VNAV not doing right

[Rhinozherous 90]

Hey Guys!

Please bare with me, I fly Boeing and Airbus and other birds in simulations for  a few years now. But the Mad Dog is really something different, I like the challenges it sets for me.

My Problem is that VNAV is not guiding accurate by any means...

I was reaching the TOD on FL300 into EDDT via the MILG1C star for ILS  08R. As I reached the TOD I started early descend via the DES page "start descend" (I am used to do this approx 10NM out of TOD on my Boeing birds).

It started desending, but at some point I realized that we dont make the right alt for waypoint REGBA - I had set an alt restriction for REGBA on 3000ft (not above or below) but somewhere near Berlin I was still wide over FL200 and I tried to get it down with IAS hold and VS mode. Is VNAV that unreliable in the real thing? Or did I something wrong?

[MauB 74]

Yes, AFAIK the real Maddog VNAV isn't that useful on descent. Better to use other vertical modes like VS or IAS.

Edited February 28, 2018 by MauB

[FormerSF3 15]

There are 2 options on the DES page.  DES NOW and DES DIRECT.  DES NOW is to start and early descent but protect any AT OR ABOVE. 

DES DIRECT I have never used in the real airplane.  I wouldn't even begin to know how to tell the programmer how it works.  Supposedly it ignores all constraints until the final altitude.

The real plane has problems with STARS that contain speed and altitude restrictions.  It usually ends up high and fast.  Pilot intervention is required.

Unlike the Airbus, you can let the MD80 fly to the TOD and it will start down on it's own as long as the Altitude has been dialed down.

 

Edited February 28, 2018 by FormerSF3
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[ahsmatt7 1,199]

You have to remember that this airplane was built a long time before rnav arrivals....a lot of the technology in the current maddogs are most likely retrofits. This comes with some cool things that help to reduce workloads but at the same time, can make an autopilot struggle.

Just use vertical speed mode and watch the descent. 

[Rhinozherous 90]

Thank you guys, now i know i did not wrong. I like a more hands on descent and approach.