How to Disable ADS-B for Formation Flight?

[Reaver]

When doing formation flights, all aircraft except the lead are required to turn off ADS-B out and put their transponder to Standby. Does putting the Skyview transponder into Standby automatically disable ADS-B out, and if not how does one do so?

To avoid any arguments that this is a requirement, see https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap4_section_1.html and search for "1203".

 

[skysailor]

Putting your transponder in Standby will indeed disable your ADSB out as desired assuming the Dynon transponder is your ADSB out source. Since my Echo UAT is my ADSB out I installed a switch to disable that for formation flight.

 

[Rhino]

The SBY button on the Transponder page puts the transponder in standby.

 

[RV8JD]

At least on the SkyView Classic and Touch, the "Standby" mode (SBY) is active when none of the other modes are active (It does not have its own 'SBY' button to select it).

Per page 6-2, "Transponder Operation", of the SkyView Classic/Touch Pilot's Guide:

"...
a. SBY: The transponder is on, but will not reply to any interrogations. This is the mode that the transponder is in when none of the modes below are active.
..."

Transponder menu example below. In this case the 'ALT' mode is selected. If 'ALT' was deselected and no other modes selected, the transponder would be in the 'SBY' mode.

 

[Rhino]

Yes, I assumed HDX since he didn't state otherwise.

 

[Reaver]

Correct this is for HDX. Nowhere in the user or install manual that I can find does it actually say that Standby turns off ADS-B out. Does someone have a source to cite for that?

 

[jakej]

Standby 'turns off' anything associated/connected with/to the Transponder - most likely not in the manual. Trust me.
Ps - There is no usable (by FAA or other aircraft) data when in standby mode.

 

[PaulSS]

Unless you specifically have an ADSB module, then ADSB is provided by sending GPS position from the HDX to the Mode S transponder's extended squitter. Therefore, as advised above, putting the transponder in standby prevents the transponder responding to interrogation AND from transmitting data using the extended squitter.

 

[lrg775]

SBY doesn't, however, turn off ADS-B In and associated traffic alerts.

 

[PaulSS]

Of course it doesn't. The transponder's extended squitter is only used for the transmission of ADSB data. Whatever is used to receive ADSB is totally separate to the transponder.

 

[lrg775]

Useful to note in the context of formation flights, unless you're someone who enjoys listening to traffic alerts.

Formation flight w/ ADS-B in

When flying with friends, we often form up (either in close or "loose" formation, depending on who is in the group) for our trips. When doing this, only the lead aircraft should have their transponder on. But, I still get traffic alerts via the ADS-B In box *on the lead aircraft*, even if MY...

forum.flydynon.com

 

[swatson999]

Of course it doesn't. The transponder's extended squitter is only used for the transmission of ADSB data. Whatever is used to receive ADSB is totally separate to the transponder.

Not totally separate (from the user's point of view), and not *of course*. I note that the Garmin GTX 345 XPDR is both ADS-B Out *and* In in one box, and they specifically note that in SBY, ADS-B In is still received, so it's very conceivable that (for some odd reason) someone would design an XPDR where SBY turns them both off. Yes, the subsystems are likely "totally separate" within the box.

Point being...don't assume anything unless it's in the documentation for the *specific* devices in question.

 

[ty1295]

I fly 80% of my time in formation and use the Standby switch more than I use the transponder in automatic mode. Traffic alerts are almost never an issue.

 

[OldBoldPilot]

I'm thinking about installing an ADS-B In Inhibit switch for formation stuff. There's only 4 wires to choose from: power, ground, data in, and data out. Putting the switch on the power wire would be an on/off switch for the ADS-470 module. I'm wondering if there's any advantage or disadvantage to putting it on the data TX line (module remains powered but can't talk to the display). Either way, I would expect to see the "ADS-B IN OFFLINE" message, but might there be other side effects that make one or the other preferable? (e.g. boot-up time, other nuisance messages, inrush current spikes, etc.)

 

[Rhino]

You should be able to put the transponder in standby by grounding pin 17, as stated as a requirement in the Aeronautical Information Manual (AIM) paragraph 4-1-20.

 

[N941WR]

What the others have said about putting the Dynon Transponder in Standby does disable ADS-B out; however, the ADS-B in still works and you will get traffic warnings, which can be annoying.

A little food for thought from the AIM, the FAA now requests that Lead squawks 1203 when not receiving ATC services.

 

[OldBoldPilot]

This has been discussed above--having my transponder in stby/off/failed will prevent me (as the wingman) from causing a traffic alert in the lead's aircraft (and in the ATC facility). But my ADS-B In unit is still powered, still receiving, and still knows its position from my GPS. So I expect the incoming signal from the lead aircraft's transponder would generate nuisance traffic alerts in my cockpit.

I suppose turning off my GPS might inhibit the traffic alerts, since the ADS-B would no longer know where it is. But since it's a GTN-650, that would kill a comm radio and VHF nav as well, plus generate whatever alerts from Skyview complaining that the ADS-B position info is lost, so I think the side effects are too severe.

You should be able to put the transponder in standby by grounding pin 17

But you have given me an idea: if I used a DPST inhibit switch, I could kill ADS-B In and put the xpdr in standby with a single switch instead of 2 separate operations.

 

[Rhino]

I would experiment with that. The SBY function isn't connected to pin 17, and may well function differently. Pin 17 was designed for putting one transponder in standby on aircraft with two transponders. Mutual suppression on pin 18 was designed for any transmitters on adjacent frequencies, and disables output transmissions on other devices with 24 volts out. It disables the transponder when receiving more than 10 volts in on the same pin from other devices when they are are transmitting, presumably to block incoming transmissions on the transponder. It seems counterintuitive to allow ADSB In from two transponders at the same time. It also seems counterintuitive to have two different pins perform the same function. So, I personally would confirm what both pins 17 and 18 actually do in my aircraft. Or, I would just ask Dynon directly.

 

[OldBoldPilot]

From the install manual:

External Standby Input (Pin 17) (optional) This input, when connected to Ground, places the SV-XPNDR-261/262 in Standby mode. It should be used to switch between transponders in an installation with two transponders. The input is active low and will be asserted when the voltage to ground is pulled below approximately 4 Volts.

So it looks like connecting this pin to an Inhibit switch and then to ground would work, but I'll confirm with Dynon before I do anything. I guess I'll also ask them about the best way to inhibit ADS-B In, having received no replies about that here.

 

[OldBoldPilot]

From David Readout @ Dynon:

Those are options that likely would get you what you're looking for, however, there may be an even easier method to try first. With your system there are some settings in the traffic setup menu, specifically for the ADSB ghost targets that might help. I would go to SETUP > TRAFFIC SETUP > SHOW ADSB GHOST TARGETS > adjust the range and altitude settings here to make your "bubble" around the airplane bigger and any traffic target that would show up within that range initially won't be defined as a target and won't trigger a warning. Most customers will adjust these when flying in formation and it helps to not get nuisance warnings.

So it appears there is a software solution/work-around.