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FAO: Gabe. Relentless Takeoff Pull Up. FOFFIEness.

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  • FAO: Gabe. Relentless Takeoff Pull Up. FOFFIEness.

    Remember my fear of a good, "high-performance" takeoff pull up (From Row 35A where I don't have an ASI nor yoke)?

    Since I discovered that my smartphone GPS works in the airplane mode, I've been monitoring speeds.

    It helps a LOT to NOT_see the speed decay as we point more and more upwards and rocket skyward!

    Interesting observations: Often times as our altitude zooms, our speed creeps (if not downright marches) upward to really fat dumb and happy levels. In fact- I see very little speed stability in flight- except during cruise.

    On a couple of takeoffs, we have slowed a bit (hitting ~140 kts) (as a contrast to the more typical 'ongoing speed up'). Of course, that's ground speed, so the airspeed might have been (ok, VERY LIKELY WAS) quite healthy.

    On my very last flight during latter descent- I saw us hit~120 knots while clean- just before the flaps started out (E-170)- closer to landing we were back around 135-140 kts (again, ground speed and not air speed acknowledged.)

    More often than not, we do not hit final approach speed until fairly short final (yeah, true IMC/ILS is an exception).

    I still say that good attitude and good speed control are more important than AOA...just so long as it's not the ONLY thing you watch, and understand that pulling up hard with the stall warning going off is often a good way to stall
    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

  • #2
    Another piece of hardware that also works with the cellphone in airplane mode is the MEMS sensors (accelerometers, gyros and magnetic field detectors).
    You can download a free PFD app and have a virtual PFD in your hands, with AD (pitch and bank), groundspeed tape, altitude tape, vertical speed and heading.
    You may find the pitch never exceeding 20 deg at least as reassuring as the speed, which is tricky due to the wind to convert GS into TAS and then the density to convert TAS into CAS/IAS.
    You could ever write some code (some of these apps are open source) to add the ground AoA, which would match the real AoA if there is no head/tail wind component.
    You just get the flight path angle as asin(VSI/GS) and subtract it from the pitch angle (using always appropriate units and +/- signs).

    Regarding your observation of an ever-increasing speed until up at cruise, of course (almost).
    Let's review a typical Jet climb schedule (provided that there are not ATC restrictions).

    Rotate, stabilize the plane for V2+10/V2+20 (which will take a pitch of 15 to 20 deg), climb to 1500/3000ft, reduce thrust to CLB, reduce climb to accelerate, flaps retraction, keep accelerating until 250 kts, then adjust pitch to keep 250 until 10000ft, then reduce climb again to accelerate to the cruise climb speed (typically 270/290kts) and then adjust pitch to keep that speed, then at the Mach transition altitude adjust pitch to keep the climb Mach (IAS will go down), when you reach the climb altitude level off and let the plane accelerate until cruise Mach, then reduce thrust to keep cruise Mach.

    We see 5 zones of "constant" speed:
    1- V+10/+20 until starting the flaps retraction.
    2- 250 kts until 10000ft
    3- Cruise climb speed
    4- Cruise climb Mach
    5- Cruise Mach.

    Even assuming zero wind, the zone 5 is the only one where the groundspeed will be really constant (provided there are no changes in OAT).
    In zones 1, 2 and 3, IAS is constant in a scenario of increasing altitude, which means decreasing density, which means increasing TAS/GS (for constant IAS).
    Zone 4 is tricky. The IAS will go down as you climb at constant Mach. But Mach is proportional to TAS and to the SQRT of OAT. So whether the TAS/GS increases, remains constant, or reduces while climbing at constant Mach will depend on how altitude changes along the climb. Typically it will reduce or tend to remain constant (the IAS model predicts a sharp transition form a temperature diminishing with altitude to constant temperature as you keep climbing past that transition altitude which happens to be in the same region that the typical IAS/Mach transition altitudes).

    So your observation of an ever-increasing GS from brakes release until cruise is not surprising, except perhaps for a "pause" during the last portion of the climb (Mach climb).

    Regarding the speed increase during approach from 120kts to 140kts, it is very possible that there was a somehow strong headwind. Wind is slower near the surface of the Earth, so the 120 kts GS could be for example 160 KTS TAS with a 40 kts headwind while the 140kts in short final could be the same 160 KTS with a 20 kts headwind.

    There is a very good reason why pilots don't use GPS speed (or other form of ground-referenced speed, or even TAS) for the "aviate" part, although it is obviously necessary for the "navigate" part.

