Fly By Wire: The crash of Air France flight 296
Tags: France, Aviation

Actual video of the crash of Air France flight 296. (via nh6central on YouTube)

On the 26th of June 1988, a brand new Air France Airbus A320 on a charter flight with 136 people on board performed a low speed fly-by at an airshow in the city of Mulhouse. But as hundreds of spectators looked on, the plane plowed into a forest and crashed, sending fire billowing up over the airfield. Remarkably, almost everyone on board managed to escape before the plane burned over, but three passengers — including two children — perished in the smoke and flames. The crash pitted pilot against plane: was the Airbus and its radical new fly-by-wire design at fault, or had Captain Michel Asseline grossly misjudged the maneuver? The crash spawned decades of misinformed conspiracy theories, many of them propagated by Asseline himself, which are still widely believed today. This is the true story of Air France flight 296 and its controversial aftermath.

The first version of the A320 during a test flight. (aeronewstv)

In the early 1980s, with McDonnell Douglas in financial trouble and Lockheed having left the market, Boeing was poised to dominate the commercial airplane manufacturing industry for years to come. Of course, there was also Airbus: a joint state-run consortium founded in 1970 by the governments of France and West Germany. But the two aircraft it had produced by that point — the wide body A300 and its shorter derivative, the A310 — had not made much impact on the global market, and the company was not taken particularly seriously by its competitors. At the highest circles of the company, there was a sense that they would need something radically new to prevent Boeing from permanently cornering the market on passenger jets. Something like the Airbus A320.

The A320 was a brave departure from the design philosophy adopted by virtually every airliner that came before it. From the outside, the A320 didn’t look that special: it had two normal-looking wings, two engines, a tail, a two-pilot cockpit, and room for around 150 passengers, which put it squarely in competition with the Boeing 737, already one of the most common passenger planes in the sky. The real magic was under the hood. Instead of mechanical linkages between the yokes and the control surfaces (or their hydraulic actuators), the A320 incorporated a fly-by-wire system, where the pilots made inputs to a bank of computers which in turn flew the airplane. Instead of a traditional control column, the A320 had a side stick, which was located next to the pilot instead of in front of him. Instead of artificially creating feedback forces on the controls to help pilots intuit changes in control sensitivity at different speeds and configurations, the designers of the A320 concluded that this was a crutch, and did away with feedback altogether; pilots could now move the side stick as much as they liked, and the computers would determine how far the actual control surfaces could safely be moved at that precise moment.

An example of one of the A320’s flight envelope protections, specifically, bank angle protection. (AviationChief)

The centerpiece of this design was a series of built-in failsafes called flight envelope protections. The principle behind flight envelope protections was that as long as the controls were working properly, it would be impossible for the pilots to lose control of the plane, no matter how hard they tried. If the pilot pushed the side stick all the way to the right, the plane would roll up to about 67 degrees, the steepest bank that it could safely maintain. Any further right roll was simply not allowed. If the pilot pulled all the way back on the side stick, the plane would pitch up to about 30 degrees and pull 2.5 G’s, but no more. And if the pilot slowed down and pitched up in an attempt to stall the plane, the flight envelope protections would accelerate the engines and gently push the nose down to keep the angle of attack below the critical point. In theory, the plane would be impossible to stall.

This design acknowledged what no other manufacturer was willing to point out publicly: that most crashes were caused by the pilot, not the plane. The A320 wasn’t the first plane to incorporate fly-by-wire technology; in fact, the Concorde had already done so in the early ’70s, and some military jets did it even before that. Even the Soviet Tupolev Tu-154 had a sort of pseudo-fly-by-wire, in the form of an always-on autopilot that corrected for the airplane’s downright terrifying manual flight characteristics. But the A320 was the first jet to have no manual backup, and the first to include flight envelope protections that could not be overridden by the pilot. The reason was simple: the flight envelope protections defined the outermost limits of safe flight, beyond which there was no reason to go. Why should a pilot be able to override them?

Test pilots pose for a picture in front of an early A320. (Airways Magazine)

While it might seem like common sense, this proposition resulted in massive backlash from pilots and considerable skepticism from the flying public. Pilots liked to feel that they were the ones ultimately in control, and passengers didn’t trust computers on principle. Airbus’s attempt to dramatically reduce pilot error accidents by physically preventing pilots from crashing their airplanes was unpopular not because pilots wanted to be able to crash airplanes, but because it was impolite to acknowledge that they sometimes did so anyway. Fortunately for Airbus, airlines were a little more open to the idea than pilots were at the time; otherwise, the A320 would have been dead in the water.

