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Thread: indonesia LionAir crash

  1. Top | #11
    Fair dinkum thinkum bilby's Avatar
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    Quote Originally Posted by Worldtraveller View Post
    Quote Originally Posted by Jimmy Higgins View Post
    Are analog attitude indicators problematic and get stuck? I would presumably want a gyro over a small LCD screen. Not often, but sometimes, the analog is better... heck we still are using the pitot tubes for velocity.
    There are a few recent exceptions that I know of (the new Boeing plane may be one), but until recently, the FAA interpreted FAR 25.1333 as either needing a non-powered backup, or at the very least, having a non-powered backup as the best/easiest option.

    I work mostly on older aircraft anyway (and I'm a structures guy, not avionics), and I have yet to see a commercial aircraft without the non-powered instruments at least to meet the requirement above. That's not to say there aren't any, I have seen some newer business jets for instance, that don't have them.

    Pitot tubes are required for airspeed regardless of the nature of the display, since airspeed is based on reading the difference between the static pressure and dynamic pressure. There is at least one incident I know of (out of Lima, Peru, I forget which airline) where the dynamic port was covered with tape on the ground, and the pilots didn't notice it on their walkaround. The plane crashed shortly after takeoff because they couldn't get accurate speed/altitude readings and went into the water at night.

    I suspect the FAA might hit Boeing with some fines, and issue an AD requiring training and updating the flight manuals of the aircraft with this new system.
    Brisbane has a problem with a local solitary mud-dauber wasp, which makes mud nests in small holes. They have a tendency to build them in the pitot tubes of aircraft at YBBN, unless the tubes are covered after landing - but of course that means that someone needs to ensure that they are uncovered before takeoff.

    I believe it's now mandatory under CASA rules to inspect and cover pitot tubes at YBBN if the aircraft has been on the ground for more than two hours. We haven't had any crashes, but we have had aircraft forced to turn back to the airport after strange instrument readings at or shortly after takeoff.

  2. Top | #12
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    Quote Originally Posted by Loren Pechtel View Post
    Quote Originally Posted by Jimmy Higgins View Post
    Are analog attitude indicators problematic and get stuck? I would presumably want a gyro over a small LCD screen. Not often, but sometimes, the analog is better... heck we still are using the pitot tubes for velocity.
    Analog systems can be made to work without any power. Digital systems can't.
    Yes, thank you for that random reply.

  3. Top | #13
    Contributor barbos's Avatar
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    Quote Originally Posted by Loren Pechtel View Post
    Quote Originally Posted by Jimmy Higgins View Post
    Are analog attitude indicators problematic and get stuck? I would presumably want a gyro over a small LCD screen. Not often, but sometimes, the analog is better... heck we still are using the pitot tubes for velocity.
    Analog systems can be made to work without any power. Digital systems can't.
    Too bad that without power these working systems are useless on big planes

  4. Top | #14
    Contributor barbos's Avatar
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    Quote Originally Posted by Worldtraveller View Post
    I suspect the FAA might hit Boeing with some fines, and issue an AD requiring training and updating the flight manuals of the aircraft with this new system.
    I think it's much worse than that. Boeing introduced a system which crashed a plane in a matter of months since introduction.

  5. Top | #15
    Contributor barbos's Avatar
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    The 737 MAX is an airframe design that dates back to 1967. It is the latest in Boeing's line-up, includes a "fly-by-wire" (that is, computer controlled) electronic flight control system and highly efficient turbofan engines. Because the engines are also more powerful and heavier than previous versions of the airplane, the tendency for an "underslung" (under the wing) mounted engine to cause the nose of the airplane to rise when thrust is increased, especially at lower airspeeds, becomes more pronounced.
    Boeing compensated for the nose-up tendency by programming the flight control computers to apply nose-down stabilizer trim automatically, a function that is invisible to the pilot even when hand-flying the airplane.
    Looks like the reason for this system is engines which are too powerful.
    So turning it permanently off is not really a good option. Boeing is in serious shit.

    How can pilots compensate for a malfunction if they are not aware of how it works? And recognition is key. If crews don't understand the abnormality, they can't react via an appropriate emergency checklist. For Lion Air, their altitude of 5,000 feet didn't leave much time to analyze the situation and then react.
    This is a crust of the problem. Pilots simply don't know what and why is happening.
    Last edited by barbos; 11-30-2018 at 06:46 AM.

