An airplane in my list though not on the map, ICAO 400910, is incorrectly showing the Union Jack flag with country of registration being the UK and registration and aircraft type being n/a. This airplane is currently owned and operated by the Philippine Air Force with registration # 10669. It’s a Fokker F27 500 Friendship built in 1984. (Oddly, VirtualRadar’s database also shows it to be registered in the UK. I wonder where both databases are getting their information from?)
The 400000-43FFFF range of addresses is allocated to the UK, so that’s why it’s showing the UK. If the aircraft is actually Philippines-registered, then its transponder is incorrectly configured (the Philippines range is 758000-75FFFF)
Generally the way that this works is that each national aircraft registry allocates a Mode-S address from their range when assigning tail numbers. When an aircraft tail number changes (and especially when it changes country of registration) the avionics needs to be updated to reflect this change. Unfortunately it’s often missed. Another way this can happen is if a second-hand transponder is installed and not re-configured for the new aircraft.
Aircraft type lookups are all keyed off the aircraft’s Mode-S address, so if the address is wrong, everything else will be too.
Alternatively, this can be the military playing games with their addresses. Though Hanlon’s razor probably applies here.
Thank you so much for that information. Now I understand how it works. I suspect that the avionics tech didn’t change the Mode-S address after the PAF purchased the aircraft from the UK. I’ve seen other PAF aircraft that do indeed show the Philippines as their country of origin or ownership. Being an Air Force plane it’s never in communication with civilian air traffic systems anyway.
I’ve seen another plane, a small, privately-owned, single-engine eastern European Bristell, which shows up as being Russian but with a Czech registration number which is probably also due to the Mode-S address not having been changed to the proper Philippine one. I’ve also seen other smaller planes that still have American N tail numbers in the database. Now I understand why. Thanks again.
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Previous registration of this F-27 was G-ECAH. Looking up that reg on G-INFO web site shows the ICAO address was 400910.
Hence you are correct that the address was not changed when it went to PAF.