BAe 125 Series 800
Flight Crew Air Transport Pilot (ATP)
Training / Qualification
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Returned To Clearance; Flight Crew Became Reoriented
Human Factors; Procedure
Upon arrival into CYYZ airport we were issued a descent clearance. At the time we were cruising at FL260. The clearance issued was as follows. 'Descend 240; Descend Via Arrival (Nuber2)' So we began our descent to FL240 then continued our descent VIA the Arrival as instructed. Passing FL230 controller came on and asked where we were going we were instructed to descend to FL240. My reply was correct; then we were given descend via the arrival so we were planning our first cross which was at ROKTO between 14000 and 12000. The controller responded with an explanation how they are changing phraseology in Canada and that my clearance to descend via didn't actually mean I could descend via. It meant that I was only cleared to the altitude given but was required to meet STAR restrictions in the process. The way the clearance was given and the meaning of the clearance was very confusing. We discussed for a few minutes; I voiced my concern that the way the clearance was given was very confusing. The controllers did not appear to be bothered; almost as this was not the first encounter with the confusing instructions. He simply gave me a new attitude and we proceeded in as normal. Be more specific when you issue and clearance with the DESCEND VIA phraseology. This gives the impression that the pilots are expected to descend via the instructions on the given chart. A better way to say what this controller wanted was perhaps to say; 'Descend FL240 and COMPLY with STAR'. This says right away that I am only cleared to FL240. Descend to FL240; Descend VIA the arrival - to me this means start your descent to FL240 now and then descend VIA the arrival. The difference being the first is a hard altitude and clear do not go below; the second says start down and meet restrictions per the chart.
Hawker 800 Captain reported misunderstanding a Canadian Controller's instruction to descend to FL240 and descend via NUBER2 arrival. The descent was continued after reaching FL240 without clearance to make the ROKTO crossing restriction.