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bdincer

VNAV

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I am not sure how to explain this problem but the plane overspeeds in high altitude flight when LNAV and VNAV is both enganged and no speed shows on the IAS/Mach display. What supposed to be displayed on PFD let's say when you are at FL350 and doing .82m?

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One obvious question - do you have the autothrottle engaged? At the top of the outside screen (PFD), what do you see in green in the autopilot annunciator section? It is not abnormal for the speed window to be blank. To activate it you need to press the speed selector button/knob and dial in a speed - if you wish to deviate from that planned in the FMC.


GregH

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Hello,Right now I'm cruisng at FL370 with LNAV and VNAV engaged, the actaul Mach number is displayed at the bottom of the speed tape (e.g. 0.849 in white). The set speed is at the top of the speed tape in pink.If you click on the VNAV button on the FMC, the CRZ speed should be showing at LSK 2L which should match your set and current speeds.PFD is showing SPD, LNAV, VNAV PTH.Hope this helps?Regards,


Spoiler

System specs: MFG Crosswind pedals| ACE B747 yoke |Honeycomb Bravo throttle
Now built: P3Dv5.3HF2: Intel i5-12600K @4.8Ghz | MSI Z690-A PRO | Asus TUF Gaming RTX3070 OC 8Gb| 32Gb Corsair Vengeance LPX DDR4 3200Mhz |Samsung 980Evo Pro PCIe 500Gb | WD Black SN850 PCIe 2Tb | beQuiet 802 Tower Case|Corsair RM850 PSU | Acer Predator 34p 3440x1440p

Mark Aldridge
P3D v5.3 HF2, P3Dv4.5 and sometimes FSX!

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Hello,Right now I'm cruisng at FL370 with LNAV and VNAV engaged, the actaul Mach number is displayed at the bottom of the speed tape (e.g. 0.849 in white). The set speed is at the top of the speed tape in pink.If you click on the VNAV button on the FMC, the CRZ speed should be showing at LSK 2L which should match your set and current speeds.PFD is showing SPD, LNAV, VNAV PTH.Hope this helps?Regards,
Thanks Mark will try tonight and make sure these are showing on PFD "SPD, LNAV, VNAV PTH . Some reason I guess I was thinking IAS is set for ristriction or changing the speed. I was assuming if it is blank , FMS is controling the speed since VNAV was selected. I guess my assumption was wrong.

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Hi,Typically in LNAV/VNAV mode, on the MCP, the IAS/Mach Speed display is blank since FMC has control over the speed, however this can be over-ridden by a pilot-selected speed by clicking the center of the SPEED button and then selecting the appropriate speed. To revert back to FMC-commanded speed (as displayed in the VNAV page of the FMCs) click the center of the speed button again and the speed display should go blank.Regards,


Spoiler

System specs: MFG Crosswind pedals| ACE B747 yoke |Honeycomb Bravo throttle
Now built: P3Dv5.3HF2: Intel i5-12600K @4.8Ghz | MSI Z690-A PRO | Asus TUF Gaming RTX3070 OC 8Gb| 32Gb Corsair Vengeance LPX DDR4 3200Mhz |Samsung 980Evo Pro PCIe 500Gb | WD Black SN850 PCIe 2Tb | beQuiet 802 Tower Case|Corsair RM850 PSU | Acer Predator 34p 3440x1440p

Mark Aldridge
P3D v5.3 HF2, P3Dv4.5 and sometimes FSX!

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Thanks Mark will try tonight and make sure these are showing on PFD "SPD, LNAV, VNAV PTH . Some reason I guess I was thinking IAS is set for ristriction or changing the speed. I was assuming if it is blank , FMS is controling the speed since VNAV was selected. I guess my assumption was wrong.
I think FMS is controlling the speed based upon the cost index entered during preflight. Right now I am flying from KMSP to KTPA and since starting FSX and selecting the 747-400 to fly I have not touched anything that would change the 200 that appears in the IAS/MACH window. I do not think you can control the speed unless VNAV is disingaged. Press the HOLD button and it will light up along with the SPD button and the current speed will appear in the IAS/MACH window. Then speed can be adjusted using the knob below the IAS/MACH window.Hope this helps.Mike Cubine

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