Nevertheless, the company still needed to prove to the world that the A320 really did represent the future of commercial aviation. A number of orders had already been placed when the program was officially unveiled in 1984, but many more were needed. Airbus and its customers launched an aggressive marketing campaign based around the A320’s radical new features, which continued through the airplane’s entry into commercial service with Air France on April 18th, 1988.

The planned route of Air France flight 296. Make sure to pay attention to the numbering to get the events in order. (Google)

It was just over two months later, on the 26th of June 1988, that Air France pilots Michel Asseline and Pierre Mazières stepped aboard a brand new A320 for what was to be one of the most unusual flights of their long careers. The flight had been chartered from Air France on short notice by a local flying club in the eastern city of Mulhouse as an “aerial baptism” featuring a scenic flight around Mont Blanc. The passengers had won tickets on the flight as part of a promotional event organized by local businesses, and many of them (including several unaccompanied children) had never previously been on an airplane. The flight’s other purpose was as an air show attraction. The Mulhouse flying club had arranged an air show at Mulhouse-Habsheim Airport for the 26th of June, and they wanted the exciting new A320 to make an appearance. The plan was for the A320 to depart Paris Charles de Gaulle International Airport, fly to Basel-Mulhouse Airport, take off again and overfly Mulhouse-Habsheim Airport twice, then fly to Mont Blanc, circumnavigate the mountain, fly back to Basel-Mulhouse, then return to Paris.

F-GFKC, the A320 involved in the accident. (Original author unknown)

The plane they would be flying was F-GFKC, the ninth Airbus A320 to roll off the assembly line, and the third delivered to Air France. Captain Michel Asseline had picked it up from the factory two days earlier, and it had accumulated just 22 flight hours. Asseline, a former air force pilot, was keen to demonstrate its capabilities: he held a high-level position in the team at Air France in charge of introducing the A320 to its fleet, and he was impressed with its performance. He had even been making frequent appearances on TV and in the newspapers to promote the plane.

Joining him in the cockpit was Captain Pierre Mazières, himself a senior Air France captain with over 10,000 flying hours, similar to Asseline. After ferrying the plane empty from Paris, Asseline and Mazières arrived in Mulhouse early in the afternoon, where they oversaw the boarding of 130 passengers. The passengers included journalists, first-time flyers, and several children, one of whom was quadriplegic. They were assisted by a standard company of four flight attendants, bringing the total number of occupants to 136. One of the passengers was also a flight attendant at another airline, and she and another woman passenger were apparently invited to sit in the cockpit, where they joked with Captain Asseline about a “prehistoric” early-generation jet that was taxiing past them on the apron.

After finishing the startup sequence, Asseline pulled out the flight plan that had been provided to him by Air France and proceeded to brief the plan for the two flyovers at Habsheim airfield. The flight plan was rather bare bones: it called for a low speed flyover along runway 02, the airfield’s only paved runway, followed by a high-speed flyover in the opposite direction, and left the details to Captain Asseline, who was judged to be capable of coming up with the rest himself.

An aerial view of Mulhouse-Habsheim Airport. (Mapio)

What he came up with sounded something like this: they would fly north from Basel-Mulhouse Airport at 1,000 feet above the ground until spotting Mulhouse-Habsheim Airport, at which point they would descend in line with runway 02 to a height of 100 feet with the flaps in position 3 and the landing gear down. Asseline would then pull back on the side stick to increase the angle of attack until it reached “alpha max,” the highest angle of attack allowed by the flight envelope protections. They would then fly level at alpha max until Asseline instructed Mazières to apply takeoff/go-around (TOGA) power, at which point they would climb away and circle around for the second flyover. Asseline noted that he would need to disengage the “alpha floor,” a secondary flight envelope protection which would attempt to initiate a go-around automatically as they approached alpha max. This could be accomplished by holding down a button on the throttle levers for 30 seconds at an earlier point in the flight. When Mazières expressed a shadow of doubt about the maneuver, Asseline was quick to reassure him: after all, he asserted, he had done this “20 times” and it had never caused any problems.

After giving a less technical version of the briefing to the lead flight attendant (including a request that all passengers fasten their seat belts for the flyover), Asseline went on the public address system to brief the passengers.

