Narrative:

While departing bwi runway 33R a discrepancy between operation planning and ATC expectations apparently occurred; likely due to the 'climb via; except...' phraseology. The clearance received prior to departure from bwi was to climb while maintaining visual separation from an aircraft that had just departed; turn left 290 deg and contact departure. The clearance received from clearance delivery on the ground prior to taxi was 'clear from bwi to ZZZ via the TERPZ6.ottto etc as filed; runway 33R; climb via departure except maintain 4;000 ft. The TERPZ6 departure has climb via fixes along all departure routes except runway 33R; which has a radar vector segment with no climb fixes until terpz. The bwi takeoff clearance negated the dp; as I was not on any part of the published dp headings. Upon hand-off to ATC departure control I was given a clearance direct to terpz and climb via; except I had already leveled off at 4;000 feet on the 290 degree heading. Given the new clearance; I initiated a turn direct to the fix and programmed the climb. The requirement to cross terpz at 11;000 feet then became an issue. I could easily make the crossing restriction; even delaying the climb while programming the FMS; however the controller was alarmed and perplexed with my delay in climbing. He queried me over the radio why I had leveled off; to which I responded that 4;000 feet was my prior clearance limit; but was now initiating a climb. I began the climb and he decided to take me back off the dp; and issue vectors and yet another altitude. Again; climb via terpz; except maintain FL190. The top of the dp is 17;000 feet. Although we as pilots generally understand the intent of a clearance; this 'climb via; except' has become an abused phraseology. Although amending the altitude to another in a dp or STAR and issuing the 'climb or descend via...' instruction may make sense when the altitude assigned is within the top or bottom of the published procedure. It makes no sense when the new altitude is not within altitude limits of the procedure at all. Especially if on vectors as you cannot climb via a procedure unless on a published segment of that procedure (no fixes to climb to). You can climb to be abeam; before; after; or just make an altitude by a time requirement; but the climb via is being modified to the point it often makes no sense to even issue it as an instruction. The new RNAV SID/dps and stars are supposed to eliminate unnecessary radio communication; they often do not as their 'amendment' of published happens more than half the time. This is indicative of a problem with the navigational routing solution chosen. To my knowledge; a climb or descend via with crossing restriction does not require an immediate climb or descent; only that the aircraft must be level at the assigned altitude by the fix via normal procedures. If a constant angle or rate of climb or descent is required or expected then the angle or rate should be published in the procedure.

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Original NASA ASRS Text

Title: Citation Captain reported confusion over ATC phraseology used that resulted in an altitude deviation.

Narrative: While departing BWI Runway 33R a discrepancy between operation planning and ATC expectations apparently occurred; likely due to the 'climb via; except...' phraseology. The clearance received prior to departure from BWI was to climb while maintaining visual separation from an aircraft that had just departed; turn left 290 deg and contact departure. The clearance received from clearance delivery on the ground prior to taxi was 'clear from BWI to ZZZ via the TERPZ6.OTTTO etc as filed; Runway 33R; climb via departure except maintain 4;000 ft. The TERPZ6 departure has climb via fixes along all departure routes except Runway 33R; which has a radar vector segment with no climb fixes until TERPZ. The BWI takeoff clearance negated the DP; as I was not on any part of the published DP headings. Upon hand-off to ATC Departure control I was given a clearance direct to TERPZ and climb via; except I had already leveled off at 4;000 feet on the 290 degree heading. Given the new clearance; I initiated a turn direct to the fix and programmed the climb. The requirement to cross TERPZ at 11;000 feet then became an issue. I could easily make the crossing restriction; even delaying the climb while programming the FMS; however the Controller was alarmed and perplexed with my delay in climbing. He queried me over the radio why I had leveled off; to which I responded that 4;000 feet was my prior clearance limit; but was now initiating a climb. I began the climb and he decided to take me back off the DP; and issue vectors and yet another altitude. Again; climb via TERPZ; except maintain FL190. The TOP of the DP is 17;000 feet. Although we as pilots generally understand the intent of a clearance; this 'climb via; except' has become an abused phraseology. Although amending the altitude to another in a DP or STAR and issuing the 'climb or descend via...' instruction may make sense when the altitude assigned is within the TOP or BOTTOM of the published procedure. It makes no sense when the new altitude is not within altitude limits of the procedure at all. Especially if on vectors as you cannot climb via a procedure unless on a published segment of that procedure (no fixes to climb to). You can climb to be abeam; before; after; or just make an altitude by a time requirement; but the climb via is being modified to the point it often makes no sense to even issue it as an instruction. The new RNAV SID/DPs and STARS are supposed to eliminate unnecessary radio communication; they often do not as their 'amendment' of published happens more than half the time. This is indicative of a problem with the navigational routing solution chosen. To my knowledge; a climb or descend via with crossing restriction does not require an immediate climb or descent; only that the aircraft must be level at the assigned altitude by the fix via normal procedures. If a constant angle or rate of climb or descent is required or expected then the angle or rate should be published in the procedure.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.