NavCanada has temporarily suspended use of new International Civil Aviation Organization (ICAO) “climb via SID” and “descend via Star” phraseology it had adopted on April 27. The agency said the move was made “out of concern over altitude deviations we were seeing in the system and the unforeseen large increase in workload as a result. We are continuing to communicate with airlines, aircraft operators and our employees as we revert to the phraseology rules that were in place prior to this change.” That clearance phraseology includes both lateral path as well as vertical constraints.
Previously, ICAO adoption of the new phraseology signaled international acceptance of “climb/descend via” clearances that the FAA implemented in 2014, but the effort to harmonize ATC phraseology did not change some key differences in ICAO-member specific procedures.
When an FAA controller issues a “descend via” clearance, it tacitly cancels any ATC-assigned speed restrictions, said NBAA's ATC, Airspace and Flight Technologies Working Group chairman Rich Boll. When NavCanada issues a “descend via” clearance, the controller expects pilots to continue to comply with any ATC-assigned speed, rather than the speed(s) published on the chart, he said.