Flight Radar...missing GA.
 

Hi,

I live near a popular aerodrome and see GA aircraft all the time, but they don't display on FR24...however they do on ADSB exchange?

Why is this?

Thanks,

Various options:

1. There might not be an FR24 feeder in the area;
2. FR24 won't show an Mode-S aircraft until it has achieved a certain threshold distance of calculated flightpath*;
3. The traffic might be using Pilot Aware or another transponder protocol that isn't fed to FR24;
4. The pilots might have requested that their aircraft be elided from FR24


* this very frustrating when one has an alert set for a particular reg and FR24 never triggers it even though it 'knows' the aircraft is airborne

Many (most?) GA aircraft don't have ADS-B, only Mode S (and a few not even that).

For aircraft without ADS-B, the flight trackers can only determine where they are by using a technique called multilateration (broadly analogous to triangulation). That's only possible if several feeders are simultaneously receiving transmissions from the aircraft in question at the same time.

That's why you will often see GA aircraft on one flight tracker network but not on another.

I wondered the same thing as we have GA and Military air traffic and there seemed to be inconsistencies.
I'm not sure if you've looked at this page on FR24, but I found it quite useful.
https://www.flightradar24.com/how-it-works

All three of the two seat Spitfires operating out of Biggin sometimes show up, sometimes not, even though I can see/hear them. I did receive a targeted ad on one of the sites the other day asking for hosts to run a receiver in my area.

One of the Spits just took off... the Gippsaero camera ship is showing up but not the Spit.

Edit: just heard a muted rumble, MJ772/G-AVAV showing up.as returning.

Slight thread drift, but interestingly the Biggin Spits usually show up on Heathrow's public WebTrak system, which was extended recently to cover pretty well all activity in most of the London TMA and beyond.

Here's a recent example:

https://cimg9.ibsrv.net/gimg/pprune....3926c9f6b4.jpg

Just another example.
I spotted what I thought was an Airbus test flight and had a look on FR24 but it was a French Air Force A330.
Went outside an took a couple of photos thought couldn't see much.
Zooming in revealed it was refueling (practice I assume) an AWACS, which did not show on FR24.
I appreciate this is not GA BTW
https://cimg5.ibsrv.net/gimg/pprune....d0e3affb02.jpg
https://cimg7.ibsrv.net/gimg/pprune....2f6ff7de8e.jpg