Too Slow, Too Low and Obstacles Ahead: Air France flight 296
On the 26th of June in 1988, one of the first in-service Airbus A320s flew a demonstration flight over Habsheim airport and ended in tragedy. I’ve written an introductory piece which explains the background along with the technical issues which are required to understand what happened that day.
Rudy Jakma has mentioned he has some information which may differ from the BEA sequence of events, so be sure to check out the comments to this piece.
At the time, no one saw a reason to ban passengers from a demonstration flight. A raffle was held at the Habsheim Airclub and the winners, along with a number of journalists, were invited for the flight, making for a total of 130 passengers.
The flight plan was for the Airbus A320 to board the passengers at Basel and then fly to Habsheim runway 02/20. There they would overfly the airfield twice at 100 feet above the ground: once low and slow at the maximum angle of attack and a second at high speed. Then the aircraft would fly to Mont Blanc to circle the famous peak before bringing the passengers back to Basel.
The flight crew were both experienced and the captain, a test pilot for Air France, knew the aircraft as well as anyone. He had pushed it beyond its operational limits and found the Airbus A320 could do things he’d never been able to do. He was confident about the demonstration.
The co-pilot, acting as Pilot Monitoring, had 25 years experience at Air France, six of which as a training captain. He had over 10,000 hours flight time and had qualified as captain on the A320 three months earlier.
Air France’s Operations Director and the Flight Safety Department had approved the demonstration.
No one ever saw any need for a test run.
The two pilots received their flight plan the morning of the flight. No details of the aerodrome or the flyover were included.
They flew from Paris to Basel where Air France held a press conference. Then the passengers boarded and the captain briefed his co-pilot. They would take off from Basel, retracting the landing gear but leaving the flaps at 1 (10° when going below 100 knots). Then a nice and easy turn to the right and look for Habsheim.
Because Habsheim was a small airfield with only a 1,000 metre runway (3,280 feet). It was not listed on the flight computer; the flight crew would need to locate it visually and then prepare for the low and slow pass as they descended.
The captain told his co-pilot that, as soon as they had the runway in sight, he should take the flaps to 3 (20°) and extend the landing gear. Then he would descend to 100 feet and disengage the alpha floor protection, so that the aircraft would not increase the thrust as they approached stall speed. They would then pass 100 feet over the runway at just above stall speed.
The co-pilot’s monitoring duties included calling out when they’ve reached 100 feet and watching the instruments.
The captain told him, “if I tell you that it is hard, you help me, and you hold the power to keep zero vertical rate.”
Flying at right at stall speed, the aircraft will become sluggish. At 100 feet above the ground, it’s important that they don’t lose any height at all during the low pass. The co-pilot is thus briefed to watch the power settings to make sure that the aircraft doesn’t sink and that the captain isn’t struggling. Because the captain is disabling the alpha floor protection, he has to rely on the co-pilot to adjust the engine thrust so that they can maintain straight and level flight. They didn’t discuss airspeed but a typical approach speed on the A320 is 130-140 knots; I assume that they had planned to stay at the low end of this.
Then, at the captain’s signal, the co-pilot is to increase the thrust to TO/GA power. As they climb away, the captain would turn, ready for the high-speed pass at 340 knots (391 mph/ 629 km/h).
The briefing was clear and covered the details of the flight. The captain split up the tasks and made sure that the co-pilot understood the plan.
But things didn’t go according to plan.
After the briefing, the A320 departed Basel and climbed to 1,000 feet and turned right, just to find that they couldn’t see the airfield. It was 8.6 nautical miles (16 km) to Habsheim, plenty of time to set up descend; however, by the time they’d made visual contact, they were only 5.5 nautical miles (10 km) from the airfield. They throttled the engines back to idle in order to allow for the faster and steeper descent.
They extended the landing gear and selected flaps 2 and then, a few seconds later, flaps 3 as they descended through 500 feet. Everything was happening very quickly.
At 200 feet above the ground, the flight crew suddenly saw that the crowds were not at the concrete runway (02/20) for which the demonstration was planned. Instead, they were lined up along the sides of a grass strip at a 40° angle from the main runway. Descending at 600 feet per minute, the captain quickly turned right to align the aircraft to the grass strip.
This must have been insanely disorientating.
The aircraft reached 100 feet above the ground. The pilots had no time to think about their fast descent at idle power or the changes to the plan. The co-pilot called out 100 feet (monitoring their height above the ground) but the captain never responded. He never gave the command for the co-pilot to increase thrust to keep them at 100 feet.
The radio altimeter also called out 100 feet. And then 50 feet, 40 feet, 30 feet. The captain finally levelled out somewhere between 35 and 30 feet above the grass runway. The speed decayed to 122 knots.
