FighterControl

Rexently picked up an Apache flying near LGW that was showing up onAdsb as ZJ194. As this airframe is back in Mesa it has obviously had its box swapped out to another machine. Can any of the Wattisham locals advise if they have made a Mk 1 eyeball on whichever aircraft is currently pinging as ZJ194?

Many thanks

ZJ215 & 230 which visited Brize Norton recently were showing on ADSB as different aircraft as well.

I read off ZJ195 at Duxford the other day , it was showing as ZJ192

Is it deliberate or a lazy avionics engineer - should be a quite simple task to update the aircraft ID when a box is taken off one aircraft and subsequently fitted to a second aircraft?

Cuillin wrote: ↑

Tue Apr 27, 2021 4:49 pm

Is it deliberate or a lazy avionics engineer - should be a quite simple task to update the aircraft ID when a box is taken off one aircraft and subsequently fitted to a second aircraft?

The box doesn't transmit the reg, hence the need for a database, which falls out of date when a box-swap takes place.

Cuillin wrote: ↑

Tue Apr 27, 2021 4:49 pm

Is it deliberate or a lazy avionics engineer - should be a quite simple task to update the aircraft ID when a box is taken off one aircraft and subsequently fitted to a second aircraft?

Why should they need to? Just so it matches up with some enthusiasts database?

As long as the code is unique and within the allocated range, that is fine.

Wait for the AH2 they are being delivered with serials taped over !!

AyrForce1 wrote: ↑

Tue Apr 27, 2021 5:11 pm

Cuillin wrote: ↑

Tue Apr 27, 2021 4:49 pm

Is it deliberate or a lazy avionics engineer - should be a quite simple task to update the aircraft ID when a box is taken off one aircraft and subsequently fitted to a second aircraft?

The box doesn't transmit the reg, hence the need for a database, which falls out of date when a box-swap takes place.

Are you sure?

My understanding is that the ADS-B (or military equivalent) is an off the shelf box that will be updated (hex code/aircraft registration etc) when fitted to a particular airframe.

AAC Apaches seem to have a high average of registration output’s that don’t match the airframe compared to other military aircraft let alone comparing to civil aircraft. Other such instances of military aircraft mismatches are rare (there is a single Osprey operating out of Mildenhall whose box doesn’t match the airframe).

The hex code and reg should be pre-loaded in the avionics on a particular airframe whilst the call sign on the day (QID21, HKY664) would be inputed by the crew prior to flight.

I suspect that the box has been fitted to airframe A, operated on airframe A, removed from airframe A, placed on shelf for a few months, fitted on airframe B but has not had the hex code/registration updated for airframe B.

Let me know if I am wrong - happy to be corrected.

Only for the road transit.
Regards
Mark

Northsky wrote: ↑

Thu Apr 29, 2021 5:51 am

Wait for the AH2 they are being delivered with serials taped over !!

They don't transmit registrations, they transmit a binary code along with height and position data (if enabled).

The octal code is then decided to octal, which is then further decoded to the hex code you're more used to. For commercial/ATC purposes this can then be queried against a flightplan to ensure its the correct radar return.

At no point does the aircraft transmit it's registration as part of its Mode-S data. This comes from local databases on the receiving end. For hobbyists, that's ADS-B Exchange, FR24, Planeplotter, etc. For commercial/ATC that's data provided to the ATS provider or from flightplan data.

So yes you are likely right that the code being transmitted has changed because the Mode-S transponder unit has changed. But that's not a problem for military aircraft operators. A code not matching what hobbyists think the airframe should be is a problem with the hobbyist's database, nothing more.

You are quite correct EGVP - the 24 point binary code is reduced to the 6 point hex code which is allocated to a particular airframe - hence the registration ‘appears’ to the appropriate receiver once the hex code is received and translated.

I, personally, don’t give a jot about what ‘reg’ appears on FR24 - it was just an attempt to answer why so many AAC Apaches (and occasionally other military aircraft) registrations are displayed wrongly at the receiving end.

The registrations (on mode S displays, civil and military) are there for the same reasons as they are painted on the side of an aircraft - otherwise, why would any aircraft have a registration?

I think that we agree that a box has been changed between airframes and the hex code, most likely, has not been updated.