The 1983 Madrid Runway Disaster: Analysis

The charred tail of a Boeing 727 lies on the runway in Madrid after the collision. Image source: Eulixe.com

On the 7th of December 1983, Iberia flight 350 was taking off on a fog-shrouded runway at Barajas Airport in Madrid when the Boeing 727 collided with an Aviaco Douglas DC-9. The horrific collision killed all 42 people aboard the DC-9, while the 727 broke apart and caught fire, leading to a desperate rush to escape that ultimately claimed the lives of 51 of its 93 passengers and crew. This was the second major air disaster in Madrid in just ten days, and the safety of Spain’s largest airport was called into question — was there something wrong with Barajas? As it turned out, the two crashes were unrelated, but an investigation did uncover significant problems with the way airport design interacted with human behaviour in low-visibility conditions.

On the morning of the 7th of December, dense fog lingered over Madrid’s Barajas Airport, and by 8:20 a.m. it showed no signs of abating. All planes coming in to land were forced to abandon their approaches and divert to other airports because it was impossible to find the runway. With visibility around 100 meters, and runway lights visible within 300 meters, the possibility of landing was out of the question. Nevertheless, takeoff remained feasible, and several aircraft were preparing to leave.

An Iberia Boeing 727. Image source: Wikipedia

One of these was Iberia flight 350, a Boeing 727 bound for Rome with 84 passengers and 9 crew on board. The pilots of flight 350 requested to push back from the gate at 8:25, but they were delayed by two minutes because several unsuccessful landings had caused a queue of aircraft waiting to take off. At 8:27 permission to push back was granted, and the 727 pulled away from the gate.

An Aviaco McDonnell-Douglas DC-9. Image source: Wikipedia

At 8:29, Aviaco flight 134, a DC-9 operating a domestic flight to Santander with 37 passengers and 5 crew aboard, had already pushed back from the gate and requested permission to taxi. Taxi clearance was finally granted at 8:33, with the controller instructing the DC-9 to taxi to the “holding point runway zero one via outer taxiway, and report when leaving northern apron and entering the taxiway.” The diagram below shows the route that the DC-9 should have taken to reach the threshold of runway 01.

Map of Barajas Airport with taxiways, runways, and locations of relevant aircraft.

The DC-9 was parked on an apron to the west of the intersection of runways 01/19 and 15/33. Between the apron and the inside edges of the two runways, there were two parallel taxiways designated “inner” and “outer” based on their distance from the apron. Additional taxiways connected the outer taxiway to the runways at 90 and 45 degree angles. The DC-9’s taxi instructions would take it across the inner taxiway and into a five-way intersection, where a 90 degree right turn was necessary to enter the outer taxiway. The controller chose this route because the outer taxiway had better lighting than the inner taxiway, and because the inner taxiway passed in close proximity to planes and vehicles on the apron, which made it hazardous in low visibility.

Meanwhile, Iberia flight 350 had finished pushing back from the gate and requested permission to taxi to the threshold of runway 01 for takeoff. The ground controller granted the 727 permission to taxi the short distance over to the holding point to await takeoff clearance.

Detail of the relevant area of the airport, with taxiway labels and progress of the DC-9.

At 8:36, Aviaco flight 134 called the tower to report that it was leaving the “parking area.” The controller asked flight 134 to “report entering segment Oscar 5” (O5 on the map above). This referred to the first segment of the outer taxiway south of the intersection of the two runways. To reach this segment, the DC-9 needed to make a 90 degree right turn followed by a 45-degree right turn. The crew of flight 134 acknowledged the command to report entering Oscar 5.

Upon reaching the 5-way intersection involving the outer taxiway and the crossing taxiways J1 and J2, the pilots of flight 134 were faced with a confusing situation. With dense fog, the distortion of the windshield, and the perceptive limits of the human eye, they probably could not see more than 50 meters at best. Furthermore, the intersection was large, some signs were faded, and one outdated sign had been completely blacked over. There was also no marking on the pavement to indicate the centerline of the 90-degree turn onto the outer taxiway. A “NO ENTRY” sign was located on the left side of the J1 taxiway, since that route was only intended for planes exiting runway 15/33, but visibility was so poor that the pilots likely couldn’t see it. While trying to find the right turn onto the outer taxiway, they passed it right by and instead made the 45-degree turn onto taxiway J1, without spotting the “NO ENTRY” sign through the fog.

