Garmin GDL-88 Pirep

[Bennett]

Just flew back from Scottsdale to San Carlos. Decent weather at both ends so flew VFR with flight following. Executive Air Maintenance at KSDL was, as usual, on time, accurate in their cost estimate, and everything was installed correctly. Executive summary: The GDL-88 coupled to a Garmin GTN 750 is truly an amazing combination. (ADS-B in/out, dual frequencies) I also had them trade out my GNS 430W, and replace it with a new GTN 650 (capable of cross feeding data with the GTN 750 and 796). The GTN 650 is miles ahead of the 430 W for my purposes, and while I have to study the manual a bit more, I'm sure I will become proficient with it. THe larger screen of the GTN 750 is much easier to use. The real star is TIS-B traffic from the GDL 88. Works exactly as the materials say it should. In fact I had two situations on the flight back that proved the worth of system. One was a direct head on closing situation with the opposing aircraft level 500' above me. In flight visibility was actually terrible over the California Great Valley, even though it was great at KSDL and KSQL. Little ground contact, thin overcast, smoke, haze and dust. The traffic overlay on the GTN 750 showed an opposing aircraft early enough for me to take notice. I was talking to ATC, as was an RV. At about 5 miles, ATC alerted both of us that there was traffic at our respective 12 o'clock positions. I continued to watch, and shifted to the Traffic display page, which showed the other aircraft holding steady 500' above me (wrong altitude for his direction of flight). I told ATC I had him on the scope, and we each reported back to ATC that we had a visual at less than a quarter mile. The Traffic display gave me the confidence to hold my course and altitude. The second situation was potentially dangerous, and I really appreciated the traffic display. This was a converging situation with both aircraft at the exact same altitude. Once again I spotted him as traffic on the GTN 750 as a traffic overlay. It was apparent that we were on a direct convergence. The other aircraft was not talking to ATC, and at about 5 miles ATC gave me an alert that there was traffic in the area. They did not mention that convergence was happening. I again switched to the traffic page, and when it was obvious that avoidance was necessary, I informed ATC I was deviating in direction and altitude. I finally saw the oblivious aircraft at about a half mile, and then returned to my prior heading and altitude. All the visual and aural alarms worked as they should. Wow! what a great safety feature this is. On the other hand I am not at all impressed with the winds/temperature aloft as presented by Nextrad. The XM presentation on the 796 is far superior on all the weather types in Nextgen that I viewed on both units, and so I will (reluctantly) keep up my XM subscription, at least for now. There was no real weather to view on this trip, so I cannot comment on areas such as lightning strikes, etc, While my aircraft was at EAM they brought all the software and firmware for the GTN 750 up to date. This included Garmin's 3D sound for the remote audio panel. Once the DIP switches were properly set on my Zulu headsets, I was able to listen to ATC in one ear, and a second frequency, like ATIS in the other ear. Surprising clarity, and not at all difficult to understand both at the same time. A really helpful addition. I know we (including me) gripe about Garmin's prices, propriety software - doesn't like to talk with others, but much like Apple, their "stuff" works well. The GDL-88, is in my opinion, well worth its cost, and while there are some altitude restrictions (relative to the 2020 requirements for above 18,000'), and some out of country limitations, which may or may not apply in the future, TIS-B traffic alone should justify the installation. I have previously used a ZAON portable unit coupled to the 796 for traffic, and in all candor, I hated it -- false positives, errors in azimuth, missed aircraft, etc., and while it was better than nothing, I could never trust it. There are many aircraft in narrow areas here in California (like several other states), and while mid-airs are rare, near collisions (near misses, as the press calls them) are not so rare. Bennett

[Nathan Peterson]

Bennett,

 

Thank you for the details of the GTN 750, 650 and the GDL-88.

