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For aviation fans: Immelman turn in a B-47

Discussion in 'Bad Dog Cafe' started by KokoTele, Jun 8, 2013.

  1. abracadabra

    abracadabra Tele-Meister

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    Airbus aircraft have switches for the computers right there on the overhead panel. some checklists for various faults require the computers to be turned off.

    there have been bulletins issued advising that if certain unlikely failures occur the correct response is to turn off, for example, two air data reference units (out of three). those are not the FBW computers themselves, but turning two off will force the plane into alternate law, and believe me, alternate and direct law has no pitch and roll protection. you should also note that older Airbuses, 737s, and most if not all other Boeing aircraft, have no pitch and roll protections.

    Airbus designed their system to be safer, but they are very well aware of the dangers of complacency with FBW. their type rating courses focus on the need to understand what their computer systems do and and do not do, and most importantly what to do if it things go wrong. they designed the system specifically so that the aircraft and or the pilots can revert the system to act like a normal non-FBW aircraft if things go wrong.

    the AF447 330 crash is an example of the pilots not diagnosing and correctly responding to the fault at hand. I have experienced what they went through in the simulator and it would have been a very harrowing event. the aircraft received erroneous dual overspeed warnings, due to the pitot probes icing up, and the FBW system responded by putting the aircraft into a climb to reduce the speed, except the speed wasn't high at all, and this resulted in the speed reducing. I've done this, you push the sidestick all the way forward and nothing happens, the aircraft keeps pitching up and ignores your input commands. after a short time the system 'realised' something was wrong and reverted to alternate law, which would have allowed the aircraft to pitch down and recover from the stall, except in this case they did not correctly diagnose the problem and did not recover. there have been at least two other cases of this exact scenario occurring and both the other occasions resulted in the correct diagnosis and the flight being recovered in alternate law (this suspect pitot-probe design has now been replaced across the Airbus fleet).

    you have to remember that if it all goes to **** in an F-16 you can simply get out. we cannot do that, and the manufacturers have to give the pilots the tools to diagnose and react to problems, and if that means turning off computers then that's what it takes. we have to land and to do that we have to be able to take complete control of the aeroplane if required. isolated events like the one in Russia don't have anything to do with FBW. FWIW, they crashed an older non-FBW A310, and it's not like the FBW Airbuses can't be crashed. you could say that the first A320 crash happened (in 1988) because of the FBW system, although the crew were ultimately at fault.

    also, modern fighters cannot physically fly without the computers because they are so unstable. Airbus airliners are very stable platforms (as you would hope them to be!) and can be flown with the computers simply translating sidestick movements into direct movements of the flight controls, the same as would occur if they were attached by physical wires.

    I would be very wary of stepping into an aircraft whose systems cannot be downgraded in the event of a failure, especially one involving erroneous inputs, which you can't eject from. the manufacturer and the airlines train and trust their crews to act properly. trust me, the idea that in normal law you cannot roll more than 60 degrees or pitch outside +30 to -15 does not make me personally feel any safer. I have no intention to do that anyway! :)
     
  2. Joe-Bob

    Joe-Bob Doctor of Teleocity

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    Most of the aircraft that are/were nuke capable can do the toss-bomb thing. A-6s and A-7s could. I'm pretty sure the F-18s can as well. Nowadays, I think they want to deliver from further away than that.
     
  3. tfsails

    tfsails Friend of Leo's

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    Everything you've said here makes perfect sense. I never considered the inability to punch out of an airliner when considering FBW. Now that you mention it, the F-16 has a way for the pilot to revert to standby gains for exactly the reasons you mention. We don't like to lose airplanes if we don't have to. It's been almost eight years since I've even poked my nose into the cockpit of an F-16, and I'm starting to forget things.

    I thought every Airbus ever built was FBW, but obviously I'm wrong. Thanks for educating me. I would not be interested in rolling an airliner of any make, although I know it's been done (B707 prototype at the Seattle boat races ca. 1955)

    I'm amazed that they found the two recorders of the Air France A330. That was harder than finding a needle in a haystack.
     
  4. KokoTele

    KokoTele Doctor of Teleocity Vendor Member

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    Of course pilots say that. In general, we're control freaks and a little macho and want to believe that we can do anything better than a machine. However, crash history supports the fact that this isn't always the case, and a hell of a lot of macho control freak pilots have made a bad situation much worse.

    The 1988 Airbus crash was cited in the book as a prime example of how the Airbus flight rules enhance safety. As almost anyone would have in that situation, the crew kept trying to pull up and would have stalled if the airplane let them. A stall in that situation likely would have lead to a gruesome outcome. Instead, the airplane glided into the ground under full control and had a much gentler impact, and injuries were relatively minor.

    The very things that the pilots you know (and damned near all Boeing fans) cite as reasons why the restrictions are less safe are the same reasons that many Airbus pilots and fans cite for the aircraft being more safe.

    I tend to rely more on the input of people who are highly educated on a system than those who aren't :)
     
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