“Ladies and gentlemen, hello and welcome aboard this Airbus A320, number three of the series for Air France, and which has only been in service for two days. We shall soon take off for a short tourist flight starting at the Habsheim flying club, where we will do two flyovers to demonstrate the continuity of French aviation, and then we shall make a tour of Mont Blanc, depending on weather conditions and air traffic. I wish you all a very agreeable flight.” He then proceeded to repeat the announcement in German.

At 2:41 p.m., Air France flight 296 lifted off the runway at Basel-Mulhouse Airport and turned to the north to fly to Habsheim, which was only about five minutes’ flying time away. Their immediate task was to make visual contact with the airfield in time to descend from 1,000 feet to the flyover height of 100 feet. The weather was fair with a thin layer of high overcast — nothing that would complicate matters in any way. But the pilots seemed to be uncertain about the location of the airfield.

“You’re at eight nautical miles there, you’ll soon see it, there’s the motorway,” said Mazières. A motorway ran past both airports, and they intended to follow it to Habsheim.

“We’ll leave the motorway to the left, won’t we… it’s to the lef… no, to the right of the motorway,” said Asseline.

“It’s slightly to the right of the motorway, so you… you leave the motorway on the left.”

“Okay, as soon as we identify we descend quickly then.”

The route of flight 296 as it made its way toward Habsheim for the flyover. (BEA)

One minute later, at 2:44, Asseline announced, “There’s the airfield, it’s there, have you got it?” At this point they were only about one minute out from the runway, so Asseline pulled the throttles back to idle and put the plane into a quick descent. Hurrying to get ready, Mazières set flaps 3, lowered the landing gear, and entered the local barometric pressure reading. It was around this time that Asseline observed that the spectators weren’t lined up along runway 02 — they were all standing next to runway 34R, a much shorter, grass runway that intersected runway 02 at a 40-degree angle. At the last minute, he turned slightly to the left to line up with runway 34R, sweeping in over the forest surrounding the airport.

Still descending at 600 feet per minute, flight 296 lined up with the runway. “TOO LOW, TERRAIN,” the ground proximity warning system blared.

“Two hundred feet,” announced the robotic voice of the radio altimeter.

Mazières made a comment about an Air France flight safety officer who was in charge of determining whether crews were observing the required safety margins. This may have been an oblique reference to the fact that they were currently exceeding several of the aforementioned margins.

Seconds later, the A320 approached 100 feet, and Asseline hadn’t reined in their descent rate at all. “Okay, you’re at 100 feet there, watch watch — ” said Mazières.

“One hundred feet,” said the radio altimeter. “Fifty. Forty.”

“Watch out for the pylons ahead, see them?” Mazières warned.

“Yeah, yeah, don’t worry,” said Asseline.

“Thirty,” said the radio altimeter.

Runway 34R is highlighted with runway 02 in the foreground. The pilots were beginning to turn right to line up with runway 02 when they realized the air show was happening on runway 34R, forcing them to turn back to the left. (Mayday)

Asseline pulled out of the descent at just 30 feet above the ground. It was obvious to both passengers and spectators that the plane was lower than it was supposed to be. With alpha floor disengaged and the engines still at idle, Asseline pulled the side stick back, rapidly slowing the plane as the angle of attack rose toward alpha max. Airspeed dropped below 120 knots.

Suddenly, Asseline and Mazières realized that there was a forest directly beyond the end of the runway, and they were headed straight for it. Asseline jammed the throttles straight to maximum power, and Mazières called out, “Go around track!”

But it takes around eight seconds for the A320’s engines to accelerate from idle to go-around power, and they didn’t have eight seconds. With surreal grace, the plane glided past the crowd of spectators and plowed straight into the forest. “Merde!” Asseline shouted, the last word captured on the cockpit voice recorder.

Still photo of Air France flight 296 crashing into the forest. (crashdehabsheim.net)

As disbelieving spectators stared with cameras rolling, the A320 eased down into the trees, its jet blasts sending out twin plumes of dust and broken branches as they disappeared into the greenery. For a few seconds, the nose of the plane could be seen reaching up out of the trees as though straining to escape from the forest’s leafy embrace. But it too slipped beneath the canopy, and moments later, a massive plume of smoke and fire erupted from behind the tree line, curling up into the summer sky like a mushroom cloud. Air France flight 296 was down.

