2010-08 · NASA ASRS report 904967
CL604 Flight Crew experiences a TCAS RA just after commencing descent per ATC instructions. Controller issues climb and turn instructions just before the TCAS alert.
Inbound to DAL on the BOWIE ONE arrival. After deviating around some weather; we were cleared direct to GREGS and the GREGS 6 arrival. We were then given a descent clearance to cross GREGS at 10;000 FT. The FMS was programmed and calculated our descent rate to be 2;000 FPM. While I was loading in approach numbers; ATC told us to 'turn right immediately and climb to 17;000'. We were approximately 18 miles west of GREGS Intersection. I looked up at the altimeter and saw 16;300 descending. The First Officer disconnected the autopilot and began a climbing right turn. At the same time the ATC Controller finished that clearance; the TCAS called 'TRAFFIC' and very shortly after that the TCAS called 'CLIMB'. We ended up climbing to about 17;500 and about a 90 degree turn to the right. After the conflict was resolved; we were issued a new clearance back to GREGS. The ATC Controller was noticeably shaken after the event. He apologized to us and was relieved shortly after that. The ATC Controller caught his mistake only seconds before the TCAS alerted us. If the Controller had not caught his mistake; I am confident the TCAS alone would have prevented a collision. There was a loss of separation during this event. I did not see the other aircraft but the TCAS showed the aircraft at 400 FT below us at the closest point. I believe the other aircraft involved in the incident initiated a TCAS descent.
Our flight was cleared to cross GREGS Intersection at 10;000 FT. We departed 17;000. Approximately 20 miles west of GREGS I became aware of TCAS traffic that was approaching our course and our altitudes were less than 1;000 FT apart. As we got closer to each other I started slowing our descent and at 400 FT separation I started to climb. At that moment the TCAS gave us a 2;000 FT/minute climb RA and Ft Worth gave us an 'immediate turn to 170 degree heading and climb to 17;000.' We complied immediately and only then did I see the other aircraft who was also complying with an RA. After the aircraft passed we were re-cleared to cross GREGS at 10;000 FT. We checked with our Flight Attendant who advised that all passenger and herself were okay. The rest of the flight was completed with no further issues.I feel that this situation was caused by a probable miscommunication between controllers due to the existing thunderstorms; holding aircraft and the dynamics caused by these conditions. Thanks to TCAS and the quick reaction of all involved a bad situation was averted.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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