I picked an aircraft at random (a PA28) that was live and showing MLAT. Then went back to look at previous flights for the same aircraft and they showed as MLAT too. Just to see what ADSBExchage recorded for historical flights.
So isn’t Mode-S shown as MLAT and with added ES becomes ADSB. If so it looks like things are working on the aircraft in question.
Thanks for the clarification Jeremy.
You are of course correct, that Mode-S aircraft are reported as (and using) MLAT - otherwise, without their own ground radar, it would of course be impossible for the tracking sites to report the position and track of aircraft transmitting solely Mode-S signals.
You are also correct that Mode-S with ES is ‘accepted’ colloquially as ADSB and reported as such on tracking sites, even though the type of signal transmitted (known as DF17) is measurably different from ‘True ADS-B’. In practice FLARM and PilotAware are also forms of ‘ADSB’ (Automatic Detection Surveillance (by) Broadcast (of position and other relevant information). They just operate on a different frequency to the normally accepted 1090 MHz used by ‘Traditional ADS-B’.
Together with cellular-based systems like SafeSky, PilotAware and FLARM are now referred to by EASA as part of the ‘ADSB-Light’ suite of surveillance tools being considered by EASA and the CAA as acceptable for use in ‘common usage airspace’ known as ‘U-Space’ - where it is anticipated that manned and unmanned aircraft will be allowed to operate together
without the need for exclusion zones. This being the case, might the tracking sites not simply be using the generic term ADSB to describe reports derived from ‘known-position’ transmissions of any sort, possibly combined where available with positions derived by MLAT of ‘Pure Mode-S’?
I am not convinced that the label ‘ADSB’ on a tracking site, without further clarification and corroboration, provides incontrovertible proof that a Mode-S/ES installation is operating as intended. If that was the case, how do you account for the lack of
specifically DF17 ADSB reports from the multiple sites on the ATOM-GRID Network which reported P3i and FLARM data from the G-RUVE, when the database also contains multiple DF17 reports from other aircraft in the same area during the same time periods?
Unless and until we can find another explanation, the logic clearly supports the likelihood of a problem with DF17 Mode-S/ES transmissions from G-RUVE rather than the reverse.
Regards
Peter
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