GPS 175 satellite-navigation receiver

The Garmin GPS 175 is a panel-mounted GPS/WAAS navigator for aircraft, a satellite-navigation receiver with a touchscreen moving-map display that serves as the position and guidance source in a certified installation.

It is a 2-inch unit with a capacitive full-colour touchscreen, a Power/Home button, a dual concentric rotary knob with push entry, an SD card slot and a photocell for automatic backlight adjustment. The bezel is 2 in high and 6.25 in wide and is shaped to fit the location of older 2-inch avionics such as the GNC 255 or GTR 225, which allows it to replace existing equipment without altering the panel. The maker's maintenance documentation covers it as part of a Part 23 approved-model-list installation.

In navigation terms, the GPS 175 provides TSO-C146e compliant GPS/WAAS navigation for en route, terminal, non-precision and precision (LPV) approach operations when it is connected to a course deviation indicator. WAAS/SBAS correction is what allows the approach capability. The unit is also a certified ADS-B Out position source, so it can feed a transponder or an ADS-B transmitter such as the GTX 345 or the GDL 88 in the same system. The internal AHRS sensor is limited to attitude display on a non-certified portable electronic device.

For integration, the receiver offers ARINC 429 inputs and outputs with configurable data formats and speeds, RS-232 serial ports (port 1 can also operate as RS-422 on the GNX 375 variant, not on the GPS 175) and analog and discrete interfaces, including an OBS resolver input and a link to autopilots, displays, fuel and air data computers and a CDI. A GPS antenna with a clear view of the sky is required, and the installation menu lets the installer enter the antenna height and offset. Built-in Bluetooth carries flight plans and GPS position to a portable device, and the optional Flight Stream 510 in the SD card slot adds database transfer. The GPS 175 shares its documentation with the GNX 375, which adds a Mode S transponder and ADS-B receiver, and with the GNC 355, which adds a VHF communication radio.

Typical applications are certified general-aviation and light-aircraft installations needing a WAAS navigator with LPV capability, retrofits in a 2-inch radio position and installations that need an ADS-B Out position source. In that environment it acts as the reference GNSS source for the rest of the avionics.