Garmin VHF Nav / COM Radio GNC 255A / 255B For Experimental Aircraft

Select Model:
GNC 255A 10WGNC 255B 16W
Select Harness:
Unit OnlyUnit with Single Com Custom Wire PigtailUnit with Custom Wire Pigtailto Audio Panel


Important Notes:
  • Standard Kit comes with Rack, Connector Kit, and Back plate.
  • "Standard Kit + Harness" model includes all the same + the harness.
New series of VHF NAV/COM radios, the GTR and GNC series. As the replacement products for the popular SL30 and SL40 models, the GTR series COM transceivers and GNC series NAV/COM radios include a breadth of new features to reduce pilot workload, while also offering an affordable solution to meet the requirements of the 8.33 kHz channel spacing mandate recently enacted by the European Union under the Single European Sky (SES) initiative.

These products have truly reinvented the stand-alone aviation COM radio with novel features like reverse database look-up and the COM monitor function, which bring new efficiencies to cockpit radio management. Beyond that, these products demonstrate Garminís commitment to aviators worldwide, providing the solutions they need to meet the latest regulatory requirements in their regions, such as the recent SES mandate.

The SES mandate
The SES mandate aims to enhance safety and efficiency of air transport in Europe by tripling the number of channels available for aircraft communications. This mandate requires all European aircraft using European airspace to be equipped with 8.33 kHz radios by December 31, 2017. Select GTR and GNC models offer both 25 kHz and the 8.33 kHz operational capabilities required to comply with the law.

The GNC series NAV/COM
The GNC series NAV/COM radios offer all of the same COM features, while also adding navigation capability with VOR/ILS with Glideslope. The GNC series works well with select Garmin flight displays including the G500, G600, G500H and G3X to display the NAV indicators in the primary field of view, and can integrate with most autopilots.

The GTR and GNC series are more powerful than their SL-series predecessors with versions available with 10- or 16-watt transmit power. The GTR 225 includes 10 watts of transmit power and 25 kHz frequency spacing.

All products in the series have received the Federal Aviation Administrationís (FAA) Technical Standard Order (TSO) authorization.

Night Vision Model
Night Vision Goggle (NVG) capable COM and NAV radios. The GNC NAV/COM and GTR COM series of radios are now even better with the addition of new, NVG capable versions.

This latest edition grows our list of NVG capable products which already includes NVG specific GTN series navigators as well as G500/G600/G500H flight displays.


  • The series offers a variety of original features never seen before in a stand-alone COM radio. A unique frequency database makes it easy to find all the frequencies associated with a given airport or facility just by entering the location name or station ID. And when manually tuning a frequency, the reverse lookup function will automatically provide the navaid and/or airport identifier. Pilots can also find the nearest airport, area control center, flight service station, weather frequencies and VORs. All models also include a COM monitor function, which provides the utility of two receivers in one, allowing the pilot to listen to transmissions like ATIS without leaving the active ATC frequency, as one example.
  • The GTR and GNC series automatically store the 20 most recently called frequencies. Plus, the radios allow for storage of up to 15 favorite frequencies such as the pilotís home airport or other frequently visited destinations. A familiar flip-flop feature allows channels to be entered in a standby window, and then activated with a press of a button. All models also include a built-in, voice activated two-place intercom making it a great solution for a two seat aircraft without an audio panel. A built-in timer can assist with approaches, holds and other assigned maneuvers.


  • GNC 255A: COM, NAV, 10 Watts, 8.33kHz
  • GNC 255B: COM, NAV, 16 Watts, 8.33kHz
  • Frequently Purchased With
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I had to repair or replace and I’m glad I replaced an old Narco with this, the features this little box has is amazing. Hard to believe what all it can do and it’s just a nav comm

Brad S Verified Purchase


November 15, 2023


Please note, Aircraft Spruce Canada's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce Canada assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Which CDI indicators will works with the GNC NAV/COM?

For a new glideslope and LOC/VOR CDI receiver the GI 106A is the first recommendation under part number 11-05768.

Q: Will the GTR & GNC units operate without purchasing and maintaining a current database subscription from Garmin?

Yes, the database is an optional feature on the GTR & GNC series.

Q: Will these radios integrate with the Dynon 180 like the SL 30 model does?

Yes, the GNC series will still output the NAV like the older SL 30 units.

Q: Is the a wiring like with the 430W units to a Sandel 3308?

Yes the Garmin GNC Nav/Com has a 429 Arinc output which can go to the Sandel.

Q: What size circuit breaker does the GNC 255A 10W version require? What is the maximum current draw?

For the Com side 5A @ 28V & 10A 14V and for the Nav side 2A @ 28V & 4A @ 14V. The amp draw varies based on the Com and Nav as well as 14 and 24 volt systems. Always refer to the manual before installation.

Q: What antennas are recommended for the GNC 255A Nav/Com radio? Is there a wing tip antenna that can be used for this radio?

There is no recommended antenna for any radio as almost any Com and Nav antenna can be used. They are built for different speed ratings, mounting locations and some are certified (TSO'd) and some are for experimental aircraft only. Type antennas in the search box on Aircraft Spruce website for our product selection. Archer and Advanced composite are two wing tip types but both are not certified (TSO'd) as they are intended for experimental aircraft only.

Q: Does the integrated intercom offer an auxiliary audio input (for something like an MP3 player)?

No, it is a basic intercom, for a stereo option or 3.5mm input you will need to go with an external intercom.

Q: What voltage do these units operate on?

It can operate on a 14 or 28 volt system.

Q: Is it possible to purchase the installation tray and wiring harness separately from the GNC 255A NAV/COM unit?

It is possible but we will have to special order this for you and may not cost or have the same lead-time as Garmin does not stock it this way. Please call us and we can get pricing and lead-times.

Q: Does the GNC 255A provide the same radial display of the standby VOR like the SL 30? With the primary VOR/LOC frequency providing guidance to your HSI or CDI, the standby frequency can be tuned to a second VOR to display the current radial on which your aircraft is flying.

In speaking with Garmin, the GNC 255 does not have the standby VOR like the SL 30.