    --- 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


    • #3
      Originally posted by Gabriel View Post
      ...Regarding your observation of an ever-increasing speed until up at cruise, of course (almost)...
      My point is that it's often pretty rapid. 140 at lift off, then 180 within a minute and 200 a minute after that.

      And it's pretty clear when you are in a light-traffic environment- they let the speed build- whereas in higher traffic environments, they probably have to keep things slower.

      Also, the speed varies a lot as the plane reaches numerous level off's and then climbs.

      In other words, it's pointless to sit down and analyze as you did with increasing wind velocities, thinning air, changing speed targets...

      Sure, they monitor airspeed and control it and deal with speed restrictions (and probably also enjoy autothrottles), but I do not see the speed being "locked down" very much. Instead, it's very often varying.

      ...the plane is powerful and picks up speed quickly unless they really are hauling back on the stick (those two times I've seen the ground speed decline a bit).

      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

      Comment


      • #4
        Originally posted by 3WE View Post
        My point is that it's often pretty rapid. 140 at lift off, then 180 within a minute and 200 a minute after that.
        consider that the single largest drag device, the landing gear, is retracted almost immediately after t/o and given that thrust is usually constant at that stage of flight, the increase in speed once the gear is up is dramatic.

        Comment


        • #5
          Originally posted by 3WE View Post
          Remember my fear of a good, "high-performance" takeoff pull up (From Row 35A where I don't have an ASI nor yoke)?

          Since I discovered that my smartphone GPS works in the airplane mode, I've been monitoring speeds.

          It helps a LOT to NOT_see the speed decay as we point more and more upwards and rocket skyward!.........................
          Try flying out of John Wayne Airport sometime - the aircraft blasts off and then cut power - one gets that roller coaster feeling.
          http://www.ocregister.com/articles/j...e-airport.html

          Comment


          • #6
            Originally posted by TeeVee View Post
            consider that the single largest drag device, the landing gear, is retracted almost immediately after t/o and given that thrust is usually constant at that stage of flight, the increase in speed once the gear is up is dramatic.
            ummm....yes and no.

            If ATC asks the pilots to keep it slow, OR there's a big hill ahead, (or a few other possibilities) it's possible for the airspeed to stay right where it is (no thrust reduction necessary).

            Some rule of thumb that Gabriel's infatuated with- pitch controls altitude or something like that.
            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

            Comment


            • #7
              Originally posted by TeeVee View Post
              consider that the single largest drag device, the landing gear, is retracted almost immediately after t/o and given that thrust is usually constant at that stage of flight, the increase in speed once the gear is up is dramatic.
              The energy equation is Power = speed rate + veetical speed + loss (due to drag).
              At that stage (initial and second segment climb), most of the power goes, by large, to increase the airplane's potential energy (i.e. altitude), especially once the target climb speed is achieved (V2+10 to V2+20). Once the speed is stabilized, all the excess power (that is, engine power - drag loss) goes to vertical speed. Retracting the gear, thus, increases the vertical speed rather than the speed. And, again, increasing the plane's energy takes most of the engine power, so retracting the gear, while it makes a difference, it doesn't change the situation dramatically.

              For consideration:
              - The plane must be able to climb out with only one engine (in twins), so a single engine must provide for all the energy lost in drag and then have a surplus for climb. 100% of the second engine's power goes to climb.
              - Making a plane climb some 3500 fpm takes much, much more energy (power) than keeping it flying straight and level at say 180 kts. This is the same than saying that most of the engine power goes to climb rather than to drag.

              --- 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


              • #8
                Originally posted by Gabriel View Post
                The energy equation is Power = speed rate + veetical speed + loss (due to drag)....blah blah blah...it doesn't change the situation dramatically...


                No, not this either.

                At the risk of putting words in Tee Vee's mouth (apologies) I heard him sort of say, "the plane can't help but accelerate due to the loss of the drag from the gear".

                I don't agree with that.

                However, I do think he nailed it that on a largely unrestricted takeoff, the guys might just let the speed build (with gear retraction contributing to the prompt speed increases I've observed.)

                Post Script:

                I know a trimmed airplane will tend to keep it's speed, but I'm getting the feeling the crews are selecting a slightly fat dumb and happy attitude, and also suspect that a true maximum performance climb might indeed be uncomfortable. (Let the professionals laugh at my assumptions and ass-hat parlour talk).

                I also think you (and I) may be suffering from light plane mentality, where you stabilize several minutes at a solid climb to get a healthy altitude buffer whereas the airliner guys arrive there before you can count to five...
                Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                Comment


                • #9
                  Originally posted by 3WE View Post
                  However, I do think he nailed it that on a largely unrestricted takeoff, the guys might just let the speed build (with gear retraction contributing to the prompt speed increases I've observed.)

