> 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/mcdu-guide/basics.md).

# Basics

> 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/mcdu-guide/basics.md).

## Basics

The custom FMS is operated from the two MCDUs on the pedestal. Captain and First Officer units are independent displays and scratchpads, but they share **one** flight plan.

{% hint style="info" %}
On power-up the MCDU shows **RADIO**. Before **RTE**, **FPL**, **PERF**, **PROG**, or **NAV** can be used, **NAV IDENT** must be displayed once (confirm date, UTC, and the active navigation database).
{% endhint %}

### Function keys

| Key             | Page                                         |
| --------------- | -------------------------------------------- |
| **RADIO**       | Radio 1 (COM / NAV / XPDR)                   |
| **RTE**         | ACT RTE                                      |
| **FPL**         | ACTIVE FLT PLAN                              |
| **PERF**        | PERF INDEX 1/2                               |
| **PROG**        | PROGRESS 1/3                                 |
| **NAV**         | NAV INDEX 1/2                                |
| **DLK**         | Datalink MAIN MENU                           |
| **TRS**         | THRUST RATING SELECT                         |
| **MENU**        | MENU                                         |
| **CB**          | Circuit breaker pages                        |
| **PREV / NEXT** | Previous / next page of the current function |

See RTE, F-PLN, PERF, PROG, NAV, DATALINK, RADIO, MENU, and TRS.

### Scratchpad and line-select keys

Type into the scratchpad, then press a line-select key (LSK) to insert the value.

* **CLR** — clears an alert, then the scratchpad, one character at a time.
* **DEL** — puts `*DELETE*` in the scratchpad. Press an LSK to delete that field.
* Alphanumeric keys, **.**, **/**, and **+/-** enter data.

### ACT and MOD

Edits to the route or flight plan create a **MOD** (temporary) plan. The title shows **MOD**.

* **ACTIVATE** (typically LSK 6R) copies the modification into the active plan.
* **CANCEL** discards the modification and returns to the active plan.

Captain and First Officer can independently view ACT or MOD while sharing the same FMS data.

### Dual MCDU

* Left and right MCDUs have separate brightness, scratchpads, and onside sensors (GPS / IRS / ADS).
* The **primary** MCDU follows the autopilot source (SRC on the glareshield).
* There is no dedicated DIR key. Direct-to is done from the flight-plan page (left LSK).

### Keyboard entry

Click the MCDU to capture the keyboard. **Tab** releases it.

| Keyboard                | MCDU             |
| ----------------------- | ---------------- |
| Letters, numbers        | Scratchpad       |
| Backspace               | CLR              |
| Delete                  | DEL              |
| **.** **/** **+** **-** | Dot, slash, sign |
| F1–F6                   | LSK 1L–6L        |
| Shift+F1–F6             | LSK 1R–6R        |
| Left / Right            | PREV / NEXT      |
| Up / Down               | BRT / DIM        |
| `[`                     | PERF             |
| `]`                     | MENU             |
| End                     | NAV              |
| `\`                     | DLK              |
| Insert                  | FPL              |
| Home                    | PROG             |
| Page Up                 | RTE              |
| Page Down               | RADIO            |