Originally Posted by
InfrequentFlier511
I keep wondering about the flight deck asking atc for their speed, when it should be available on the PFD. (I know, UAS, but why think ATC would know any more than you?)
Sadly, that may have been more of a forlorn hope than an expectation.
To clear up any confusion, it now seems that ATC are unlikely to have had the necessary equipment (specifically EHS) to see JT610's IAS. And even if they did, it wouldn't necessarily have been any more reliable than what the crew's ASI(s) were displaying.
Re groundspeed, ATC would have access to that (probably both the GPS-derived GS being sent by ADS-B and a less accurate PSR-derived GS). Having said that, the crew would have also have had groundspeed in front of them, on both the PFD and ND, again derived from GPS and therefore not subject to any UAS issues.