                  I know a trimmed airplane will tend to keep it's speed, but I'm getting the feeling the crews are selecting a slightly fat dumb and happy attitude, and also suspect that a true maximum performance climb might indeed be uncomfortable. (Let the professionals laugh at my assumptions and ass-hat parlour talk).

                  I also think you (and I) may be suffering from light plane mentality, where you stabilize several minutes at a solid climb to get a healthy altitude buffer whereas the airliner guys arrive there before you can count to five...
                  3WE, the big-iron guys are much less liberal than us regarding the take-off and climb profile.
                  They will rotate at a prescribed pitch rate until reaching 15 degrees and then finely tune the pitch to keep the speed in a prscribed range (like 10 to 20 kts past V2), and then keep controlling the pitch to keep in that range (as drag changes with the gear retraction sequence, of if there are turns) all the way up to the PREDEFINED (partial) level-off altitude, where they will reduce climb, reduce thrust from TO to CLB, and let the plane accelerate as they retract flaps and slats following a PREDEFINED flaps retraction schedule, and then adjust the pitch again to keep and maintain the cruise climb speed.

                  There is no "oh, trafic is low today, let's let it speed up soon and retract the flaps early".

                  a true maximum performance climb might indeed be uncomfortable.
                  Please explain what exactly you mean with that. Whether it is a max performance take-off or nor has more to do with positioning to the last inch of the runway, using the max permitted TOGA, and a given flaps setting, than with what you do after lift off. Whether you use the excess thrust to accelerate or gain altitude doesn't change the "feeling" of being pushed back. You can't tell acceleration from inclination, which is the basis of full motion flight sims and the source of disorientation in accidents like Tatarstan (and in many take-offs directly into IMC).

                  --- 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


                  • #10
                    Originally posted by Gabriel View Post
                    ...There is no "oh, trafic is low today, let's let it speed up soon and retract the flaps early"...
                    My recent experience monitoring speed does not support this and that's my point.

                    And don't get sucked into too much semantics. I'm sure that the crew is very much "in control" and aware of speeds and restrictions and altitudes and that we aren't wantonly retracting flaps sooner than necessary for safety...

                    At a big hub- every departure is essentially saturated. Planes spaced out every six miles (or whatever) on "all four" departures. Planes are kept slower. ATC will give speed restrictions and planes will follow published speed restrictions on the DP.

                    At a po-dunk flyover type place, the plane head of you did a 180, the plane ahead of him went right 45 degrees and for you to go left 45 degrees towards your destination- it's wide open- ATC may lift speed restrictions (yeah you still obey ultimate speed limits like 200 kts, etc, BUT they can get to crusie climb a lot faster than what you are thinking.)

                    (Don't forget that 1000 or 2000 feet before reaching an assigned altitude, pilots will reduce the rate of climb so that when they do level off, everyone's stomach isn't up in the overhead bins!...they fly really powerful planes with bad ass climb rates (and the ability to build speed quickly.))

                    Repeating- from what I have seen with my own eyes: when traffic is light, I kick, scream and yell that my smart phone indicates 180 kts within two minutes and 200 kts two minutes after that and when the plane reaches initial altitudes, the power stays higher. When traffic is heavy (going out of ATL or PHL), 150 to 180 for a full 5 minutes and much heavier power reductions for initial altitudes.

                    I've seen it with my own eyes (just like Boeing Bobby and the center fuel tank). Fire up your smart phone, download a speed app, check some different scenarios and stop arguing (from your keyboard) with what I am seeing first hand!

                    Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                    Comment


                    • #11
                      FAO: ATL Crew, Snyder, V-Nav.

                      Is there upwards of 50 kts of variability in your climb out speeds below 10,000 feet that are somewhat associated with the level of traffic?
                      Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                      Comment


                      • #12
                        caveat: i'm not an aero expert, pilot or anything else but me. having said that, your statement that retracting the gear doesn't increase speed it increases vertical speed, is, dare i say, misleading. in anything that flies other than a rocket, or perhaps an F-15 that can climb ballistic for a very long time, vertical speed in a steady aTTitude climb is necessarily connected to the forward velocity of the plane. assuming the following completely HYPOTHETICAL scenario: climb angle is set at 10 degrees; initial forward velocity is 180 kts; vertical speed after wheel leave the ground is 1000 fpm; gear retracted and forward velocity increases to 220 kts. vertical speed MUST increase.