Actual video of Air France flight 296 crashing. (via nh6central on YouTube)

On board the plane, the impact with the trees at first resembled a hard landing, but it quickly became much worse. Trunks and branches tore at the fuselage; both engines ingested leaves and failed catastrophically. On impact with the ground, the right wing sheared off, ejecting fuel forward like a flamethrower as the plane skidded to a halt. The plane came to rest after just a few hundred meters, essentially intact except for the right wing, but surrounded by fire. On board, the electrical system failed and all the emergency lights went dark. The aisles were illuminated mainly by the light of the flames. Many passengers had been thrown against the seats in front of them on impact, resulting in widespread head injuries; there were broken bones, lacerations, and bruising — but by and large, the injuries weren’t serious. Indeed, all 136 passengers and crew had survived the crash.

An alternate angle of the crash. (via nh6central on YouTube)

Although everyone was alive, it was obvious that they wouldn’t have much time to escape before fire consumed the plane. The breaching of the right wing fuel tanks had caused a massive fire to break out along the entire right side of the plane, and a smaller leak on the left side triggered another fire around the left wing root. Within seconds of the crash, fire and smoke began to pour into the cabin through breaches in the floor around rows 10–15 and a pair of broken windows on the left side of rows 8 and 9. Captain Asseline attempted to call for an evacuation, but the public address system was dead. In the cabin, flight attendants and passengers rushed for the doors, only to find that six of the plane’s eight exits were totally unusable: all the exits on the right side and the two overwing exits on the left were blocked by flames. To make matters worse, the flight attendants found that the left front door was blocked by tree branches and wouldn’t open all the way, causing the slide to deploy partially inside the plane. A passenger and a flight attendant managed to push hard enough on the door to free the slide, which sprang outward with such force that both men were thrown out of the plane.

One of the first photos of the burning plane, taken just a couple of minutes after the completion of the evacuation. (Bureau of Aircraft Accidents Archives)

In the rear of the cabin, which had become separated from the front by a wall of fire, the passengers were in capable hands: the flight attendant seated here had conducted an emergency evacuation before, after an Air France 747 caught fire during an aborted takeoff in Mumbai in 1975. Guided by his calm and reassuring voice, passengers filed off the plane in an orderly manner, even though the escape slide had been deflated almost immediately by sharp tree branches. In the front, however, passengers panicked, shoving past each other and piling out the door into a bloody melee of shredded branches that might ultimately have caused more injuries than the crash itself. To make matters worse, not everyone had managed to get out of their seats: in the heat of the moment, no one had remembered to assist the quadriplegic boy in seat 4F. A seven-year-old girl a little further back had also become trapped, unable to undo her seat belt after a seat back collapsed on top of her. Her younger brother tried to free her, but he was carried away by the panicked crowd. One woman’s hair burst into flames; another passenger’s clothes caught fire and were extinguished by a flight attendant.

Panoramic overview of the crash site, the impact zone, and the airport. (Bureau of Aircraft Accidents Archives)

Within a few minutes — how long exactly couldn’t be determined — the last passengers appeared to have left the plane. The flight attendants attempted to call back into the smoke-filled cabin, but there was no answer. As the flight attendants made their exits, Asseline picked up Mazières, who had been injured in the crash, and dragged him right out the door. He attempted to go back into the plane to check one last time for stragglers, but he was beaten back by the smoke and flames.

At first it seemed as though everyone had gotten out. It wasn’t until hours later, after accounting for all the survivors, that three people were found to be missing. One was the quadriplegic boy; another was the girl who couldn’t undo her seat belt. The third was a woman who left her husband before evacuating the plane and returned to the cabin in an attempt to save the little girl, only to be overcome by the smoke. All three victims died from inhaling toxic gases well before the airplane burned over.

The spectacular crash, coming just three months after the A320’s introduction to service, made headlines around the world. TV stations played one spectator’s crystal clear video of the final seconds over and over again. Skeptics of the A320 — and there were many — immediately speculated that the fly-by-wire system was responsible, that the computers had somehow overridden the pilots and stopped them from climbing away. Captain Asseline, formerly one of the Airbus’s biggest proponents, fueled this speculation by reporting that the engines didn’t produce power when he commanded them to accelerate. If the allegations were found to be true, it would be disastrous for Airbus, and with it the entire European aviation industry. Investigators from France’s Bureau of Inquiry and Analysis (BEA) would have to go to great lengths to remain as objective as possible, knowing that their conclusions could have consequences that would last for decades.

