Narrative:

While flying a departure; we were leveling at FL230 when we received a frequency change. Upon checking in; ATC issued a clearance to climb to FL250. The captain responded appropriately and set 250 in the altitude set window on the flight guidance panel. As he pointed at the altitude window and said aloud '250;' I verbally responded '250 set and armed' as I also pointed at the flight guidance panel as well as the mode select panel. While we were verbally confirming the altitude ATC reported that we had traffic at FL250 and would climb when clear. (Since we were talking when he was talking; neither of us caught that the traffic was at the altitude we had been cleared to.) the autopilot was flying the aircraft and began to capture FL250. Just as we began to level at 250; three things happened almost simultaneously: 1) amber traffic appeared on our TCAS display almost superimposed over our aircraft. 2) we received a verbal TCAS 'traffic; traffic' alert. 3) the controller queried with some sense of urgency 'XXX confirm level 240.' the captain replied we were level 250 as assigned. Things then began to happen in a blur. ATC urgently told us to climb to FL260; and I began a climb with the vertical speed wheel on the autopilot. Almost immediately; we received an RA to climb as well as a visual indication to climb at least 2000 FPM. I disconnected the autopilot and autothrottle and executed the conflict resolution as the captain informed ATC we were responding to the TCAS RA. At no point prior to the sudden TA did the converging traffic appear on our TCAS. The TCAS was set on the 40 NM scale with 'above' selected on the tilt option. After contacting the ATC facility after the flight; the tape was played for us confirming that we had been cleared to FL250 and that we clearly responded accurately to that clearance. The controller had meant to clear us to FL240 and actually entered 240 in the computer. Because of the verbal altitude confirmation between the pilot; we both completely missed the altitude given by the controller for our traffic. Somehow; neither of up seemed to completely process the information. There was absolutely no idle cockpit talk; and we were both alert and focused on the flying at hand. Moments later; as I thought about the irritating step climb; I believed the controller must have advised us of traffic at FL260 since that made the most sense. We both were looking for it on TCAS but it never appeared until it was almost on top of us. Compounding the situation; the kingair was on a different frequency. We never saw the traffic visually although we found out later he did have a visual on us. We are not sure just how close we came to an actual midair; but it was the most harrowing few seconds in my 25 plus years of flying. There were errors by the controller; an inexplicable failure by both pilots to process the developing situation; and a failure of the TCAS to provide that additional level of information by providing traffic information in a timely manner.

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Original NASA ASRS Text

Title: An Enroute Controller erroneously issued an air carrier aircraft an intermediate climb to an altitude occupied by oncoming traffic. A TCAS RA and ATC alert were issued simultaneously commanding an evasive climb to clear the traffic.

Narrative: While flying a departure; we were leveling at FL230 when we received a frequency change. Upon checking in; ATC issued a clearance to climb to FL250. The Captain responded appropriately and set 250 in the altitude set window on the flight guidance panel. As he pointed at the altitude window and said aloud '250;' I verbally responded '250 set and armed' as I also pointed at the flight guidance panel as well as the mode select panel. While we were verbally confirming the altitude ATC reported that we had traffic at FL250 and would climb when clear. (Since we were talking when he was talking; neither of us caught that the traffic was at the altitude we had been cleared to.) The autopilot was flying the aircraft and began to capture FL250. Just as we began to level at 250; three things happened almost simultaneously: 1) Amber traffic appeared on our TCAS display almost superimposed over our aircraft. 2) We received a verbal TCAS 'Traffic; Traffic' alert. 3) The Controller queried with some sense of urgency 'XXX confirm level 240.' The Captain replied we were level 250 as assigned. Things then began to happen in a blur. ATC urgently told us to climb to FL260; and I began a climb with the vertical speed wheel on the autopilot. Almost immediately; we received an RA to climb as well as a visual indication to climb at least 2000 FPM. I disconnected the autopilot and autothrottle and executed the conflict resolution as the Captain informed ATC we were responding to the TCAS RA. At no point prior to the sudden TA did the converging traffic appear on our TCAS. The TCAS was set on the 40 NM scale with 'above' selected on the tilt option. After contacting the ATC facility after the flight; the tape was played for us confirming that we had been cleared to FL250 and that we clearly responded accurately to that clearance. The Controller had meant to clear us to FL240 and actually entered 240 in the computer. Because of the verbal altitude confirmation between the pilot; we both completely missed the altitude given by the Controller for our traffic. Somehow; neither of up seemed to completely process the information. There was absolutely no idle cockpit talk; and we were both alert and focused on the flying at hand. Moments later; as I thought about the irritating step climb; I believed the Controller must have advised us of traffic at FL260 since that made the most sense. We both were looking for it on TCAS but it never appeared until it was almost on top of us. Compounding the situation; the Kingair was on a different frequency. We never saw the traffic visually although we found out later he did have a visual on us. We are not sure just how close we came to an actual midair; but it was the most harrowing few seconds in my 25 plus years of flying. There were errors by the Controller; an inexplicable failure by both pilots to process the developing situation; and a failure of the TCAS to provide that additional level of information by providing traffic information in a timely manner.

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.