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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,


Mark Aldridge
P3D v5 HF2 & 4.5HF2 and sometimes FSX!

i7-8700K @4.5Ghz | MSI Z370 HD3 Tomahawk | MSI GTX 1070Ti Armor 8Gb |16Gb Corsair 3000Mhz DDR4 DRAM| Samsung EVO 850 500Gb Windows|WD Blue 1Tb SSD SATA disk | Adata XPG SX8200 Pro 2Tb NMVe SSD disk | Asus 32" PB328Q 2560x1440 |beQuiet Dark Rock Pro 3 cooler | beQuiet Silent Base 800 tower  beQuiet Pure Power 10 600W PSU

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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,


Mark Aldridge
P3D v5 HF2 & 4.5HF2 and sometimes FSX!

i7-8700K @4.5Ghz | MSI Z370 HD3 Tomahawk | MSI GTX 1070Ti Armor 8Gb |16Gb Corsair 3000Mhz DDR4 DRAM| Samsung EVO 850 500Gb Windows|WD Blue 1Tb SSD SATA disk | Adata XPG SX8200 Pro 2Tb NMVe SSD disk | Asus 32" PB328Q 2560x1440 |beQuiet Dark Rock Pro 3 cooler | beQuiet Silent Base 800 tower  beQuiet Pure Power 10 600W PSU

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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

Michael Cubine
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