Firefighters, investigators, and other officials gather at the crash site. (Bureau of Aircraft Accidents Archives)

After an exhaustive analysis of the flight data, the video, the cockpit voice recording, several real-life test flights, and a number of simulator tests, the BEA determined that all the flight controls and the engines responded normally to Captain Asseline’s commands. The response of the engines was a particularly important question. But despite Asseline’s allegations, the FDR data, a spectral analysis of the engine sounds on the CVR, and a similar analysis of the spectator video all agreed that Asseline accelerated the engines between 5 and 5.4 seconds prior to impact with the trees, by which point the engines had accelerated to 84% power, easily on track to meet their certification requirements, which stipulated that they must reach 94% power within eight seconds after being accelerated from idle.

An analysis of the airplane’s overall performance explained why this was insufficient to prevent the crash. Because the pilots spotted the airport so late, they had to pull back the engines to idle in order descend quickly enough to reach the planned flyover height. Consequently, upon leveling off and pulling up to alpha max, the plane entered an extremely depleted energy state. While the flight envelope protections kept the plane from stalling, the margin was razor-thin, as the drag from the high angle of attack rapidly bled off the A320’s remaining speed. With no height to lose and little thrust from the engines, the plane had neither the potential energy nor the kinetic energy needed to climb. The only way to go around would have been to wait for the engines to accelerate to full power, but Asseline applied TOGA thrust too late to avoid the crash.

Aerial view of the wreckage of the A320’s tail section. (Bureau of Aircraft Accidents Archives)

This stood in contrast to previous flights at alpha max which Asseline had conducted both in the simulator and in real life. He wasn’t lying when he told Mazières that he had done this 20 times, but there was a key difference between those flights and this one: the position of the throttles. During previous flights at alpha max, he had always left the engines at a fairly high power setting. This allowed the engines to quickly develop max power when Asseline commanded it, because going from 60% power to 100% power takes considerably less time than going from 20% to 60%. This quick acceleration allowed the plane to gain altitude within a couple seconds of initiating the go-around. It’s not hard to understand why Asseline, having always been able to accelerate out of alpha max with relative ease in the past, would have thought in the moment that something was wrong when five seconds went by without the plane climbing after he applied TOGA power.

However, when the BEA internally came to these conclusions, Captain Asseline cut off all cooperation with the investigation and began to make television appearances in which he alleged that a coverup was underway and that he was being scapegoated. In one such appearance, he made a new claim: that when he pulled up to try to avoid the trees, the nose pitched down instead, which in his opinion was an egregious malfunction of the fly-by-wire system. Checking the data, investigators found he was actually telling the truth — but his statements about what it meant were a gross mischaracterization. The flight envelope protections actually did intervene at the last second to push the nose slightly down, because the plane was on the hairy edge of a stall at the moment Asseline tried to pull up. In fact, if he had been allowed to pull up steeply when he tried to do so, the plane would have stalled and dropped like a rock to the ground, most likely resulting in far more casualties than were inflicted in the actual event.

Aerial view of the remains of the plane. Tree debris and bushes were cleared out from around the plane to provide better access. (Bureau of Aircraft Accidents Archives)

The BEA also explored possible reasons why the flyover was conducted at 30 feet instead of 100. Although the radio altimeter could clearly be heard calling out the altitude on the CVR, and Mazières appeared to react to it, Captain Asseline claimed he couldn’t hear it because the callouts weren’t piped over the pilots’ headsets. He also stated that he was using his barometric altimeter to determine their height above the ground rather than his radio altimeter. The barometric altimeter measures height above sea level, but it can be used to read height above the ground by comparing the value to a marker or “bug” representing the elevation of the airport. The radio altimeter directly measures height above the ground and every pilot is trained to use it when flying at low altitudes. Although Asseline claimed that the digital radio altimeter was too hard to read compared to the analog barometric altimeter, the barometric altimeter is simply not precise enough to be used for low altitude flight. Besides natural barometric altimeter error margins, other factors which could have influenced the descent below 100 feet included the small size of the airport, with a short runway and a diminutive control tower which could have created a false sense of scale; and the high nose-up attitude of the aircraft, which placed the pilots higher above the ground. Although Asseline fervently denied it, the BEA also felt that a desire to show off to the spectators and to the female passengers in the cockpit could have led him to take extra risks.

Police and investigators examine the wreckage. (Bureau of Aircraft Accidents Archives)

Nevertheless, it was clear that neither pilot knew about the forest at the end of the runway until just seconds before the crash, and if they had, they might have acted differently. Furthermore, the pilots appeared to be unaware that the flyover was to be on runway 34R until they spotted the location of the spectators. All of this suggested a lack of adequate planning, especially on the part of Air France.

