Flight tracking and military aircraft

I've seen a lot of posts, both here and elsewhere, about tracking military aircraft on ADS-B Exchange or FlightRadar24. Many of them say that the plane turned its transponder off at some point and "disappeared". This thread is going to attempt to clear things up a little bit.

The first is that the aircraft doesn't turn off its transponder, unless it's in an operational mission area, such as an RC-135 flying near Russia. Their transponder, which is used by air traffic control to track them, is still broadcasting for them to see. What we see online is the Mode S, or ADS-B Out portion of the transponder signal.

When you're tracking a military aircraft, it's important to note what type of signal it is.

Here are two examples using a pair of C-130s over the western US.

The first is an HC-130J from Davis-Monthan AFB in Arizona:

The second is a C-130H from Colorado.

If you look on the left side, where the aircraft information is, under "Signal" you'll see the type of tracking that is taking place. In the first, it's using ADS-B to track the aircraft. That means that the ADS-B Out signal is active, and it's automatically sending a position signal using the GPS data from the aircraft navigation system.

In the second, you see that it's using something called MLAT. While appearing to be the same as the ADS-B track, it's actually quite a bit different. MLAT stands for Multilateration. MLAT uses a method known as Time Difference of Arrival to track an aircraft. In this case, the MLAT ground stations "listen" for a signal from a Mode S transponder equipped aircraft. When three to four of these stations triangulate the position of the aircraft, you get a pretty accurate position on the tracking map.

The thing about MLAT however is that it's line of site. If the aircraft leaves the range of the receivers, you lose the signal, and it drops off the tracking map. This usually happens when they fly out to sea, but it can also happen over land in areas there aren't many receivers. If you watch parts of west Texas you'll see aircraft show a dashed line, and the position will jump around. Frequently it will appear to turn back and go a couple hundred miles in the other direction, then suddenly jump back and show a solid track again when it comes into range of receivers again.There's nothing nefarious about what's happening, and they're not trying to keep their location secret, they just aren't broadcasting it for everyone to see.

a reply to: Zaphod58

S&F... thanks Zaphod!


I've gotten better over the years, and there is much room for improvements. Flightradar24 has been doing a wee bit better at tracking too this past year.

Still can't track an F-18 out of Fallon or any F-22... but again the KC135 that took off next door sometimes does not appear.

a reply to: Bigburgh

The F-18s are starting to show up. I've caught several of them in the last couple of months. For some reason they show up as F-18S on ADS-B Exchange though.

originally posted by: Bigburgh
a reply to: Zaphod58

S&F... thanks Zaphod!

I've gotten better over the years, and there is much room for improvements. Flightradar24 has been doing a wee bit better at tracking too this past year.

Still can't track an F-18 out of Fallon or any F-22... but again the KC135 that took off next door sometimes does not appear.

On this screen, on the right, there are often more planes spotted than are listed...Any way to get all of them? And, on the far right it has the column with the heading 'seen'...Any idea what that is?

a reply to: Zaphod58

F-18's won't do it on my end. F-35's Will on ADS-B in the vicinity of Arizona and southern California.

I'm also having discrepancies with newly licenced aircraft pulling an old radio or transponder from a mothballed or junked aircraft.

Saw one aircraft today that was an experimental using and old glider radio.

In all honesty I'm looking at with maybe far less than 10% accuracy. The rest comes down to what data shows. Altitude, speed, range.. then watch to see where the aircraft goes. So 2%. It's become quite a hobby watching these.

I'm on the east coast. My day starts by 6:30 7am.. then I start watching the time zones. I always end up at Edwards/Mojave by 9 my time.

I'll get better.

originally posted by: Iscool

originally posted by: Bigburgh
a reply to: Zaphod58

S&F... thanks Zaphod!

I've gotten better over the years, and there is much room for improvements. Flightradar24 has been doing a wee bit better at tracking too this past year.

Still can't track an F-18 out of Fallon or any F-22... but again the KC135 that took off next door sometimes does not appear.

On this screen, on the right, there are often more planes spotted than are listed...Any way to get all of them? And, on the far right it has the column with the heading 'seen'...Any idea what that is?

