No Time for Caution: The crash of TAP Air Portugal flight 425

Aftermath of the crash of TAP 425. Image source: Alan Cordwell

On the 19th of November 1977, a fully loaded Boeing 727 struggled to land in darkness and rain at the rugged Portuguese island of Madeira. After being driven back twice, the pilots made one final attempt to land on the perilously short runway. But the 727 touched down well past the threshold, and despite using maximum braking power, the crew was unable to stop it in time. The plane flew off the end of the runway, plunged down a 28-meter embankment, and smashed into a bridge, shattering the fuselage and scattering burning wreckage onto the beach below. Of the 164 people on board, only 33 survived the fiery accident, making it Portugal’s deadliest plane crash ever at the time. But while the proximate causes were a misjudged approach speed, psychological pressures to land, and poor braking conditions, the real problem lay in the airport itself. Its runway was so short, the surrounding terrain so precipitous, that little margin for error existed. An accident was inevitable — it was simply a matter of time.

Madeira’s extremely rugged terrain makes it a popular tourist destination, and also a difficult place to build an airport. Image source: Thorsten Kuttig

The archipelago of Madeira is a group of several small islands and one large island in the Atlantic Ocean, situated some 1,000 kilometers southwest of Lisbon and 875 kilometers west of Casablanca. The main island of Madeira is made up of the eroded remnants of an extinct shield volcano rising from the ocean floor, resulting in a landscape of impossibly steep cliffs and ravines running straight down to the sea from its mountainous central spine, which reaches an altitude of 1,862 meters at Pico Ruivo. Although the island may have been known to Mariners as early as 72 BC, and appeared on maps in the 1330s, it was officially discovered and claimed for the Portuguese crown in 1419. Settlement began around 1425 with the establishment of the town of Funchal, which became the island’s main urban center. Today, the island is home to more than 289,000 people, of which over 110,000 live in Funchal. In addition to the permanent inhabitants, some 1.4 million tourists visit the island each year to see its stunning scenery and experience the local cuisine.

Madeira International Airport in the 1960s or 1970s. Image source: Juan Carlos Díaz Lorenzo

When the prominence of Madeira as a tourist destination began to rise in the early 1960s, it quickly became clear that the island needed an airport. But building one would be no easy task: after all, the only remotely level part of the island was already taken up by the city of Funchal. To overcome this problem, engineers and architects devised a runway that occupied a hilly peninsula between two bays, standing atop earthen fill placed between the hilltops. In 1964, the airport opened to traffic with a single 1,600-meter runway, perched atop a 58-meter-high mound within spitting distance of the beach. In addition to the precipitous drops on all sides, the runway itself was on an incline, its east end sitting 16 meters higher than the west end. Although it was theoretically just long enough for the new generation of jet airliners, such as the Sud Caravelle and Boeing 727, it had become clear by 1972 that the runway would need to be extended if it was to accommodate the ever increasing flow of tourists. However, despite the recognized need, by 1977 the runway extension plan still hadn’t broken ground.

TAP Air Portugal Boeing 727 CS-TBS, sister ship of the accident airplane, CS-TBR. Image source: Piergiuliano Chesi

On November 19th of that year, a Boeing 727 operated by Transportes Aéreos Portugueses, also known as TAP Air Portugal, prepared for a scheduled flight from Brussels to Funchal with a stopover in Lisbon. Designated as flight 425, the route would be flown by Captain João Lontrão, First Officer Miguel Guimarães Leal, and a flight engineer whose name has not been released.

To land at Madeira International Airport, pilots had to undergo special training that would prepare them for the difficult approach pattern and the extremely unpredictable winds that tend to form where the mountainous island meets the sea. The three pilots had all received this special qualification, and by all assessments were fully prepared for the difficult conditions they would likely encounter. That day, the pilots knew to expect widespread cumulonimbus cloud formations and possible thunderstorms in the vicinity of Madeira.

