Engine Monitoring

Engine Monitoring

Engine readings are drawn by four gauge instruments: vertical bars, horizontal bars, arcs and plain numbers. On the bench panel the Engine tab holds a row of four CHT bars over a row of four EGT bars. The stock EMS screens use the same gauges. The instrument types are vertical_bar_gauge, horizontal_bar_gauge, arc_gauge and numeric_display.

The bench simulator sends no engine data, so the picture above shows every gauge in its no-data state. With live data the bands are bright green, yellow and red, and the readout is white.

Reading a gauge

Each gauge shows one FIX value against its normal range and its limits.

Part	What it shows
Band	The range, coloured green where normal, yellow inside the warning limits and red inside the alarm limits.
Indicator	A white line across a bar, or a pointer on an arc, at the current value.
Readout	The value, white when normal, yellow past a warning limit, red past an alarm limit. Units follow it when the gauge shows them.
Name	The label you gave it, such as CHT, OIL P or a cylinder number.

A segmented gauge draws its band as blocks, like an LED bar, and dims the part beyond the value instead of drawing an indicator line.

Where the range and limits come from. Not the panel: they are the aircraft's numbers. Each gauge's range is its FIX item's minimum and maximum, and its limits are the item's lowAlarm, lowWarn, highWarn and highAlarm values. Enter them under Aircraft parameters in the configurator and copy the aircraft.ini to the device. A limit left blank draws no band for it.

When data is flagged

You see	It means
Dark grey, dark yellow and dark red bands, grey text	The value is old or bad.
xxx (or X in every digit), with the indicator at zero	The value has failed.
A red name and units	The item is annunciating.

Cylinder groups

The configurator palette has ready-made groups in its engine category: CHT — 4 cyl, EGT — 4 cyl, CHT — 2 cyl, EGT — 2 cyl, and Engine — 4 cyl (CHT+EGT), which is CHT over EGT as on the bench. A group drops in as one unit, scales as one, and can be ungrouped. Its bars read CHT11..CHT14 and EGT11..EGT14 and are named 1 to 4.

Leaning: EGT modes

A vertical bar set up for it (egt_mode_switching: true) responds to four EGT buttons. The stock EMS screens carry them; a configurator panel gets them by adding buttons with the action Set EGT mode.

Button	What it does
Normalize	Takes each cylinder's present EGT as its reference and shows the change from there, across normalize_range (the shipped bars use 400). Use it to compare cylinders.
Peak	Tracks each cylinder's peak and draws a magenta mark at it. Once a cylinder has fallen 10° or more below its peak, its readout shows how far below, in magenta.
Lean	Resets the peaks and turns on Normalize and Peak together: the usual leaning view.
Reset Peak	Starts the peaks again from the present values.

Choosing one clears the others, and the active button is green. In Normalize the colour bands stay on the absolute scale, and the indicator turns blue.

Hottest cylinder. Give a bar a highlight_key, such as EGTMAX1 or CHTMAX1, and it draws a magenta ball at its foot while it is the hottest. The palette groups do not set one.

Alerts on the stock screens

On the stock screens, the EMS button turns red while any CHT or EGT is annunciating, so you can see from the PFD that the engine wants a look. Touch it to go to the EMS screen.

Setting a value with a gauge

A gauge can also set the value it shows. Give it an encoder_set_key and select it with the knob: turn to change it, push to keep it. Leave it and it goes back to where it was. With touch_edit on, a touch selects it too. A selected bar or arc turns orange.

Customizing

In the configurator

Option	Bar gauges	Arc	Numeric	What it does
FIX key (dbkey)				The value shown.
Name (name)			—	The label.
Decimal places (decimal_places)	1	1	1
Show units (show_units)	on	off	off
Segments (segments)	0	0	—	0 draws a solid band; more draws that many blocks.
Name location (name_location)	—	top	—	top or right.
Font mask (font_mask)	—	—	000	The widest value the readout makes room for.

The configurator also shows each gauge's range and limits, read-only, because they are set in the aircraft parameters, not on the panel.

The EGT mode, highlight and editing options (egt_mode_switching, normalize_range, highlight_key, encoder_set_key, touch_edit) are not in the configurator's list. Add them in the YAML pane; pyEFIS applies them and logs that they are undeclared.

In YAML

One bench CHT bar, and a leaning-ready EGT bar:

- type: vertical_bar_gauge
  options:
    dbkey: CHT11
    name: '1'
- type: vertical_bar_gauge
  options:
    dbkey: EGT11
    name: '1'
    egt_mode_switching: true
    normalize_range: 400
    highlight_key: EGTMAX1

The stock screens build their cylinder rows from the shipped includes/bars/vertical/ files; see Customizing Beyond the Configurator.

Feeding them

Each gauge reads its own FIX key, with the item's minimum, maximum and four limits. EGTMAX1 and CHTMAX1 are needed only for the hottest-cylinder ball. The EGT buttons write EGTBTN1..EGTBTN4. See FIX Database Keys.

See also

• Engine & Data Gauges: every option
• Designing Your Panel