 

Nate

[Bob_Belville]

Bennett, thanks for the pirep. I just picked up my plane yesterday with the new GDL-88 which was not shipping when my panel was redone in December. I glad to get the positive appraisal, I did not see a single target on my 70 mile flight home - I might have it set on a pretty tight range! I have a 750 (which got a software update at 6 weeks old including removing the fuel management communications with the JPI), an Aspen and a 696 with XM weather which i will be trying to drop but like you I'll wait until I'm sure the free info is as useful. Bob  

[Bennett]

Bob, I played with the traffic windows - altitude difference and range, and I finally narrowed the vertical range because I was picking too many aircraft that I thought were outside of concern. By the way I use a single belly antenna. I opted to not instal the diversity double antenna on top as I already have too many antennas. I use the JPI. 830 for fuel management taking data from the GTN 750

[Bob_Belville]

Bennett, I have not checked yet where the traffic vertical/horizontal ranges are set. I suppose 5 nm and 2000' might be a reasonable place to start. I'd like to see a target now and then to be sure it's working! I only have one antenna, i think. Yeah, my JPI 930, linked to the 750, gives me great fuel management info. The 750 software update change which does not permit manual FF rate entry into the 750 is not likely to be a real issue. The avionics shop was simply pointing out that the Feds made Garmin disable a feature even though the 430/530 have had the same capabilities for years.

[larryb]

Bob and Bennett:

 

     Yesterday I did my first flight with the GTN650 and GDL88. I'm not seeing all the traffic I should, including one aircraft pointed out to me by ATC same direction, same altiude, 1 mile. However, I do see some traffic. I was also seeing an icon on the map page that I did not understand during the flight, but which I found later in the GTN manual for software 3.0. The icon is "Not within coverage of a TIS-B ground station when connected to GDL88" I do however, receive the FIS-B weather just fine. I'm in the San Francisco bay area, so I would expect to receive TIS-B easily. Here is the icon:

 

 

     My question for each of you, which of the two icons do you see?

 

Thanks, Larry

[Bennett]

I'm in the San Francisco Bay Area and my 750 and 650 show many aircraft - far more than I thought were out there I did not pay attention to the icon you mention, but if I saw anything with an X through it, I'm sure I would have investigated. Have you set up the altitudes and vertical ranges for the TIS -B traffic?

[Bennett]

While the Traffic can be set for either Absolute, or Relative, I find Relative to be more useful. I like seeing the predicted course lines shown for threats. In Relative, you will not see all the traffic, just those who are potential threats. You should also see Traffic Alerts on the GTN screens. In my setup I use the GTN 750 as my primary moving map with either a Direct To, or flight plan. Traffic will show as an overlay, but can get lost in the clutter. I therefore use the GTN 650 display for Traffic at a 6 mile range. This allows me to focus on traffic when it might be a concern. As mentioned in another thread, I use the 650 in the VLOC mode, with its own display head, as a backup to GPS. I still like XM weather, and this is displayed as a overlay on the Aera 796. Certainly overkill, but this setup provides a great deal of useful information without a lot of button pushes, or screen changes. Garmin has a GDL 88 manual of sorts on its web site.

[Bob_Belville]

Bennett, Larry, I finally got to fly today, 1.4 hours, 3 approaches to 2 airports to get familiar with how the 750, Aspen and STEC50 behaved together.

 

The 750 was displaying traffic from the GDL 88. The target triangles were tagged with a relative altitude and a direction of flight arrow. Nice. The triangle was either hollow or solid depending on threatening or non as per chapter 10 of the GTN 750 Pilot's Guide. There is a Traffic Status Key at the bottom of the map. (I made a couple of long approaches with proc turns to MRN, my home base, a somewhat rural, uncontrolled field. There was a Cherokee doing touch and goes but as he did not get above pattern altitude he did not show up as traffic. I think I've noticed Center does not see us on climb out to pick up a clearance until we're a couple of thousand feet AGL.)

 

I am flying again tomorrow, MRN/HKT/LYH/HKY/MRN almost 3 hours and 3 landing at control tower fields so I should be able to learn a lot more.