The aircraft is now too low and too slow and the alpha floor protection is turned off. There’s nothing to save them from a stall but themselves but both pilots must have been struggling to process what was happening.
To make matters worse, the grass airstrip had trees at the end: trees which were not marked on the chart and that the flight crew didn’t know about. The trees weren’t a problem for aircraft taking off from the runway; under normal circumstances an aircraft would climb away to 50 feet above the ground as it cleared the runway and pass over them.
But this was a low straight-and-level flight along the length of the grass strip, planned for a runway which was clear of terrain on both ends.
The aircraft was set up for the low pass: wheels down, flaps fully extended. Their airspeed was only 122 knots. They were flying lower than the surrounding obstacles. And their engines were at flight idle.
It seems pretty clear that the captain applied TO/GA power at this point. The captain later said that he applied the power and nothing happened, so he had to pull back and apply it again, losing precious seconds. But this doesn’t match the logs on the Flight Data Recorder or the sounds on the Cockpit Voice Recorder where the clicking of the power being increased is clearly audible.
The problem is that the total energy available to the aircraft at that moment was not enough to clear the trees. The angle of attack was already near maximum, intentionally as close as possible.
The captain increased the pitch but without the engine thrust, that aircraft could not climb. The engines needed more time to accelerate to a useful level of thrust.
For certification, an engine must be able to spool up in eight seconds. For the first four to five seconds, there’s very little increase in thrust, it all comes at the end. On a normal approach, the thrust is stabilised, usually above idle. The pilots are targetting a specific approach speed and only minor changes are needed. In this case, the speed had been quietly decaying since they started their descent.
The aircraft flew into the tops of the trees. The engines, almost to the point of spooling up, began to suck in the leaves and small branches. At 4.5 seconds after the application of TO/GA power, both engines failed and the aircraft impacted the trees. The right wing was torn off and the fuel tank breached, spilling jet fuel which immediately ignited.
Inside the aircraft, the passengers were dazed and confused, having hit their heads on the backs of the seats in front of them. The senior cabin crew membmer attempted to give instructions for an emergency evacuation, but the PA system had broken on the impact. He opened the left-side door which only partially opened, blocked by the trees. The emergency escape slide immediately began inflating, still stuck inside the fuselage. The cabin crew and passengers forced the door fully open but fell from the aircraft. Another cabin crew member attempted to evacuate the remaining passengers but they were unable to get clear of the trees and branches at the bottom of the slide. The cabin crew member continued to evacuate the passengers while those below cleared a route for passengers to move away from the aircraft. Cabin crew members at the rear also evacuated passengers as quickly as possible but the overwing emergency exits weren’t usuable for those in the middle of the aircraft.
By now a fierce fire raged on the entire right side of the fuselage and the fuel in the left wing had ignited. The fire breached the cabin and passengers trying to push forward from the middle of the aircraft were burnt and suffering from smoke inhalation. The fire trucks could not make their way to the scene, blocked by the trees. The aircraft was destroyed by the fire.
Three passengers were unable to escape the burning aircraft: two children and a woman who turned back to help them. Of the 133 who were successfully evacuated, 34 were treated for burns and injuries. Honestly, the fact that anyone actually survived this is amazing.
The investigation found that the accident was unavoidable from the moment that the aircraft passed the tower: by then, it was too late to get up and over the trees.
Captain Asseline, First Officer Mazière, two Air France officials and the president of the flying club sponsoring the air show were all charged with involuntary manslaughter. All five were found guilty. Asseline was initially sentenced to six months in prison along with 12 months of probation. The others were sentenced to probation.
The captain argued that the barometric altimeter was set wrong; he said that it displayed 100 feet when he went to climb away and so he never knew that he’d descended below the target height. Even if this was true, flying at such a low height, he should have been using the radio altimeter for his precise height above terrain, but he said it was hard to see.
This also may have been true but when it comes down to it, his job was to be looking outside the aircraft and relying on the co-pilot to monitor the instructions. The co-pilot (and the radio altimeter) called out 100 feet while the aircraft was still descending but the captain, likely fixated, never heard it.
The captain also argued that he would have cleared the trees but the aircraft forced him down. He said that the alpha protection wouldn’t let him climb.
Airbus attempted to recreate the situation as closely as possible, but on a much longer runway which was clear of terrain at the departure end. They found that they were able to recreate the aircraft elevators moving down (as the pilot said) as a part of the alpha protection. Although Airbus confirmed that the elevators moved down as he attempted to clear the trees, that’s not damning proof that the Airbus system is flawed. It simply underscores what we could already see from the FDR data: that aircraft was not capable of flying over those trees in the configuration it was in.
