To be fair, ignoring user input could have potentially have saved Air France 447... I mean I actually can't think of an automated fool proof system that would've fixed 447, but incorrect input was a major factor.
The co-pilot apparently didn't realize that the sensor issue that disabled the autopilot also disabled the stall prevention. And that's despite an audible "STALL" warning being repeated in the background.
The captain was not in the cockpit when the whole situation started, but as he re-entered the cockpit during the stall he saw one of the co-pilots holding back on the yoke and told him to push the yoke forward to prevent the stall. The co-pilot followed the instructions, but only for a few seconds before pulling the yoke back again.
All of this is to say if the plane hadn't been known to ignore user inputs in most situations, the co-pilot might not have assumed the Airbus would do the right thing and climb no matter what when pulling back on the yoke. So in a sense, never ignoring user inputs might have also saved Air France 447.
Every piece of software is a mechanism. In order to truly be able to safely use something without outside aid, one must have a complete mental map of the mechanics of the system in question. Abstraction helps; but not when you start getting into high-risk contexts.
This might have convinced him that easing off on the stick was actually causing the stall, which was tragically misguided.
This is not a problem with how the system works, since this behaviour is explicitely communicated to pilots. It even says right on the instrument panel what control law the plane is in. There are only a handful of control laws and the differences aren't that complex. Anyone with sufficient experience in flying Airbus products knows this.
At least according to the official accident report, neither of the pilots at the controls consistently made nose down stick inputs.
The fact that the co-pilot in question kept holding the stick to the back stops was the main reason that the aircraft wallowed into the sea. Weirdly, he did let go of the stick for a brief few seconds, which was the only time during the harrowing descent that the aircraft started to behave normally, but then he pulled it back and held it back right up until impact.
Yep, the aircraft could have ignored these inputs, but the inputs are counter to what any reasonably skilled pilot would have done. (Note: Different to the MAX crashes where pulling back on the stick under speed IS the accepted way to stop a descent.)
Except on an Airbus. If the plane is in "normal law", it won't go into a stall condition. Here's the Airbus training video.[1] Note, by the way, that the automatic recovery includes going to full throttle. The throttle levers don't move, though. Unlike Boeing, where the levers are moved by the computers and the pilot can overpower that. In the 737 Max, though, it's worse, because the engines are mounted too high and full thrust pushes the nose down. So "full power and back off on the stick" will not work.
This description isn't consistent with what's in the accident report. Where are you sourcing it from?
Obviously there was some significant pilot error in this case, but a big contributor mag have been that the pilot who was trying to correct the stall didn’t understand that the plane was ignoring his input because of the averaging.
From this link: https://en.wikipedia.org/wiki/Air_France_Flight_447#Human_fa...
In April 2012 in The Daily Telegraph, British journalist Nick Ross published a comparison of Airbus and Boeing flight controls; unlike the control yoke used on Boeing flight decks, the Airbus side stick controls give little visual feedback and no sensory or tactile feedback to the second pilot.
Ross reasoned that this might in part explain why the pilot flying's fatal nose-up inputs were not countermanded by his two colleagues.
In a July 2012 CBS report, Sullenberger suggested the design of the Airbus cockpit might have been a factor in the accident. The flight controls are not mechanically linked between the two pilot seats, and Robert, the left-seat pilot who believed he had taken over control of the aircraft, was not aware that Bonin continued to hold the stick back, which overrode Robert's own control.
That suggest there was only ever one pilot flying and the way that pilot reacted to the situation had a big part to play in the final crash.
"Pilot flying" is a human-factors title, not a software function-lock. It just indicates who has control responsibility at that moment but it is not enforced by technical means.
It is intended to eliminate ambiguity in crew functions; the PF can be a newbie copilot even if the commander of the aircraft is a 30-year-service Captain who would become the PNF at that point. Its all part of Crew Resource Management theory.
There should only be one PF in a cockpit at any one time, precisely to avoid the situation that arose with the Air France flight where the computer was receiving inputs from two pilots.
Might point was I doubt that this was in fact happening and there was only ever one pilot in charge.
> the Air France flight where the computer was receiving inputs from two pilots.
The link and quotes I posted suggest that was not happening.
The system was just ignoring the other pilot (and that was the designed fault) because it also failed to tell that other pilot he was being ignored.
It didn't fail to tell him. That's what the dual input alarm is for.
Now if that alarm was raised then that suggests both pilots were in error as they both seemed to have ignore that alarm.
However that was never the reason for my original reply.
All I was replying to was idea that the flight control was doing some sort of averaging of the two pilot inputs.
That to me just seems illogical as it would asume two pilots trying to fly the same plane and that scenario will never end well.
The sounding of the alarm is in the transcripts in the accident report.
The Airbus does average the inputs if both pilots are making inputs at the same time.
Do you have a url/link/pdf that describes this behaviour?
"When both sticks are moved simultaneously, the system adds the signals of both pilots algebraically."
In particular it also says this:
To avoid both signals being added by the system, a priority P/B is provided on each stick. By pressing this button, a pilot may cancel the inputs of the other pilot.
From this link: https://en.wikipedia.org/wiki/Air_France_Flight_447
As pilot flying, Bonin took control of the aircraft via the side stick priority button and said, "I have the controls."
Which again suggests at least in this case, Bonin was the only one flying the aircraft.
But, it’s the same basic idea. The PNF thought he’d gotten control of the plane, and didn’t understand why his input wasn’t having an effect. He didn’t get feedback from the stick telling him a different input was being honored. And neither pilot appears to have been fully aware that they were in a flight control mode where there was a risk of stalling. The PF especially never seemed to have made that connection, and the PNF took a fairly long time to call it out. As a result, the PF may not have been aware that he needed to actively keep the angle of attack inside the flight envelope.
So, PNF tries to pitch down, but isn’t aware the plane got put back into a mode where he isn’t in control. PF is pitching up, but isn’t aware the plane switched to a mode where this could lead to a stall. That’s the similarity I was getting at.
From the reported control traces, there was no prolonged period of dual input. There were 3 or so brief moments of dual control input (1 - 2 seconds), during which a warning was sounded. The pilots never spoke out loud about it, but we can infer that they heard the dual input warning and were aware when it happened because the sequence of events was the same each time; inputs from both joysticks received -> aural dual input warning -> input from one joystick stops.
Something about the idea of two pilots inadvertently fighting each other for control of the aircraft has definitely caught peoples’ imagination. But it didn’t happen.
The available evidence suggest this averaging thing never happened and certainly was not the cause of the crash.
What we have is situation of two pilots in close proximity to each other not communicating and the captain unfortunately caught in the toilet.
But there are multiple major factors leading up to that, including the lack of high altitude training in direct law, and that the simulator didn't exactly simulate high altitude stalls, and that the stall warning stopped when the angle of attack was beyond the sensor limit. All of these things are major and the final report really sank a lot of blame on Airbus and Air France as well as pilot startle effect basically stopping their brains from working the problem. The senior pilot who arrived didn't have that, and quickly figured out the source of the problem but by then it was too late, not enough altitude to recover.
A principle of zero automation fallback in case of confusion ? something that is hardcoded deep in the design so that people in charge (pilot crew) can know for sure that whatever happens is in their hands ?