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Gabriel
Gabriel
Senior Member
Last Activity: Yesterday, 18:08
Joined: 2008-01-18
Location: Buenos Aires - Argentina
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  • And here are the spammers again...
    Check the "The Briefing Room" forum. Where did the "report" button go?
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  • Aeroplanies, but can be extended to technology in general....
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  • That would be unfair unless we do the same filtering with the old technology. Unless you want to call it stoogery when it is the new technology but human factors when it is the old one....
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  • Excuse me, have you read the 2nd and 3rd paragraph of my previous post? (i.e. exactly the 2 paragraph that you did not quote)...
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  • LH, this is not Randazzo's PDMG running on FSX..

    This is a REAL full-motion, 6-degrees-of-freedom, collimating-graphics, level D sim that Delta used to train REAL 737-200 pilots. You could get the whole type rating in the sim and your first flight in a real plane would be with paying passengers in the back.

    Expensive? Maybe, in the sense that it is a good bunch of money that you need to give.
    But unreasonably expensive? Compared to what? What's your point of reference?

    Do you mean it should cost less? Take into account that the sim has an acquisition cost of 12 million dollars, it is quite maintenance-intensive, it consumes quite a bit of energy, and you have an instructor with you. Plus, the ride can be shared between 4 persons. Because the actual flight is 45 minutes (not counting the 15-minute briefing and the 5-minute debriefing), you can make 2 crews that fly 20~25 minutes each (the instructor doesn't need to occupy a pilot seat). So now...
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  • Link?...
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  • There are some trade-offs of course. This accident would have never ever ever ever ever happened in a 737 because they direct hydraulic elevator does whatever the pilot commands with the control column, no matter squat switches, flight control computers, etc.

    We do know that increased automation, redundancy and technology create new failure modes, ways to crash that didn't exist before. Including ways that were not even foreseen when those systems were created.
    But, if done right, the number of accidents of old failures mode that are AVOIDED by the new technology greatly exceeds the number that is CREATED by the new technology, thus constituting a positive progress in safety.

    That said, my perception is that some times these new systems are made more complex than actually needed. Why isn't the direct mode a DIRECT mode? I.e. a mode where the analog output of the sidestick is a direct analog input to the hydraulic actuator and there is no computer having...
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  • Yeah, because you know, airlines make the decision to retire or not a type based on jubilee, age and emotional factors. Operating costs, capacity, flexibility, airline strategy and resale value have nothing to do....
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  • For me the main reason why it looks more like an A380 than a B-747 is the shape and sweep angle of the wings. Judge by yourself.

    ...
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  • Nice!

    Can you just walk-in or you need to make reservations in advance to be able to get a slot in the sim? And how long do they let you use it?
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  • Was there a split elevator at any point?
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  • I am not talking so much about this specific accident as the design philosophy. Why would you leave the airplane without any elevator control when there is no real reason to do so? And is this real quadruple redundancy? Only if you are willing to call 3 pitots triple redundancy... (and when you 1 single cause making 2 of them fail you are left with zero airspeed indications). The 2 ELACs were put off line by the same cause, and the 2 SECs put each other off-line. Again, all 4 computers were receiving correct, valid and agreeing values of sidestick input and elevator position feedback. That's all you need for direct law (actually you only need 2 of the 4 agreeing). So why would you provide direct law control in any scenario that you don't even need to define specifically but that has the characteristic of of having at least 2 agreeing sidestick and elevator position data regardless of whatever clusterf*ck is happening around to complete the scenario....
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  • You had the maintenance crew that left the outflow valve in a on-standard configuration, you had the green light, you had the cabin preparation checklist that was skipped (or at least this step was), you have the intermittent tone warning that was sounding for several minutes of useful consciousness, you have the AMBER AND CHIME master caution in front of each pilot, plus the "overhead" AMBER light that directs you to look for the problem on the overhead panel, you have (I think) the amber light of the O2 masks released, and the recording playing the instructions (and possibly some screams)...

    There was ample room to prevent this accident.