 

Bob

[Piloto]

Bob and Bennett:

 

     Yesterday I did my first flight with the GTN650 and GDL88. I'm not seeing all the traffic I should, including one aircraft pointed out to me by ATC same direction, same altiude, 1 mile. However, I do see some traffic. I was also seeing an icon on the map page that I did not understand during the flight, but which I found later in the GTN manual for software 3.0. The icon is "Not within coverage of a TIS-B ground station when connected to GDL88" I do however, receive the FIS-B weather just fine. I'm in the San Francisco bay area, so I would expect to receive TIS-B easily. Here is the icon:

 

traffic.jpg

 

     My question for each of you, which of the two icons do you see?

 

Thanks, Larry

TIS-B traffic data comes from a radar site while FIS-B weather data comes from a UAT ground station at a different location. Reception of one does not imply reception of the other. There is nothing wrong with your GDL-88. Typically for reception of TIS-B traffic data you need to be higher than for reception of weather data.

 

José 

[larryb]

Jose:

So far I can tell you that 5,500 feet isn't working out. I have seen that "no signal" icon 100% of the time flying around San Jose, CA for 3 flights now.

It is good to know that the transmitting sites are different, thanks for that info. I was wondering how I could receive 1 and not the other.

Larry

[Piloto]

Bennett, Larry, I finally got to fly today, 1.4 hours, 3 approaches to 2 airports to get familiar with how the 750, Aspen and STEC50 behaved together.

 

The 750 was displaying traffic from the GDL 88. The target triangles were tagged with a relative altitude and a direction of flight arrow. Nice. The triangle was either hollow or solid depending on threatening or non as per chapter 10 of the GTN 750 Pilot's Guide. There is a Traffic Status Key at the bottom of the map. (I made a couple of long approaches with proc turns to MRN, my home base, a somewhat rural, uncontrolled field. There was a Cherokee doing touch and goes but as he did not get above pattern altitude he did not show up as traffic. I think I've noticed Center does not see us on climb out to pick up a clearance until we're a couple of thousand feet AGL.)

 

I am flying again tomorrow, MRN/HKT/LYH/HKY/MRN almost 3 hours and 3 landing at control tower fields so I should be able to learn a lot more.

 

Bob

The GDL-88 will not show Mode C traffic in view like that Cherokee doing touch and go unless the Mode C traffic is detected by a an ATC radar site that relays the data to a UAT. To detect Mode C traffic directly in the pattern you need a Mode C capable receiver such as the Monroy Traffic-Watch. I have one and it shows traffic in the pattern while taxing for take off. It has kept me from take off after alerting me of traffic on short base legs.

 

José  

[Bob_Belville]

José, I could google it, but does the Monroy display on your GPS moving map? 

[Piloto]

José, I could google it, but does the Monroy display on your GPS moving map? 

They will have this option in April for the G530/430/750 but not for the portables. It requires two added wires to the display unit. If you do not have a heading input to either Garmin unit traffic will only show on the traffic screen and the little inset window. If you have heading into the Garmins traffic will be overlaid on the moving maps. Most G530/430 installations do not have heading inputted so you will need to switch to the traffic page to see traffic relative altitude or check on the Monroy LED display. Besides traffic the Monroy display shows your transponder baro altitude, SQUAWK code and bus voltage. In practice while enroute the range selected for the moving map is too large (50nm) to see any nearby (less than 5nm) traffic in detail at the same time, so you will normally switch to the traffic page or the Monroy LED display when alerted.

 

José 

[Bennett]

I am definitely seeing GA aircraft that I am sure have nothing more than mode C. I've had good visuals on more than a few old Pipers, Cessnas, and a couple of RVs while less than 3000' MSL in the vicinity of San Carlos airport while approaching for landing, or climbing out. I flew to San Jose airport this last Tuesday and there were targets on both GTNs with traffic alerts. Prior to the installation of the GDL 88 I had a Zaon unit on the glare shield wired to the 796, and I hardly saw as much local traffic as I do now.

