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  • #61
    ...by the way, this is a little bit personal. As a bad ass 35 hour student pilot, I was shooting stop and goes in a 172 on a 3000 ft runway with a 500 Ft displaced threshold on both ends due to terrain and obstructions.

    The idiot pilot forgot to turn off the carb heat... It didn't feel right, but then again, it seemed on target...I got to flying speed and kind of drug over some houses with barely ok clearance...as I FINALLY got to pattern altitude, there was the damn carb heat...I'm glad I maintained airspeed, but there were voices suggesting a little more pull up.

    Right or wrong, I think I know what the Air Florida guys were thinking... it feels wrong, but we ARE accelerating... seems like we'll make it, we always have before.

    So, Bobby, that's nothing compared to your experience, but then again, it's kinda sorta exactly what were discussing (although no one told me a seconds to 40 knots figure to use.)
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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    • #62
      Originally posted by Gabriel View Post
      Not to mention that in 6 seconds they will be stalling...
      What is the proper approach-to-stall procedure when you are still on the ground?

      Comment


      • #63
        Originally posted by Gabriel View Post
        Yes, that may work, but there are 2 issues with that:

        1- It should be "X sec to 80 knots", and X be calculated for each take-off. The 20 seconds rule of thumb is too inaccurate, blah, blah, blah.
        Yes, I recognize your inaccuracies, but really wonder if they are significant on 'typical' runways... fudge some numbers and show me where you'll run off a 8000 Ft runway with 80 knot or 20 second rolls.

        For a true maximum performance deal maybe, but then again, Bobby is aborting at 80 knots, generally well before V1.
        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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        • #64
          Originally posted by 3WE View Post
          Yes, I recognize your inaccuracies, but really wonder if they are significant on 'typical' runways... fudge some numbers and show me where you'll run off a 8000 Ft runway with 80 knot or 20 second rolls.

          For a true maximum performance deal maybe, but then again, Bobby is aborting at 80 knots, generally well before V1.
          15% less acceleration means 32% more runway, so in an 8000ft runway that would be 2500ft.

          Given that a=F/m, and in big planes, the MTOW is about twice the empty weight (so there may be a lot of mass variation between take-offs), and F=thrust which is influenced by air density which is affected by QNH, elevation and temperature (three things that can have quite a big variation too, especially elevation and temp), the acceleration in different take-offs has a variation range that is much more than 15% (and we are talking about the expected one).

          80 knots in 20 secods is 4 knots for second. That is a representative value of a typical take-off acceleration. Now it can be 3 kts/sec, which is 25% less, or 6 kt per sec, which is 50% more acceleration.

          2 seconds delay in reading the seconds is 10% of the 20 seconds.

          And I didn't even start yet with the point 2 that you didn't quote: At what point do you start the stopwatch?

          --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
          --- Defend what you say with arguments, not by imposing your credentials ---

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          • #65
            Originally posted by Evan View Post
            What is the proper approach-to-stall procedure when you are still on the ground?
            Given that they are climbing 1000 fpm, that plane is either not on the ground or running along a runway with a heck of a slope!

            --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
            --- Defend what you say with arguments, not by imposing your credentials ---

            Comment


            • #66
              Originally posted by 3WE View Post
              ...fudge some numbers and show me where [inaccuracies will cause you to...] run off a 8000 Ft runway with 80 knot or 20 second rolls...
              Originally posted by Gabriel
              Blah, Blah, Blah, inaccuracies, blah, blah, blah.
              Ok, I'm Joe Patroni, clinching my cigar (or Boeing Bobby on a bad day).

              I wheel onto the runway at 10 knots, firewall the throttles, think about the hostie I hooked up with last night and THEN start my stop watch 10 seconds later. I'm going 50 knots and have used ~590 feet of runway.

              Suddenly, my copilot Evan makes the first mistake he's ever made in his life and relaxes his toes on the brakes while simultaneously pulling the circuit breaker for the brake-on warning light...and my rear end (Ok, I can't be Bobby) doesn't sense it.

              20 seconds later, we're only going 79 knots...that's not good! I have used an additional ~3,020 ft of runway for 3,610 total. I'm on a typical 8,000 ft runway, that leaves ~4,400 feet to slow from 80 back to zero. (Or 2,200 if I'm on a shorter runway).

