Strange trail on Skyview

Today I captured a very strange trail on Skyview.

I have seen it before but never been able to confirm it wasn’t a problem in my system

Today I also caught it on my second system. The only connection between my two systems is the pole their antennae are mounted on.

Has anyone near Melbourne or Moorabbin seen this?

Anyone any idea what is causing it?


The plot thickens slightly.

Whilst I was watching it the Ident changed from 23 8796 to EVQ and quite quickly back again.


23-8796 is an Aeroprakt A32-L Vixen light sport aircraft.

Also known as VH-EVQ

Seems it has a split personality and can’t decide its identity from one moment to the next.

I wonder if the reg painted on the side of the plane changes every time its ADS-B ident changes just like James Bond’s Aston Martin?


Somewhere in the system there is an out of date hexcode/callsign correlation I suspect.

I was watching the Skyview and it was changing there every 30 seconds or so for a while.

I assume that means the plane is actually sending erroneous data.

I have been seeing it for some six months or so but this is the first time I have seen it on both my receivers at the same time.

Maybe someone else in Melbourne has also viewed it.


The two usual causes are:

  1. The ICAO code is the same for two planes. ICAO codes should be unique.
    This looks like this is the case with the 2 registered planes with the same ICAO.

  2. The GPS receiver in the plane is malfunctioning. There is a bit flip that can cause the plane to jump back and forth.

Although I didn’t get a screen shot yesterday then aircraft was popping all over the place including suddenly appearing 400NM east or 500NM west or 350NM North West of here. The plane would only appear there for a second or two.

Whilst it is possible I will get a legitimate position report over those distances every now and then it is really not possible for it to be two planes with the same ICAO and then seemingly returning to normal at about 5 NM. for a few minutes before exhibiting Warp speed again.

It is probably significant that it is changing ident between EVQ (VH-EVQ) and 23 8796 which seem to be the same aircraft (Aeroprakt as belzybob noted above.

That would account for the sudden location changes but not the change in Ident.

I can’t find 23-8796 even though the photo clearly shows that painted on the fuselage. Is that a registration number?

It makes a mess of my Skyview which is interesting but it is just my hobby and really of no consequence.

Does that data get fed into Flightaware (and Planefinder etc) and cause any anomalies further up the chain?


Yes, this can mess up the end data. There is someone on the FA staff that looks through this type of stuff.

  1. If you click on the plane in Skyview and then click on the FlightAware link it will take you to the Flight page. See if the path is the same as on your Skyview map as on the FA website.
  2. Click on the “Report inaccuracies on this page” button and then type in what you see.


I’ll follow up on that as I don’t want to be sending you erroneous data.