As it turned out, Air France’s plan, drafted just two days before the flight, called for a low-speed flyover and a high-speed flyover but included very little specific information. Air France conducted a feasibility study for the flyovers which was based off runway 02, not runway 34R, because the airline failed to ask the air show organizers where the event would take place. On top of that, because neither runway was capable of handling an A320, French air show regulations required that the flyovers be conducted at a height of at least 170 feet, but Air France had been using 100 feet on all its air show flyovers, often in violation of the law. Regulations also required that the flight crew meet with the air show organizers before the demonstration flight, but Air France never arranged such a meeting. The organizers met with every other pilot scheduled to participate in the air show, but they weren’t worried about the absence of the A320 pilots because Air France had always performed flawlessly at previous air shows. And at no point was it ever proposed that the pilots make a reconnaissance flight to familiarize themselves with the airport, which they had never been to before.

Flames surround the cockpit before it burned over. (Bureau of Aircraft Accidents Archives)

That meant that most of the planning had to be done by the pilots on the day of the flight. Captain Asseline chose a height of 100 feet because it was what Air France rules specified; he was not aware of the regulatory minimum of 170. Had he known that he would be flying on runway 34R and that there was a 40-foot-high forest just a few meters beyond the end of the runway, he might have included a higher safety margin, but Air France hadn’t furnished him with that information, and the forest didn’t show up on his charts either.

Asseline’s decision to perform a flyover at 100 feet while at alpha max was therefore informed by a set of assumptions which didn’t reflect reality. This maneuver required a relatively long runway with no nearby obstacles, and runway 02 might have qualified, but runway 34R definitely didn’t. By the time the pilots learned that the flyover was to be conducted on runway 34R, it was far too late to adjust their plan to compensate. And the actual scale of the forest didn’t become apparent until they were already practically level with it. Asseline expected to glide along at alpha max for much longer than he actually could, given the length of the runway, and the sudden appearance of the forest caught him completely off guard. By the time he understood what was going on, it was already too late to react given the airplane’s precarious energy state.

The A320 cut a long path through the trees on its way down. (Bureau of Aircraft Accidents Archives)

But at the end of the day, the question had to be asked: why on earth did Captain Asseline think it was a good idea to perform a low-altitude, alpha max flyover at an air show with 130 passengers on board? Certainly this was a gross error of judgment. He was in a position where spectacle would be rewarded, and he was known as a bit of a risk-taker (his colleagues sometimes called him “Rambo.”) But part of the answer might also be the A320 itself. Asseline was more familiar with its systems and capabilities than almost any other pilot, and he likely had great confidence in its ability to keep him and his passengers safe. That might have obscured the inherent danger of the maneuver. Certainly no one would have tried to perform a flyover at the equivalent of alpha max in a Boeing, even without passengers on board; the risk of stalling and pancaking into the runway would have been much too great. Ironically, the fact that the Airbus protected pilots from exceeding the airplane’s limits may have encouraged Asseline to fly much closer to those limits than he ever would have done otherwise.

Police and firefighters at the scene of the crash. (Bureau of Aircraft Accidents Archives)

The BEA’s final report largely blamed Captain Asseline for the crash, with some criticism also reserved for Air France, which failed to give him all the information he needed to plan the flight. Asseline and his supporters, which included a major French pilots’ union, denounced the report as the result of a cover-up to protect the reputation of Airbus. Supporters of Asseline hired a Swiss criminology institute to examine the conduct of the investigation, while a documentary film crew hired a British “aircraft accident consultant” named Ray Davis to help them refute the findings.

Key to their assertions was an allegation that the flight recorders had been tampered with (or replaced with entirely new flight recorders) in order to mask how long it actually took for the engines to respond when Asseline called for TOGA power. This camp believed that the A320’s computers had detected that it was in a landing configuration at low speed approaching the ground and had entered landing mode, preventing Asseline from going around. This wasn’t how the landing mode worked, (landing mode is not a flight envelope protection and can be easily overridden by the pilots using the TOGA switches) and investigators had conducted live flight tests to show that the computers wouldn’t go into landing mode anyway, but the argument looked convincing to people who didn’t know (or believe) the findings. Davis specifically alleged that four seconds were missing from the final moments of the flight — enough to put the engine response outside the certification requirements. His main evidence was an apparent disagreement between the time stamps on the ATC transcript and the flight data recorder. The FDR had a “radio transmit” parameter, which showed up in the data four seconds after the final air traffic control transmission. But this was actually a really basic misunderstanding of how the FDR works: the “radio transmit” parameter is only recorded when one of the pilots makes an outgoing transmission, not when an incoming transmission is received. The data point corresponded to Mazières’ reply to the transmission, not the transmission itself, and matched up perfectly with the official timeline.

