6.3.5.3     Autopilot basic functionality

 

Types of automatic flying

There are three autopilot modes types:

-          The BASIC modes allow basic flight maneuvers in all dimensions.

-          The RADIO NAVIGATION modes enable to capture and follow simulated radio navigation aids from the navigation database.

-          The FLIGHT PLAN modes control the flight based on the defined or loaded flight plan.

 

Autopilot mode states

For each autopilot mode one or more states are applicable. The following states exist:

States

Description

select/hold

Autopilot modes that offer these two states allow setting a target value which immediately becomes effective. Any previously active mode of the same channel is immediately deactivated.

arm/capture/ hold

Autopilot modes that have these three states offer to select a target which first needs to be approached using another mode of the same channel. Initially these modes are in armed state. The target is then automatically captured (with a soft transition), the previous mode becomes deactivated and the previously armed mode is put in the hold state.

activate

These modes have no target value and are just activated. The mode, which was active before for the same channel is immediately deactivated.

 

Autopilot channels

The FlightZoomer autopilot modes all belong to one of the three processing channels LATERAL, VERTICAL and SPEED. These channels are processed largely independently, so you can e.g. follow a planned route laterally with the LNAV mode but fly any vertical profile using the four basic vertical modes ALT, VS, FPA or FLCH.

 

Autopilot mode compositions

If the autopilot is engaged, one mode needs to be active for each channel. Additionally, for the two channels LATERAL and VERTICAL, a second mode can be in the armed state.

As a result, the two channels LATERAL and VERTICAL basically are composite channels which at any time can have one or two modes: At least one which is in the hold or activate state, and optionally a second one which is in the armed state. The following tables shows all the possible combinations.

The notation is <active mode> + <armed mode>

These are all valid LATERAL composite combinations. In the table, the short names for the modes are used:

Possible combinations with both active and armed modes

TRK + LOC

Fly Track Over Ground and capture a VOR radial:

Using the TRK mode, the radial of an armed radio navigation aid (VOR) can be approached. The moment, it is reached, the LOC mode becomes active.

TRK + APP

Fly Track Over Ground and capture the ILS:

Using the TRK mode, the localizer of an armed ILS approach can be approached. The moment, the current track intersects the localizer, the APP mode becomes active.

Note: the lateral and the vertical channel of the APP mode also work independently: the localizer and the glideslope don't need to be captured in the same moment. Instead, each is captured as soon as it is reached.

HDG + LOC

Fly Heading mode and capture a VOR radial:

Same principle as described above for the TRK mode

HDG + APP

Fly Heading mode and capture the ILS:

Same principle as described above for the TRK mode


A special case is the TurnRate-mode. Whenever either the TRK- or the HDG-mode are active, the selected turn rate is applied during the turns.

These are the VERTICAL composite combinations:

Possible combinations with both active and armed modes

ALT + ALT

Fly in Altitude hold mode and arm a new altitude

A new altitude can be armed, while the aircraft continues to fly the previously selected target altitude. Either VS, FPA or FLCH then can be activated to climb or descend to the armed altitude.

ALT + APP

Fly in Altitude hold mode and capture the ILS glideslope

While flying in active ALT hold mode, the ILS can be armed, so the glideslope will be captured the moment it is crossed.

VS + ALT

Fly in Vertical Speed mode and capture the armed altitude

While climbing or descending with the VS mode, an altitude can be armed, which will be captured the moment it is reached.

VS + APP

Fly in Vertical Speed mode and capture the ILS glideslope

While descending with the VS mode, the ILS can be armed, so the glideslope will be captured the moment it is crossed (the same would be possible also while climbing in VS mode, but such a maneuver would be very unnatural).

FPA + ALT

While climbing or descending with the FPA mode, an altitude can be armed, which will be captured the moment it is reached.

FPA + APP

While descending with the FPA mode, the ILS can be armed, so the glideslope will be captured the moment it is crossed (the same would be possible also while climbing in FPA mode, but such a maneuver would be very unnatural).

FLCH + ALT

Before the FLCH mode can be activated, a new target altitude needs to be armed. Activating then the FLCH mode, the required climb or descend is initiated and later, when reaching the armed altitude, it will be captured.

 

See in the following sections, how all this dry theory supports intuitive and easy flight operations!