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JRBarrett

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About JRBarrett

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  2. I have a dedicated button on my yoke for autopilot disconnect. Pressing it once disconnects the AP, and the warning horn sounds. Pressing the button a second time silences the warning, but the AP remains disconnected. Pressing the “Z” key on the keyboard (twice) should have the same effect if you do not have a dedicated button assigned. One difference between the sim and the real aircraft is that the disconnect bar does not drop down when using the yoke disconnect button. I think it does that in the sim because default P3D/FSX code is being used internally for at least some of the autopilot functions for simplicity. For anyone who cannot get the autopilot to engage at all, be sure that the yaw damper buttons, horizontal stabilizer trim buttons and Mach trim button have been activated before takeoff.
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  6. That should work. If the ground winds are higher than that, the aircraft should probably not be flying in any case! JB
  7. The wind vector can indicate on the ground, but only if the aircraft is not moving. In that case, the displayed arrow will always show a direct headwind, because the aircraft has no way of knowing actual wind direction - it is only sensing pitot pressure higher than static pressure. When the IRU accelerometers detect that the aircraft is in motion, the wind vector should be suppressed if the aircraft is still on the ground. (i.e. weight on wheels is detected). This may indeed be a “bug” of sorts in the real aircraft, in the sense that air data computer speed is normally suppressed below 40 knots. It may depend on the specific software revision level of the FMS. In flight, the wind vector is calculated by the FMS, which receives current true airspeed (TAS) generated by the Air Data Computer (TAS is Indicated Airspeed corrected for pressure altitude and temperature). It calculates ground speed (GS) by measuring the change in aircraft position over time. The magnitude component of the displayed wind vector is the difference between TAS and GS. With a headwind component, TAS will be higher than GS. With a tailwind component, GS will be higher than TAS. The direction component of the wind vector is calculated based on the difference between aircraft heading (which comes from the IRS), and the aircraft’s actual course over the ground (also measured by the IRS or GPS). This same calculation can be done on the wind grid on the back side of an old-fashioned E6-B mechanical flight computer. Beginning flight students learn to do this as part of flight planning for cross county trips. (At least they did when I was going through the private pilot course back in 1988!) When flight planning, the pilot usually knows what course they will be flying between waypoints (heading), and knows expected winds aloft from the forecast. With those two pieces of information, the E6-B can be used to calculate expected ground speed and wind correction angle required to hold the plotted course. Nowadays, all this can be done automatically by flight planning software, but I hope that students are still taught how to do it the “old way”, with charts, plotters and either a mechanical or electronic E6-B). The reverse calculation can be done in flight on the E6-B wind grid based on actual ground speed and actual wind correction angle being used to hold the course - which is what the FMS does in the real aircraft using ADC airspeed and IRS ground speed and drift rate. In the sim, there is no actual IRS or Air Data Computer of course. Current wind speed and direction are available directly from sim connect, as are all the other parameters (TAS, IAS, Mach, GS, position and heading etc.) My suggestion to Hans would be to simply suppress the display of wind speed and direction on the PFD when the aircraft is on the ground, which is what the actual aircraft does - with the exception that it might appear (in the real aircraft) if the aircraft is not moving - but as I said, that probably depends on the specific software the FMS is using. Most large aircraft simply suppress the wind vector until airborne.
  8. Do you have external power connected, or APU running? If the aircraft is operating only on battery power, then only the two center displays will be lit.
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