The ACS is further limited to 15 degrees angle of attack (AOA) and 0-3 G, as measured by the aircraft instruments. It is not recommended to engage the autopilot at AOAs exceeding 12 degrees. If AOA exceeds 12 degrees while the autopilot is active, the pilot should immediately advance the engine throttles to increase airspeed and thrust.

The “momentary override” mode is engaged by pressing and holding [Alt-~] in any autopilot mode (corresponding to the “SAU” trigger on the control stick of the real Su-25T). This mode allows temporary manual control of the aircraft, usually to adjust the desired attitude and/or altitude. This override mode has two peculiarities in the “Combat steering” ACS mode (see the description of the “Combat steering” mode further below).

Pressing [Alt-9] will disable any engaged ACS modes (corresponding to the «OTKL. SAU» trigger on the control stick of the real Su-25T).

· “Route-following” mode - АУ-МАРШР. This mode is selected by pressing the [А] key with the aircraft avionics in the “ENROUTE” or “RETURN” navigation operational mode. The autopilot follows the assigned flight path.

· “Landing” mode - АУ-ПОСАД. This mode is selected by pressing the [А] key with the aircraft avionics in the “LANDING” navigation operational mode, which is switched to automatically from the “ENROUTE” and “RETURN” navigation operational modes when approaching a runway. The “Landing” ACS mode keeps the aircraft on the landing aerodrome’s glide slope beacon. The ACS switches off automatically after descending to 50 meters altitude above ground level (AGL). If the aircraft departs the glide slope beacon for any reason, the ACS mode switches automatically from “Landing” to “Attitude to horizon” mode. The “Landing” ACS mode is normally disengaged by the pilot for a manual landing from an altitude of 100-200 m AGL. Autopilot descent to the 50 m AGL minimum is recommended only in conditions of poor visibility, when the runway is obscured by fog.

· “Combat steering” mode - АУ-МАРШР-КВ. This mode is selected by pressing the [А] key when a target or terrain point is locked by the onboard “Shkval” targeting system. The autopilot uses bank to steer the aircraft onto the locked target bearing. The pitch axis is used to maintain altitude. Engaging the “Momentary override” mode АУ-МАРШР by pressing and holding [Alt-~] allows the pilot to control the aircraft only in the pitch axis - the ACS retains control of bank angle. After releasing the “override” mode, the autopilot returns the aircraft to the initial altitude.

· “Attitude hold” mode - АУ. This mode is selected by pressing [Alt-1]. It stabilizes the current angles of pitch and bank.

· “Barometric altitude and bank angle hold” mode - АУ-КВ. This mode is selected by pressing [Alt-2]. It stabilizes the current pressure altitude above sea level (ASL) and angle of bank. It is convenient for making continuous level turns.

· “Emergency leveling” mode - АУ-ПГ. This mode is selected by pressing [Alt-3]. It brings the aircraft to straight and level flight from any initial attitude. While the initial bank angle exceeds ±80 degrees, ACS control is applied first in roll, then in pitch. When bank angle is within ±7 degrees and pitch angle within ±5 degrees, the “barometric altitude hold” ACS mode is activated and bank is further reduced to zero.

·  “Barometric altitude hold” mode АУ-КВ. This mode is selected by pressing [Alt-4]. It stabilizes the current pressure altitude ASL.

·  “Radar altitude hold” mode - АУ-РВ. This mode is selected by pressing [Alt-5]. It stabilizes the current radar altitude AGL. In this ACS mode the “terrain avoidance” submode is also active.

The “terrain avoidance” submode is engaged whenever:

· The current altitude AGL as measured by the radio altimeter is half or less than its initial value in the “barometric altitude hold” ACS mode, or

· The rate of descent measured by the radio altimeter exceeds –50 m/s.

In the absence of an assigned waypoint, glideslope beam or locked target (e.g. in non-navigation avionics operational modes), pressing [A] to engage the autopilot will default to the “emergency leveling” mode, illuminating the corresponding pushbutton on the ACS-8 panel.

When landing crosswind exceeds 10 m/s, it is recommended to disengage the ACS autopilot at a radar altitude of not less than 100 m AGL to revert to manual control.

In the “ENROUTE” and “LANDING” navigation operational modes of the aircraft avionics, the “attitude hold” АУ [Alt-1] and “altitude hold” (“barometric” АУ-КВ [Alt-4] or “radar” АУ-РВ [Alt-5]) ACS modes are available. When one of these modes is engaged, the “route-following” or “landing” ACS modes cannot be selected until the prior mode is switched off by a repeat press of [Alt-1], [Alt-4] or [Alt-5].

“Terrain avoidance” is engaged automatically from the “radar altitude hold”, “barometric altitude hold”, or “attitude hold” ACS modes, and also in “ENROUTE” and “LANDING” navigation avionics operational modes with any attitude or altitude hold ACS mode (e.g. “radar altitude hold,” “barometrical altitude hold”) engaged.

“Emergency leveling” ACS mode can be deactivated by pressing either [Ctrl-9] or [A]. So in the navigation operational mode, switching from the “emergency leveling” to “route-following” ACS modes requires two presses of the [А] key.

In the “combat steering” ACS mode, loss of target or terrain point lock for any reason causes the ACS to automatically switch to the “emergency leveling” mode.