FGCS Vertical Modes

FLIGHT PATH ANGLE (FPA)

The FPA is the basic vertical mode (except for the TO).
The FPA can be used for vertical navigation by selecting a higher or lower altitude on the ALTSEL and then pressing the FPA button.
The flight path reference line (FPR) is displayed when the FPA is active. Pressing the FPR button in the display controller panel displays the FPR line, regardless of vertical mode active.
Flight path angle (± 9.9°) is selected in the FPA SEL selector knob on the guidance panel.

FPA ACTIVATION

When the autopilot is engaged and no FD mode is active;
Pressing the FPA button on the guidance panel.
A lateral mode is activated and there is no vertical mode active.
Deselecting the current vertical mode.

TAKEOFF (TO)

The takeoff mode is represented by crossbars and is used during the takeoff phase to maintain a pitch attitude based on flap selection, airplane weight and V2 speed.

TO MODE ACTIVATION

TOGA button is pressed on ground.

TO MODE DE-ACTIVATION

When another vertical mode is selected.

TO PITCH ANGLE CALCULATION

To calculate the TO pitch angle the FMS uses the actual airplane weight and the following information inserted in the MCDU TAKEOFF page:

TO pitch will be dashed if necessary information is not inserted.

TO PITCH ANGLE LOGIC

The system will guide the Pitch initially to the calculated angle. When airborne and IAS is greater than speed target, the guidance will be as follows:

All engines operating: V2 + 10 kt.
One engine inoperative:
- Engine failure below V2: guides V2.
- Engine failure between V2 and V2 + 10 kt: guides present speed.
- Engine failure above V2 + 10 kt: guides V2 + 10 kt.

In TO mode the pitch is limited to a minimum of 8° and a maximum of 18°. The maximum speed target is Vfe - 5 kt and minimum speed target is Vshaker + 10 kt for all engines operating. For one engine inoperative the minimum speed target is Vshaker + 3 kt.

ALTITUDE SELECT (ASEL)

The altitude select mode captures and levels off at the selected altitude. A green ASEL is displayed on the FMA while altitude select mode captures the pre-selected altitude, followed by a green ALT display when level off at the selected altitude.

Altitude select is automatically armed whenever a vertical FD mode is used to fly towards the desired altitude.

FLIGHT LEVEL CHANGE (FLCH)

FLCH provides commands to Climb or Descend to the altitude selected (ALTSEL) according to the speed selected.

During FLCH the speed selected will be controlled via pitch changes through elevator inputs, and the FMA will show SPDE.

FLCH ACTIVATION

Pressing the FLCH button.

FLCH DE-ACTIVATION

Pressing the FLCH button.
When another vertical mode is selected.

FLCH LOGIC

The FLCH mode can be FMS (magenta) or non-FMS (green).

During a FLCH descent, selecting an altitude above the current airplane altitude will command the airplane to climb. The airplane will not reach the altitude selected if AT is disengaged and sufficient thrust to climb is not available.
During a climb, selecting an altitude below the current airplane altitude will command the airplane to descend. The rate of descent is a result of the amount of engine thrust being used.

TRANSITION FROM MACH / IAS

The selected speed is displayed in the box on the top of the speed tape. When the altitude is approximately 29000 ft the display switches from IAS to Mach readout during climb and from Mach to IAS readout during descent.

ALTITUDE HOLD (ALT)

The ALT mode indication on the FMA indicates the altitude hold mode and the altitude selected is being maintained.

ALT MODE DISENGAGEMENT

The ALT mode can be disengaged by selecting a different altitude via ALTSEL knob and activating a new vertical mode.

This logic is valid for all vertical modes except for Glide Slope (GS) and VGP. Switching from ALT mode to GS or VGP mode occurs without change in ALT SEL selection.

ALTITUDE HOLD BUTTON (ALT)

Pressing the ALT button on the GP engages the altitude hold mode. The altitude hold mode maintains the altitude displayed on the Altimeter at the moment the ALT button is pressed.

VERTICAL SPEED (VS)

The VS mode maintains a vertical speed rate. The VS mode is activated by pressing the VS button on the GP. Vertical speed is selected rotating the vertical speed thumbwheel on the GP.
The vertical speed command range goes from -8000 ft/min to +6000 ft/min.
The increments of the Vertical Speed target value are: 50 ft/min (below 1000 ft) and 100 ft/min (above 1000 ft).

GLIDE SLOPE (GS)

The GS approach mode allows the ILS approach mode functions. The GS mode arms when the APP button is pressed and activates when the glide slope is captured.

GO-AROUND (GA)

This mode is not simulated.

WINDSHEAR (WSHR)