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> Behind the scenes, the loss of valid airspeed data had triggered a shift in the Airbus’s complex flight control laws. In “normal law,” computers interpret pil
by legitster 3y ago
> Behind the scenes, the loss of valid airspeed data had triggered a shift in the Airbus’s complex flight control laws. In “normal law,” computers interpret pilots’ side stick inputs and move the control surfaces in accordance with what is reasonable at that altitude, speed, and configuration. This improves the handling of the airplane to such an extent that no particular skill is required to fly it gracefully. Normal law also comes with full flight envelope protections in roll, pitch, speed, and load factor.
> If sensor failures occur, the controls drop down a level to “alternate law.” This law contains several sub-laws with slightly different configurations, but in general, alternate law means that some or all computer moderation of control inputs remains, but flight envelope protections are removed. The autopilot and auto thrust cease to function.
> In the event of further failures, the controls can enter direct law, in which there are no flight envelope protections and side stick inputs correspond directly to the position of the control surfaces, with no adjustment by the computer. This makes the airplane fly rather like a classic airliner, similar to most older Boeing models.
When you think of all of the Tesla accidents, this still seems to be the failure mode for autonomous systems. It's safer 95% of the time. But when it fails, it's because the users are so dependent on the systems that they don't even have the simplest of skills to prevent catastrophe.
- akira2501 3y ago> it's because the users are so dependent on the systems that they don't even have the simplest of skills to prevent catastrophe. One pilot was pushing full nose down. The other full nose up. The system _did_ tell them that they were doing this, but in the sea of other alarms, it didn't register with them. The lack of alarm prioritization and the lack of crew resource management training in the face of an emergency seem like the major human factors here. Half of that is in the design of the plane, the other half in how the company trains their pilots to handle severe emergencies.
- _cenw 3y agoI'd be hesitant to compare these. The aircraft still operated as designed. It detected that the input data was bad and turned the automation off. The pilot flying just didn't seem to grasp what that means. Most Tesla Autopilot failures aren't drivers that don't know how to drive, it's the automation making bad inputs.
- mardifoufs 3y agoNo, some warnings were also thrown away and never shown to the pilots because the automated systems thought they were erroneous (since they were so outside the flight envelope IIRC).
- _cenw 3y agoIf by warning you mean the audible stall warning - that's because below 50 knots, the airspeed is considered unreliable / erroneous, because to get to that speed without flaps you'd have to be stalling the aircraft for over a minute (getting that exact warning) and surely nobody would manage to do that... As I said elsewhere, the airplane was quite literally falling as fast as it was moving forward. I don't really fault the plane for considering that condition erroneous. And it didn't throw away a warning, it instead marks the speed tape with a bright red "SPD" instead of showing any airspeed. This is likely the better alternative over getting persistent stall warnings if one of your airspeed indicators fails. Here's how that condition would've looked: https://docs.flybywiresim.com/pilots-corner/a32nx-briefing/pfd/flags-messages/ https://docs.flybywiresim.com/pilots-corner/a32nx-briefing/p...
- mardifoufs 3y agoActually, you are right. I think I either got confused with another crash or thought it was more than just the audible stall warning. And I totally agree, there's no good solution to helping the pilots in such a catastrophic situation. They were probably going to ignore audible warnings and most visual cues anyways, considering how tunnel visioned they were from the moment the auto pilot gave back the controls to the pilots.