> For the complete documentation index, see [llms.txt](https://docs.flightsim-studio.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.flightsim-studio.com/e-jet-series/autopilot-guide/fgcs-vertical-modes.md).

# 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.

<figure><img src="https://cdn.document360.io/417c2d4d-fdb8-4d4d-b11d-011fe445d776/Images/Documentation/image-1670233914325.png" alt=""><figcaption></figcaption></figure>

**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:

<figure><img src="https://cdn.document360.io/417c2d4d-fdb8-4d4d-b11d-011fe445d776/Images/Documentation/image-1670233925023.png" alt=""><figcaption></figcaption></figure>

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.

{% hint style="info" %}
Altitude select is automatically armed whenever a vertical FD mode is used to fly towards the desired altitude.
{% endhint %}

### 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 **FLCH**) or non-FMS (green **FLCH**).

* Green FLCH is selected with the **FLCH** button on the Guidance Panel. Speed is controlled by pitch (FMA shows **SPDE**).
* Magenta FLCH (**VFLCH**) is the VNAV equivalent. It is commanded by the FMS when VNAV is active in climb or when a climb is resumed from a constraint. Speed comes from the FMS speed schedule, or from the Speed Selector when it is set to **MAN**.
* 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 GP. Switching from ALT mode to GS or GP 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)

Go-around is a non-selectable vertical mode. Pressing **TOGA** in the air engages **GA** on the FMA (green). Lateral mode automatically goes to **TRACK**.

**GA ACTIVATION**

* TOGA is pressed while airborne.
* Radio altitude below 2,500 ft AGL (or baro altitude below 17,000 ft if radio altitude is invalid).
* Also used for a bounced landing / touch-and-go: TOGA pressed with weight on wheels for less than 5 seconds after being airborne this flight.

**GA GUIDANCE**

* Initial pitch is based on the takeoff pitch schedule (same source as TO), limited between approximately 7° and 18°.
* As airspeed approaches the go-around target, guidance blends to speed-on-elevator (**SPDE**).
* Target speed is approximately stall-reference + 20 kt, limited between stick-shaker + 10 kt and Vfe − 5 kt.
* Autothrottle commands go-around / MAX rated thrust.

**GA DE-ACTIVATION**

* Another vertical mode is selected (FPA, FLCH, VS, ALT, VNAV, etc.).
* Cancelling the vertical GA mode does **not** drop lateral **TRACK**. Select HDG, LNAV, or LOC as required.

### WINDSHEAR (WSHR)

{% hint style="info" %}
This mode is not simulated.
{% endhint %}

### VERTICAL NAVIGATION (VNAV)

{% hint style="info" %}
VNAV requires FMS as the selected NAV source. Magenta FMA annunciators indicate FMS vertical modes.
{% endhint %}

VNAV provides FMS-commanded vertical guidance along the flight plan: climb (VFLCH), path descent (VPTH / **PTH**), altitude capture (VASEL / magenta **ASEL**), altitude hold (VALT / magenta **ALT**), and glide path (**GP**) for non-precision approaches.

**VNAV ACTIVATION**

* On ground: press **VNAV** on the Guidance Panel to arm magenta **FLCH**. VNAV captures after takeoff above the VNAV capture altitude (default 800 ft AFE, as set on DEPARTURE LIMIT).
* In flight, with FMS NAV source selected: press **VNAV**. The armed/active submode depends on the flight phase and the altitude error to the FMS target:
  * Within 25 ft of the FMS target → magenta **ALT**.
  * Descent in cruise / descent / approach with LNAV active → magenta **PTH** is armed.
  * Otherwise → magenta **FLCH**.
* VNAV will not remain active if the NAV source is not FMS. It reverts to green **FPA**.

**VNAV SUBMODES (FMA, magenta)**

| FMA      | Mode       | Function                                                                                                                                                                           |
| -------- | ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **FLCH** | VFLCH      | FMS flight level change. Pitch controls FMS or MAN speed. Altitude target is the FMS constraint, limited by ALTSEL when ALTSEL lies between present altitude and the FMS altitude. |
| **PTH**  | VPTH       | Geometric path descent. Used from TOD to the next constraint / BOD. Vertical deviation is shown when FMS is the NAV source.                                                        |
| **ASEL** | VASEL      | Captures the FMS (or ALTSEL-limited) altitude. Automatically follows VFLCH or VPTH. Then transitions to VALT.                                                                      |
| **ALT**  | VALT       | Holds the captured FMS altitude.                                                                                                                                                   |
| **GP**   | Glide path | Non-precision final approach path. ALTSEL is ignored so missed-approach altitude can be set, same procedure as an ILS.                                                             |

**PATH vs FLCH**

* Climb / go-around / departure: VNAV uses **FLCH**. A climb of more than 200 ft from a constraint resumes VFLCH.
* Cruise / descent / approach: VNAV captures **PTH** when the aircraft is in the path-capture window. Level-off uses VASEL → VALT.

**VNAV DE-ACTIVATION**

* Press **VNAV** again.
* Select another vertical mode (FPA, VS, green FLCH, GS, GA).
* Change NAV source away from FMS.

**ALTSEL INTERACTION**

* VNAV respects the altitude preselector except in **GP** (and GS). Set ALTSEL to the next cleared altitude during climb/descent.
* Switching from VALT to GS or GP does not require changing ALTSEL — set missed-approach altitude after GP/GS is captured.

### OVERSPEED PROTECTION (OVSP)

{% hint style="info" %}
OVSP is automatic. It is not selected on the Guidance Panel.
{% endhint %}

Overspeed protection (**OVSP** on the FMA) reduces the chance of staying above Vmo/Mmo (barber pole).

**OVSP ACTIVATION**

* Airplane airborne, flight director available.
* IAS more than approximately 1 kt above the overspeed threshold.
* Can override ASEL, ALT, TO, FLCH, VS, FPA, VNAV submodes, GS, GA, and flare.

**OVSP GUIDANCE**

* Pitch commands a speed slightly below the overspeed threshold (about 5 kt below Vmo/Mmo) using speed-on-elevator.
* When IAS is more than 5 kt below the overspeed threshold, OVSP deactivates and the previous vertical mode is restored.