I isolated that for military only... also that helicopter was adjusting it's gps when i cought it a +90 feet. It was actually at 100feet

a reply to: Iscool

That shows the total number of aircraft being tracked, and the number of aircraft being tracked in the area of the map. In this case, as he said, it's filtered for military. There's only one military aircraft flying in that area, so there's only the one showing. If you have it set to show all aircraft, and pull the map back you'll start seeing more aircraft.

a reply to: Zaphod58

I don't typically follow the flights nor do I know enough to determine what is odd or normal when it comes to tracking these flights.

So in your opinion have you seen anything to suggest something out of the ordinary is going on in the background since January to suggest some military events are brewing in the background as many of these threads and sites are proposing with moving target dates?

Don't worry I will keep it just between you and me and the internet

Bigburgh, Zaphod got me hooked to watching late at night ...back when Iran shot down that plane by mistake.

a reply to: interupt42

Not really, no. There have been a couple interesting flights, but nothing on any scale that suggests anything is going on. Some interesting callsign stuff, but again nothing that suggests anything.

Thanks for this, was wondering about all the chatter about these flights...

originally posted by: Zaphod58
...
In the second, you see that it's using something called MLAT. While appearing to be the same as the ADS-B track, it's actually quite a bit different. MLAT stands for Multilateration. MLAT uses a method known as Time Difference of Arrival to track an aircraft. In this case, the MLAT ground stations "listen" for a signal from a Mode S transponder equipped aircraft. When three to four of these stations triangulate the position of the aircraft, you get a pretty accurate position on the tracking map.

The thing about MLAT however is that it's line of site. If the aircraft leaves the range of the receivers, you lose the signal, and it drops off the tracking map. This usually happens when they fly out to sea, but it can also happen over land in areas there aren't many receivers. If you watch parts of west Texas you'll see aircraft show a dashed line, and the position will jump around. Frequently it will appear to turn back and go a couple hundred miles in the other direction, then suddenly jump back and show a solid track again when it comes into range of receivers again.There's nothing nefarious about what's happening, and they're not trying to keep their location secret, they just aren't broadcasting it for everyone to see.

Interesting... similar to the old LORAN-C navigation systems maintained by the USCG way back (I was an electronics tech that worked at a monitoring station in Kodiak AK in '78/'79, and a transmitter station on Marcus Island Japan in '81/'81)...

So, as one with knowledge of such things, do you see any indications of unusual activity over the last few weeks/months?

ETA: sorry, I see you already answered this...

a reply to: tanstaafl

I'm just kind of glad the big Japan swap didn't get noticed. People really would have freaked out.

originally posted by: Zaphod58
a reply to: tanstaafl

I'm just kind of glad the big Japan swap didn't get noticed. People really would have freaked out.

Guess I'm not as in the know as you assume...

What was the 'big Japan swap'?

a reply to: tanstaafl

One of the F-18 units forward based in Japan came back to the US with all their aircraft, and were replaced by a unit flying F-35Bs.

originally posted by: Zaphod58
a reply to: tanstaafl

One of the F-18 units forward based in Japan came back to the US with all their aircraft, and were replaced by a unit flying F-35Bs.

Is that good or bad?

Rotflmao!

Ok, so, I'm obviously much, much less in the know than you are still assuming...

a reply to: tanstaafl

It's perfectly routine. We used to get a bunch of planes through at the start of the year as the squadrons in Japan changed out aircraft. The start of the year was always a fun time because you got all kinds of aircraft you didn't normally see.

originally posted by: Zaphod58
a reply to: tanstaafl

It's perfectly routine. We used to get a bunch of planes through at the start of the year as the squadrons in Japan changed out aircraft. The start of the year was always a fun time because you got all kinds of aircraft you didn't normally see.

Ah, ok, so when you said 'people really would have freaked out', you mean those in the Q thread that are getting all worked up about routine air traffic.

Got it, thanks for your patience!

a reply to: tanstaafl

And those who see any kind of exercise happening, and jump straight to we're going to war, or martial law is happening.

originally posted by: Zaphod58
a reply to: tanstaafl

And those who see any kind of exercise happening, and jump straight to we're going to war, or martial law is happening.

It looks like Boeing has been trying out some new tech on their planes. I have been watching them on AirNav the last couple of days. They are leaving Tacoma and doing large flight patterns across Washington and Idaho. There was even a Janet Air flight yesterday on the same flight pattern.

Maybe they are just repairing a bunch of planes and testing them?

There is an IsAir flight doing touch and gos in Pendleton which seems odd but again maybe they are trying out new tech on the planes🤷‍♀️