Map of the route of flight 425 with its designated alternate airport. Map source: Google

The flight from Brussels to Lisbon was entirely routine, and after landing, 156 passengers and 8 crew boarded the plane for the next leg, filling it nearly to capacity. Flight 425 took off for the approximately one-and-a-half-hour flight to Funchal at 7:55 p.m., cruising normally across the Atlantic Ocean until 9:10, when the pilots radioed the control tower on the island of Porto Santo and requested permission to begin their descent. That was when things started to get more complicated. The latest weather report, issued at 8:50, described widespread cumulonimbus formations with a cloud base at 1,500 feet and intermittent rain showers. During their approach briefing, the pilots noted that if the weather prevented them from landing in Madeira, their alternate airport would be Las Palmas in the Canary Islands, 340 kilometers to the south.

Madeira International Airport didn’t have an instrument landing system; only a visual approach could be used to reach the runway. This required the pilots to be able to maintain visual contact with the runway at all times. At night with scattered rain showers and significant cloud cover, this would be challenging.

At 9:18, as flight 425 lined up for an approach to runway 06 from the southwest, the controller in Funchal reported, “425, Funchal, for your information we have showers over the airport, now visibility is 3km.” Just minutes earlier the visibility had been 4–5km; conditions seemed to be worsening, and the pressure to land began to grow.

At 9:22, the controller reported that visibility had slightly improved, but the pilots of flight 425 still couldn’t see the airport. They requested that the runway lights be turned up to their maximum intensity, to which the controller replied that he had already done so. But in fact, not all of the lighting could be turned on simultaneously. With the way the circuitry had been installed, it was impossible to illuminate both the touchdown zone lighting and the Visual Approach Slope Indicator System (VASIS) at the same time. The VASIS is a set of four bright lights which change colour depending on the angle from which they are viewed. From the perspective of a pilot on approach, if all four lights are white, they’re too high; if all four lights are red, they’re too low; and if two are white and two are red, they’re on the optimal approach path. To help the pilots of flight 425 execute the visual approach, the controller had turned on the VASIS lighting, which meant that the lighting on the runway indicating the touchdown zone would be off.

Diagram of a Visual Approach Slope Indicator System in use. Image source: Adeel Nawab

After descending to an altitude of 980 feet, Lontrão and Leal still could not catch sight of the runway, despite the lights. Having reached the minimum descent altitude without visual contact, they had no choice but to go around and try again. The pilots reported to the controller that they were climbing back to 3,500 feet and would loop around to try landing on runway 24 — the same runway from the opposite direction — in the hope that conditions there would be better. This runway, while angled downhill, would also allow them to land into the wind.

At 9:33, with the airport in sight, flight 425 lined up to approach runway 24. But the shifting clouds foiled the approach a second time. At 9:34, the control tower asked, “Can you still see the runway?”

Flight 425 replied, “Negative, TAP425 is making a missed approach and is returning to the MAD [beacon].” At an altitude of just 600 feet, the pilots had lost sight of the runway, forcing another go-around. As they returned to the beginning of the approach pattern, flight 425 told the controller, “Okay, I was on final watching 24, and suddenly after passing MAD I completely lost visual. Now I’ll try one more approach, and if I can’t get in this time, we’ll go to Las Palmas.” The stakes had now been made plain: the third attempt would be the last before making a costly diversion to the Canary Islands.

The controller offered another option. “The front has been passing quickly,” he said. “Now it’s holding on longer. I think if you wait, maybe you can land.”

But the pilots of flight 425 could not afford to sit in a holding pattern and wait for conditions to improve. The pilot on the radio replied, “I can’t, I only have fuel for one more approach.” Basic flying rules dictate that pilots must not keep holding or making approach attempts for so long that they become committed to landing, without enough fuel to reach their designated alternate airport. In 1970, the crew of ALM Antillean Airlines flight 980 made that mistake, attempting to land too many times at Sint Maarten before diverting to the Virgin Islands. The plane ran out of fuel before reaching St. Croix, forcing the pilots to ditch in the open ocean. 23 people lost their lives. Similarly, the crew of flight 425 knew that if they waited too long to divert, they could be forced into a situation in which landing at Madeira was impossible but they lacked sufficient fuel to go anywhere else. Therefore, it would be unwise to enter a holding pattern and wait for conditions to improve — after all, what if they didn’t?

