree turn from their direction. The Pan Am first officer asked ground, “Would you confirm that you want us to turn left at the third intersection?” The controller replied, “The third one, Sir…one, two, three…third one.” The Pan Am flight crew began their pre-takeoff checklists as they continued searching for the third taxiway. The ground controller told them to report leaving the runway, and the first officer acknowledged the instructions.
Meanwhile, the KLM crew had reached the end of the runway and had made their 180-degree turn for the departure heading on runway 30. The Pan Am flight crew heard the KLM pilot ask the controller to turn on the runway centerline lights. The controller replied to both the KLM and the Pan Am flight crews that the lights were out of service.
Shortly thereafter, at 1705, the KLM captain allowed the aircraft to roll forward. The first officer stopped him and said, “Wait a minute, we don’t have an ATC clearance.” The captain stepped on the brakes and replied, “No…I know that. Go ahead and ask.” The first officer then contacted the tower controller, “KLM 4805 is now ready for takeoff…we’re waiting for our ATC clearance.” The tower controller replied with their departure clearance.
As the first officer began to read back the clearance to the tower controller, the captain released the brakes and started the takeoff roll saying, “Let’s go.” By the time the first officer completed the read-back, the aircraft was six seconds into the takeoff roll, so he added, “We are now at takeoff.” The tower controller interpreted the comment that the KLM was ready for takeoff. He told the flight crew, “OK…standby for takeoff…I will call you.”
Upon hearing that the KLM jet was “at takeoff,” the Pan Am first officer called the controller and said, “We are still taxiing down the runway.” The tower controller replied, “Roger, Clipper [universal Pan Am call sign] 1736, report clear of the runway.” The first officer responded “Roger will report when clear.” The tower controller acknowledged, “Roger papa alpha 1736, report the runway clear.” Inexplicably, the control used “papa alpha,” a call sign that would not typically register to other flight crews as a Pan Am Clipper jet. Compounding this ambiguous remark, and unbeknownst to the Pan Am flight crew and the tower controller, when the first officer made his urgent call to tell the controller that they were still taxiing on the runway, he “stepped on” the final portion of the controller’s transmission to the KLM flight crew. All they heard was “…k,” followed by a three-second, high pitched squeal. Instead of, “OK…standby for takeoff…I will call you.”
About 20 seconds into their takeoff roll, the KLM second officer asked the captain and first officer, “Did he not clear the runway then?” The captain asked, “What did you say?” The second officer repeated, “Did he not clear the runway, that Pan American?” Both pilots answered unequivocally that the Pan Am had cleared the runway.
The Pan Am jet was still taxiing on the runway after the flight crew missed the intersection for the third taxiway. The captain, apparently uneasy about remaining on an active runway in poor visibility told his crew, “Let’s get the hell right out of here!”
A few seconds later, the Pan Am flight crew saw the diffused landing light of the KLM jet begin to shake through the fog bank, indicating that the aircraft was moving down the runway. The Pan Am captain exclaimed, “There he is…look at him…[expletives]…coming!” Pushing the throttles full forward and turning a hard left, the captain made a desperate attempt to get off the runway. The first officer frantically yelled, “Get off! Get off! Get off!”
The Pan Am jet was at a 45-degree angle relative to the runway centerline. The KLM first officer called “V1” most likely at the precise moment that his captain saw the Pan Am jet directly in front of him. The KLM captain instantaneously rotated, scraping the tail for a distance of 65 feet. Fully airborne, its nose gear narrowly passed over the Pan Am, but there was not enough clearance and the main landing gear slammed broadside against the Pan Am. The impact sheared off the fuselage, destroying the upper deck just behind the flight deck. Both aircraft caught fire. The KLM jet remained airborne for a few seconds before hitting the ground 150 meters past the crash site and then sliding another 300 meters on the runway. The aircraft violently burst into a raging inferno.
*Accident Survivability
A Total of 583 passengers and crew perished between both aircraft making it the most deadly accident in aviation history. There were 234 passengers and 14 crew on board KLM Flight 4805; none survived.
On Pan Am Flight 1736, there were 335 fatalities, including nine members of the cabin crew. There were 77 survivors, including the flight crew. The impact destroyed the first-class lounge on the upper deck, causing the lounge floor to collapse onto the first-class section in the main cabin. None of those in the first-class lounge survived. According to some survivors, the shock of impact was not excessively violent, leading them to believe that the cause of was an explosion.
Many of the Pan Am passengers who were seated on the right side of the aircraft were killed instantly from the initial impact. Dozens more, who were seated in the center and aft of the fuselage, survived the impact but became trapped by the twisted metal and debris and thus were unable to escape the spreading fire. There were reports of other passengers who survived the impact but who became incapacitated from shock and fell into catatonic states, unable to move from their seats and flee the burning aircraft.
*Analyses and Lessons Learned
Communication errors, a rushed departure, monitoring and challenging errors, and poor visibility proved a deadly combination of factors that culminated with a disaster of historic proportions. While individually these factors posed a threat to safety, the most critical error committed that day was when the KLM captain departed without takeoff clearance, in the fog, when he knew that under the unusual circumstances other aircraft would be back-taxing to the departure end of the runway.
The safety analyst believed it was possible that the KLM first officer who had only 95 hours in the 747, and who was flying with the KLM Chief 747 Instructor, may have become intimidated by the captain’s legendary status. Being new to the jet and crewed with someone so well-respected may have caused him to second guess the circumstances.
*Reference
“Subsecretaria de Aviacion Civil” Accident Report, 1978. ICAO Circular 153-AN/56. Shari Stamford Krause.
Tenerife Airport Disaster - Wikipedia
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