Air Inter Flight 148 was a short-haul flight between Lyon and Strasbourg, France. On January 20, 1992, with 90 passengers and 6 crew onboard, Air Inter 148 crashed into the side of the Vosges Mountain range, just 19 kilometers from the runway. It took four hours for rescuers to locate the burning wreckage, and during that time, one of the plane’s black boxes were destroyed by fire exposure. In episode 125 of Take to the Sky: The Air Disaster Podcast, we explore the key events that led to the crash of this brand-new Airbus A320 and killed 87 out of 96 people. First, the controller gave the pilots an incorrect heading while vectoring them to runway 05, which put Flight 148 on a course directly over the mountain as opposed to parallel to them. Second, the captain forgot to switch from one autopilot mode where the value was entered as a descent rate in feet per minutes to a mode with a value representing the flight path angle in degrees. The captain thought he entered -3.3 degrees; instead, he inadvertently instructed the plane to descend at an astonishing rate of -3,000 feet per minute. This was the catastrophic error that put Flight 148 on a collision course with the mountains. Lastly, the BEA found that had the A320 been fitted with a ground proximity warning system (GPWS), everyone onboard could have been saved. However, at the time, France did not require airlines to have this system on its fleet, and Air Inter had not yet equipped the A320s with GPWS. The BEA made dozens of recommendations for better pilot training that spent more time on the transition from legacy aircraft to the automated A320; greater durability in the black boxes to sustain fire exposure; having a GPWS on every aircraft; and the redesign of the autopilot displays that more distinctly differentiated between modes.
Air Inter Flight 148 Represented the Airline’s Shift to Greater Automation in the Cockpit
Air Inter Flight 148 has just departed from the airport in Lyon, France at 5:20 local time on the evening of January 20, 1992. It’s on its way to Strasbourg, France, in the Alsace region of France near the German border. As this is a quick, fifty-minute flight, this route is flown frequently by business travelers. Tonight, onboard are 90 passengers who are in the hands of 6 crew members, including 2 flight crew and 4 cabin crew attendants.
Flight 148 is being commanded by 42-year-old Captain Christian Hecquet and 37-year-old First Officer Joël Cherubin. The captain had been with Air Inter since 1979 with over 8800 hours total flying time. The first officer had been with Air Inter since 1999 and had more than 3600 hours of flying experience. Although both men were experienced pilots, they were new to the aircraft they’re flying tonight: the Airbus A320. In fact, Captain Hecquet had just 162 hours on the type, while First Officer Cherubin had just 61 hours, and he first flew passengers on the A320 less than a month earlier. Both pilots had extensive experience flying Air Inter’s legacy fleet of 1960s-era Mercure and Caravelle aircraft.
But this wasn’t unusual given the changes that had recently happened with Air Inter. Known for its short haul flights, Air Inter catered to frequent business travelers. It made the decision to upgrade its fleet to the Airbus A320, which was the first fully automated, fly-by-wire aircraft, in which pilot inputs are fed to computers that then move the control surfaces. It was also the first jetliner to have several never-before-seen manually selectable autopilot modes.
The A320 upgrade was a massive technological leap for the airline and for its pilots. This change in turn required a considerable investment from the airline for this shift to be managed effectively. To facilitate the transition to the newer aircraft, Mercure and Caravelle pilots like Captain Hecquet and First Officer Cherubin were retrained in large numbers to fly the A320.
Air Inter 148 Captain Had Consternation About Non Precision Approach into Strasbourg
Back in the cockpit of Flight 148, the plane is nearing its destination. The pilots configure the plane for landing and program its autopilot to land on the runway at Strasbourg. Due to a weather notification about winter weather and high winds happening in the area over the airport, they will now need to land on a different runway.
Strasbourg Airport had two runways: runway 05, which ran southwest to northeast, and runway 23, which ran the opposite way. Only runway 23 had an instrument landing system (ILS) that could automatically guide the plane all the way to landing, and because of this capability, Captain Hecquet wanted to land on this runway. Runway 05 lacked an ILS. Landing there would mean making a so-called “non-precision approach” in which the pilots would need to manually work out the descent profile. Captain Hecquet found another option: he planned to program the autopilot to land on runway 23 so he could use the ILS to guide him to the airport, and then once he had the airport in sight, the captain would take over the controls, and then loop around to make a visual landing on runway 05.
