Garmin GNC 300XL Install question

[rv8builder]

I am in the process of wiring the panel of my RV-8 to include a Garmin GNC 300XL system.

I have two questions about the wiring of the external switching required to make the device compliant with TSO 129a ClassA(1) (ie the GPS approach mode).

Question 1: The switch that is wired to pin 9 of J101 (the "GPS Approach Arm control)........should that be a simple "momentary on" switch??

Question 2: The swich that is wired to pin 13 of J102 (the "Sequence/Hold" control)......is that a SPST switch??

Thanks in advance,
Dale

 

[Dave Cole]

Yes

Mid-Continent Instrument Co. makes an annunciator control unit (MD41-444) for use with Garmin approach-certified GPS receivers. The installatin and opearting manual describes those switches as follows:

GPS/APR is a momentary switch that, when pressed, will control GPS Approach Mode.
​

GPS/SEQ is an alternate-action switch that, when pressed, will select between AUTO and HOLD modes.
​

Altenate-action describes a pushbutton that toggles alternately from off-to-on or on-to-off with each push of the button. You could use a SPST toggle switch for that purpose.

 

[DGlaeser]

300xl installation

In order to meet the TSO Spec, you need the equivalent of an annunciator panel - switches and lights to show status.
What are you using for a CDI - a 'real' CDI or an EFIS?
If a 'real' CDI, will it be shared with a VOR radio?
My EFIS (GRT Sport) has both a GPS CDI and a VOR CDI (if connected to an SL30), so I went with an AK 950L. The 'L' means 'light' - does not have the multi-contact switch that allows a single CDI to be driven by either a VOR or the GPS. The AK950 was easier, neater, and smaller than trying to design all the switches and status lights myself. I got my stuff from Stark Avionics.

 

[skips]

300xl switches

I believe all the 300xl lights are controlled by the 300xl, EXCEPT for some to me odd reason the Sequence, I recall some schematic using a dpdt to switch the annunciator light along with the mode.

That is, there is no output for the Sequence light. Odd. Please correct me if I am wrong.

Regards, Skip