              Yeah, all of this assumes a constant acceleration (which is of course flawed, please feel free to do some higher powered math if you see the need)...but looks like a fairly robust system to me- can you come up with a scenario that puts us in the approach lights?

              I do acknowledge that this will not_detect the problem if Evan puts on the brakes AT 80 knots (which of course will never happen since I won't tell Evan how it could happen with a single specific answer- even though I know of actual cases of lost acceleration AND crashes past 80, but before V1).

              Anyway- since we've gone all reasonable and all, I kinda think Bobby's 20 second/80 knots rule of thumb is pretty darn robust and (along with gluteal accelerometers) will catch an awful lot of cases.

              Yeah, it won't catch all possible scenarios, but I still give it to Bobby that a false TOPMS right around V1 (like any other major warning right around V1) will occasionally trip up idiot pilots and cause them to follow improper procedure...so maybe it all equals out.

              PS: Pure speculation here, but since Betty is already giving taxi updates, maybe this is simply gonna happen regardless of what we (and that's everyone) thinks...just cuz the I-phone app does seem pretty damn simple.
              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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              • #67
                Originally posted by Gabriel View Post
                Maybe I wasn't clear. I am not mad at BB due to difference in technical issues.

                I am mad with his attitude...
                Why are you mad at all? This is supposed to be free entertainment. Then "we" have the matter of you opening your post with a "fuck you", which, I guess, is supposed to be an example of a "good" attitude...

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                • #68
                  Originally posted by 3WE View Post
                  ...
                  What about these scenarios?

                  a) You do get to 80 kts in 20 seconds, except that it was a rolling take-off that started when you were already at 20 knots, so in fact you accelerated only 60 knots in 20 seconds. If the expected acceleration was really 20 kts in 20 sec, that is 75% of the expected acceleration, or about twice the runway run to any speed and, if the reduced acceleration is due to a real weight that is higher than the one used for the take-off calculation, that means that when you reach to Vr (in twice the expected runway) and rotate, the plane will not lift off and keep consuming even more runway, quite a bit more runway.

                  b) You do get to 80 kts in 20 seconds, and the expected acceleration was indeed 4 kts per second. Life is good. Except that you started with a 25 kts headwind, so in fact the ASI only increased 55 kts in 20 seconds. That's more the double of the expected runway at any speed (probably the back-end accelerometer will be telling something, whether the pilot realizes it and reads the clue or not is a different history, many times they didn't). As in the previous example, if that difference is caused by a heavier real weight compared to the one used for the calculation, not only you will reach Vr more than twice down the runway, but also you will be nowhere near lifting off at that point.

                  c) Let's make it canonical: Brakes on, take-off thrust set, wait until it stabilizes, release brakes and simultaneously start the stopwatch. The acceleration will be the nominal one since second zero. The PM calls "80" and I, instead of looking at the ASI to say crosscheck, look at the stopwatch exactly at the same time of the "80" call. 23 seconds. Damn. Ok, no problem. Throttles back, easy abort, I have plenty of runway ahead, I barely need to brake at all to make a comfortable slow speed turn in the next intersection. Let's check all the parameters, let's redu all the take-off computation... Ok, let go take-off again. "80" - "24". Damn!!!. Except that for this take off we are quite heavy (more mass), we are high and hot in La Paz (13500 ft, that's elevation, not runway length, so the engine thrust will be lower than normal). So we will have a quite slower acceleration than in our typical take-off. Not only that: The REAL acceleration will be quite lower. The INDICATED acceleration (as seen in the ASI) will be even lower because the IAS will be lower than the TAS due to the high and hot conditions, so we will need to be going say 100 kts TAS to read 80 kts. So 24 seconds to 80 knots is the expected acceleration. Sure, that procedure is safe. Instead of not aborting when needed (like in the previous examples), you are aborting when not needed, and at a slow speed. But it is pretty stupid too.

                  What you (and BB) are proposing, is akin to saying "oh, V1 in this plane is typically about 140, so let's stop computing it and let's just use 140".