Flattened trees surrounded the plane before first responders cleared them away. (Bureau of Aircraft Accidents Archives)

Davis also claimed that the flight data showed the plane decelerating in the final seconds before it hit the trees, rather than accelerating, as it would if the engines were spooling up normally. This was also a misunderstanding caused by a lack of relevant knowledge. In France (at least at that time) positive acceleration was written with a minus sign, and negative acceleration with a plus sign, something that Davis could have easily confirmed by looking at the data for the rest of the flight, which would have made no sense otherwise. The plane was actually accelerating in the final seconds, exactly as it should have been.

Asseline and his supporters also pointed to evidence which appeared to indicate that one or both engines had failed to produce power just before impact. The original transcript of the cockpit voice recording contained the words “boom, boom” just before the end of the recording, which Asseline said could be the sound of a compressor stall. A compressor stall can occur when airflow into the engines is interrupted at high angles of attack, but had one occurred, it would have been clearly audible on the spectator’s video, which it was not. The words “boom, boom” were simply the transcriber’s attempt to write down what they were hearing, and actually described the sound of impacts with trees. It was also alleged that the BEA’s measurements of the heights of the trees showed that the left engine was higher than the right engine, indicating an imbalance in engine thrust — but the locations of the two points of measurement were 16 meters apart, while the engines are only 11.5 meters apart. The right side height measurement was lower simply because it was taken in an area struck by one of the plane’s low-slung engines, while the left measurement was not. Furthermore, although the engines were no longer producing power by the time they struck the ground, the presence of plant matter deep inside the cores showed that they were functioning normally when they first hit the trees and had not failed in flight.

This diagram from Airbus’s lengthy rebuttal to Davis’s findings illustrates why the height measurements don’t show that one engine was producing less power and pulling that side down. (Airbus)

Despite these detailed rebuttals and the glaring errors in Ray Davis’ report, allegations that the Airbus A320’s fly-by-wire system caused the crash of Air France flight 296 are still widely believed. Michel Asseline continues to make appearances on TV programs and in news articles in an attempt to clear his name, where little effort is typically made to push back against his claims. Notably, Pierre Mazières, who could be heard on the CVR expressing veiled skepticism about the wisdom of Asseline’s flight plan, has never spoken publicly about the crash or about Asseline’s allegations.

Fortunately, the BEA investigators didn’t lose sight of their mission. After determining the cause of the crash, they issued a long list of safety recommendations, including that every demonstration flight have a comprehensive flight plan with the expected flight parameters and emergency procedures; that pilots who will fly demonstration flights engage in reconnaissance of the destination, and (if possible) conduct a practice run on a simulator; that demonstration flights be conducted without passengers; that the internal rules of French airlines be checked for compliance with national regulations; that A320 training emphasize that performance limitations must be considered despite the existence of flight envelope protections; that crews performing demonstration flights receive special training; and that all the A320’s audio alerts be played through the pilots’ headsets. Several recommendations also pertained to cabin safety and passenger survival, including that flight attendants receive more detailed aircraft conversion training; that authorities study how to create realistic evacuation simulations for flight attendant training; that flight attendants receive training on how to project calm during an emergency; that French airlines instruct passengers on how to unfasten their seat belts during pre-flight safety briefings and on the safety cards; that the seat belt buckles both unfasten and physically separate with a single action; and that the backs of seats be designed to lessen injuries to passengers’ heads during a crash.

The most lasting consequence of the crash is probably the total prohibition of passengers on board demonstration flights at air shows, something which in hindsight seems like common sense. But, as they say, regulations are written in blood.

The tail section continued to smoke shortly after the fire was extinguished. (Bureau of Aircraft Accidents Archives)

Shortly after the crash, French authorities stripped Captain Asseline of his pilot’s license, and he never flew in France again. After the publication of the BEA’s final report, French prosecutors charged Michel Asseline, Pierre Mazières, two Air France officials, and the president of the Habsheim flying club with manslaughter in connection to the crash. In 1997, Asseline was sentenced to six months in prison, while the other four were handed 12-month suspended sentences (meaning they would not see prison time unless they committed another crime). Mazières quietly accepted this outcome and kept flying for Air France, but Asseline appealed — only for the appeals court to increase his sentence from six months to ten.

