ADS-B To OSH

[Jim Rosenow]

I didn't want to drift Ron W's Fatal Accident thread so....

We bit the bullet last month and added full-up rootin' tootin' bi-directional ADS-B to our Cessna. The OSH trip was our first long one since doing so. It was amazing to see the difference in the amount of traffic compared to what we 'saw' with only the ADS-B In we had previously. Like Mike Edwards said in another thread, a bit distracting to know how many folks are close, but a great new tool.

The Cessna has become somewhat of a working lab for ADS-B at the moment, more by accident than design. We have the previous GDL39 that talks to a 795 on the pilot's side via cable and a tablet on the co-pilots side via Bluetooth. The new ADS-B box pulls WAAS info from the panel mount GPS and displays traffic/wx back to that unit. Nice thing is they're all saying the same thing when traffic is around. Point being, you don't need a fancy new GPS to display the ADS-B. Once your 'Out' is in place, most anything that receives will display your traffic on a cheap tablet.

One of those things that make you go 'hmmmmm'.....While leaving OSH, transponder in stand-by, the ADS-B was still picking up targets (including two warbird formations almost same altitude as us and closing) that presumably also had their transponders in stand-by mode. I would have thought the transponders would have had to be active for ADS-B?

Jim
EAA 64315

[WLIU]

" I would have thought the transponders would have had to be active..."

You can not have multiple aircraft in formation all running their transponders. ATC sees the wrong code. So lead talks and squawks and everyone else has their xpdr on standby.

Best of luck,

Wes
N78PS

[Jim Rosenow]

Yup....makes sense, Wes. Is that the procedure during Airventure for local formation flights also? I think they ask everyone else for stand-by only, in and out-bound anyway. If lead has his transponder active, it makes sense we'd see that.

There was a flight of 12...mostly Yak's, I think, and a flight of 3 L-birds. The ADS-B picked em up before we could see 'em.

Jim
EAA 64315

[TedK]

It was amazing to see the difference in the amount of traffic compared to what we 'saw' with only the ADS-B In we had previously. Like Mike Edwards said in another thread, a bit distracting to know how many folks are close, ...

Jeez, maybe I ought to just do Out and hope that everybody else does In.

[Jim Rosenow]

Jeez, maybe I ought to just do Out and hope that everybody else does In.

I know you're goin' for the joke, Ted, but you probably know that for many a/c that will be eminently practical. With Out you're legal for any airspace (in the ADS-B sense anyway), and full ADS-B folks can see you....it's a 'good' thing (sorry Martha).

To those who may be considering such a thing for the future, remember to make sure your box has a certified WAAS source (which can be your WAAS GPS or inside the new box)....needed to be legal for 2020. At least one vendor at OSH we talked to didn't 'fess up their internal WAAS wasn't certified till specifically asked.

Another observation relating back to my rant on the thread from this Spring. Luck of the draw has it that one of the ADS-B ground transmitters is located on our airport. Being 'line-of-sight' and being visible from in front of our hangar, my logic says we should see overhead traffic while sitting on the ground (haven't looked when there was observable traffic yet).

Jim
EAA 64315

[MEdwards]

One of those things that make you go 'hmmmmm'.....While leaving OSH, transponder in stand-by, the ADS-B was still picking up targets (including two warbird formations almost same altitude as us and closing) that presumably also had their transponders in stand-by mode. I would have thought the transponders would have had to be active for ADS-B? Jim

Hi Jim. I checked with the ADS-B expert on another forum I watch (no " " around the expert--he really is) and, if the transponder is in standby the ADS-B Out is still transmitted. The transponder info is empty or null, but the position data is there and can still be received and processed by a ground station or by your In receiver. So that's probably why you saw the aircraft approaching Oshkosh, and why I saw lots of aircraft around the field (didn't count them, I was looking out the window!) as I arrived. (Of course, some people probably still had their transponders on, even though it says otherwise in the NOTAM.)

Me, too, my airport has an ADS-B tower on the field and is line of sight to our house. You can indeed see people flying overhead. I've never seen anybody except airliners, but lots of them because being near El Paso we are under a busy route between Texas and the SE USA over to Phoenix and LA. Just this morning we had a big rainstorm, so I fired up the ADS-B and iPad to see what it looked like. Even before the weather appeared, two AAL flights appeared, and two more showed up later. Some airlines seem to have equipped with 1090 ADS-B Out and others not.

Now that you have the laboratory, you're the source! Sounds like you have NEXRAD displayed on both a tablet (what program?) and a 796. How do the radar displays compare? To Oshkosh and back I compared XM weather on a 396 to ADS-B (actually FIS-B weather) on an iPad running WingX Pro. The displays were recognizably the same weather, but the XM/396 looked so much better. Sharper, crisper, more believable (probably meaning more like what you see on TV). I wondered how much of that was the source and how much was the display.

I know the XM radar is really good, because we use it in the car on long-distance drives. More often than not, when we enter the first green cell we get rain on the windshield within a minute.

Thanks,

Mike E

[Jim Rosenow]

After thinking more about it, it makes sense that the ADS-B and transponder interact separately, which explains why my perceived anomaly actually isn't. :-)

You're right, Mike...We have the ADS-B wx displayed on the 795 (which is just a 796 minus XM capability) and a V1 Nexus 7 tablet (Garmin Pilot software). To be honest, I haven't paid enough attention to compare the wx on the two displays. Will take a look next time there's wx around, and report back.

One significant difference between both of them and the new stuff (GTN650/GDL88) is that the 650 constantly shows and updates the 'age' of the wx, which is a very good thing. Oldest we've seen so far is 6 minutes.

Mike...did you get my PM? Sent one but it doesn't show in my Sent box.

[MEdwards]

You're right, Mike...We have the ADS-B wx displayed on the 795 (which is just a 796 minus XM capability) and a V1 Nexus 7 tablet (Garmin Pilot software). To be honest, I haven't paid enough attention to compare the wx on the two displays. Will take a look next time there's wx around, and report back....did you get my PM?

Since you're running Garmin Pilot, I hope the displays are comparable on the Garmin box and the Garmin app. My results with another app may be different.

Afraid I did not get your PM. I hate it when that happens. Hope it wasn't too long. Thanks.

Mike E

[rleffler]

Hi Jim. I checked with the ADS-B expert on another forum I watch (no " " around the expert--he really is) and, if the transponder is in standby the ADS-B Out is still transmitted. The transponder info is empty or null, but the position data is there and can still be received and processed by a ground station or by your In receiver. So that's probably why you saw the aircraft approaching Oshkosh, and why I saw lots of aircraft around the field (didn't count them, I was looking out the window!) as I arrived. (Of course, some people probably still had their transponders on, even though it says otherwise in the NOTAM.)

I know that at least with Navworx, this isn't true. I can't speak for other vendors. From the Navworx documentation:

When in Mode A or Mode C the UAT transmitter is enabled. When in Standby/Off mode the UAT transmitter is disabled.

With that said, if somebody else in the vicinity has their UAT transmitter enabled, then you will continue to receive traffic and weather even when your transponder is in standby. All it takes is for one aircraft in the area to be transmitting UAT (ADS-B out) for the appropriate data to be sent. Then everyone benefits from the data, including those that operate in receive mode only.

[Jim Rosenow]

Interesting about the Navworx Bob! The Garmin GDL88 manual makes no mention of needing to have the transponder on, for what that's worth.

Jim
EAA 64315