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V1 is or is not a LOCATION on the runway...

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  • #46
    BB, you're not getting the idea. It's not markers for every type. Its not at V1. Just one marker, all types. Think of it being like the old rule of thumb, 80 kts at the fat markers. Instead though you have an actual speed at which the aircraft, when accelerating correctly, will pass that marker. Or your 100kts after 30 seconds, except you would know exactly how fast you should be at 30 seconds, or how long to

    You have 15 years on type and know exactly what it should feel like. How about someone who flies multiple variants, different weights and thrusts, and with a far greater range of available assumed temperatures than the 747? Pilot flies the A330 mostly and then has limited time on the A340? How is he supposed to know?

    The point is that it would not be difficult to set up a takeoff config style alarm for insufficient acceleration, and there have been more than enough accidents to highlight that it would be of benefit. SQ have done it, EK have done it... And they're the ones with major damage. Plenty of other narrow escapes... And in all of those cases pilots did not notice the low acceleration until too late.

    As for your rigid interpretation of v1... You can say its v1 all you like, and operationally we treat it that way. But it's of no value whatsoever if you aren't meeting the performance it is predicated on.

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    • #47
      Come on. Even BB can't tell the difference between a longitudinal acceleration of 0.19g and one of 0.21g, and even if he could he would not know which one is the correct one for a given take-off. And by when you reach the rotation speed of 160kts, with 0.19g you'll be more than 500ft farther down the runway than with 0.21g. If you had an engine failure just after V1, your TOD would likely be more than 1000ft longer.

      Another quiz. Two identical planes (same type, same variation, same engines) are one after the other waiting for take-off. For today's flights, airplane A is somehow heavy and airplane B is somehow light. Aircraft B will accelerate slower and take more seconds to lift off. It will also have a lower climb rate in the initial climb. Both take-off calculations were correctly done, the airplanes performed as expected, and the take-offs were correctly executed by the crew. Possible?

      --- 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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      • #48
        Originally posted by Gabriel View Post
        BB, since you are a very experienced pilot in general, and in particular on the 747, I'd like to hear your opinion on this take-off. Is it normal?

        KLM has been flying out of here for years in the 74. Runway is a bit short but there have never been any problems. It has been a favorite with the photographers as well. Remember that they are usually shooting with a telephoto so the picture is "stacked up" and things look a little closer than they actually are.

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        • #49
          Originally posted by MCM View Post
          The point is that it would not be difficult to set up a takeoff config style alarm for insufficient acceleration, and there have been more than enough accidents to highlight that it would be of benefit. SQ have done it, EK have done it... And they're the ones with major damage. Plenty of other narrow escapes... And in all of those cases pilots did not notice the low acceleration until too late.
          I wonder if it will take a major accident to begin dialogue on this, as AF447 did with the AoA indicator.

          I can see a more futuristic scenario where the a/c communicates with runway edge lights so that they turn amber at the expected V1 position, so if you are rolling short of V1 and you are in the amber zone you abort the takeoff.

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          • #50
            Originally posted by Evan View Post
            I wonder if it will take a major accident to begin dialogue on this, as AF447 did with the AoA indicator.

            I can see a more futuristic scenario where the a/c communicates with runway edge lights so that they turn amber at the expected V1 position, so if you are rolling short of V1 and you are in the amber zone you abort the takeoff.

            I give up! Scotty, beam me up!!!

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            • #51
              Originally posted by Gabriel View Post
              If you had an engine failure just after V1, your ASD would likely be more than 1000ft longer.
              AFTER V1, YOU FLY THE AIRPLANE! PERIOD!!

              And you are looking for STOP MARGIN, not accelerate stop distance.

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              • #52
                Originally posted by BoeingBobby View Post
                AFTER V1, YOU FLY THE AIRPLANE! PERIOD!!
                Correct, sorry. I meant "If you had an engine failure just after V1, your TOD would likely be more than 1000ft longer."

                I'll correct the other post too. Thanks.

                --- 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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                • #53
                  Originally posted by gabriel View Post
                  correct, sorry. I meant "if you had an engine failure just after v1, your tod would likely be more than 1000ft longer."

                  i'll correct the other post too. Thanks.


                  tod?

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                  • #54
                    Originally posted by BoeingBobby View Post
                    tod?
                    "Take-off distance". The distance from brakes release to the point where you get to V2 and 35ft AGL if an engine fails at V1 (in fact at Vef) and you continue the take-off.

                    What I meant is that relativelly small variations in the acceleration that even you would not be able to detect as "too slow for this particular take off" can have measurbale effects on the take off distances, and hence on the ability to complete the take off or stop within the runway limits.

                    --- 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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                    • #55
                      Originally posted by Gabriel View Post
                      "Take-off distance". The distance from brakes release to the point where get to V2 and 35ft AGL if an engine fails at V1 (in fact at Vef) and you continue the take-off.

                      What I meant is that relativelly small variations in the acceleration that even you would not be able to detect as "too slow for this particular take off" can have measurbale effects on the take off distances, and hence on the ability to complete the take off or stop within the runway limits.
                      I am not going to even dignify this one with an answer. What you, Evan, 3WE and couple of other guys are trying to do here is make flying an airliner into rocket science. In the 43 years I have been doing this for a living I have never once had to give Houston a call for a launch window.

                      P.S. In my day TOD stood for either takeoff dry (look that one up) or top of decent.

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                      • #56
                        Originally posted by BoeingBobby View Post
                        Evan, 3WE and couple of other guys are trying to do here is make flying an airliner into rocket science.
                        Hey! 3WE is all about stick and rudder, go with your gut nonsense. Don't drag him into this.

                        But those couple of other guys, such as Airbus, Boeing, Embraer, Bombadier, and yes, even Sukkoi have indeed been trying to turn flying into rocket science since, oh, about the time we were using them to shoot dogs and monkeys into space.

                        I agree with you that it still comes down to human piloting (See: Ho Lee Fuk). As I see it, today it's all about the partnership between pilots and technology: the pilot is in charge and the technology is there to inform the pilot, remind the pilot and take over when piloting is not necessary. Now, doesn't it stand to reason that the technology should inform the pilot when take-off performance is compromised, especially when technology is the one controlling the power setting?

                        How do you feel about configuration warnings? Is that rocket science?

                        Originally posted by BoeingBobby
                        P.S. In my day TOD stood for either takeoff dry (look that one up) or top of decent.
                        Top Of Descent... I think he got you there Gabe.

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                        • #57
                          Originally posted by Evan View Post
                          Top Of Descent... I think he got you there Gabe.
                          No, he didn't

                          TOD vs TODA
                          TOR vs TORA
                          ASD vs ASDA

                          It's the basics of take-off performance claculation.

                          TOD menas Top Of Descent too.

                          --- 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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                          • #58
                            Originally posted by Gabriel View Post
                            TOD menas Top Of Descent too.
                            Great. How many crashes is this going to cause...

                            The investigation revealed that the when captain asked for the take-off-distance, the F/O gave him the top-of-descent altitude, leading the captain to believe he had 35,000 ft of available runway. The investigation attributes his acceptance of this erroneous runway length to to fact that he got 15 minutes of sleep the previous evening.

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                            • #59
                              Vector Victor, Over Oveur, Roger Roger, We have clearance Clarence.

                              --- 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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                              • #60
                                Originally posted by Gabriel View Post
                                Vector Victor, Over Oveur, Roger Roger, We have clearance Clarence.
                                ...and don't all me Shirley.

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