Narrative:

I was the captain and pilot not flying. We were level at FL370 when the TCAS issued a traffic advisory. Approximately 20 seconds later; the TCAS issued a 'climb; crossing climb' resolution advisory. The first officer disengaged the autopilot and started a climb while I informed center that 'air carrier XXX is responding to a resolution advisory'. The navigation display indicated a red target 300 ft below us with an up arrow and decreasing lateral separation. Shortly after starting our climb; the TCAS issued an 'increase vertical speed' prompt even though we were climbing at approximately 1500 FPM. At this point; I noticed that in spite of our climb; we did not appear to be gaining any additional vertical separation. The target maintained 200-300 ft below our altitude throughout our climb. The first officer acquired visual contact with the target and started a right turn. I considered the turning maneuver to be necessary and appropriate under the circumstances in order to ensure separation. After we established our turn; I saw the target and detected a gradual 'bearing break' i.e. Target bearing change. The relative motion of the target made me believe that we were no longer in danger of a collision although we continued to comply with the RA climb command. I estimate our closest point of approach was 0.5-1.0 NM northwest and 200-300 ft above the target. After the TCAS issued a 'clear of conflict' prompt; we descended back to FL370 and notified center. The remainder of the flight was conducted without further incident. After returning later that day; I discussed the incident with the supervisor on duty. Based on this discussion; I have made some conclusions about the cause of the incident. The other flight had been at FL380 but descended without clearance below our altitude outside the advisory range of TCAS. After the other pilot realized his mistake; he attempted to correct it by returning to his original altitude. However; by this time he was inside the TCAS threshold range which started the chain of events previously described. I think that a language difficulty may have caused the other captain to believe that he had descent clearance when he actually did not. The center supervisor stated that the other captain spoke english poorly. I have no explanation as to why he continued to climb after the RA process was initiated; as his TCAS should have been ordering a descent in that situation.

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Original NASA ASRS Text

Title: A foreign air carrier crew deviated from their assigned altitude causing another air carrier crew to respond to a TCAS RA at FL370.

Narrative: I was the Captain and pilot not flying. We were level at FL370 when the TCAS issued a Traffic Advisory. Approximately 20 seconds later; the TCAS issued a 'Climb; crossing climb' Resolution Advisory. The First Officer disengaged the autopilot and started a climb while I informed Center that 'Air carrier XXX is responding to a Resolution Advisory'. The Navigation Display indicated a red target 300 FT below us with an up arrow and decreasing lateral separation. Shortly after starting our climb; the TCAS issued an 'Increase vertical speed' prompt even though we were climbing at approximately 1500 FPM. At this point; I noticed that in spite of our climb; we did not appear to be gaining any additional vertical separation. The target maintained 200-300 FT below our altitude throughout our climb. The First Officer acquired visual contact with the target and started a right turn. I considered the turning maneuver to be necessary and appropriate under the circumstances in order to ensure separation. After we established our turn; I saw the target and detected a gradual 'bearing break' i.e. target bearing change. The relative motion of the target made me believe that we were no longer in danger of a collision although we continued to comply with the RA climb command. I estimate our closest point of approach was 0.5-1.0 NM northwest and 200-300 FT above the target. After the TCAS issued a 'Clear of conflict' prompt; we descended back to FL370 and notified Center. The remainder of the flight was conducted without further incident. After returning later that day; I discussed the incident with the Supervisor on Duty. Based on this discussion; I have made some conclusions about the cause of the incident. The other flight had been at FL380 but descended without clearance below our altitude outside the advisory range of TCAS. After the other pilot realized his mistake; he attempted to correct it by returning to his original altitude. However; by this time he was inside the TCAS threshold range which started the chain of events previously described. I think that a language difficulty may have caused the other Captain to believe that he had descent clearance when he actually did not. The Center Supervisor stated that the other Captain spoke English poorly. I have no explanation as to why he continued to climb after the RA process was initiated; as his TCAS should have been ordering a descent in that situation.

Data retrieved from NASA's ASRS site as of April 2012 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.