I have never used vertical navigation in a non jet aircraft which has an FMC but knew how to use it in the B738 with the FMC.

I have set altitudes at various waypoints and set then to be 'at'.

I set the altitude to a value less than the next waypoint and then 'pressed' the VNAV 'button' on the auto pilot panel.

Firstly nothing changes in the display window in the auto pilot panel and I assumed that it would. Have I not set up correctly for VNAV to work?

Even when I arrive at TOD nothing happens.

I cannot find a video tutorial.

Can someone help me with the correct procedure in using VNAV in the Cessna 414?

Thanks.

Hi Jarnie. This is using the SWS 414 in MSFS 2020? The 414 doesn't really have an FMC as such. At least nothing like a Boeing.

Are you using the stock GNS 530 unit or a GTN750?

As mentioned in the manual the VNAV mode is not enabled on the GFC600 autopilot fitted when you have the GTN 750 GPS units installed and there's no VNAV mode at all on the older autopilot that used when you choose different avionics.

So any descents have to be flown manually (typically using VNAV or IAS mode if the autopilot is enabled) though the GPS may provide advisory VNAV information showing Top of Descent position and Descent speeds required to hit the specified target .
if the GPS doesn't show that or your aren't using a GPS then a separate ToD and Descent speed calculator can be used or you can get a pretty good estimate of the ToD for a 3 degree descent by allowing 3 miles per 1000 feet you want to descent and multiplying your Ground Speed by 10 to get the rate of descent.

So to go from 12000ft to 2000ft at GS of 150Kts you'd want to start the Descent at 30NM (10x3) to go at a descent rate of 1500fps (150x10)

Edited May 15, 20251 yr by Matchstick

@Matchstick👍

Excellent answer!!!

9 hours ago, Matchstick said:

So to go from 12000ft to 2000ft at GS of 150Kts you'd want to start the Descent at 30NM (10x3) to go at a descent rate of 1500fps (150x10)

For a 3 degree descent your descent rate should be 5 x ground speed, not 10 times the ground speed. 

When flying, however,  I find it mentally easier to multiply my ground speed by 10 (just add a 0 to the end of the GS value) and then take about half (divide by 2) to get the rate of descent. I typically then round up a bit since winds and GS will change with altitude and I usually would rather get down a little before my target instead of ending up higher than I wanted to be. 

Al

Edited May 15, 20251 yr by ark

12 hours ago, DD_Arthur said:

The 414 doesn't really have an FMC as such. At least nothing like a Boeing.

Thanks. Yes I am aware of that. I am using the 414 with the GTN750. I referred to the FMC only meaning that I can get vertical navigation to work in the B738 which has an FMC.

 

10 hours ago, Matchstick said:

As mentioned in the manual the VNAV mode is not enabled on the GFC600 autopilot fitted when you have the GTN 750 GPS units installed

Thanks. I didn't see that. I will have to check the manual to see if there are any variants of the 414 which have an autopilot fitted where the vertical navigation is enabled.

And thanks for the excellent explanation on how to fly a descent which I had seen in video tutorials but was a bit lazy to use hoping the autopilot would do it for me. I have some learning to do.

1 hour ago, ark said:

For a 3 degree descent your descent rate should be 5 x ground speed, not 10 times the ground speed. 

When flying, however,  I find it mentally easier to multiply my ground speed by 10 (just add a 0 to the end of the GS value) and then take about half (divide by 2) to get the rate of descent.

Thanks for that information which too I think I have seen mentioned in a video.

Also (forgot to mention and this confused me) that when I run my mouse pointer over the VNV button on the autopilot panel it actually displays what it is (see image below - may need to click on the link). Shouldn't it really display Not In Use OR not be highlited the object as other knobs and buttons in other aircraft do when they are not operative? Just a bit confusing.

Maybe it's not possible to program it so that it only displays when it is actually operative?

https://i.postimg.cc/MKHNyxz3/vnv.jpg

Edited May 16, 20251 yr by Jarnie

14 hours ago, Jarnie said:

Thanks. Yes I am aware of that. I am using the 414 with the GTN750

I use the PMS50 GTN750 (payware) and it has a VNAN calculation.
Pilot would set his V/S to this value.

 

 

 

 

 

Thanks Vaughan,

That prevents and mistakes I might make with calculation.

I love the GTN750 due to its ease of use.