    That said, there was a warning sound that was shared between 2 different situations and was just a sound not a speaking alarm. That could have helped....
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  • Not satisfactory. If I am understanding correctly (and I very well may not), the discrepancy was in the THS and not in the elevator. The elevator was working perfectly ok all the time until it did not work at all. Who cares if the aircraft is in the ground or air to control the elevator in direct law? Even further, if the law had degraded to direct the THS would have been in manual anyway and you would not have the ELACs commanding any THS motion and hence would not have had the disagreement between COM and MON. But the most important part is that you had 4 computers receiving correct inputs from the side stick and feedback from the elevator encoder but due to a discrepancy somewhere else "decide" to shut down entirely (oh, but they did command elevator to neutral even when all 4 of them were receiving correct and agreeing sidestick inputs and elevator encoder feedback). Again, leaving the elevator without authority should be a last resource that is done if there is no other alternat...
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  • Hmmm, some things I beleive are not exactly accurate in that sentence, which would make your point even stronger:
    - I believe the masks deploy (and deployed) at 14,000ft, not 17,000. That would be yet another full minute of useful consciousness.
    - The master caution light is accompanied by an aural alarm.
    - I think that, other than the outflow valave manual green light, there is a specific amber warning light for the pax O2 masks released.
    - And I think that there is a recording played for the pax automatically when the masks are released, with instructions to put them one immediately and how to do it, which can also be heard in the cockpit....
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  • I think that it is the same in all 737s. Call it a horn if you want. It is an intermittent "toot toot" very similar to the "busy" tone in the landline telephones.

    Like this one (this is the take-off configuration alarm in the LAPA accident, a 737-200, but it is the same alarm than the cabin altitude and I believe the same in the CL and all other 737s.)

    https://youtu.be/pku8UZlaYSE?t=1830

    This is what the Helios pilot heard during the climb after passing 10000 ft. They had a few minutes of useful consciousness with that alarm sounding and them not reacting to a cabin altitude issue....
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  • Why? I mean, I don't know if it was done, but apparently the SECs were controlling the elevators correctly when the ELACs stopped doing so... until the point where the SECs also stopped doing so.

    What I don't understand (or rather the most important thing I don;t understand, because there is a lot I don't understand in this accident) is why the elevator wasn't available even in direct mode, where the trim is manual anyway. Having an issue with the HTS and confusion about whether the plane is on the ground or in the air doesn't seem like enough to make direct law elevator impossible....
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  • Gabriel
    started a topic What is it doing now?

    What is it doing now?

    Evan dismissed this accident too quickly in the other thread. As he said, it is quite complex and I am still struggling to understand the facts. But in summary, it seems that due to a number of issues and conflicting information FOUR FLIGHT CONTROL COMPUTERS gave up on the elevator, leaving it frozen at zero, not providing even direct law control for which as far as I know said computers don't need any information or input other than the sidestick input, which was not compromised. And, as a side note, here we have an Airbus pilot facing a very confusing situation and improvising a procedure where there was none (for loss of pitch control in take-off or landing) and resorting to manually turn the trim wheel to have some degree of pitch control, in an airplane where you NEVER make trim inputs (neither with switches or manual mechanisms) except in the sim or in a very bad day. At the same time, the same pilot did NOT improvise and strictly followed the procedure to reset the ELAC to fix th...
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  • That said, leveraging the same alarm sound (an intermittent too-too-too) for 2 different purposes on the same airplane doesn't seem like the brightest idea. Yes, the pilot should know that the take-off config warning works only on the ground and that the same alarm sound is used for the cabin altitude alarm when not on the ground. But an upgrade to an alarm that SAYS "Spoilers" or "Trim" or "Flaps" or 'Brakes" or "Cabin altitude" doesn't seem to be too complicated or unreasonable. And that said, we also have cases where the pilot absolutely knew that there was a cabin altitude issue and prioritized other tasks over punting his mask on, and passed out. There was an emblematic case. The cabin altitude warning goes off. The senior captain just positions the mask partially on his face but starts to troubleshoot and passes out. The senior flight engineer puts his mask but then takes it out to assist the captain and passes out. The flight attendant comes to the rescue with portable O2 and ...
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  • For that you have the simple blood oximeter. Which by the way will work for all kind of hypoxia, pressurized or not....
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