4 ms·

Funnily enough, A380, A350, B787, and other new aircraft have their brakes connected by Ethernet (specifically AFDX, a modified variant of Ethernet) so braking

by p_l 2y ago

Funnily enough, A380, A350, B787, and other new aircraft have their brakes connected by Ethernet (specifically AFDX, a modified variant of Ethernet) so braking actuator signals (and sensor data back) goes as UDP messages. But it makes the system less complex and easier to handle, as there's one kind of cabling, and complex functions like ABS equivalent are handled from avionics bay

wakawaka28 2y ago
Aircraft don't need their brakes to be as responsive as cars do. There is virtually no chance of hitting a person or another plane while landing or maneuvering on the runway.
- p_l 2y ago
  Aircraft brakes are life or death issues that require instant response times to changing conditions, which is why ABS originated in aircraft. The aircraft braking systems are very complex, including active thermal management and automated braking systems that take multiple data sources to manipulate breaking force, including understand how long the brakes survive when taken beyond melting point (RTO setting on autobrake)
  - wakawaka28 2y ago
    I don't think ABS originated in aircraft because of the required braking response time. It originated in aircraft because aircraft must regularly operate in wet and icy conditions, and the performance of aircraft brakes is correlated to the length of runway required to land, which relates closely to the cost of everything in aviation. It was thus economical to use cutting-edge tech on planes long before it was economical to do the same for cars, which are mass-produced and must be affordable to individuals. There is approximately zero chance of an aircraft pilot needing to stomp on the brakes because of a random pedestrian or animal, whereas that happens constantly for cars. Cars stop and go all the time and have to avoid each other. Aircraft hardly do that at all when they are on the runway. They use their brakes to not accidentally roll or be blown about, and in the process of landing. Those applications don't need epic response time.
    - p_l 2y ago
      Being slightly off in adjustment of brakes when landing an airliner results in dead passengers. It's not as visible for manual braking, but that's because the brakes have been "brake by wire" for some time. The scope of inputs in brake control loop is also much wider in aircraft than in typical car, at times including calculated mass, calculated ground speed, brake temperatures, tire temperatures, pressure on gear, etc. Now consider that the same network used to control the brakes also is sufficient to control every other sensor and servo on the aircraft s well.
      - wakawaka28 2y ago
        That is all pretty interesting but I think we've gotten far away from my original comment, which was that planes don't need brakes to be as responsive as cars do. The typical application you're describing is in landing, not in puttering around in the airport. Landing involves executing some braking program continuously until the plane is on the ground. What I'm really getting at here is that the pilot is not going to be taken by surprise and have to apply the brakes in the same way as a driver would. It stands to reason that despite the lower speeds that cars go, they need to brake spontaneously in all kinds of conditions (on worse surfaces than the typical runway, in many cases). I don't know why this point matters anymore but that's what I was trying to say. I would like to add, brake by wire may be more reliable on planes than cars because planes are maintained very well by experts. Automobile design should strive for simpler and more failsafe options because owners are usually clueless people with limited budgets, who want to do as little maintenance as possible. The fact that hydraulic brakes work so well even in very old cars says a lot about how good they are. When they do get blamed for poor performance, it's usually due to something stupid like the owner not replacing worn out hoses after 20+ years of heavy use. I only found out about that one recently. Old hoses start breaking down and they gradually get congested.

by p_l 2y ago

wakawaka28 2y ago

Aircraft don't need their brakes to be as responsive as cars do. There is virtually no chance of hitting a person or another plane while landing or maneuvering on the runway.

p_l 2y ago
Aircraft brakes are life or death issues that require instant response times to changing conditions, which is why ABS originated in aircraft. The aircraft braking systems are very complex, including active thermal management and automated braking systems that take multiple data sources to manipulate breaking force, including understand how long the brakes survive when taken beyond melting point (RTO setting on autobrake)
- wakawaka28 2y ago
  I don't think ABS originated in aircraft because of the required braking response time. It originated in aircraft because aircraft must regularly operate in wet and icy conditions, and the performance of aircraft brakes is correlated to the length of runway required to land, which relates closely to the cost of everything in aviation. It was thus economical to use cutting-edge tech on planes long before it was economical to do the same for cars, which are mass-produced and must be affordable to individuals. There is approximately zero chance of an aircraft pilot needing to stomp on the brakes because of a random pedestrian or animal, whereas that happens constantly for cars. Cars stop and go all the time and have to avoid each other. Aircraft hardly do that at all when they are on the runway. They use their brakes to not accidentally roll or be blown about, and in the process of landing. Those applications don't need epic response time.
  - p_l 2y ago
    Being slightly off in adjustment of brakes when landing an airliner results in dead passengers. It's not as visible for manual braking, but that's because the brakes have been "brake by wire" for some time. The scope of inputs in brake control loop is also much wider in aircraft than in typical car, at times including calculated mass, calculated ground speed, brake temperatures, tire temperatures, pressure on gear, etc. Now consider that the same network used to control the brakes also is sufficient to control every other sensor and servo on the aircraft s well.
    - wakawaka28 2y ago
      That is all pretty interesting but I think we've gotten far away from my original comment, which was that planes don't need brakes to be as responsive as cars do. The typical application you're describing is in landing, not in puttering around in the airport. Landing involves executing some braking program continuously until the plane is on the ground. What I'm really getting at here is that the pilot is not going to be taken by surprise and have to apply the brakes in the same way as a driver would. It stands to reason that despite the lower speeds that cars go, they need to brake spontaneously in all kinds of conditions (on worse surfaces than the typical runway, in many cases). I don't know why this point matters anymore but that's what I was trying to say. I would like to add, brake by wire may be more reliable on planes than cars because planes are maintained very well by experts. Automobile design should strive for simpler and more failsafe options because owners are usually clueless people with limited budgets, who want to do as little maintenance as possible. The fact that hydraulic brakes work so well even in very old cars says a lot about how good they are. When they do get blamed for poor performance, it's usually due to something stupid like the owner not replacing worn out hoses after 20+ years of heavy use. I only found out about that one recently. Old hoses start breaking down and they gradually get congested.