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Air speed Low!! call out is nagging me

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    #1

    Air speed Low!! call out is nagging me

    On the PMDG 373, in MSFS, if say I am doing 280 kts at level flight say at 5000 ft (I know >250 kts) but well above the stall limit, and I do a sudden climb, the AOA indicator goes full lest, the yellow and red speed tapes jump up and catch me and I get an "AIR SPEED LOW" warning. How is that when I am so far above the stall speed?
    Paul Gugliotta
    13900K CPU - 4090 GPU
    Tags: None
    #2
    The problem is that you aren't far above the stall speed. Stall speed is not solely based on airspeed, but G-loading is also a big factor. It is possible to stall the aircraft at any speed, including at red-line speed. If you are flying straight and level at a constant airspeed and suddenly pull back on the control column, you are going to increase the G-loading on the aircraft's wings. Depending on how much you pull, you may increase the G-loading significantly. I forget the exact numbers, but if you pull hard enough to create double the G-loading on the aircraft (2 Gs), your stall speed will increase by approximately 40%. If you double it again (4 Gs), your stall speed will now be 2 times what it was in straight and level unaccelerated flight.
    Tim Lincoln
    My YouTube Channel

    Comment

      #3
      Solution: Don't do a sudden climb. I'm not sure why you're climbing so rapidly anyway, but the passengers certainly wouldn't like that.
      Captain Kevin

      Kevin Yang
      • 👍 1

      Comment

        #4
        Congrats. You’ve figured out something about aerodynamics.

        Stall “speed” isn’t how wings work. Wings stall at the critical angle of attack, regardless of speed.
        Ryan Argue

        Comment

          #5
          Originally posted by FishermanIvan View Post
          Congrats. You’ve figured out something about aerodynamics.

          Stall “speed” isn’t how wings work. Wings stall at the critical angle of attack, regardless of speed.
          AKA angle of attack....
          Bob Cardone

          Comment

            #6
            An aircraft can be stalled at any airspeed, in any attitude, at any power setting. That's the opening sentence of any basic aerobatics, spin, or UPRT lesson I've ever taught. We talk about the "why" of that statement, then go out and demonstrate it.
            ​​​​​​
            ​​
            Andrew Crowley

            Comment

            • FlyingBear01
              #6.1
              FlyingBear01 commented
              18Sep2023, 18:29
              Editing a comment
              Didn't you point out some time back that the amber low speed band moving with load factor is a PMDG bug? Doesn't that make the OP's air speed low call out a bug as well, since that call out is supposed to be tied to the amber low speed band, not the red and black low speed band? Or should we get that call out when the air speed readout turns red even if it did not turn amber first?
            • Stearmandriver
              #6.2
              Stearmandriver commented
              18Sep2023, 22:20
              Editing a comment
              The moving amber band is a bug. I don't actually know if the Airspeed Low call is tied to the amber band itself, or separately tied to a dynamically calculated buffer above the current calculated stall stall speed for load factor (top of the red band), so it's hard to say whether it should be sounding here. Plus, it depends on the speed with which the wing is loaded - in a fast-onset situation, you'll never get the Airspeed Low warning because you'll go right into shaker. This can happen at high altitude, in moderate turb or mountain wave for instance, when you experience a significant temperature change (because of compressibility effects at high altitude / mach number.).
            #7
            Originally posted by bobsk8 View Post

            AKA angle of attack....
            That's.... what I said lol.
            Ryan Argue

            Comment

              #8
              I get what you all say. But I’m no rookie here. I have 1000s of landings. And I am not at level flight and trying to pull a loop. I make subtle changes to climb (less than 1000 fpm) and the AOA goes to poop immediately. I just think it is a bit too reactive and should allow me a second to adjust my climb before yelling at me. No biggie. I know all the flight dynamics and how to solve it. Just think it is too quick to react.
              Paul Gugliotta
              13900K CPU - 4090 GPU

              Comment

              • Stearmandriver
                #8.1
                Stearmandriver commented
                20Sep2023, 08:22
                Editing a comment
                It's not the rate of climb or the pitch attitude that loads the wing. It's the rate of pitch change. Pop the yoke back suddenly, even briefly, and you can certainly exceed the critical angle of attack. This is in fact how you do a snap roll.

                In reality, you're feeling the g and it's a great measure of how hard you're pulling. We don't get that in the sim, and with the variety of controls we use... you can, especially at high altitude where this is much more sensitive, easily pull too hard.
              #9
              Originally posted by Paulyg123 View Post
              I get what you all say. But I’m no rookie here. I have 1000s of landings. And I am not at level flight and trying to pull a loop. I make subtle changes to climb (less than 1000 fpm) and the AOA goes to poop immediately.
              Okay, but in your initial post, you literally said you did a "sudden climb." Now you're saying the complete opposite by saying you're making "subtle changes to climb." Which is it. It can't be both.
              Captain Kevin

              Kevin Yang

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