                  --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                  --- Defend what you say with arguments, not by imposing your credentials ---

                  Comment


                  • #69
                    Originally posted by ATLcrew View Post
                    Why are you mad at all?
                    I think I explained it already. If any doubt, read my new signature.

                    This is supposed to be free entertainment.
                    Well, I hoped that this place could be something a little more than just free entertainment. A place where we could also discuss about a subject we love, exchange opinions, and perhaps, learn something in the process. Maybe I was expecting too much.

                    Then "we" have the matter of you opening your post with a "fuck you", which, I guess, is supposed to be an example of a "good" attitude...
                    No, it was not. I am a human too. I make mistakes too. And... I was really mad because in a previous thread BB, who again was wrong with what he was saying, defended his point and attacked mine not by discussing the subject but again but by throwing all his credentials, certifications and experience at me and asking me if I had any of that (that is, questioning whether my credentials are good enough to even open my mouth in the subject). Then I asked him, well, exactly what my signature says.

                    And here we are again, and again he is wrong but he feels he has the "right" to be right and that I am noone to judge his point because I am a small plane pilot with many hours of MSFS how has no fucking idea of what I am saying (so, not that being second is any better, but it seems that I was not the only one or the first one to use this verb here).

                    Combine that with the fact that I was not (and still am not) in a good moment and mood due to unrelated personal issues.
                    And that, as I said, I am an imperfect human, with finite amounts of patience, different moods, and times when I get angry.

                    So I said fuck you. And I actually think that BB reacted to that more maturely than I did.

                    Now, if you asked me, I prefer that you say fuck you to me rather than disdaining me because you are the oh so mighty pilot and I am a little ant that has no fucking idea of what I am talking which automatically means that anything that I say WILL hold NO merit period. Even when I am right and you are wrong.

                    Look, I can be wrong. I have been and will be wrong many times. And yes, you can say I am stubborn maybe, because when I am convinced of something, and I defend it with arguments, saying "you are wrong, and believe me, because I am officially an expert" will not convince me. You need to use arguments to show me that I am wrong and why, and to explain how is right and why.

                    Is that so complicated? Is there any inferiority complex in the experts that they need to impose their credentials instead of the arguments?
                    I do have my credentials too. Whenever you pilots input the data and get the vee speeds and take-off configuration, you are using tables (in paper or software) made by engineers, not pilots. But I would feel very very bad with myself if I used the credentials for anything else than saying "hey, this are my credentials, you may be interested in what I have to say" (and, even then, with reservations: I believe that a total outsider may have something interesting to say too), but not to defend my point. And that's why I want. And I expect the same from others.

                    But, again, maybe I am expecting too much.

                    --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
                    --- Defend what you say with arguments, not by imposing your credentials ---

                    Comment


                    • #70
                      Originally posted by Gabriel View Post
                      ...What you (and BB) are proposing, is akin to saying "oh, V1 in this plane is typically about 140, so let's stop computing it and let's just use 140"...
                      Actually, I am a slow, but hands-on learner but still do not necessarily agree with you.

                      Shortly after my post, it hit me...the problem is with the 20 knots head start, I can hit 80 in 20 seconds with a possibly real acceleration issue and continue my takeoff or worse my not_takeoff.

                      That being said, I still think you are being overly pedantic that EVERY takeoff needs a calculated seconds to 80. Yeah, sure, I get it that it will vary, but I'll challenge you with this question- will it vary THAT MUCH...I'm saying that Bobby's 20 second check, is sooooo early in the takeoff run that do you really need to have the exact time?

                      In fact, I'll up it one (and these comments are very important)...to hell with Evan-black-and-white thinking....If you miss the stopwatch by a few seconds, but still hit 80 somewhere around 20 seconds [God forbid the pilots improvise and check at 17 seconds since they knew they did a Southwest Airlines power-first-align-second takeoff.] + the glutae feel fine and everything looks and sounds as it always does...

                      (and figure in the risk of later problems vs. false alarms vs. the eyes and buttocks...c'mon, we're getting REALLY damn safe here)

                      Yeah, maybe I'll think about your deal if it's truly a need-all-the-runway affair, but still...

