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Comment by mmaunder | Hacker News Reader

Im surprised to see military traffic over the US. They tend to fly with ADSB out turned off and have an agreement with FAA to be able to do that. Also surprised to see gliders who generally don’t broadcast ADSB out. In the US, we are required to have ADSB out within most controlled airspace and within the mode C veil of a major airport (within 30nm and up to 10,000 MSL). So most GA planes have it but remote areas have planes without ADSB out.

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If you look at https://globe.adsbexchange.com, and filter for military/interesting (the U button at the top of the screen), you'll see that at any given time there are a LOT of military flights over the US. Most are transport, refueling tankers and what seem to be pilots-in-training (mostly in Texas and Florida, some in Colorado), but there are plenty of helicopters and smaller Lear-type jets. When the president or vice president is flying somewhere there are typically one or more E-3 AWACS planes in the air to provide radar coverage.

There are certainly military planes that fly without ADSB, but for flights where secrecy doesn't matter, they seem to fly with it on. I've seen all manner of planes with ADSB, from U2 spy planes, F-15, F-16, A-10, the occasional B-52, and more.

Cool. Whenever I see military traffic here in Colorado they don’t show up on adsb except for the DA20 trainers in the pattern south of Springs.

Fighters often don't have ADS-B, but there are lots of other military aircraft that routinely use it (transports, etc.). Go to https://globe.adsbexchange.com and press U to show only military.

My town, north of Dayton, OH was recently overflown by a group of fighters (I believe F-18's). I was surprised that they didn't appear on the ADS-B tracker site I ran inside and looked at. I guess it makes sense.

I'm just a couple of miles from DAY and see a lot of traffic every day. It would be interesting to know how military aircraft like that coordinate with civilian air traffic control.

(I like to listen to Dayton approach while watching an ADS-B tracker site. I enjoy seeing the traffic fly over my neighborhood. I find it oddly amusing to look up at a plane I just heard getting clearance to land knowing that I just heard the voice of somebody up there thru my speakers. I don't know why it's so pleasing...)

I tracked, briefly, a F15E flying past yesterday.

I'd read about small retro reflectors they bolt on when not in combat so the stealth fighters will show on domestic radars

Edit: they're called Luneburg Lenses

I'm surprised about this, I thought it's pretty easy to add ADS-B to modern IFF module and they can just switch between different modes.

Just speaking from experience, in Colorado no military has it on except for the trainers. Having a chinook pass under you and be totally invisible on the iPad is a weird feeling.

The ADS-B Out situation with gliders in the USA is complex. Many high-performance modern gliders used for racing and cross country flying are equipped with Mode-S transponders with 1090ES Out (either 14 CFR 91.227 ADS-B Out compliant or TABS/TSO-C199 ADS-B Out compliant) as well as the glider specific FLARM traffic awareness system that broadcasts and receives proprietary low-power position data. FLARM systems, at least as used in the USA also typically receive 1090ES In so they drive the integrated traffic display and warning systems in these modern glider cockpits. For historical and technical reasons gliders use a FLARM modified NMEA serial data protocols for traffic data in the cockpit instead of what is found in GA aircraft ADS-B traffic display systems.

Gliders potentially face very different risk scenarios and their owners will hopefully equip for what is the most significant risks to them and others. e.g. gliders often fly close to each other, especially when thermalling together, if flying with other gliders in remote areas then the FLARM system optimized to handle glider on glider threats is optimal (where GA focused ADS-B produces far to many false alerts), if flying near lots of GA aircraft ADS-B Out (and In via FLARM) is likely optimal, if flying near airliners, fast jets and tactical military aircraft then transponders alone even without 1090ES Out may be most critical item for their SSR, TCAS and IFF compatibility. Ideally owners do equip with all three... Mode-S, 1090ES Out, and FLARM.

The challenge may be more where there are low-cost/low-value gliders, maybe trainers and glider club owned gliders especially those located in busy traffic areas. You would hope those owners long ago got the message they should be equipping with some forms of supplementary traffic broadcast/awareness systems.

UAT adoption in gliders is nearly non-existent as FLARM systems only receive directly on 1090ES In and you don't want to rely on ADS-R coverage in remote or mountainous areas.

TABS/TSO-C199 is an easier route to an approved installation of ADS-B Out systems in type-certified gliders. TSO-C199 was developed by industry and the FAA following the 2006 mid-air collision between a glider and Hawker business jet near Minden NV. Experimental category gliders will typically have 14 CFR 91.227 compliant installations done under the same "meets performance requirements" clauses as many experimental power aircraft.

I started playing around with ADS-B and military aircraft are all over the place, at least on the east coast of the USA.

In fact, this Seahawk just flew over: https://globe.airplanes.live/?icao=ae6904

For general transport/rebasing, it seems like it would just make life easier on air traffic controllers, and probably also other traffic in the air (I think TCAS uses ADS-B?). By way of analogy, the military might have permission to drive around at night with their lights off, but it'd make me more comfortable if they did that only when it was operationally useful (i.e. I assume B-2s taking off from Missouri to go bombing have transponders off the whole way.)

One of the "tells" for military aircraft flying without ADSB is when you see refueling tankers (KC-135) doing loops for periods of time, and no other military aircraft around. Those tankers are refueling something, they don't just fly around for grins.

Military aircraft operators in the USA are pretty cautions about non-ADS-B Out or non-transponder operations. Air Force bases etc. will have active MACA (Mid-Air Collision Avoidance) programs, with aircraft and controllers working to reduce conflict potential with civilian traffic. Many bases will have MACA information on their web sites and staff to contact, and they are typically very responsive. Ironically the ones I have worked with were trying to encourage more civilian GA aircraft to adopt transponders, and to utilize the flight following services of their ATC/RAPCON.

TCAS uses active transponder interrogation from the TCAS unit interrogating a threat target's Mode-C or Mode-S transponder. TCAS only uses ADS-B In in an indirect way, in large part to acquire traffic in the area that is not yet a threat, and reduce it's RF congestion caused by excessive interrogation, especially of legacy Mode-C targets. A TCAS II system will fly you right into say a UAT out equipped aircraft without issuing an RA (resolution advisory) if that threat aircraft has no transponder or an inop transponder.

TCAS II only issuing an RA based on active interrogation of a threat aircraft's transponder is a kind of safety feature given the potential spoofing of ADS-B Out data.

"ADSB" data isn't always ADSB, either. The big ADS-B mapping sites (adsbexchange.com, and the ones that popped up after its acquisition) also collect MLAT data from their volunteer stations to triangulate aircraft with ADS-B disabled but can otherwise be detected, if not located directly (via Mode S, mostly, I think).

Those Reaper drones show up on FlightRadar24 and ADSBExchange while patrolling over the Black Sea monitoring Crimea and beyond.

There's plenty of H60s and H47s out of Lewis McChord on ADSB, not to mention P8's, C17's, etc...if you're on flight following you'll get advisories or even just watching "the fish finder" you'll see them.

Sometimes they forget to turn it off:

https://theaviationist.com/2023/11/22/usaf-ac-130j-iraq/

That article states that it's unlikely that they forgot, and much more likely that it was deliberate.

Interesting, when it happened at the time the theory was they forgot.

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