ALM 980 underscored the importance of diverting in a timely manner. Image source: The Weather Channel

At 9:44, flight 425 lined up to land for the third and final time. The pilots had the lights of runway 24 firmly in sight; success hovered tantalizingly before their eyes. The controller reported that a major downpour had begun near the control tower, but the pilots could still see some of the runway lights protruding from the edge of the rain shaft, so they pressed onward. For a brief moment, they seemed to lose it, but then at the last moment the lights hove back into view.

“425, for your information, I now have calm wind on runway 24,” the controller said. “Will you try it?”

“Okay,” said flight 425, “I’m on final and I’ll land.”

“Okay, it’s calm, cleared to land,” the controller replied. This was the last anyone heard from the 727.

Simulation of flight 425’s long, slippery landing. Video source: Rádio e Televisão de Portugal

Flight 425 came in hot, passing over the threshold 44kph (24 knots) faster than the normal landing speed for Madeira’s runway 24. The pilots flared the airplane, raising the nose for landing, but at that speed — combined with the gentle downward slope of the airport — the 727 started “floating” down the runway, skimming along a couple of meters above the surface, unable to touch down. The plane overshot the normal touchdown zone by a significant margin before finally making contact with the ground nearly half way down the 1600-meter runway, still traveling 35kph (19 knots) faster than the optimal landing speed. Even under normal conditions, this would have been cutting it close. But these were not normal conditions. The downpour that drenched the airport only moments earlier had left a layer of water on the runway which was slow to drain off. The runway had been carved with crosswise grooves to allow water to run off to the sides, but over time these had worn down enough to allow some quantity of water to instead run straight along the runway toward the downhill end. As a result, when the 727 finally touched down, it did so on a surface contaminated with a continuous layer of water. Passengers on board flight 425 would later describe so much standing water that they seemed to be landing on the ocean instead of the runway.

When a wheel passes through standing water at high speed, a wedge of water builds up in front of the tire and lifts it off the surface, creeping underneath it and preventing it from making contact with the runway. The plane then begins hydroplaning, sliding out of control on top of a thin layer of water. Flight 425 hydroplaned immediately upon touchdown, so when the pilots slammed on the brakes to bring the plane to a stop, they proved completely ineffective. Desperate to slow down, the crew then applied maximum reverse thrust, but they were already out of control. An errant rudder input sent the plane skidding to the right, then back to the left again. Flight 425 slid wildly across the runway, rapidly eating up the remaining up distance with no hope of stopping in time. Seconds later, it ran out of room. The 727 flew off the precipitous west end of the runway at 145 kilometers per hour, and for a moment, 164 lives hung in the balance.

Simulation, continued.

Moving too slowly to fly but too fast to stop, flight 425 plunged down the 28-meter embankment at the foot of the runway, clearing the airport perimeter road before smashing tail-first into a disused stone bridge spanning a dry ravine. The brutal impact shattered the fuselage into four pieces and broke off both wings, leaving the tail section high and dry atop the bridge while the rest of the plane cartwheeled onto the rocky beach below. The right wing sheared off on impact and fell on the inland side of the bridge, while the cockpit plowed nose-first into the tideline, where it was crushed underneath the disintegrating passenger cabin. A fireball erupted over the crashing surf as the fuel tanks exploded, setting the wreckage ablaze. Against all odds, some people managed to survive the fiery crash: a few passengers from the last row found themselves still strapped into their seats on top of the bridge, protected from the inferno raging below them. Quite a few others had been thrown from the plane as it broke apart, including some who landed in the ocean, where they too avoided the worst of the flames.

My original drawing of the moment of impact.

