B737-800
Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Communication Breakdown; Confusion
Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Human Factors; Procedure
We received CPDLC clearance of TERPZ6 RNAV departure; except climb to 4000 feet. During departure; at around 2500 feet; Departure gave us the following clearance: 'Climb via the TERPZ6 departure.' To me; this is a very confusing clearance since we previously had a clearance limit of 4000 feet; and no additional altitudes were mentioned. As we approached the 4000 foot limit and began to level off; and of course after we had discussed between the two of us what we were really expected to do (level at 4000 feet or continue the climb to 17;000 FT); we did what were are trained to do and queried the controller for clarification. Of course we were instructed to continue the climb to 17;000 FT (as per the RNAV top altitude instructions); which we complied with. I just think this is a horrible clearance! As pilots; we are used to hearing and reading back an altitude; a frequency; a heading; etc. and this clearance leaves room for ambiguity and misunderstanding and potentially doing the wrong thing and ending up with a violation. After the fact; I consulted the FOM; Clearances [chapter]; and found that the FAA clearance of 'Climb via SID' means: 'Comply with all published restrictions up to the charted top altitude.' (A handy piece of information to have memorized; along with the other 5;000 pages in the FOM; just in case you get - what I consider - a vague clearance!) Now look at the ICAO clearance: 'Climb via SID to altitude'. Now how clear is that!? I don't even have to read the ATC expectations to know what to do! I don't have to memorize this page in the FOM! I don't have the entire FOM memorized! FAA needs to adopt the ICAO clearance format! Much less ambiguous!
B737-800 flight crew member reported confusion resulted when cleared to 'climb via' an RNAV departure following 'climb via' with an intermediate altitude.