                        Comment


                        • #13
                          Originally posted by TeeVee View Post
                          ...climb angle is set at 10 degrees; initial forward velocity is 180 kts; vertical speed after wheel leave the ground is 1000 fpm; gear retracted and forward velocity increases to 220 kts. vertical speed MUST increase.
                          Your comment is correct, BUT...

                          Gabriel's point is that the pilots tend more to select a speed such as a maximum rate of climb speed or a maximum angle of climb speed (or perhaps a good healthy speed where they have good rudder control if an engine fails)....(In all honesty all of these speeds are within maybe 20 kts of each other so no big deal...

                          BUT the pilots often select a target speed at which they want to fly...

                          As the gear comes up, the drag goes away and yeah, the plane will "want" to speed up, BUT the pilots (having cowboy, seat of the pants airmanship skills) know that the plane will "want" to speed up and will pull up even more so that the "loss of drag" goes into "more climb" instead of "more speed".

                          Nobody's climbing ballistically and if the pilot wants to nail an airspeed, he can do that with his hands (unless he's one of those over-proceduralized Evan robots). An important skill is for a pilot to maintain a single precise airspeed while power is run from "full up to full off" and gear goes up and down and flaps go up and down. (That's an over simplification, BUT is a skill I'd hope that any pilot could nail and routinely exercises to maintain speed through configuration changes). (A skill that might have helped Cogan in the Q-400!!!!!).

                          Gabe and my argument is a bit subtle here. You are continuing to push the theme that "the plane can't help but speed up"...This is pretty wrong and pilots routinely prevent this.

                          All that being said, I'm trying to tell Gabe that, from my observations, there are some times (at less busy airports) where pilots speed up more quickly and fly faster- and that's not because they retract the gear, but because they make a deliberate effort to let the plane speed up (or do not make a deliberate effort to slow it down).

                          Their control of pitch can easily be used to maintain a desired airspeed. Their control of power can also easily be used to maintain altitude (or vertical speed).

                          You are correct that if the pilot chooses to nail 10 degrees nose up, and not vary from that, and retracts the gear, he will speed up. Gabe is correct that if the pilot chooses to nail his chosen optimum speed, and not vary from that and retracts the gear, he will instinctively pull up to 12 degrees (or whatever) to keep the speed 'exactly' the same and get more climb.

                          (I'm sure Evan can cite a cryptic acronym for a fancy autopilot mode that maintains airspeed with pitch too with lots of if-then caveats like the FLCH mode where the autothrottles are shut off without you knowing about it).
                          Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                          Comment


                          • #14
                            Originally posted by 3WE View Post
                            (I'm sure Evan can cite a cryptic acronym for a fancy autopilot mode that maintains airspeed with elevator with lots of if-then caveats like the FLCH mode where the autothrottles are parked at idle until the selected level-off altitude or the GS capture or the armed mode transition without you knowing about it if you haven't read the instruction manual) But of course, that's FLCH in open descent, not climb. And never on final...
                            3WE, you provided the fancy acronym for that, but FIXD.

                            But what are you guys talking about here? It's alll mostly done on VNAV above 400ft. How many pilots are hand-flying a climb profile these days?

                            Comment


                            • #15
                              Originally posted by TeeVee View Post
                              vertical speed in a steady aTTitude climb is necessarily connected to the forward velocity of the plane. assuming the following completely HYPOTHETICAL scenario: climb angle is set at 10 degrees; initial forward velocity is 180 kts; vertical speed after wheel leave the ground is 1000 fpm; gear retracted and forward velocity increases to 220 kts. vertical speed MUST increase.
                              What you say is geometrically correct but it is not how airplanes are flown.
                              If the pilot wants to hold 180kts (and in climb pilots almost ALWAYS want to hold a given speed, not a given attitude or a given vertical speed), instead of doing what you say after retracting the gear he pitches up from a climb angle of 10 to a climb angle of 12 degrees, the speed remains at 180, and the vertical speed increases even more than in your scenario.

                              3WE, Evan,
                              Gear retraction almost ALWAYS happens very early during the climb, just after lift off, well below, when neither the speed, not the attitude, nor the vertical speed have stabilized yet. The plane is still pitching up, accelerating and increasing the climb speed, so the effect of the gear retraction is "masked" by all that variation. The only difference (if the gear is retracted vs if it is not) is if the plane will finally stabilize at 180kts, 15deg and 3000fpm or 180kts, 17 deg and 3500 fpm (invented numbers, just to forward the idea). Engaging the AP will come afterwards, when the plane is stabilized in the climb.

                              --- 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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