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TIS-B "No Service"

bjdecker

Well Known Member
Ambassador
Good Morning Fellow RV'ers,

After extensive troubleshooting, and some creepy-stalker behavior, I think have uncovered a failure of the TIS-B service in the Waco/Austin TX area.

Background:
My RV-7 is Dual G3X Touch, GTN-650, GTX-345 equipped, and configured correctly for ADS-B Out (PAPR report shows passing parameters for Link Version, NIC, NACp, NACv, SIL, SDA, etc.). Recently, I would see the TIS-B Icon indicate a failure while Air-To-Air remained steady, and certain traffic on the G3X display would disappear...

Details:
On my flights originating/terminating from KGTU, TIS-B shows "No Service" and Air-to-Air operating normally. Longer flights out of the area (to KDWH, KLBB, KMDD) show TIS-B Client availability for the percentage of the flight outside of the Austin area.

I randomly sampled various N-Numbers observed on my ADS-B receiver, and each flight shows a similar result, Air-to-Air operating and TIS-B Client is 0%.

From the forum, I see that Asheville, NC and Savannah, GA areas are having or have had similar problems and that the FAA recognized that there were equipment problems in Savannah earlier this year.

I have sent emails to [email protected] with the details & data.

If you're up for it, and you find yourself in the Austin/Waco area, take a look at your TIS-B service and report back.

Fly Safely!

B
 
Yes I have noticed the same issue near the Gray controlled airspace. I fly from DFW to T82 area 3-4 times per month, sometimes west of the restricted space but mostly east of Litle Int.
 
No TIS-B near KGTU

I noticed a ?NO TIS-B?? message on my Dynon system (Dynon 261 mode S transponder, Skyview EFIS) during a flight near KGTU about two weeks ago...
 
Wasn't the FAA planning to phase out TIS service when it replaced radars (that break and cannot be repaired?) Not sure if they would replace all radars in a service area at once, probably not. Just rampant speculation on my part.
 
Update...

Good morning y'all...

The TIS-B outage in the Austin/Georgetown area resolved briefly on Friday, 11/1. Unfortunately, it came back on Saturday 11/2.

I took a flight from KGTU to KLBB and watched my GTX-345/GTN-650 report radio station data for ADS-B; I observed that as the aircraft was 75NM Northwest of Station 11 (Rabbit Hill/Round Rock site) and began receiving the San Angelo site, TIS-B services were restored. The return trip showed the same results; TIS-B services ceased right around the Goldthwaite airport, transitioning from San Angelo to Rabbit Hill.

Emails sent to [email protected] (9-AJE-ADSB) folks...

Have a great weekend!
 
The FAA picked a bad title for that webpage, as it doesn't show ADS-B ground segment availability. It shows areas where TSO C129 (ie., non-WAAS) GPS receivers have sufficient integrity to be used as position sources for ADS-B Out.

HTH

Dave

I must be confused. I thought Non-WAAS boxes never had sufficient accuracy for ADSB use.
 
I must be confused. I thought Non-WAAS boxes never had sufficient accuracy for ADSB use.
With enough satellites in view, non-WAAS GPS receivers *might* have sufficient accuracy and integrity for ADS-B Out over the time and route of your flight but you'd have to use a coverage prediction tool to know for sure - and that's what this website provides. WAAS differential corrections and automatic integrity monitoring eliminate the need for predictions.

The FAA granted US airlines a five-year exemption from the WAAS requirement so they can use their older GPSs for ADS-B Out while updating aircraft to meet the ADS-B requirement. They'll be required to run these predictions for each flight by a non-WAAS aircraft in ADS-B airspace. Unfortunately, this exemption doesn't apply to GA.

HTH

Dave
 
Could it be a line of sight frequency on the rebroadcast positioning data. Maybe a new building was built near the ground base antenna. Segmented airspace broadcasting might exist. Also data to the antenna might be interrupted through copper wire cable or fiber fed facilities . I had a strange thing happen when monitoring the GTN650 /ADSB ABOUT FOUR YEARS AGO. Just departed the class “D” airport and was passing a 700’ High country hill when another aircraft inbound passed to my right BuUT DIDNT SHOW UP ON MY ADSB SCREEN,! What,!! The other Aircraft did not have ADSB out but did have a working transponder but the FAA radar couldn’t pick up the transponder signal because we were behind the hill and therefore they could not re-broadcast the position of the other aircraft with just the transponder. Had We been in position a mile farther out or a mile before the hill I was told I would’ve received a re-broadcast signal from the other aircraft transponder by the FAA broadcast tower. I primarily look for other aircraft visually NOW and appreciate the added ADSB added position report info.
Ron in Oregon. RV9A the grandma GRANDPA AIRPLANE,
 
TIS-B Update, a tale of two towers...

Ron,

As my father-in-law says "You can watch the dog run away for 2 days..." ;)
-- it's comparatively flat terrain-wise in Central Texas.

Your point about radar coverage is spot on. If ASR/ARSR/ATCBI doesn't "see" and correlate a target (primary + secondary), that data won't make it to the TIS-B rebroadcast and therefore "disappear" from your display.

This issue is something more fundamental, our TIS-B receivers are not allowed to receive TIS-B service (Client is 0%).

TIS-B Service DID function on 11/1 and 11/9.

I have observed my GTX-345 flip between tower sites and TIS-B service availability come & go during that transition; roughly midway between two tower sites (see http://towers.stratux.me/ ) in San Angelo, TX and Round Rock, TX. At 9500' the aircraft is able to receive a number of towers, and it will use the data received from the site with the best signal strength/quality.

More email sent to ADS-B program director at FAA and response received, but no update on root cause -- yet.

B
 
It took a while for my observations at KSAV to generate any action. Tower reported that all the hardware checked out properly, ASRS report went nowhere. Turns out it was a software problem and the hardware was working properly, just doing things incorrectly...

Finally I got the [email protected] email address. That email was complete in factual data and I also tossed in a bunch of extraneous but true BS about my career to give the report more weight...

Ed
 
Fixed...

I got an email back from the FAA --

--
After receiving several independent pilot reports (and the associated details), we were able to determine that a recent ADS-B maintenance action caused a software anomaly that resulted in unreliable delivery of TIS-B ?Service Status? messages in the region where you were flying. The avionics would then interpret the lack of the TIS-B Service Status message as the TIS-B Service being unavailable. However, the TIS-B Targets were still being sent by the ADS-B system and received by the avionics. The ADS-B maintenance procedures have been modified to eliminate the anomaly in the future.
--

So I guess it's fixed now...
 
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