                      Final parting shot: What if we go back to all of your near-misses and apply Boeing Bobbie's 80 knot check (with 3BS common sense adjustment, and old fashioned SA)...what would happen?

                      Seriously...Air Florida...it feels funny AND we fail the 20 sec rule...yeah...abort.

                      We miss the hitting 80 knots by a couple of seconds, but I'm situationally aware and everything looks great and maybe we were sloppy with the stop watch...seems safe to me.

                      I'm dead tired and not situationally aware and we don't make it in 20 seconds...Ok, this could go either way, but at only 80 knots, I'm going to have guarded optimism that we wake up, assess the situation and have a great opportunity to stop or go as appropriate.

                      As for dead tired and not situationally aware on a short-super-critical takeoff, yeah, that might be a bad combo, bring on Evan and his regulations.

                      Here's the scary part- the more I combine Bobby's rule with a little SA and common sense, the better it gets. It's the "I have no real clue-it feels funny, but maybe not that bad" scenario that bugs me and his method solves the "I have no real clue" aspect. Give me a clue + everything else looks great and you have really eliminated a ton of potential issues.
                      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                      • #71
                        Originally posted by 3WE View Post
                        Anyway- since we've gone all reasonable and all, I kinda think Bobby's 20 second/80 knots rule of thumb is pretty darn robust and (along with gluteal accelerometers) will catch an awful lot of cases.
                        Originally posted by ATSB
                        … it is imperative that the aviation industry continues to explore solutions to firstly minimise the opportunities for take-off performance parameter errors from occurring and secondly, maximise the chance that any errors that do occur are detected and/or do not lead to negative consequences.
                        Here's how aviation safety is supposed to work: you take a "pretty darn robust" practice that has nevertheless repeatedly failed, quite nearly leading to "negative consequences", and you augment that practice with a level of redundancy, in this case a TOPMS. Now you have "maximized the chance that any errors that do occur will be detected" before the aforementioned negative consequences rear their ugly head. Then, you run it all past pilots to see if any new dangers are created by the redundancy and if so, you weigh the risks and benefits. Finally, you train pilots to be aware of the redundancy and how to react to it.

                        So, we have one veteran pilot here that I'm aware of, rather set in his ways and with an apparently infallible gluteal accelerometer and one eye fixed faithfully on the chronometer making him immune to the errors that prompted the ATSB to publish the above recommendation. Let him please tell us what new dangers are introduced by TOPMS that could possibly outweigh the benefits...

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                        • #72
                          Originally posted by Evan View Post
                          ...So, we have one veteran pilot here that I'm aware of, rather set in his ways and with an apparently infallible gluteal accelerometer and one eye fixed faithfully on the chronometer making him immune to the errors that prompted the ATSB to publish the above recommendation. Let him please tell us what new dangers are introduced by TOPMS hat could possibly outweigh the benefits...
                          1. He did. You, apparently, were not listening.

                          2. There's a logic error in your first sentence of your full post. We do not have any evidence to say that the use of the 80-knot rule + good ole situational awareness + common sense has failed. You are falsely extrapolating.

                          2a. There is evidence that "I think it looks OK" has failed...and maybe you and Gabe are not out of line to address that here...maybe everyone should start doing Bobby's 20-second check + SA + a shred of common sense?

                          3. I gotta admit- I like computer TOPMS since it seems so harmless and my redundant statement that it's just an I-phone app away from being available. And Gabe keeps pushing his gentle trend-bug approach (hopefully with my color coding)...But I'll also admit that just because you can program it in an I-phone doesn't mean it should be programmed into the various systems and displays of aircraft...
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

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                          • #73
                            Originally posted by 3WE View Post
                            1. He did. You, apparently, were not listening.

                            2. There's a logic error in your first sentence of your full post. We do not have any evidence to say that the use of the 80-knot rule + good ole situational awareness + common sense has failed. You are falsely extrapolating.

                            2a. There is evidence that "I think it looks OK" has failed...and maybe you and Gabe are not out of line to address that here...maybe everyone should start doing Bobby's 20-second check + SA + a shred of common sense?