Where the pilots of the DC-9 thought they were vs. where they actually were.

The DC-9 continued forward, its pilots believing they were on the outer taxiway, until they reached a six way intersection involving taxiway J1, taxiway H1, and both runways (see diagram above). However, the pilots likely thought they were at the intersection of the outer taxiway and taxiway H1, and continued straight ahead. At that point they probably spotted the centerline of runway 01 angling off to their right, and believed that this was the centerline of O5. They turned and taxied up the active runway 01 in the wrong direction, running parallel to the taxiway they were supposed to be on.

Where the pilots of the DC-9 thought they were vs. where they actually were. (2)

Since they had been asked to inform the ground controller when they reached O5, the pilots of the DC-9 started scanning the tarmac for taxiway markings to confirm their position, even going so far as to move well left of the centerline to get a better view of signs that might be on that side. But since this was a runway, they couldn’t find any.

At 8:37, Iberia flight 350 reported that it was at the holding point for runway 01, ready for takeoff. The ground controller gave flight 350 the frequency to contact the tower controller for takeoff clearance. 7 seconds later, flight 350 asked the tower controller for clearance and received it immediately. Since they were on a different frequency, the ground controller and flight 134 were not aware of the movements of the 727, which was now accelerating for takeoff.

Meanwhile, the crew of the Aviaco DC-9 was starting to realize that they might be off course. “Look, we cannot see oscar five markings on the ground,” flight 134 told the controller. “We are taxiing on… heading 190, and apparently we were entering the segment [O5].” It is thought that at the time of this transmission, the captain might have realized that they were in fact on the runway and turned to the right, crossing back over the centerline. He probably believed that he had missed the turnoff onto O5 and had continued straight onto the runway. If this had been the case, then there would have been a taxiway just to the right onto which they could exit. But instead they reached the edge of the runway and were faced with only grass, forcing them to stop in their tracks.

Final path of the DC-9, including the last second turn to the right (bottom of picture). Image source: Technical Report

At that moment the Iberia Boeing 727 was speeding down runway 01 straight at the hapless DC-9. With effective visibility reduced to 100 meters or less, neither crew had any time to react. Just as the 727 started to rotate, it slammed broadside into the DC-9, which had just come to a stop on the runway a split second earlier. The left wing of the DC-9 ripped into the forward cabin of the 727, instantly killing five passengers. The force of the impact collapsed the DC-9’s left main landing gear and wrenched the plane around ninety degrees in a fraction of a second, causing the left wing of the 727 to tear through the cockpit of the DC-9. The smaller plane took the full force of the impact of the 727’s wing and rear fuselage and disintegrated utterly, spewing burning debris across the runway as both planes’ fuel tanks simultaneously exploded. The 727 slid out of control down the runway for a considerable distance before it spun 180 degrees, broke into three pieces, and came to a stop surrounded by fast-spreading flames.

My original illustration of the impact, depicting the point just after the DC-9 spun 90 degrees to the left.

In the control tower, the ground controller was still responding to the last message from flight 134. “Okay, received,” he said. “Yes, I understand, got it.”

The sound of a distant bang was distinctly heard in the control tower as the two planes collided. “What was that?” someone asked.

“One moment, please,” the controller said to flight 134. He did not yet know that the crew he had put on hold was already dead.

The collision had almost completely pulverized the Aviaco DC-9, instantly killing all 42 people on board. However, most of the 93 passengers and crew on board the Iberia 727 were still alive. As fire tore through the wreckage, there was no time for an orderly evacuation. Many of the passengers had been badly injured in the crash and were unable to escape, quickly succumbing to the smoke and flames. Among those still alive were 8 of the 9 crew members, including the pilots, who helped passengers escape the plane. The captain reportedly shouted to one passenger over and over, “The runway was mine! The runway was mine!”

The remains of Iberia flight 350 after the crash. Image source: RTVE

Airport workers and emergency crews knew there had been a crash but struggled to find it through the thick fog. They were only able to locate the wreckage after survivors stumbled out of the mist and pointed them in the right direction. Some survivors reported that emergency services didn’t arrive at the scene until 20 minutes after the accident. All told, 51 people on board flight 350 lost their lives, most due to smoke inhalation and burns, bringing the total death toll to 93.

