Date: 201602
Local time of day: 1201-1800
Location: BWI.Airport, MD
Flight conditions: IMC
Light: Daylight
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B BWI
ATC / advisory: TRACON PCT
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Confusion; Communication Breakdown; Situational Awareness
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Undershoot; Deviation / Discrepancy - Procedural Clearance
Detector: Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: My First Officer received a full route clearance via radio. ATC assigned; 'climb via TERPZ 6.' The TERPZ 6 RNAV Departure top altitude for our transition is 17;000 feet. We are used to receiving 'climb via TERPZ 6 except maintain 4000 feet.' For that reason; we called back Clearance Delivery to confirm if the clearance was truly 'climb via TERPZ 6 to 17;000 feet.' Clearance apologized that he made a mistake and corrected the clearance to 'climb via TERPZ 6 except maintain 4000 feet.' We were glad that we rechecked with Clearance since we have always received a clearance of 'climb via TERPZ 6 except maintain 4000 feet.' After takeoff when Tower switched us to Potomac Departure (128.7); I checked-in; 'leaving 1800 feet climbing to 4000 feet.' ATC responded; 'Roger; climb via;' with no top altitude assigned. Shortly after leveling at 4000 feet; my First Officer and I queried ourselves about the 4000 feet level off and usually get assigned; 'climb via except maintain a top altitude.' We were about to query Potomac; when Potomac came back and asked us if we were aware that the top altitude of the SID was 17;000 feet. I responded that we were aware; but our last clearance limit we had received was 4000 feet. When we initially checked-in with Potomac; we were still climbing and complying with the previous clearance of 'climb via TERPZ 6 except maintain 4000 feet.' The standard verbiage used by Potomac ATC; for the last 16 years of flying out of Baltimore; has always been 'climb via TERPZ 6' (accompanied with a top altitude); NOT ' Roger; climb via.' We understand 'climb via' can mean to climb to the top altitude while complying with all published altitude restrictions; however; that is not standard phraseology used by Potomac ATC; hence; our need to seek clarification; which we were unable to get. Twice I asked for altitude clarification; and twice Potomac would not clarify. Potomac pointed out traffic twice and again did not clarify our climb clearance until they placed us in a traffic conflict. At that point; Potomac ATC assigned us 17;000 feet. We initiated the climb and complied with all published altitude crossing restrictions. They wanted me to copy down a phone number while I was still below 10;000 feet in a sterile cockpit environment. My First Officer's priority; as well as mine; is flying the aircraft; not copying down phone numbers. When I refused to take the number down; another Controller (claiming to be a Supervisor); also tried to get me to copy a phone number down. Again; I refused and told him we would deal with this later. The Controller's tone was totally unprofessional; threatening as well as inappropriately timed.The next day; I flew Flight XXXX; BWI-ZZZ; and received the same clearance of 'climb via TERPZ 6 except maintain 4000 feet.' When switched over to Potomac; I received an assignment of 'climb via TERPZ 6 except maintain 17;000 feet;' the published top altitude of the SID. This is how we have always received our clearances from Potomac ATC. My point is; there is a lack of standard phraseology from Potomac ATC. Same departure; both days; why was there a difference in phraseology?


Second narrative: [Report narrative contained no additional information.]


Synopsis: While on the TERPZ 6 SID out of BWI; the flight crew reported receiving a confusing; non-standard 'climb via' clearance that resulted in a TCAS TA.