Reading through here and other forums I see a few are having issues getting VNAV to work. Here is just a little tutorial I whipped up on my way to LOWW.
Step 1. During cruise.
Ok, so you're at your cruise altitude, and in my case this is 21000'. I brought up my 2D FMS.
- Select FPL- what you are looking for are your altitude constraints and also the altitude you want to be at for your approach. For this example I'm going to ignore some of the constraints and only worry about getting myself at the correct altitude for the approach, which is the ILS 29 into LOWW. Use the NEXT and PREV keys to cycle through your flightplan to find a reference waypoint.
- In this screen you will see WW951 at 3000 and I29 at 3000. BRK is technically my FAF, but, I want to ensure I'm at altitude a little sooner, so I'll use WW951 as my reference point.
Step 2. Click VNAV on the FMS.
- On the right you will see your future waypoints laid out. Use the NEXT and PREV keys to cycle through them, and find WW951 (or your reference waypoint.
- Dial in the number associated with the waypoint, in my case "10", and press ENTER.
Step 3. Now you will be at the VNAV PATH page.
- You will see a white box and an altitude next to the TO waypoint, which is WW951 (or your reference waypoint).
- Press enter. Now you will see the altitude box is highlighted. Verify it is the correct altitude that you want to be at that waypoint by. It is set at 3000' already.
- Press enter. Now you will see the target vertical speed (TGT V/S) is highlighted. Input your desired vertical speed for the descent.
- Press enter. Now, you've got yourself a TOD!
Step 3. The descent.
Okay, so now you've got your TOD, and you will see it on your ND.
- When you are 2 minutes out from TOD, you will see your VNAV indicator pop up on the PFD.
- Now, dial in your altitude into the autopilot on the AFCS, in this case 3000.
- Click VNAV on your AFCS to arm VNAV.
And that's it! At TOD, the autopilot will start the descent, so be ready to back out the power a bit!
There may be other tutorials out there already, but I've seen this come up here and elsewhere a few times today anyways. This was a little hasty in putting together, but hopefully it will help a little bit! Just apply what I said here to your flight, and you should be good to go!