4 ms·

kind of surprised that tail strikes are even possible on airbus, tbh. i thought the whole idea was that the computer maintains safety margins and clamps pilot

by a-dub 5y ago

kind of surprised that tail strikes are even possible on airbus, tbh. i thought the whole idea was that the computer maintains safety margins and clamps pilot input if it would result in a stall, collision, etc

thehappypm 5y ago
Software overriding manual pilot behavior is how we got into trouble with the 737 MAX
- a-dub 5y ago
  long before boeing tried and failed to paper over a singularity in the flight dynamics of a retrofit airframe with software and computers, there was the classic airbus vs. boeing debate. regardless of whether fly by wire was implemented (which eventually came for boeing) there were two competing philosophies. boeing believed that when in manual control, the pilot has the final say. airbus built something new that looked more like a modern drone. if the pilot issued a control input and the aircraft thought it was dangerous, it would override it. similar to how it ranges from impossible to hard to flip a drone. in the early 80s, a demonstration flight of the new airbus system at an airshow in toulouse ended in a fireball when a pilot attempted a low fly by and the plane switched into landing mode, ignoring his inputs to ascend and landing the aircraft in trees. of course, official story was that the computer (and the multi billion dollar bet behind it) was fine and the pilot and crew were declared responsible. (i think they survived, only to be jailed)
  - deleted 5y ago
    [deleted]
  - thatswrong0 5y ago
    The landing mode theory doesn't hold up under scrutiny. I'd recommend reading this article about it: https://admiralcloudberg.medium.com/fly-by-wire-the-crash-of-air-france-flight-296-55f8ec38375b https://admiralcloudberg.medium.com/fly-by-wire-the-crash-of... : > 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 The pilot was flying low and slow, over a different runway than they had originally planned, at 30ft instead of 100ft, without knowledge of the trees at the end of the runway, with a flight full of passengers, right at the edge of the flight envelope. It was incredibly irresponsible and dangerous, and that's why they crashed. Another choice quote: > 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
    - a-dub 5y ago
      what about all the business around chain of custody issues with the flight data recorder and the claims that sections right before impact had evidence of post-accident editing?
      - thatswrong0 5y ago
        Read the article: > 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.
      - a-dub 5y ago
        interesting. this all came from mid-2000s era wikipedia, which has since been updated. live and learn.
TylerE 5y ago
Doesn't kick in until clear of the ground.
geocrasher 5y ago
Juan Browne goes into the different [software based] flight laws (modes) governing Airbus aircraft at different phases of flight and how this could have happened. https://www.youtube.com/watch?v=-0wh2pZHSjc https://www.youtube.com/watch?v=-0wh2pZHSjc TL;DR: different flight laws (modes/parameters) are loaded until airfact has been airborne for 5 seconds and this could have allowed it.
nikau 5y ago
I believe it depends which control mode the plane is in, eg normal law vs direct law
mannykannot 5y ago
When implementing such controls, careful consideration must be given to all plausible scenarios, and there are cases (an engine failure on takeoff above V1 - the 'takeoff decision speed' - for example) where the alternatives are a tail strike or running off the end of the runway.

by a-dub 5y ago

thehappypm 5y ago

Software overriding manual pilot behavior is how we got into trouble with the 737 MAX

a-dub 5y ago
long before boeing tried and failed to paper over a singularity in the flight dynamics of a retrofit airframe with software and computers, there was the classic airbus vs. boeing debate. regardless of whether fly by wire was implemented (which eventually came for boeing) there were two competing philosophies. boeing believed that when in manual control, the pilot has the final say. airbus built something new that looked more like a modern drone. if the pilot issued a control input and the aircraft thought it was dangerous, it would override it. similar to how it ranges from impossible to hard to flip a drone. in the early 80s, a demonstration flight of the new airbus system at an airshow in toulouse ended in a fireball when a pilot attempted a low fly by and the plane switched into landing mode, ignoring his inputs to ascend and landing the aircraft in trees. of course, official story was that the computer (and the multi billion dollar bet behind it) was fine and the pilot and crew were declared responsible. (i think they survived, only to be jailed)
- deleted 5y ago
  [deleted]
- thatswrong0 5y ago
  The landing mode theory doesn't hold up under scrutiny. I'd recommend reading this article about it: https://admiralcloudberg.medium.com/fly-by-wire-the-crash-of-air-france-flight-296-55f8ec38375b https://admiralcloudberg.medium.com/fly-by-wire-the-crash-of... : > 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 The pilot was flying low and slow, over a different runway than they had originally planned, at 30ft instead of 100ft, without knowledge of the trees at the end of the runway, with a flight full of passengers, right at the edge of the flight envelope. It was incredibly irresponsible and dangerous, and that's why they crashed. Another choice quote: > 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
  - a-dub 5y ago
    what about all the business around chain of custody issues with the flight data recorder and the claims that sections right before impact had evidence of post-accident editing?
    - thatswrong0 5y ago
      Read the article: > 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.
    - a-dub 5y ago
      interesting. this all came from mid-2000s era wikipedia, which has since been updated. live and learn.

TylerE 5y ago

Doesn't kick in until clear of the ground.

geocrasher 5y ago

Juan Browne goes into the different [software based] flight laws (modes) governing Airbus aircraft at different phases of flight and how this could have happened. https://www.youtube.com/watch?v=-0wh2pZHSjc https://www.youtube.com/watch?v=-0wh2pZHSjc TL;DR: different flight laws (modes/parameters) are loaded until airfact has been airborne for 5 seconds and this could have allowed it.

nikau 5y ago

I believe it depends which control mode the plane is in, eg normal law vs direct law

mannykannot 5y ago

When implementing such controls, careful consideration must be given to all plausible scenarios, and there are cases (an engine failure on takeoff above V1 - the 'takeoff decision speed' - for example) where the alternatives are a tail strike or running off the end of the runway.