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J van E

Need help for VNAV step descend

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I know how to setup VNAV for a descent to a specific waypoint. However, afaik it should also be possible to use VNAV for for instance a STAR and approach where the AP keeps all constraints etc. So far I've not been able to do that (my plane goes straight through all constraints in VNAV) and I can't find tutorials that show me how to do this, only how to create a TOD for one waypoint and how to get there. Which I already know.

I also asked this on the Majestic forum but so far it's still not made clear to me how to get this done. The only tip I got was to not use Alt Sel (while Airline2Sim tells me to ALWAYS use it).

Maybe someone here knows how to get this done? How can I make the plane stop descending at a contraint and continue descending when it's allowed again, and all that automatically?

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In the real world the Q400 VNAV feature is rarely used, if not used at all. Real pilots make use of the VS to plan for the descent and to follow the STARS according to the altitude limitations or ATC indications.

Cheers, Ed

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Ok... So they always calculate the TOD themselves? Using VS to fly the STAR is easy indeed but the TOD after cruise is slightly more complicated. At the same time I have to say it isn’t complicated for me because I use ProATC and it always tells me when to descent. Which sometimes is problematic because my VNAV TOD sometimes is different. But well, if I want to do it as realistic as possibility I should simply forget about VNAV? Airline2Sim, which is supposed to be totally realistic uses VNAV all the time afaik.

I have to add that doing it with VS may be more fun anyway because it keeps you busy. ;)

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1 hour ago, J van E said:

Ok... So they always calculate the TOD themselves?

That's correct. The FMS in the Q400 allow them to do an approximate calculation of the required VS from the current position to the destination waypoint, whichever they select, using its VNAV function (the Airline2Sim video shows how to do it), but just as a "calculator". They also have to follow ATC, so they need to change VS very often according to such indications.

For this specific aircraft, which require a lot of pilots activity, I recommend you the Airline2Sim instructional videos.

Cheers, Ed

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Ah, I understand, they use it mainly as a calculators and then fly using VS. 

BTW I just managed to do an entire approach using VNAV: the trick was to NOT use alt sel at any moment. I first set up VNAV for the very first point of the STAR and then selected the altitude on the AP panel of the last waypoint. I pressed VNAV when it was in reach and the plane descended all the way keeping all constraints. In the end I even did the final approach this way by lowering the alt to the airport alt. 

Anyway, now I at least know how it works. I will probably use VS more often because I mainly fly with ProATC who tells me when to descend and where to anyway. 

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Typically I use PFPX and predict the runway for landing based on the arrival Wx.  I also use an app on my phone to look at METARs and TAF (Takeoff - iPhone).  So I'll input my arrival and approach plate with ILS.  I leave the discontinuity in between the STAR and IAF on the approach plate for the flight.  I tune ATIS in the second radio and monitor the arrival ATIS until it comes alive and I can see which runway is in use.  I also keep checking the METAR in case FSX and AS16 haven't synced yet.  I had this happen yesterday, whereby the FSX ATIS was reporting incorrectly until I got closer.  

So for tonight, my flight was KEGE to KPDX.  I use the real world FP from FlightAware and that was ZEGRO and the HHOOD4  STAR with YENTL transition.  I believe I picked up ATIS before YENTL, but still saw that 10L was gonna be my RWY choice based on winds.  I put ILS 10L in with the BUXOM transition.

On the HHOOD4 (marked HHOOD3 in the FMS for some reason), I saw that NNUTT was the last waypoint and that BUXOM was even displayed on the STAR page.  So based on the altitudes needed on the STAR and IAP, I used NNUTT and set VNAV up for @4000 feet and just let it descend to NNUTT in VNAV continuously at -1800 FPM.  The TOD using VNAV was right around YENTL, so luckily I had heard ATIS and set VNAV up beforehand. 

Once crossing NNUTT at 4000, I dialed down to 3000 and entered VS, used HDG and turned to get lined up for BUXOM.  Then the next waypoint was 2300 feet so I dialed that in and set my APPR mode active for the LOC. 

That is how I usually do the flights in the Dash.  I don't see many steps or leveling off in this plane online.  In the real world you have the luxury of ATC giving you descent instructions and that helps in some ways.  Simply put in the new altitude ATC gives and use VS.  HHOOD4 has a bunch of hard constraints, but I wouldn't be too worried about making them as long as your descent in continuous at or around 1800 fpm.  If you want descend at 1000 fpm, just plan earlier and change it in the VNAV screen.  The profiles online for these descents always appear to just be a continuous one.  And as long as you are setting it to make that IAF on your approach plate, then you are fine.  Real world controllers are often gonna deviate you from the STAR anyhow. 

Aside from any terrain issues that may exist, you're okay to just make a nice steady descent. 

I did have a weird STAR into KPSP yesterday with the NGX though.  It was the SIZLR2 STAR.  It called for a hard constraint of 16,000 feet at PZUKY.  Why?  Because it takes you directly over the mountain range north of KPSP.  So, those are the things in the sim you have to be careful of and plan for.  Just use SkyVector and look at terrain for your flight so you can see what MSAs are and you'll be ok.  99% of my flights are PNW Horizon flights and the STARs seem to keep you clear of mountains so that leveling off isn't an issue...so far.

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