Crossing KOZAR the airplane is established on the STAR. Per FAA Order 7110.65Y:
- Aircraft will meet all published speed restrictions when on any route or procedure with published speed restrictions regardless of climb via or descend via clearance.
The same Order references ATC use of Mach number at or above FL240. At FL240, 300 knots is equivalent to M70. What if M70 is your speed at FL240. The transition is for spacing, as such logically it doesn’t make sense that aircraft in descent must slow at transition to 280, but the airplane at FL240 can maintain “300 knots” since that is what was maintained in “cruise”.
‘Consider an airplane at FL360 and M84. This equates to 280 knots indicated, which would require 280 knots to be maintained crossing KOZAR.
Here is a NASA report for the HAWKZ RNAV arrival in KSEA, which includes the same note: NOTE: Turbojet aircraft descend via mach number until intercepting 280K. Maintain 280K until slowed by the STAR:
Title: An A319 flight crew; descending via the HAWKZ RNAV STAR to SEA and maintaining assigned .73M; was criticized by Center for not being at 280 KTS when checking in with the next Controller. The chart; however; specifies flights are to descend via Mach number until 'intercepting' the required 280 KIAS until slowed by ATC.
Narrative: SEA Center controller assigned us to slow to .73 Mach. Got a frequency change to SEA Center 128.3. The 128.3 controller asked us our speed and we told her 310 kts. We had not intercepted 280 kts yet. She told us we were supposed to be at 280 kts. Note on Hawkz3 reads Speed restriction: Turbojet aircraft descend via Mach # until intersepting 280 kts. Maintain 280 until slowed by STAR. Flight continued without incident.
Of course querying ATC is good practice if unsure, but the argument for 300 knots to EEEZI is pretty thin in my view.