Among the survivors was 17-year-old Emanuel Torres, who found himself immersed in seawater with only minor injuries. In a spur-of-the-moment act of heroism, he picked up a 2-year-old boy struggling in the surf and carried him to safety. His was not the only brave act that night. Witnesses who rushed to the scene fought fire and smoke to cut wounded passengers free from their seat belts, dragging them away in the nick of time. Airport firefighters also saw the explosion off the end of runway 24 and sped toward it, only to discover that the plane had fallen down off the elevated airport and onto the beach, forcing them to drive back the way they came and down onto surface streets to access the site. By the time they got there, local police and firefighters had already arrived and had set about saving the survivors.

Families of the passengers soon gathered at the airport, distraught and desperate for news of their loved ones. In an effort to comfort them, emergency workers told them that there were “many survivors,” despite knowing that this was a lie. In all, first responders and the survivors themselves did manage to save the lives of 31 passengers and 2 flight attendants, most of them suffering from serious injuries. But this paled in comparison to the 131 who died (including all three pilots, whose bodies were never found). At the time, it was the deadliest aircraft accident in Portuguese history — a scandal that rocked the country. The question had to be raised: was Madeira International Airport inherently dangerous?

TAP 425 was the deadliest crash on Portuguese soil until 1989, when 144 people died in the crash of an Independent Air Boeing 707 in the Azores. Video source: the Associated Press

The investigation by Portugal’s Directorate General of Civil Aviation uncovered an unfortunate convergence of factors that doomed flight 425. The excess speed on landing caused a very late touchdown, where optimal braking conditions would have been needed to stop in time. But the poor drainage capabilities of the landing surface, as well as a possibly dangerous accumulation of rubber on the runway, prevented the plane from decelerating normally. Flight 425 hydroplaned all the way down the runway, bleeding off relatively little speed in the process. The rudder input on touchdown that sent the plane into a sideways skid also removed any possibility of making a late go-around. Furthermore, investigators found a potential design flaw in the 727’s anti-skid system. The system wouldn’t activate if a skid began immediately on touchdown because it could not detect a skid if the wheels never started turning in the first place. Several additional factors may have contributed to the abnormally long glide before touchdown. First, the absence of touchdown zone lighting — turned off so that the VASIS could be turned on — might have misled the pilots about where the zone was located. Second, the pilots were slightly late in deploying the spoilers and speed brakes, which help reduce lift and force the plane into the runway. And third, they retracted the flaps before touching down, reducing drag and making it harder to bleed off excess speed. After putting this long list of factors together, it became clear how flight 425 could have sped off the edge of the runway at 145kph.

Wreckage of the 727, seen under the bridge. Image source: Márcio Sousa

However, the official investigation did not examine any of these factors very deeply. For example, the DGCA made no attempt to explain why the pilots might have landed 35kph faster than normal. Were they not watching their speed, or did they do it on purpose? The most likely explanation is that, under pressure to land, they focused too much of their energy on trying to maintain visual on the runway and failed to monitor their airspeed during the last minute of the descent. The official report also had little to say about the failure of the grooves on the runway surface, which indicated inadequate maintenance by Madeira International Airport. While recognizing that the resulting poor drainage could have contributed to the crash, the investigation did not attempt to ascertain why the grooves had been allowed to degrade, a fact that led some to believe that the DGCA was deliberately avoiding the subject. In its final report, the agency made only three recommendations: that the airport consider modifying its landing aids (so VASIS and touchdown zone lighting could be used simultaneously); that strict adherence to minimum conditions for approach to Funchal be emphasized; and that weather observation in the area be improved. None of these really addressed the underlying issues that caused the accident.

The tail somehow remained perched atop the bridge. Image source: País ao Minuto

In short, the investigation failed to look at the bigger picture. While certain mistakes and unfortunate circumstances directly led to the disaster, the outcome was in fact the inevitable result of an airport that lacked an adequate margin for error. The runway at Madeira International Airport was unusually short and sloped downhill, had large drop-offs on both ends with no overrun areas, and was frequently battered by unpredictable winds and heavy rain. While it was possible to land safely on this runway most of the time, these reduced margins meant that a combination of factors that wouldn’t result in a crash at any other airport could end in disaster if they occurred at Madeira. That a plane would eventually encounter a set of conditions that sent it off the end of the runway was all but certain. And without any safeguards, any runway excursion would inevitably end in disaster.

