GTX 330-style transponder
A Mode S transponder in the style of the GTX 330, with its green backlit LCD showing the mode, the code and a FUNC page. FUNC pages give pressure altitude with trend, flight time, an altitude monitor, OAT / density altitude and count-up / count-down timers. The model picker also offers the GTX 330ES (ADS-B Out).
- Modeled on
- Garmin GTX 330-style Mode S transponder
- Category
- Radios and panels
- Size
- 2 × 1 cells
- Version
- 1.0 · 2026-10-19
- Plan
- Pro
- Simulators
- MSFS 2020 · MSFS 2024 · X-Plane 11 · X-Plane 12
Variants
GTX 330v1.0
Mode S transponder
Picker: MODEL > GTX 330
GTX 330ES (ADS-B Out)v1.0
Same unit with ES shown on the display
Picker: MODEL > GTX 330ES (ADS-B Out)
Features
- Green backlit LCD, dark characters; unlit when the transponder is OFF
- Mode (OFF, STBY, ON, ALT, or GND on the ground with the automatic ground mode), R boxed while replying, IDENT while identing
- Large seven-segment code; while typing, digits then dashes
- FUNC pages: PRESSURE ALT (FL, with an up / down trend arrow), FLIGHT TIME, ALT MONITOR (feet ABOVE / BELOW, a caution tone 200 ft off), OAT, DALT, COUNT UP, COUNT DOWN (EXPIRED flashing at zero, a tone), CONTRAST, DISPLAY
- CONTRAST and DISPLAY bar graphs set the LCD's ink and backlight (8 / 9 keys)
- VFR key: the VFR code, pressed again the code before it
- R flashes as radar sweeps pass (4.8 s / 12 s) and while identing (18 s)
- Display dark without avionics power; dimmed at night with the faceplate under the red flood light
On the iPad
- Tap IDENT to ident; tap VFR for the VFR code (again: the previous code)
- Tap ON, ALT, STBY or OFF to set the mode
- Tap four of the 0-7 keys to enter a code (sent on the fourth)
- Tap FUNC to step through the pages
- Tap START STOP to start / stop the altitude monitor, count-up or count-down
- Tap CRSR to cancel a code entry, or on COUNT DOWN (stopped) to type its minutes and seconds on the keys
- Tap CLR to erase a digit, reset the timer shown, or reset the flight time
- On CONTRAST / DISPLAY, tap 8 / 9 to lower / raise it
Settings
- Model: GTX 330 or GTX 330ES (picker variant)
- App Settings (shared by all transponders): VFR code (1200 or 7000) and the automatic ground mode on/off
Keys and controllers
Map any of these to a key, a game controller's button or axis, or a MIDI knob (how):
- Transponder IDENT
- Transponder STBY
- Transponder ALT
Simulator data
What the Hub reads from the simulator for this instrument, and what the instrument sends back. Names are the simulators' own: MSFS SimVars and events, X-Plane datarefs and commands.
Reads
| Value | MSFS | X-Plane |
|---|---|---|
| Transponder mode: 0 off, 1 standby, 2 test, 3 on, 4 altitude (enum) | TRANSPONDER STATE:1 (number) | sim/cockpit2/radios/actuators/transponder_mode |
| Transponder code as its four digits (e.g. 1200) (code) | TRANSPONDER CODE:1 (number) | sim/cockpit2/radios/actuators/transponder_code |
| Transponder identing (1/0) (bool) | TRANSPONDER IDENT:1 (bool) | sim/cockpit2/radios/indicators/transponder_id |
| Pressure altitude (ft) | PRESSURE ALTITUDE (feet) | sim/flightmodel2/position/pressure_altitude |
| Indicated altitude (ft) | INDICATED ALTITUDE (feet) | sim/cockpit2/gauges/indicators/altitude_ft_pilot |
| Outside air temperature (degC) | AMBIENT TEMPERATURE (celsius) | sim/cockpit2/temperature/outside_air_temp_degc |
| On the ground (1/0) (bool) | SIM ON GROUND (bool) | sim/flightmodel/failures/onground_any |
Sends
| When you… | MSFS | X-Plane |
|---|---|---|
| IDENT | XPNDR_IDENT_ON | sim/transponder/transponder_ident |
| OFF (0), STBY (1), ON (3), ALT (4) | SimVar write: TRANSPONDER STATE:1 | sim/cockpit2/radios/actuators/transponder_mode |
| Fourth digit typed, or VFR | XPNDR_SET | sim/cockpit2/radios/actuators/transponder_code |
Add-on aircraft with their own systems may use other variables; the Hub reads the standard ones.
Changes
The instrument's version counts what its faces share (the case, the mechanism, the data, the sounds); a face's own version counts that face alone.
- 1.0 2026-10-19
- First numbered version.