  6. Top | #16
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    Quote Originally Posted by Loren Pechtel View Post
    Personally, I think the answer is an in-between approach: Let the plane enforce safety limits etc, but give the pilot a switch--big, obvious but under a cover. Hit that and the plane will quit trying to keep you from leaving the safe envelope and switch to announcing what it thinks the danger is, instead. In reality the plane may be confused about the envelope, in reality the choice may be between something risky and certain disaster.
    It seems many crashes occur either when the plane fucks up or the pilots only think the plane is fucking up, but it isn't. There is no reconciling this.

    I would also like the plane to have a better picture of the bottom of the airspace. We have the technology, give the fly-by-wire planes an elevation map of the world. Combine that with GPS and the plane knows where the terrain is and the fly-by-wire can avoid maneuvers that would cause it to hit that terrain. (And in a hijack scenario this could be made non-overridable--while hijackers could crash a plane through fuel exhaustion they couldn't 9/11 a target.)
    Two crashed into towers, not the ground. The funny thing about this would make the landing in the Hudson impossible as well.

  7. Top | #17
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    Quote Originally Posted by Jimmy Higgins View Post
    Quote Originally Posted by Loren Pechtel View Post
    Quote Originally Posted by Jimmy Higgins View Post
    Are analog attitude indicators problematic and get stuck? I would presumably want a gyro over a small LCD screen. Not often, but sometimes, the analog is better... heck we still are using the pitot tubes for velocity.
    Analog systems can be made to work without any power. Digital systems can't.
    Yes, thank you for that random reply.
    It's not random--I was giving a good reason for having some analog backup instruments.

  8. Top | #18
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    Quote Originally Posted by Jimmy Higgins View Post
    I would also like the plane to have a better picture of the bottom of the airspace. We have the technology, give the fly-by-wire planes an elevation map of the world. Combine that with GPS and the plane knows where the terrain is and the fly-by-wire can avoid maneuvers that would cause it to hit that terrain. (And in a hijack scenario this could be made non-overridable--while hijackers could crash a plane through fuel exhaustion they couldn't 9/11 a target.)
    Two crashed into towers, not the ground. The funny thing about this would make the landing in the Hudson impossible as well.
    The terrain map would include the buildings. In hijack mode it would have forced the plane to climb over the towers instead of impacting. And since the Hudson plane wasn't hijacked the pilot could have turned it off.

  9. Top | #19
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    Quote Originally Posted by Loren Pechtel View Post
    Quote Originally Posted by steve_bank View Post
    In reliability engineering there is an idea that as you add complexity to a systm to make it more safe you end up making more unsafe.
    Yeah, you have to evaluate the risk of the system doing something undesirable vs the benefit of it avoiding something undesirable.

    There is a video of an Airbus crash at a Paris airshow. The pilot was making a low pass with wheels down. He got into a situation where he tried to pull up but the computer would not let him. The computer thought the pilot would stall.

    There also can be limits in fly by wire systems on gs. It won't let you exceed a limit in a turn. The flip side is in an emergency you may need to pull a lot of gs.
    Personally, I think the answer is an in-between approach: Let the plane enforce safety limits etc, but give the pilot a switch--big, obvious but under a cover. Hit that and the plane will quit trying to keep you from leaving the safe envelope and switch to announcing what it thinks the danger is, instead. In reality the plane may be confused about the envelope, in reality the choice may be between something risky and certain disaster.

    I would also like the plane to have a better picture of the bottom of the airspace. We have the technology, give the fly-by-wire planes an elevation map of the world. Combine that with GPS and the plane knows where the terrain is and the fly-by-wire can avoid maneuvers that would cause it to hit that terrain. (And in a hijack scenario this could be made non-overridable--while hijackers could crash a plane through fuel exhaustion they couldn't 9/11 a target.)
    At least through the 90s the Air Bus policy was computer over pilot, and Boeing was the opposite. U worked on avionics that went into Air Bus and Boeing and went through aircraft certification.

    The black box level and aircraft level certification process is pretty rigorous. Sometimes bugs get through but are usual minor. In designing test plans an obscure not so obvious set of events are not tested for.

    Out at Everett Boeing has alarge structure where complete airframes are twisted and bent while pressure is cycled.

    Back in the 80s a jet went down when a single thrust reverser deployed ib flight, Now there are indendnet redundant back up systems that will force a thrust reverser to stow it if deploys in flight. Safety is an evolutionary process.

  10. Top | #20
    Contributor barbos's Avatar
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    Another Boeing 737 max crash.
    https://edition.cnn.com/world/live-n...ash/index.html

    This is becoming a statistics

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