The captain’s argument shows a flawed understanding of the alpha protection. The alpha protection wasn’t stopping him from climbing, it was stopping him from stalling. If the aircraft had been capable of climbing, it would have climbed, even an Airbus. Especially an Airbus.
If the trees hadn’t been there and the aircraft had been flying over the concrete runway, ending up in the same position, then because it was a fly-by-wire aircraft with alpha protection, they would have got away with it. The end of the runway was clear of terrain, so they would have just needed to keep straight and level until the engines spooled up and the aircraft gained airspeed, at which point they could climb away. The alpha protection, in this case, would allow the pilots to do this with maximum efficiency and ensuring that they recovered from the stall.
If the aircraft had levelled off at 100 feet, as planned, there would not have been an issue, even if the power had not been increased until the very last minute, because they would have remained clear of the trees.
If they’d been flying a Boeing, it would have sounded alarms at the flight crew. It would not have made it over the trees. It couldn’t. The aircraft would have stalled as it crossed the tree line.
The Airbus overrode the pilot’s setting in order to prevent the stall. It couldn’t prevent the crash.
The accident was caused by a combination of factors:
- no overflight or practice runs for the demonstration, so the pilots did not know the details of the airfield
- the A320 was configured for slow flight, not for climbing away
- the organisers changed the target runway at the last minute (or at least, herded the crowds to the wrong runway)
- the flight crew was distracted with their late descent and change in plan at the last moment
- the airspeed had dropped to below what they had planned
- the aircraft was only 30 to 35 feet above the ground
- the engines were at idle
- by the time go-around power was applied, it was too late
As a result of this crash, passengers are banned from demonstration flights and flight crews are expected to receive the proper reconnaissance of airfields, although the Sknyliv air show disaster in 2001 suffered this same fault, where the pilots did not know the airfield and, at the last minute, realised that the display line was not where they expected.
It’s not often that an accident report looks like poetry but I could not resist sharing this excerpt from the Airbus report with you.
Airbus concluded that by the time the captain pitched the nose up, there was nothing that could have been done to avoid crashing. The only question was whether the aircraft would crash nose down or nose up.
Airbus theorised that the captain had became overconfident after the success of his test flights in the A320. The aircraft had so precisely done everything that he wanted it to do that he hadn’t realised that he had pushed the aircraft beyond the limits of its ability to fly.
There’s another discussion to be had here about Just Culture, where front-line operators are not punished for their actions or decisions within the scope of their role and training. Specifically pilots and ATC are at great risk of being ‘punished’ so that the public can see that something has been done, restoring their faith in safety. It doesn’t mean that no one ever can be prosecuted but it means that there needs to be a case of gross negligence. If the captain had decided that he was going to fly at 30 feet for the sake of it, when the organisers told him to stay 170 feet above the ground, then there’s a case for negligence. If he had refused the opportunity to overfly the runway and do practice runs and then changed runways on the day and then purposefully flown at 30 feet – yes, I would be more open to the idea of criminal charges.
But the captain had not simply decided to try a risky manouevre of his own volition. Air France planned and approved the fly-over without offering the appropriate support. There were no practice runs. The flight crew were given the flight plan at the last minute. And then the unbelieveable last minute changing of the runway, a decision most certainly made by someone who simply did not understand or respect the aircraft and the flight crew.
Personally, the only actual negligence I can see is on the part of the organisers, who clearly did not understand the impact of what they were doing.
Another aspect of Just Culture is that the investigation, as handled by the transport authority responsible, is kept separate from criminal investigations. There was a recent case in the UK, where the AAIB refused to give up the details of their investigation to the police, because they argued that they would lose the trust of the community. They would be unable to conduct interviews and investigations in future if people thought that the details were going straight into a criminal investigation.
In this case, I feel that a lot of the controversy about this flight and what caused the crash comes down to the French decision to prosecute and sentence the flight crew for manslaughter.
The official report gave the following probable cause of the accident as being a combination of:
- Very low flyover height, lower than surrounding obstacles.
- Very low speed, slowing down to reach maximum possible angle of attack.
- Engines at minimum idle flight power.
- Late application of go-around power.
The BEA concluded that although the descent below 100 feet was not deliberate, it showed a failure of the crew to take proper account of the visual and aural information available to them (that is, they should have been able to hear the radio altimeter and see how close they were to the ground.
The following are the references I used for my points and analysis.
- Bureau d’Enquêtes et d’Analyses f-kc880626 page
- Scan of Official Report (in French)
- Why and how the flight recorder tapes were forged (by Christian Roger in defence of Captain Michel Asseline)
- Airbus Response
- Air France 296 Accident Case Study on Code7700
I expect there to be some robust conversation so I’d like to remind people that I expect civility and calm in the comments. I will not publish comments which engage in name calling or attack the intelligence of the other posters.