Quick little tutorial for those in trouble with VNAV descents

[lol515 1]

Thank you for the tutorial!

[spesimen 135]

I'm not making a generalization, I'm commenting on the fact that pilots hate the fms and speed hold or vertical speed is the preferred method for descent.

which pilots hate it?

 

i don't have any problem with the vnav mode, it seems perfectly useful for what it does. you even pointed out that it's more of a tool to see your descent profile than one that is intended to auto-guide the aircraft.

 

i tend to use IAS mode because speed management is my main concern on descent, i already know which altitudes i should be hitting and when, and that gives a nice optimal descent at flight idle when it's at 240.. and also that's how the RW guy did it in the tutorial.

 

this is all stuff the FMS wouldn't be able to deal with anyway because there's no autothrottle on this plane. so to say it's a 'bad' design is odd considering that very few turboprop aircraft (if any?) even have such functionality.

 

cheers

-andy crosby

[megs8888 20]

Thanks for that.

[hopskip 253]

I can see a few places where the VNAV would be useful. For instance an unrestricted descent to OCTA when the destination is in class G airspace.

 

Going into a busy class C (or even D or B) is more than likely going to involve an ATC required altitude restriction or even level-off. Once you level off (because of ATC and/or traffic considerations) you are leaving the VNAV profile. Even a Boeing 777 autopilot will have to leave LNAV in this situation and revert to ALT hold. If you are held high, you can't exactly 'fall like a rock' to 'catch up' to the VNAV profile, so it'd be time to use an optimum descent for power mode. such as the Q400's "IAS" mode at idle thrust, or maybe a V-speed. (Boeing FLCHG).

 

Only real difference is Q400 is a turboprop without autothrottle, and Boeing is a Jet with autothrottle. (and a more complicated/sophisticated VNAV that can adjust rates to meet several crossing restrictions).

[Skywolf 993]

Awesome post with solution for TOD.  Can someone sticky this

[DP10 0]

An interesting post. I use VNAV to descend into OCTA airports where I'm probably the only aircraft around. Many of these fields don't have much in the way of nav aids so VNAV can get me to a point where I can easily see the runway after which I can do a visual landing. In FSX it's not always easy to see some of the runways so knowing I'm lined up before I can see the field is good. I enter the fixes off the charts, of the nav data approaches are either non existent or don't work to my satisfaction. Thanks for the input guys.

 

DP

[luckyb52 4]

Love the explanation, which for me has taken VNAV from absolutely perplexing to absolutely clear!

[skyhawk8 0]

I know this an old thread but today I just realized how to make multiple VPath changes.

 

Basically every descent is it's own path. What I mean by that is after you make your first descent and level off you set up for the next TOD just like you did the first one. Follow the exact same procedure for every level change all the way down to the last one.

 

I made a flight and set up my own Alt constraints and I didn't miss one.

 

If you have 3 Alt constraints then you'll do 3 VNAV procedures until you are finally at your last constraint.

 

Otherwise you can fly it by hand.

 

Steve

[Renswillink 0]

thanks great topic! i have a question though:) if atc tells me decent fl (x) to be level over point (x) they want me to start decent now, using vnav (have to enter desidered decent rate)i have to calculate my decent rate with groundspeed etc to be level over point x ....is there a trick to tell the fmc decent from current pos to be level over that point ?

[F4RIO 0]

Thanks for posting this tutorial. I'm reading it for the first time.

 

The graphics (jpgs, apparently) are all missing.

 

Anyone have an idea about how to retrieve them?

 

Thank you.

[mz0824 1]

Dear All,

is it possible to get this very useful and excellent  manual placed on the first page with pictures. I am not able to see them - only names of the files instead of pictures.

Thanks !

[vc10man 732]

On 24/11/2015 at 5:09 PM, F4RIO said:

Thanks for posting this tutorial. I'm reading it for the first time.

 

The graphics (jpgs, apparently) are all missing.

 

Anyone have an idea about how to retrieve them?

 

Thank you.

Possibility as that first post was made ages ago, the Avsim server no longer stores those jpgs.

[mz0824 1]

Thanks for your prompt reply ! I suppose it is. Maybe somebody has this tutorial as a pdf or doc file and may post it once again.

[ckyliu 1,753]

Perhaps @dmbusmc could kindly repost the images? This tutorial doesn't really work without them :(

[dmbusmc 46]

4 hours ago, ckyliu said:

Perhaps @dmbusmc could kindly repost the images? This tutorial doesn't really work without them :(

I'll have to dig in some old files to see if I still have them. Not sure why they disappeared here, but it was about 4 years ago now so they might have cleaned house a bit.