First Officer Cherubin informs air traffic control (or ATC) of this plan. The controller comes back and informs the pilots that if this is the plan they want to use, then there will likely be a delay because three other planes are currently preparing to depart from runway 05. The controller asks if Flight 148 wants to hold at 5,000 feet (or 1500 m) and wait for the traffic. The captain, who can hear the exchange, becomes frustrated with the possibility of waiting. So, the controller, who is aware now of the captain’s frustration, offers another option that will save them a bit of time: he offers to vector them to a navigational waypoint on the approach to runway 05 known as ANDLO, located at 5,000 feet. This would help the pilots align the plane for landing. The captain agrees with this idea, and so ATC gives them instructions on navigating toward the waypoint: he asks them to turn left to heading 230 degrees.
Air Inter Flight 148 Gets off Course While Vectoring Toward Runway
Since runway 05 does not allow for a full autopilot approach, the pilots still must manually calculate the angle of descent. Captain Hecquet calculated that once aligned with the runway, they would need to descend at an angle of 3.3 degrees. Soon, the pilots announce to the cabin that they are preparing for descent, and on that cue, flight attendants begin to prepare the cabin for landing.
Back in the cockpit, as the plane continues its descent and is about 15 miles (or 25 km) from the airport, the controller continues to walk Flight 148 through instructions to help them align with the runway. He instructs them to turn left onto a heading of 090 degrees, followed quickly by a second command to turn to 051 degrees (northeast) in line with the runway. By immediately following these instructions, Captain Hecquet completed the turn too early, passing the ANDLO waypoint on the left instead of overflying it. First Officer Cherubin noticed this and said, “We’re going… you’re turning inside, look.” This means they are turning inside of the ideal flight course, meaning, getting off course. The captain actually did not respond, so the first officer repeated his comment, “You’re turning inside, look! You should have rolled out on 070 [degrees].”
Captain Hecquet responded with a “Yeah, yeah,” and switched to a more easterly heading to get back in line with the runway. Flight 148 was now headed toward the airport but remained slightly to the left of the approach path. The controller also notices their position and communicates to the pilots that they are slightly off course and were passing ANDLO to the right. Still, the controller clears them for landing. Next, the captain initiates the landing sequence, and the pilots adjust the flaps and lower the landing gear.
At the exact moment that Captain Hecquet selected the descent rate, a pocket of turbulence caused the plane to climb for about half a second. Now the plane is going too fast to land, so the captain applies the speed brakes to slow them down. While the captain is focused on their descent speed, the first officer was more worried about their position relative to the runway and felt that Captain Hecquet was not working hard enough to get them back on track. Even though each pilot was focused on a different concern, nothing could change what happened next to Flight 148.
Flying Too Fast and Too Low, Air Inter 148 Collides with Mountain
Suddenly, illuminated by the plane’s lights right before the eyes of both pilots, is a forest – and they’re heading straight for it. In just seconds, and with no time for the pilots to react, the landing gear of the plane first strikes the tops of trees before it continues to plummet downward through branches, careening across the forest floor. The tail section of the plane slams down next, and when it does, it breaks off. The plane comes down on its left side, skidding across the ground, its left side engine and wing breaking off. The plane’s cockpit and forward fuselage strike next, and the cockpit disintegrates, the right wing breaks off and catches fire, and the front of the fuselage peels back like a banana and folds under itself.
The rear section of the plane just in front of the tail section also breaks off and catches fire, which burns quickly through the walls and flooring. All that remained of that section on the left-hand side, were the last seven rows of passenger seats, and on the right-hand side, the last row of passenger seats and the cabin crew seat. Approximately 49 feet (or fifteen meters) down from the rear cabin floor was the central section of fuselage. Despite having suffered any mechanical damage in the crash, fire from outside the plane destroys this section. There, all the seats, as well as the passengers, are ejected into the front portion of the plane.
The controller immediately notices that the plane has gone missing from radar, and he urgently initiates a call for search and rescue. But finding the plane would prove to be one of the greatest challenges related to this crash. The plane’s transmitter was not relaying any signals, and no one had witnessed the plane go down. And compounding the problem is the fact that the airport’s radar isn’t recorded. This meant that the plane could be anywhere in the vicinity of its last known position, and given that it went down in mountainous terrain, these aren’t very helpful data points. Rescuers must basically search more than 12 square miles (or 19 square kilometers) for the missing plane. And searchers are right to locate the plane sooner than later because, unknown to them, there are survivors – and they desperately need rescue.
