speed,
Originally Posted by
43Inches
A few scenarios where the set/bugged number is not accurate, 1 in Australia ATS can't see the set IAS, 2, I could descend in VS and disable IAS control, meaning whats in the window/bugged don't matter or 3, totally ignore the automatics and hand fly meaning all settings in the windows are just alerters and reference for the pilot. Lastly I could be flying something old that does not have IAS or Altitude settings transmitted via SSR at all, I know of a few types, esp turboprops still floating around that don't connect to said system. Also add that in some autopilot set ups I can select which input side the IAS comes from, so if the FOs side is under-reading I could select that side and get a higher speed than selecting the CPTs side.
ADS-B does not transmit IAS unless the GNSS data is unavailable, GNSS easting speed, GNSS northing speed is the priority, from that the ground speed and true track is resolved using trigonometry. As a backup the aircraft will transmit IAS and heading if that data is made available to the transponder.
The data packet will also transmit a number of other parameters from the glare shied and FMC, ATC may choose to use this data, it may choose not to. The aircraft sends all the data it can, and the ATC system decodes what it wants from the raw data packet.
The raw data packet is still in the system, ATC can post process the data packets to see how the aircraft is being operated (this is what NATS to do arrival speed compliance). If you choose to turn everything off that’s fine, that can also be seen.
I would be very surprised if ASA does not look at that raw data as well as the noise measurements for arrival and departure tracks to understand how aircraft are being operated in response to noise complaints and amend procedures accordingly.