[larryb]

I'm based at KRHV. I just found a notam announcing TIS-B UAT at KSJC, just a few miles away with no terrain in between. I should be able to receive this station just off the ground, certainly less than 5,500 feet. There is a similar notam for KOAK, about 50 miles to the north. Bennett is very close by geographically and seeing much more traffic than my install. I don't see any NOTAM's for this being out of service. Something is wrong...

 

 

FDC 1/4625 SJC  NORMAN Y MINETA SAN JOSE INTERNATIONAL AUTOMATIC
     DEPENDENT SURVEILLANCE, ESSENTIAL SERVICE BROADCAST. EFFECTIVE
     NOVEMBER 10, 2011. THE FEDERAL AVIATION ADMINISTRATION (FAA) HAS
     ADOPTED TWO ADS-B DATA LINKS: 1090 MHZ EXTENDED SQUITTER (1090ES) AND
     978 MHZ UNIVERSAL ACCESS TRANSCEIVER (UAT).  THE TWO LINKS OPERATE
     SIMILARLY AND SUPPORT TRAFFIC INFORMATION SERVICE-BROADCAST

[Bob_Belville]

During my flight today to KLYH we never had traffic close enough to merit a conflict alert but the 750 displayed numerous targets. And the weather on the other side of the mountains was painted. I should have compared it to the XM on 696 but didn't think to set them up on the same range. I created a small album but you'll have to zoom in to see 750 screen. 

[larryb]

I'm happy to report the problem has been fixed and the GDL-88 is working as expected. Garmin and my dealer went back and forth regarding the configuration, but ultimately, it was a defective unit.  I now see the icon that says "Within coverage..." and much more traffic. I did not see the icon on the ground, but once I got to about 1000' it came active.

 

Larry

[Marauder]

Does anyone have one of the GDL units hooked up to an Aspen? Love to hear how they do with that config. Sent from my iPad using Tapatalk

[Cruiser]

I don't believe Aspen has been able to get Garmin to release the interface code so they can connect to the GDL88 unit.

Right now I think Garmin GDL88 will only talk to other Garmin products.

[M016576]

I don't believe Aspen has been able to get Garmin to release the interface code so they can connect to the GDL88 unit.

Right now I think Garmin GDL88 will only talk to other Garmin products.

Go figure... :-(

[Bob_Belville]

I don't see traffic on my Aspen PDF. I can report that on a recent trip to KPDK on the edge of ATL TCA I saw a lot more GDL 88 traffic on the 750 than I've been seeing out in the boondocks.

[bssaunder@gmail.com]

Hi, all- New to forum, need help with GDL-88 issue. Just intstalled GDL-88 in my C172, which has a 530W and an Aspen 1000 pro. Traffic from GDL-88 seems to display correctly, subject to the limitations outlined above. I'm not seeing any weather, and I don't have a screen on the utility page that would indicate that the 530W is set up for weather. Is this an install issue, a weather availability issue (I fly out of KGFL in upstate NY), or some issue with the unit itself? Thanks

[Marauder]

It sounds like an install issue. When you say you see no weather, are you talking about METARs, NEXRADs? Based on the Garmin site, there is some limitation on the GNS weather displayed. The GTN series allows FIS-B but the GNS series is limited to METARs, TAFs and NEXRAD: https://buy.garmin.com/en-US/digital/in-the-air/avionics-safety/weather-solutions/gdl-88-series/prod63471.html

You will also seen nothing on the Aspen as was stated above. What are you seeing exactly?

Sent from my iPad using Tapatalk

[bssaunder@gmail.com]

Hmm, interesting observation. I'm not seeing radar for sure, nor metars or TAFs. I assume the metars and TAFs will appear in some format like my Garmin 496, with icons appearing on the screen indicating availability of the data if i scroll to that spot? Thanks for help.