2009-10 · NASA ASRS report 858239
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.
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.
We leveled off at FL230 RNAV SID; and the Controller handed us off. The First Officer was flying and I was pilot monitoring. On check-in we were given a clearance to climb and maintain FL250; which we acknowledged. During initiation of the climb to FL250 with associated cockpit duties; the Controller issued a traffic advisory for FL250 traffic 10 NM away. We did not see the aircraft nor did it show up on TCAS. At this time we did not ascertain the possibility of an invalid ATC clearance or conflicting traffic call out by ATC. The following events happened quickly and close together. During altitude capture at FL250; the TCAS TA Alert sounded with a pop-up target displayed within 5 NM and slightly below our altitude. The Controller then called us and asked if we were level at FL240 to which I replied we were not; but assigned to FL250. Based on the target proximity; and the strong possibility we were at a wrong altitude; I called climb as the First Officer simultaneously initiated a climb. shortly thereafter; a TCAS RA commanded a climb. The Controller then called us again and told us to climb to FL260. We level off at FL260; and I advised ATC of the RA. The following points were brought out: 1) The Controller issued us a clearance to climb to FL250 when he actually meant to give us a clearance to FL240 for traffic avoidance. 2) The Controller informed us of the traffic at FL250; but we did not recognize the possible error in altitude assignment and did not visually or electronically acquire the target. 3) The traffic at FL250 was under the control of an adjacent sector and on a different frequency; thereby reducing some situation awareness. 4) The traffic had sight of us during the entire incident; and his Controller issued deconflicting instructions. 5) The closest proximity between aircraft was determined to be approximately 1000 FT vertical and 2 NM lateral separation. 6) Quick reaction by all concerned parties prevented a bad situation from deteriorating to something worse.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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