VNAV

[st1322]

Hi,

I am aware the vnav is not fully functional but I have no clue to which extent it’s working. Here is example: 

1. Sometimes when I approach TD nothing happens. Vnav fully on, autopilot on, altitude set to lower. Descent path indicator stays solid in centerline, nothing happens. So I trigger manual descent and all of a sudden vnav “clicks in” and shows me that I’m above my vnav path, much above it.

2. When descent works ok, all of a sudden sometimes it looses the path. It shows that I am on correct descent path and in split second it messes up and either tells me I am much above or much below. It happened few times already.

Tom

[crisk73]

Let's wait for a better vnav engine in the upcoming update. In the meantime trust only v/s mode like real pilots do.

[Scatena]

I'm having this exactly misgiving.
I'm learning to fly this bird and when I was making the tutorial about FMS, I got to T/D and VNAV disengaged, 2 miles after I noticed and I engaged it again, thereafter it worked fine.

crisk73 said about using V/S, it's the normal procedure among commercial pilots?
 

TY, loving the airplane so far, it is extremely immersive!

[Cameron]

On 5/25/2018 at 7:13 AM, Scatena said:

crisk73 said about using V/S, it's the normal procedure among commercial pilots?

The normal procedure would be LVL CHG. Jan made some very nice videos that go with the product, and you'll find links to them in the product documentation on how he, as a real world 737 captain, would fly the plane for the airline he works for.

[Shanwick]

The calculated TD by the FMC must not be blindly trusted in any plane, sim or real world aircaft . Sometimes it's spot on and sometimes the FMC is far off. One has to double check even in a real 737. The accuracy also depends on the waypoints and if they have above, below or at altitudes restrictions. Use whatever mode you like in order to keep your speed and profile within the box and/or ATC instructions. Level change and V/S mode, both have their advantages and disadvantages in a given situation. I like using both and there are many things one should know about these modes. What and how the speed is controlled, what the throttles do, kicking in of speed protections and so much more. There is plenty of quality info about these mode available on the web.

Here is some quick info on how to quickly calculate your TD. Every pilot should know this anyway. Even if you have VNAV.

http://thinkaviation.net/top-of-descent-calculation/

Edited May 30, 2018 by Shanwick