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MD-87 hits fence after takeoff from TME. All passengers survive the crash.

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  • Gabriel
    replied
    Originally posted by Evan View Post
    Dunno... Determining the state of those geared links would take the NTSB about ten minutes since the tail is perfectly intact.
    I don't think it was the same issue because the elevator (at least o1 side) would be stuck in the full nose-down position, which doesn't seem to match what we see in the pictures. Unless it unstuck during the accident sequence. But I have already heard reports (rumors) of the pilot saying that they reached Vr and the plane would not rotate from 3 different sources, including one the same day of the accident. Note that the Ameristar situation is not the only reason why a plane may fail to rotate.

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  • BoeingBobby
    replied
    Originally posted by Evan View Post

    Dunno... Determining the state of those geared links would take the NTSB about ten minutes since the tail is perfectly intact. So why no announcement, especially no emergency AD? And is that puff of white smoke and assymetrical burn marks in the grass merely coincidental?

    Rather disturbing to learn that there is no way to check elevator function during preflight. How did that get past certification?
    Evan, I know that this aircraft is McDonald Douglas designed. But Boeing bought the company in 1997. So does that make Boeing responsible? Asking for a friend.

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  • ATLcrew
    replied
    Originally posted by BoeingBobby View Post
    Out of popcorn, I'll be back in a few. ​​​​​​
    Can you grab me a Coke Zero, please? Diet would work, too, thanks.

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  • Evan
    replied
    Dunno... Determining the state of those geared links would take the NTSB about ten minutes since the tail is perfectly intact. So why no announcement, especially no emergency AD? And is that puff of white smoke and assymetrical burn marks in the grass merely coincidental?

    Rather disturbing to learn that there is no way to check elevator function during preflight. How did that get past certification?

    Leave a comment:


  • Gabriel
    replied
    Originally posted by Gabriel View Post
    Well, you are assuming that one engine was significantly underperforming. Although I am totally open to that possibility, I am not ready to discard other options yet.
    A normal acceleration to Vr plus a few seconds between that and aborting when they realized that plane would not rotate would put the plane very close to the end of the runway, perhaps more or less about where the skid marks start? Again, not saying that I believe this happened. It is just an alternate possible scenario. One that happened in this type of plane not so many years ago also with everybody surviving the high-speed overrun.
    https://www.youtube.com/watch?v=iyZT79WaaSs

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  • TeeVee
    replied
    Originally posted by BoeingBobby View Post
    The only thing missing from this discussion is our German friends explanation of how Randazos flight sim reacts to the infamous V1 cut.
    you mean how Lufthansa never flew 74s out of TME...

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  • 3WE
    replied
    Originally posted by BoeingBobby View Post
    ***Out of popcorn***
    I think gurrit ate it all.

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  • Gabriel
    replied
    Originally posted by BoeingBobby View Post
    Out of popcorn, I'll be back in a few. ​​​​​​
    Butter and salt for me, please.

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  • Gabriel
    replied
    Originally posted by Evan View Post

    The Horse That Wouldn’t DieI realize that you are being academic here but as I pointed out at the beginning, a private MD-87 with 18 souls aboard is probably not overweight (or an underweight weight calc error).
    Yeah, I was babbling about the TOPMS justification in general, not this specific accident.
    That said, few souls but probably lots of fuel since it was a quite long flight, and a short-ish runway.

    I can’t fathom any other reason for them not stopping safely at low speed.
    Well, you are assuming that one engine was significantly underperforming. Although I am totally open to that possibility, I am not ready to discard other options yet.
    A normal acceleration to Vr plus a few seconds between that and aborting when they realized that plane would not rotate would put the plane very close to the end of the runway, perhaps more or less about where the skid marks start? Again, not saying that I believe this happened. It is just an alternate possible scenario. One that happened in this type of plane not so many years ago also with everybody surviving the high-speed overrun. And in this case TOPMS would have nothing to do with it.

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  • BoeingBobby
    replied
    The only thing missing from this discussion is our German friends explanation of how Randazos flight sim reacts to the infamous V1 cut.

    Leave a comment:


  • BoeingBobby
    replied
    Out of popcorn, I'll be back in a few. ​​​​​​

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  • Evan
    replied
    Originally posted by Gabriel View Post
    That's not the main problem. V1 is only relevant in an engine failure scenario (ok, some other rejected take-off scenarios too.
    The Horse That Wouldn’t Die

    I realize that you are being academic here but as I pointed out at the beginning, a private MD-87 with 18 souls aboard is probably not overweight (or an underweight weight calc error). Also, a good indicator of degraded acceleration is found on the engine instruments which almost certainly were complaining about the #1 parameters. It’s possible that these were not being monitored (and there’s your pilot error) and perhaps the yaw isn’t very noticeable on fuselage-mounted engines. I can’t fathom any other reason for them not stopping safely at low speed.

    I think V3bs is irrelevant here. The old argument about when to give up when you decide to continue at V1 but she won’t rotate at Vr doesn't matter if you never make it to Vr.

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  • 3WE
    replied
    Originally posted by gurrit View Post
    Fiiiinnnnneee, "W-E" do not talk anymore about V...
    I think you will find it mildly amusing that we once proposed V-3BS: The speed at which you can still reject a takeoff, run off the end and have a probably-survivable crash.

    It appears to have worked well in this incident.

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  • Guest's Avatar
    Guest replied
    Originally posted by Gabriel View Post
    That's not the main problem. V1 is only relevant in an engine failure scenario (ok, some other rejected take-off scenarios too).

    The REAL problem we discussed while beating this dead horse dead again and again is what happens when you DO NOT reject the take off, which is what (almost) ALWAYS happens in the accidents and incidents involving a sub-par take-off scenario. So Vr is the problem.

    So say for example that you mixed up 2 numbers and instead of calculating the take off with your actual weight of 53000 lb you input 35000 lb.

    Now you get a given Vr and a given distance, and with that Vr comes a Vlo (lift-off) which is not shown to the pilot but is part of the "internal" algorithm.
    Is your filed length is more than the minimum needed, V1 is selectable within a range that ensures that you can reject at V1 and stop, or lose an engine at V1 and lift off, both within the the runway length (which is why Vlo is part of the internal algorithm).
    Vr is NOT selectable. Is unique for each scenario. And a unique Vlo and lift-off distance comes with it.

    But the acceleration will be 35/53=66% of the assumed one.
    And, to make things worse, to generate a lift equal to the increased weight you will need a speed sqrt(53/35)= 1.23 the calculated speed

    Since the distance needed to achieve a given speed is given by D = V^2 / 2A, we can write the assumed and real scenarios as

    Assumed: D1 = V1^2 /2A1
    Real: D2 = V2^2 / 2A2 = (1.23V1)^2 / 2(0.66A1) = 2.29 * V1^2 / 2A1 = 2.3 D1

    The real distance you will need to get the plane in the air is more than twice what you thought it would take.

    And there is NOTHING to alert you that you are accelerating less than expected and will need more speed and much more distance than expected.

    Good luck.
    Ih, ih, ih you are taking personally.

    Fiiiinnnnneee, "W-E" do not talk anymore about V...

    Happy?

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  • 3WE
    replied
    Originally posted by Gabriel View Post

    ***there is NOTHING to alert you that you are accelerating less than expected and will need more speed and much more distance than expected.***
    Nothing? Not even playing the “absolute game”: Bobby has two things* (actually many more things) and ATL has a secret system of checking something.

    *Left and right buttocks, (and many takeoffs resulting in a good, albeit fallible, system of checks…)

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