VNAV: Vertical Navigation
Before we take off, I would like to talk a little bit about VNAV. When used properly, it can control your vertical guidance throughout the entire flight. This is an overview of different VNAV modes and when they shoud be used.
The vertical autopilot modes associated with VNAV are:
- FLCH
for VNAV climb or flight level change
- ALT
for VNAV Altitude hold
- PTH
for VNAV descent
You will never see "VNAV" on the FMA (Top of the PFD) for any active VNAV mode. The only time you would see
VNAV
would be when you have VNAV armed on the ground.
🡕 Click here for the explanation of the annunciators in our demo flight video
VNAV CLIMB FLCH
Automatic VNAV engagement after takeoff
Before the takeoff, you should press the TOGA button on the throttles. This will engage the correct takeoff modes, and it will also arm VNAV. This is indicated by
VNAV
on the FMA.
- Make sure your altitude setting on the PFD is set correctly
- Then take off
- At 1200ft, VNAV will automatically switch to
FLCH
Note:
You can also change this altitude on the DEPARTURE LIMIT page on the FMS under VNAV CAP AFE
Manual VNAV climb engagement
Some operators take off with VNAV disarmed, and then engage VNAV manually later.
To disarm VNAV while you are on the ground, simply press the VNAV button.
If you then want to engage VNAV climb while you are in the air, you need to make sure that:
The altitude setting on the PFD is higher than you are
Then press the VNAV button. You will go into the VNAV CLIMB mode:
FLCH
VNAV LEVEL OFF & RESUMING VNAV CLIMB FLCH
During the climb, VNAV will either level off at the altitude you selected on the PFD, or at the waypoint altitude,
whichever one is lower
.
There are two scenarios where VNAV will level off during a climb:
- Due to altitude restrictions in the departure procedure (automatic level off)
VNAV will change to
ALT
and it will automatically level off for the altitude restrictions. After it passes the last waypoint with the altitude restrictions, it will then automatically switch to
FLCH
and it will resume the climb.
Since this was a planned interruption of the climb, VNAV anticipated it and therefore it will do it all automatically without the user’s input.
- Sometimes, ATC may tell you to stop at a certain altitude for whatever reason (manual level off)
🡕 Click here to watch this demonstrated in our demo flight video
Leveling off
You can manually force VNAV to level off during your initial climb by setting your altitude setting lower than the cruise altitude. Once you reach that altitude, VNAV will change to
ALT
.
Resuming the climb
Since this was an unplanned interruption of the climb, VNAV expects you to confirm that you want to resume the climb.
To resume VNAV climb, you need to make sure that:
- The altitude setting on the PFD is higher than you are
- Then press the FLCH button in order to confirm the change from
ALT
to
FLCH
VNAV IN CRUISE ALT
🡕 Click here to watch this demonstrated in our demo flight video
During the cruise, VNAV will stay in
ALT
and it will maintain the cruise altitude.
CHANGING CRUISE ALTITUDE FLCH
If you want to climb to a higher cruise altitude (e.g. from FL330 to FL370), you can do that by using
FLCH
(Flight Level Change):
Increase the altitude setting on the PFD to your new desired flight level
Then press the FLCH button. VNAV will climb to a new flight level in the FLCH mode
If you want to descent to a lower cruise altitude (e.g. FL370 to FL330), you can do that by using
FLCH as well:
Decrease the altitude setting on the PFD
Then press the FLCH button. VNAV will descend to a new flight level in the FLCH mode
VNAV IN DESCENT PTH
🡕 Click here to watch this demonstrated in our demo flight video
Assuming that you are cruising in
ALT
and about to reach Top of Descent (TOD).
To start the descent, all you need to do is lower the altitude setting. Upon reaching TOD,
ALT
will automatically switch to
PTH
and VNAV will start descending.
Once you are in PTH, just make sure your altitude setting was lowered correctly and then let it do it’s thing.
PTH
is reliable, so don't interrupt it unless you have to. This will result in the smoothest descent.
WHAT IF YOU MISSED TOD?
If you forgot to decrease the altitude setting, and PTH did not start at TOD, you can still start PTH by simply lowering the altitude setting even after you've passed TOD and the plane will start descending in PTH .
Do not be surprised if the initial descent rate is steeper than usual, as the plane will need to catch up with the descent path.
LEVEL OFF DURING THE DESCENT & RESUMING VNAV DESCENT PTH
During the descent, VNAV will either level off at the altitude you selected on the PFD, or at the waypoint altitude, whichever one is
higher
.
There are two scenarios where VNAV will level off during a descent:
- Due to altitude restrictions in the arrival procedure (automatic level off)
VNAV will automatically level off for the altitude restrictions but it will stay in the
PTH
mode . After it passes the last waypoint with the altitude restrictions, it will then automatically resume the descent.
Since this was a planned interruption of the descent, VNAV anticipated it and therefore it will do it all automatically without the user’s input.
- Sometimes, ATC may tell you to stop at a certain altitude for whatever reason (manual level off)
Leveling off
You can manually force VNAV to level off during your final descent by setting your altitude setting
higher
than the next waypoint altitude. Once you reach that altitude, VNAV will change to
ALT
and stay there until you command it to resume the descent.
Resuming the descent
Since this was an unplanned interruption of the descent, VNAV expects you to confirm that you want to resume the descent.
To resume VNAV descent, you need to make sure that:
- The altitude setting on the PFD is lower than you are
- Then press the VNAV button to go from
ALT
to
ALT
, and then press the VNAV button again to go from
ALT
to
PTH
Please note that this operation is currently incorrect, as you should not normally be exiting VNAV in order to resume the VNAV descent, but we will correct this feature in a future update.
MANUAL VERTICAL GUIDANCE FLCH FPA VS
If VNAV is not behaving as it should or you want to control the vertical situation yourself, simply switch to the manual modes: