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VNAV issue (in descent)


martinlest
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I am getting an issue in descent with the LevelUp planes. The speed is constantly over/undershooting the target (as in the FMC/DES page): the indication on the PFD then keeps changing between 'FMC SPD', 'RETARD' (both in green) and 'ARM" (in white) as the a/c tried (unsuccessfully) to stabilise itself.. If I click on SPD INTV things settle down, but that shouldn't be required, AFAIK?

Also, connected with this I guess, using ALT INTV or LVL CHG very soon produces a very high descent rate (up to 4800ft/min) and of course, as a result, the FMC SPD target is greatly exceeded: the excessive descent rate is not being moderated in order to reduce the ever-increasing airspeed. I have to descend using V/S to maintain any realistic control. (Oddly, below FL100 VNAV seems to work much better, moderating descent rate to achieve the required speed as expected).

Thanks! (Great planes, notwithstanding any issues!! 🙂 )

Edited by martinlest
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  • 2 weeks later...

you have 2 answers: put winds on descent forecast page aaand

it wont work 'cause its broken on level up.

on zibo, pmdg and real 737 the plane descends at idle. for this work with no problem, you have to insert the descent winds on descent forecast page (fmc, descent, descent forecast. below f310 you insert fl200, 150 and 100 and at or above 310, 200 and 100). on zibo this works fine and pmdg should do too, but on level up for me this only worked 1 time, the first time i did that. so, if the winds are not inserted, theorically the plane should "feel" the winds and and recalculate vnav idle descent without third-party help, but it also wont work on level up. results: the plane will try to maintain the speed on a low-angle slope/path (i guess u can understand what i want to say). it accelerates, then goes idle. it loses speed and again accelerates and its a loop.

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