Bodies are removed from the wreckage of Avianca flight 011, which crashed near Madrid 10 days before the runway collision. Image source: The Bureau of Aircraft Accidents Archives

This was in fact the second major accident in Madrid in only ten days. On the 27th of November, little more than a week earlier, Avianca flight 011, a Boeing 747, crashed into a hill near the city after the crew made a navigational error, killing 181 of the 192 people on board. The investigation into that disaster was just getting started when the runway collision occurred.

This new crash bore considerable resemblance to another air disaster in Spain: the 1977 Tenerife Disaster, in which two Boeing 747s collided on a foggy runway in the Canary Islands, killing 583 people. The question had to be raised: was this Tenerife all over again? Had anything been learned?

On Tenerife, the responsibility lay with the KLM 747, which took off without permission from the controller. But in Madrid, the 727 had permission to take off, and the DC-9 was taxiing on the runway when it should not have been. Figuring out how it got there was no easy task, however. The DC-9 was quite old, and under Spanish regulations at the time, aircraft manufactured before a certain date were not required to have a cockpit voice recorder. With no CVR, investigators could only make educated guesses about what might have confused the pilots, but they found no shortage of potential misinterpretations at numerous points along its route. Beginning from the moment flight 134 started moving, a long line of imprecise and misleading cues led the plane onto the active runway.

Map of the wreckage of both aircraft. Image source: the Technical Report

First, the controller’s instructions were not sufficiently precise. “Report when leaving northern apron and entering taxiway” did not specify where to exit the apron or which taxiway to report entering, leaving the pilots to figure it out for themselves. The crew of flight 134 were similarly imprecise when they reported that they were “now leaving the parking area,” because that did not indicate whether they had just started moving or whether they had just crossed out of the parking area. The controller didn’t ask for clarification and so he might have lost track of the aircraft in his mental model of the airport’s ground movements. The fact that the airport lacked ground radar and the fog made it impossible to see the plane from the control tower meant that the controller was of little help anyway. Furthermore, there were no procedures at Barajas Airport for how and where planes ought to taxi in low visibility conditions.

Diagram showing what the pilots likely could see as they entered taxiway J1. Image source: the Technical Report

The five-way intersection where the plane made its wrong turn was also poorly designed. The airport was part way through a major upgrade and some signage was not finished, including the curving line showing the route from J2 onto the outer taxiway. Its absence likely caused the pilots to miss the fact that they were crossing the outer taxiway. Signs warning aircraft not to enter taxiway J1 were too far away to be seen clearly in the fog. Once on J1, there were additional signs that they were not on the correct route, but confirmation bias — the brain’s tendency to tune out information that doesn’t support its understanding of the situation — prevented the pilots from noticing that the geometry of the intersection did not match what they thought they were seeing. Their confirmation bias was further amplified when they turned onto runway 01 and ended up parallel to taxiway O5, putting them on the correct heading, just in the wrong place. In this way the runway behaved just like how they expected the taxiway to behave. Only when they failed to find taxiway markings did they start to notice something was wrong. Even then, the crew’s attempt to clear the runway, based on an incorrect assumption about the mistake they had made, actually worsened the severity of the collision.

It was clear, therefore, that Barajas Airport, while perfectly usable in normal conditions, could become dangerously confusing when dense fog obscured all visual cues and forced pilots to taxi “by feel.” In their final report, investigators recommended that Barajas Airport develop special taxiing procedures for use in low visibility conditions; that the colors of markings on runways and taxiways be made more divergent; that additional redundant signs and markings be placed on one-way taxiways (like J1) so that pilots are more likely to see them; that special lights be placed to warn pilots when they are entering an active runway; that Spanish aircraft of all types be fitted with cockpit voice recorders; and that the International Civil Aviation Organization develop international standards for runway and taxiway markings.

After two major runway collisions in Spain in six years, there have been no more since the disaster in Madrid. But fatal runway collisions are so rare that it is hard to know whether changes made as a result of this crash had any impact on that outcome. However, as time has passed, increased knowledge of weather, human behaviour, and airport design have helped form better regulations that keep taxiing aircraft out of active runways. Today, major airports have systems that detect runway incursions and alert air traffic controllers, as well as other significant improvements. As a result, there has not been a major runway collision involving a passenger airliner anywhere in the world since 2001.

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Analyzer of plane crashes and author of upcoming book (soon™). Contact me via @Admiral_Cloudberg on Reddit or by email at kylanddempsey@gmail.com.