The crash was a rough and violent breakup, and it instantly killed both pilots and most of the passengers. Two seriously injured passengers survived the initial breakup but were unable to move, and they burned alive as the fire overtook them. But not everyone perished. One man seated in row 14 was thrown out of the plane and regained consciousness still strapped into his seat, embedded in the snow. Several more passengers and a flight attendant at the back of the plane escaped the worst of the impact, finding themselves with their seats still attached to the floor even though the roof and walls had been torn away. Eleven people initially survived the crash, including a 2-year-old girl, who escaped any sort of injury and was found wandering nearby.
Air Inter Flight 148 Wreckage is Hard to Find and Survivor Sets Out on Foot to Find Rescue
Despite air and ground searches, the wreckage was proving to be hard to find. A dozen amateur radio enthusiasts, who had been listening to emergency personnel chatter, decided to join the search efforts. They are joined by teams of professional search and rescue personnel and several journalists who have also descended on the area to do what they could to find the missing plane.
But as we have found out from other episodes, sometimes, if you need to be rescued, you must try to do it yourself. If you recall, we covered a story where this happened, the infamous Uruguayan Air Force Flight 571 crash in the Andes, which we told in episode 2.
Now here on Flight 148 a passenger will make a similar choice. Nicolas Skourias was a 26-year-old engineering student on his way to visit his girlfriend in Strasbourg. He chose a seat near the back of the plane, a choice that unknowingly saved his life. Nicolas had no idea that the plane was flying too low and too fast – everything to him seemed normal. Until a deafening crash began to erupt throughout the cabin. Once the plane came to a stop, Nicolas quickly made his way out of the wreckage and discovered that he was, amazingly, unhurt. He then found two other survivors near the wreckage, a man named Pierre Lota and an 8-year-old boy who had been traveling with his father named Romain Ducloz. Nicolas and Pierre instinctively took care of Romain, getting him close to one of the many crash fires that were safe enough to stand near with heat. Nicolas and Pierre then made their way back to the plane and pulled out several other survivors, many who had serious injuries. Along with a flight attendant who also survived, Nicolas and Pierre found blankets from the plane to give to the other shivering survivors, and the men even built shelters for some of the more badly injured. As the hours ticked away, Nicolas understood that their chances of being rescued were growing smaller. And so, he did what so many other survivors have had to do: he leaves the crash site on foot in hopes of encountering searchers in the forest that he could lead back to the crash site.
And so, he makes his way through the dense forest, in the pitch black of night, and in sub-zero temperatures. He eventually encounters journalists who have joined the search and who are there to cover the crash. They initially don’t believe him when he tells them he was on the plane. Nicolas reads their shock and can tell they didn’t think anyone could have survived this kind of crash. He convinces them to follow him back, and it is there that the journalists discover what is left of Flight 148. The plane has crashed into a forest on Mont Ste. Odile in the Vosges Mountains, which is just 12 miles (or 19 km) from the runway.
It took rescuers four hours to reach the crash site, which is later deemed to have taken too much time, and the evacuation of survivors from the mountain took even more time. The first people evacuated were evacuated, according to the final investigative report, "either on the backs of men, or with arms or even with the help of makeshift stretchers.” Two of the survivors died while being transferred down the mountain into ambulances. In total, the crash of Flight 148 claimed the lives of 87 people, while only 9 people survived. All but one of the survivors were seated toward the back of the plane.
BEA Investigation into Air Inter 148 Crash Made Difficult by Destroyed Black Box
The French Bureau of Inquiry and Analysis for Civil Aviation (or BEA) arrives on scene to begin its investigation. But they are not alone. Sensing the great public scrutiny that was about to befall the investigation into a crash of a brand-new A320, the BEA asked several international air accident investigators to join their team. But the investigation quickly runs into challenges. The French police, suspicious of the civilian investigators, initially barred them from entering the site until they had secured the scene. By the time both boxes were retrieved from the burning tail section, the flight data recorder (or FDR) had been destroyed by intense exposure to the fire, and the cockpit voice recorder (or CVR) had suffered some minor damage. Later, the BEA recommends that flight data recorders be upgraded to withstand higher temperatures and longer durations of exposure, which they were.
Fortunately, investigators were able to retrieve some flight data using the quick access recorder (QAR), a device normally used by maintenance workers for diagnostic purposes. Although it was not designed to withstand a crash, it survived mostly intact, and was able to stand in for the ruined FDR.
Here is what investigators uncover.
