Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Confusion; Communication Breakdown
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Separated Traffic; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Procedure; Human Factors
On climbout from IAD; Potomac Departure gave us a climb to 11;000. Then we switched controllers and checked in; and the new controller gave us 'climb and maintain 14;000.' A minute later; we heard the same controller tell another pilot 'traffic at 2:00 climbing to 13;000.' We were seeing an airplane at 10:00 on the TCAS descending toward us. Then the controller told us about traffic at 10:00; 15;000; descending to 13;000. We were trying to get clarification as we climbed out; but there was a lot of confusion between [the other aircraft; the controller]; and us. I was the pilot flying; and I reduced my climb rate to about 200 feet per minute as I went through 12;400. At 13;000; I started to level off; because I could see that we had a conflict. Shortly thereafter; I heard another voice say; 'Aircraft Y; level off; LEVEL OFF.' The aircraft was at 14600 and we had remained at 13000; even though we had been cleared to 14;000. Those pilots were asking for clarification and so did we. Then the second voice told us both that there was training going on; [the controller] had it settled; and handed us off to Center. If I had not leveled off early; we would have been at 14;000 when they got called to level off at 14;600. They were directly above us on a crossing path. That pilot asked about how it happened; because they had been cleared to 'descend via' and they were on the path. Make sure ATC has good training; and good supervisors. This was way too close. If I hadn't seen what was happening; we very likely could have had a midair collision.
Air carrier Captain reported an airborne conflict during climbout from IAD airport due to ATC training error.