Although the preponderance of evidence has always suggested that Asseline was at fault in the crash, he isn’t wrong to denounce the criminalization of his actions. Air France effectively set him up to fail, yet he received the brunt of the blame, when that blame ought to have been shared more evenly with his employer. And one can only imagine how he feels — caught in a situation where he had seconds to react, shocked by the terrible crash that occurred under his watch, only to be dragged through the gauntlet by officials and by the courts before he had a chance to heal. No wonder he believes there was a smear campaign against him. And the conviction of Captain Asseline was only one example of a tendency to criminalize errors of judgment that lead to aircraft accidents, a practice which doesn’t improve safety — after all, Asseline was in fact within his rights to perform an alpha max flyover at an air show with 130 passengers on board. Although it was a terrible idea, it wasn’t a crime, and that was exactly the problem. Thankfully, this obvious safety lesson has been learned.

Close-up of the tail section. (Franceleaks)

To this day, many people — maybe even most people — both within the aviation industry and among the flying public believe that French authorities covered up the real cause of the crash to protect Airbus. The aforementioned Swiss criminology institute is frequently cited for a 1998 report in which it stated that the black boxes presented at the trial were not the same ones recovered from the crash site on June 26th, 1988. But no convincing evidence has been presented which can debunk the flight data that was included in the BEA’s report and on the basis of which Asseline was convicted. In fact, there isn’t even a cohesive alternate timeline of events. Asseline and his supporters have variously contended that the plane went into landing mode, the engines physically failed, the automation pitched the nose down instead of up, and several other theories without settling on a particular one. A collection of “gotchas” is not a compelling argument for why an airplane crashed!

Looking down to the crash site from the direction that the plane came from. (Bureau of Aircraft Accidents Archives)

A large part of the skepticism surrounding the official findings stems from widespread misunderstandings of how investigations are conducted. For example, in the book “Flying in the Face of Criminalization,” Sofia and Andreas Mateou wrote that “the engine manufacturer was asked to check the engines despite the fact that an engine malfunction was suspected,” implying that this was a conflict of interest. In fact, this is standard procedure in every accident investigation. Of course the manufacturer gets to inspect the wreckage — they’re the ones who know the intricate details of how the plane works, and their participation is necessary. The inspections are carried out by engineers who have a vested professional interest in figuring out what went wrong, and in the presence of investigators. Ordinary investigative steps like these were in many cases portrayed by the media as evidence of malfeasance when in fact they are completely routine, and receive no scrutiny whatsoever in a “normal” accident. Although manufacturers (notably Airbus’s rival, Boeing) have occasionally tried to mislead investigators, there is no recorded case in which investigators colluded with a manufacturer to do so — not a single one. Despite dozens of crashes becoming the subjects of conspiracy theories throughout history, there is actually no case in a developed country of an aircraft accident investigation having been later revealed to have deliberately covered up the cause of a crash.

The crash site today is marked by this small memorial. (Jean-Loup Frommer)

At the end of the day it was probably inevitable that this crash would become the subject of conspiracy theories. After all, it really did come at a bad time for Airbus, and if the plane was found to be at fault, the consequences for the company would indeed have been grave. But that isn’t evidence for a cover-up all by itself. Eighty percent or more of plane crashes are caused by human error, and only some of the remainder by the aircraft — the odds were always that Asseline caused the crash, not the plane. What are investigators supposed to do if the evidence starts to point toward that 80% — pretend that it doesn’t? The BEA was in a no-win situation. And looking back, history has borne out the official conclusions: the A320 went on to be the second most popular airliner ever built, and not one has crashed due to a failure of the fly-by-wire system or an erroneous activation of the flight envelope protections. The new design philosophy has become so successful that even Boeing has adopted fly-by-wire control systems for its newest models.

Airbus introduced the A320 intending to create a new type of airplane that would be harder for pilots to crash. Although the planes themselves proved safe enough, Airbus didn’t achieve this goal — today, its planes crash just as often as Boeing’s. Air France flight 296 illustrated the main reason why: pilots all too often think they can’t crash fly-by-wire airplanes, only to discover that the laws of physics ultimately still apply. Just like the “unsinkable” Titanic, the “uncrashable” A320 quickly found its proverbial iceberg: the insuppressible confidence of the human ego.

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