B737-800
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 108
Communication Breakdown; Confusion; Situational Awareness
ATC Issue All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Airspace Structure; Human Factors; Procedure
Our PDC clearance was to fly the RNAV Departure and climb via the SID except maintain 4000 feet. When we checked in with Departure Control; we stated; 'Company # checking in at 2000 feet; climbing to 4000 feet via the TERPZ6.' The Controller responded; 'Roger; climb via the SID.' In my mind; we WERE climbing via the SID and I wondered if we had just had a change to our clearance. I asked the Pilot Monitoring to confirm the altitude we were cleared to and the Controller said; '17;000 feet. When I say climb via SID; it deletes all previous restrictions.' This may be true. It may be right out of the ATC Controller's Handbook. But it's the very first time I've ever heard it. Every other Controller I've ever heard modify a climb via clearance states something like; 'Roger; climb via the SID to 17;000 feet' or 'climb via SID; delete the 4000 feet restriction;' etc.; something that makes it patently clear that a new altitude has been issued.As I said; this may be entirely correct terminology; but it seems unwise to just decide; out of the blue; to start using a new way to clear that most of us have never heard before; and expect crystal clear interpretations. With something as Safety critical as an altitude clearance in congested airspace; I think it would be wise to ensure clarity in such clearances. I think it would also be wise to prescribe a climb via clearance that is issued the same all over the country. Presently there are at least half a dozen different ways such clearance show up on our PDC's. It shouldn't be a creative writing attempt. There should be a formula followed by all ATC facilities.
A 737 First Officer reported being unsure of their assigned altitude climbing out of BWI on the TERPZ6 SID due to the phraseology used by ATC.