                            3. I gotta admit- I like computer TOPMS since it seems so harmless and my redundant statement that it's just an I-phone app away from being available. And Gabe keeps pushing his gentle trend-bug approach (hopefully with my color coding)...But I'll also admit that just because you can program it in an I-phone doesn't mean it should be programmed into the various systems and displays of aircraft...
                            1. Just re-read the entire thread. No sign of that.

                            2. If a "rule-of-thumb' is skipped over, forgotten, never learned or ignored on any given flight, it has failed. And if there is no redundancy to back up that human failure, say hello to negative consequences.

                            3. Still waiting for anyone to make a valid argument against the safety of TOPMS...

                            Comment


                            • #74
                              Originally posted by Evan View Post
                              ...Just re-read the entire thread. No sign of that...
                              I'll help you with some non-black and white thinking:

                              1. This is not the only thread on this subject.

                              2. Gabe's got a burr up his butt over the topic, and that's not a personal attack against him- breaking far-end light bulbs is a tad dangerous.

                              3. Based on #2, he starts threads from time to time when incidents occur, instead of returning to an original thread.
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                              Comment


                              • #75
                                Originally posted by Gabriel View Post
                                I think I explained it already. If any doubt, read my new signature.


                                Well, I hoped that this place could be something a little more than just free entertainment. A place where we could also discuss about a subject we love, exchange opinions, and perhaps, learn something in the process. Maybe I was expecting too much.


                                No, it was not. I am a human too. I make mistakes too. And... I was really mad because in a previous thread BB, who again was wrong with what he was saying, defended his point and attacked mine not by discussing the subject but again but by throwing all his credentials, certifications and experience at me and asking me if I had any of that (that is, questioning whether my credentials are good enough to even open my mouth in the subject). Then I asked him, well, exactly what my signature says.

                                And here we are again, and again he is wrong but he feels he has the "right" to be right and that I am noone to judge his point because I am a small plane pilot with many hours of MSFS how has no fucking idea of what I am saying (so, not that being second is any better, but it seems that I was not the only one or the first one to use this verb here).

                                Combine that with the fact that I was not (and still am not) in a good moment and mood due to unrelated personal issues.
                                And that, as I said, I am an imperfect human, with finite amounts of patience, different moods, and times when I get angry.

                                So I said fuck you. And I actually think that BB reacted to that more maturely than I did.

                                Now, if you asked me, I prefer that you say fuck you to me rather than disdaining me because you are the oh so mighty pilot and I am a little ant that has no fucking idea of what I am talking which automatically means that anything that I say WILL hold NO merit period. Even when I am right and you are wrong.

                                Look, I can be wrong. I have been and will be wrong many times. And yes, you can say I am stubborn maybe, because when I am convinced of something, and I defend it with arguments, saying "you are wrong, and believe me, because I am officially an expert" will not convince me. You need to use arguments to show me that I am wrong and why, and to explain how is right and why.

                                Is that so complicated? Is there any inferiority complex in the experts that they need to impose their credentials instead of the arguments?
                                I do have my credentials too. Whenever you pilots input the data and get the vee speeds and take-off configuration, you are using tables (in paper or software) made by engineers, not pilots. But I would feel very very bad with myself if I used the credentials for anything else than saying "hey, this are my credentials, you may be interested in what I have to say" (and, even then, with reservations: I believe that a total outsider may have something interesting to say too), but not to defend my point. And that's why I want. And I expect the same from others.

                                But, again, maybe I am expecting too much.
                                I guess I'm just not sure about taking personally and wasting precious nerve cells on a subject with which one ultimately has nothing to do. By your own admission, you haven't flown anything in nearly two decades, so this is an entirely academic subject to you. It bears mentioning, too, that, for all you know, neither has BB flown anything in 18 years (or more). In fact, you have no less evidence that he is 15 and living in his Grandma's trailer than you do that he is a widebody Captain. So, getting all wrapped around the axle about him shoving his "credentials" in your face also seems pointless. Nor is it of any great importance which one of you is "right" or "wrong". Nothing either one of you (or anyone else) says on this forum makes any real difference, so perhaps taking 3WE's advice and chilling a little might be a good idea. Especially when, also by your own admission, you have some personal issues to handle.

                                Then again, your nerve cells are yours to waste, too...

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