View of the crash scene from the beach. Image source: Expresso

Madeira’s notorious reputation struck again only one month after the accident. On the 18th of December that same year, SATA flight 730, a Sud Caravelle operating a charter flight full of Swiss holiday-makers, crashed into the sea while on approach to runway 06, killing 36 of the 57 people on board. Investigators found that the accident occurred due to an incorrect altimeter setting that led the pilots to believe they were 300 feet higher than they actually were. Even after losing sight of the runway lights, they pressed onward, apparently determined to land regardless.

A SATA Sud Aviation Caravelle similar to the one involved in the flight 730 crash at Madeira. Image source: Richard Vandervord

Like TAP flight 425 before it, SATA flight 730 underscored the tendency among pilots to take risks while landing at isolated island runways like Madeira, where a diversion could be extremely costly. Had the pilots of flight 425 decided to divert to Las Palmas, the airline would have had to pay tens of thousands of dollars to put up the passengers in hotels and fly them onward to Funchal the following day. The pilots’ judgment would have been questioned and they might have faced criticism within the company. They had also had a very long day: the crew of flight 425 had been on duty for over 13 hours at the time of the accident, and they likely were looking forward to a nice hotel bed. They succumbed to “get-there-itis,” the deadly affliction that has made countless pilots take unacceptable risks while trying to cut short a long working day. Unfortunately, at an airport like Madeira, taking such risks could have disastrous consequences.

For Portuguese authorities, it was clear that more tragedies would follow unless the airport’s margins of error could be improved. Immediately after the accident, TAP Air Portugal replaced the Boeing 727–200 with the smaller 727–100 on flights to Madeira. In search of a more long-term solution, the airport established a timeline for the extension of runway 24. A costly effort expanded the runway platform outward over the area where TAP flight 425 crashed, adding 200 meters to its total length. (The expansion involved the demolition of the stone bridge that had been damaged in the crash to make way for the new perimeter road.) Even after this extension opened for use in 1986, the runway remained dangerously short. More improvements would be needed, but the airport had run up against a confounding terrain problem that seemingly prevented any further expansion. Both ends of the runway ran right up to the ocean, and building the earthen platform far out over the water would be impossible.

The extended 1800-meter runway as it appeared in 1990. Image source: Peter Forster

Over the next 14 years, the airport undertook an ambitious plan to extend the runway by more than 900 meters using a concrete “bridge” suspended over the bay on stilts. Engineers drilled support piles 18 meters into the ground to anchor them firmly in bedrock, creating a strong foundation for a forest of several hundred concrete columns that would hold up the elevated runway surface. When the landmark project was finally finished in 2000, it brought Madeira’s runway up to the standard length for a major international airport, allowing it to handle aircraft as heavy as a Boeing 747. Today, travelers to Madeira can have the unique experience of driving underneath the runway on the island’s main highway while large airliners land directly overhead. In recognition of this unique and impressive architectural feat, the International Association for Bridge and Structural Engineering gave the project its annual “Outstanding Structure Award” for 2004, marking the first and only time that an airport runway has received such recognition.

The new elevated runway “bridge” shortly after its completion in 2000. Image source: Mikael Hultkvist

Today, it is far less likely that a similar accident could occur at Madeira International Airport (which was recently renamed in honour of footballer Cristiano Ronaldo). But the airport still ranks among the most dangerous in Europe due to its unpredictable wind shear conditions, which also make it a popular destination for plane watchers who capture harrowing footage of airliners trying to land amid extreme gusts and turbulence. And some special requirements remain in place, namely that only the captain can take off and land, that captains must receive special simulator training before flying to Funchal, and that maximum braking power must always be used on landing. Nevertheless, there hasn’t been another fatal accident in Madeira since the two in 1977, and with the vast improvements that have been made in the 42 years since, that record will hopefully continue far into the future. It’s heartbreaking that changes to this airport only came after 131 people lost their lives — but everyone who flies to Madeira today should remember this sacrifice when their plane rolls safely to a stop on the runway.

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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.