BEA Investigation into Air Inter 148 Crash Finds Pilots Error Involving Use of Autopilot Mode Settings
The first contributor to the accident occurred while the controller was vectoring Flight 148 toward the ANDLO waypoint. His instructions were for them to turn left onto a heading of 090 degrees, followed quickly by a second command to turn to 051 degrees (northeast) in line with the runway. But the last heading the controller gave the pilots was actually incorrect and put them on a course over the mountains. The controller also mistakenly told the pilots that they were passing ANDLO to the right when it was on their left. And he used those exact words. One of the changes made after this crash was for all controllers to use compass points when describing directions.
Second, the plane was also descending too fast to pass over the mountains. This ends up sealing the fate of Flight 148. To start descending, Captain Hecquet calculated the flight path angle of -3.3 degrees and had entered it into the flight management system. But here is where things go wrong. The A320 flight computer had two navigation modes. The first, Vertical Speed mode, allowed pilots to control the plane by entering a compass heading and a desired rate of descent (in hundreds of feet per minute). The second, called Flight Path Angle mode, allowed pilots to create a specific vector, or track, along which they wanted the plane to fly, and is a value of degrees. To recap, mode one is the value of feet per minute, and mode two is a value of degrees.
The captain needed to put the plane into the second mode (flight path angle), which would put the plane onto a vector that would take it to the runway threshold, including a flight path angle of -3.3 degrees. This required pressing the mode change button to switch from the first mode to the second mode, then entering -3.3 degrees using the input knob. In what would prove to be a catastrophic error, Captain Hecquet forgot to press the mode change button, leaving the flight management system in the first mode. He then used the input knob to enter -33, but because the system was in vertical speed mode (the first mode), his entry of “-33” was read as “-3,300 feet per minute” (which is also 1000 meters per minute) instead of “-3.3 degrees.” A small “V/S” indication near the knob on the display panel revealed the current descent mode, but it could be hard to see because the displays for both modes are on the same window. Neither pilot noticed the mistake, even though -3,300 feet per minute is an extreme rate of descent rarely seen during normal flight.
At the exact moment that Captain Hecquet selected the descent rate of -3,300 feet per minute, a pocket of turbulence caused the plane to climb for about half a second. Because the plane was technically climbing at the exact instant that the captain input the steep descent, the onboard computer interpreted this as an emergency and pushed the plane toward the selected rate even quicker than it otherwise would have. The fact that this happened is an extreme coincidence.
The BEA finds there had been several incidents at Air Inter in which pilots accidentally selected a steep descent rate after using the wrong descent mode, only to discover their mistake when they broke through the bottom of the cloud base. Following the crash, Airbus changed the display values so that if a pilot selected a descent rate in feet per minute, the entire four-digit number was displayed instead of just two digits (which is how the angle value was displayed).
BEA Finds Air Inter Did not Properly Train Pilots on A320 Leading Up to Flight 148 Crash
Lastly, the pilots did not receive very extensive training on non-precision approaches on the A320. In fact, this was Captain Hecquet’s first time landing at Strasbourg using a non-precision approach. Both pilots were not very well-prepared to fly in these conditions and neither one of them could serve as a more senior pilot. The BEA finds that Air Inter underestimated the amount of training pilots needed to effectively transition to the A320, and in fact, rushed large numbers of pilots through training to get them back to the skies and flying. The BEA recommends that more training hours of training are required before a pilot is considered certified.
The BEA also finds that a ground proximity warning system (or GPWS) could have saved everyone, but flight 148 didn’t have one. France was one of the only countries that didn’t require such systems at the time, and Air Inter was one of the last major airlines that hadn’t installed them because of the false warnings that had been generated by the system in the past. As a result, the crew received no warning whatsoever that they were about to crash. Even though it was too late to save those who died on Flight 148, Air Inter installed GPWS on its aircraft even before the investigation wrapped up.
In 2006, 14 years after the tragedy, the French court investigating the 1992 Air Inter Flight 148 fatal crash cleared six defendants from air traffic control, the airline, and a key aviation safety agency who were charged with manslaughter related to the crash. Despite that finding, the court did find Airbus and Air Inter parent Air France liable for damages. The court found the manufacturer and operator liable and has ordered them to pay as-yet-undetermined compensation to the relatives and survivors.
For many years after the crash, survivor Nicolas Skourias only flew when he could wear the same coat he had been wearing the night of the crash. In his mind, this lucky coat would prevent him from ever again going through the same disaster. But with time, Nicolas managed to once again step onto a flight without his coat – though he never takes off his seatbelt and always makes the sign of the cross before takeoff. Of the accident, Nicolas insists he was not traumatized, but when he ever meets the families of those who perished, he feels remorse for having survived.
And THAT is the tragic story of the crash of Air Inter Flight 148.