# Primary Flight Display

The Primary Flight Display (PFD) plot renders a classic aircraft instrument panel directly inside Marple. It is part of the **Flight Testing Package** and is designed for analysing flight test data that includes navigation and attitude signals.

<figure><img src="/files/hWIBl8d11xRg64MAaIx0" alt=""><figcaption></figcaption></figure>

### Instruments

The PFD combines four independently configurable instrument gauges in a single plot tile:

* Airspeed indicator
* Artificial Horizon
* Altimeter
* Vertical Speed
* Heading

Each instrument can be enabled or disabled independently. A gauge is visible in the plot only when it is enabled.

### Adding signals

1. Open a plot and switch the plot type to **Primary Flight Display** using the plot type selector in the toolbar.
2. Open the **Settings** panel (the gear icon in the toolbar).
3. Add the signals you want to show to the available signal slots.

<p align="center"><img src="/files/caAX3qQSlBcKeDeZA7KS" alt=""></p>

### Input units

By default the PFD uses **Imperial** units (knots, feet,). Switch to **SI** units (m/s, metres) using the unit switcher at the top of the settings panel. The actual plot always shows Imperial units.

### Signal multipliers

Each signal slot has an optional **multiplier** field. Use this to rescale a signal on the fly without modifying the underlying data — for example, to convert a speed signal from m/s to knots.

### Cursors

The PFD updates in sync with the primary cursor. Drag the cursor in any linked time series plot to step through the flight and watch the instruments update in real time. If you have a realtime dataset open, you can select to use the latest value instead.

### Selected signals

For most signals, you can also specify a *selected* signal. These signals are then shown in pink (customizable) in the gauges. This is relevant for the autopilot values.

### Notes

* The PFD is a **read-only** visualisation. It does not support zooming or panning within the gauge canvas.
* All four instruments share the same cursor position.


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