capt_zman
Well-known member
- Joined
- Nov 28, 2001
- Posts
- 462
Ok, here goes a short discussion on VNAV. Let's start with the crossing restriction. "Nxxxx, cross 30 miles west of KSUS at 5000'." Let's say you are currently at 15000'. Also, I'm assuming you are currently direct to KSUS.
In the box, you create a waypoint, KSUS/-30, and you put that on 2L, then you put 5000' on 2R and then execute. Now, most important, you have to select the altitude you are going to, whether it's an intermediate altitude or the final altitude (5000') on the altitude preselector (which always overrides the VNAV alt). You'll now notice that there is a 5000 alt on the right side of the PFD in blue color. That is the VNAV altitude that the FMS is calculating a path angle for. (This all assumes you have VNAV selected on the MCP).
Now here's where we get into a couple of different options, first, the FMS is going to calculate a TOD (top of descent) for a 3 degree angle to 5000' (this VPA, vertical path angle, is setup as a 3 degree default in the FMS). Assuming that you are not past the calculated TOD point, you'll see the calculated TOD on the MFD. You also see the snowflake scale appear on the right side of the ADI, as well as a white donut on the VSI (forecasted vertical speed to make the restriction). As you approach 1 minute before the TOD, you'll see a VTA (vertical track alert), you'll notice a white TOD show up on the top left side of the HSI (message line). Five seconds before reaching the TOD, the aforementioned TOD message will blink and you'll hear a chime. The plane will then begin to descend and you'll see the VPATH mode selected as your vertical mode.
The second option is the vertical direct-to. Same setup as above, but before reaching the calculated TOD, you can press DIRECT, and then select the 5000' restriction (2R). What this does in initiates an immediate descent at the current VPA (something less than 3 degrees).
Believe me, there are a bunch of different variables here that you can do, my discussion is very brief and I'm sure others will provide feedback as well. I would definitely advise you to read chapter 15 in the AMS-5000 pilot's guide for a better understanding of VNAV, especially if shooting approaches.
I'm out of time now, later we can discuss the VGP mode, which is pretty important when flying approaches.
Z-
In the box, you create a waypoint, KSUS/-30, and you put that on 2L, then you put 5000' on 2R and then execute. Now, most important, you have to select the altitude you are going to, whether it's an intermediate altitude or the final altitude (5000') on the altitude preselector (which always overrides the VNAV alt). You'll now notice that there is a 5000 alt on the right side of the PFD in blue color. That is the VNAV altitude that the FMS is calculating a path angle for. (This all assumes you have VNAV selected on the MCP).
Now here's where we get into a couple of different options, first, the FMS is going to calculate a TOD (top of descent) for a 3 degree angle to 5000' (this VPA, vertical path angle, is setup as a 3 degree default in the FMS). Assuming that you are not past the calculated TOD point, you'll see the calculated TOD on the MFD. You also see the snowflake scale appear on the right side of the ADI, as well as a white donut on the VSI (forecasted vertical speed to make the restriction). As you approach 1 minute before the TOD, you'll see a VTA (vertical track alert), you'll notice a white TOD show up on the top left side of the HSI (message line). Five seconds before reaching the TOD, the aforementioned TOD message will blink and you'll hear a chime. The plane will then begin to descend and you'll see the VPATH mode selected as your vertical mode.
The second option is the vertical direct-to. Same setup as above, but before reaching the calculated TOD, you can press DIRECT, and then select the 5000' restriction (2R). What this does in initiates an immediate descent at the current VPA (something less than 3 degrees).
Believe me, there are a bunch of different variables here that you can do, my discussion is very brief and I'm sure others will provide feedback as well. I would definitely advise you to read chapter 15 in the AMS-5000 pilot's guide for a better understanding of VNAV, especially if shooting approaches.
I'm out of time now, later we can discuss the VGP mode, which is pretty important when flying approaches.
Z-
