Narrative:

We were climbing out sat on the alamo 6 SID and in the vicinity of seeds intersection we were given direct to lfk VOR and an interim leveloff of FL390 for opposite direction traffic at FL400. We were somewhere southwest of brenham as our altitude approached FL390 with the autoplt on and the flight level change mode engaged. The autoplt altitude window was set for FL390. Immediately prior to me watching for altitude capture by the automatic flight control system; ZHU called out the opposite direction traffic to us which we had been looking at on TCAS. We had an easy visual sighting of the other jet. The morning was so clear that it was hard not to watch the contrails of it even though it was nearly 20 mi away. Anyway; after staring at the traffic a few seconds too long; I looked at our altitude and saw that we were FL391 and climbing. I hit the afcs vertical speed mode and dialed in a descent. Our inertia carried us up towards FL393. I disconnected the autoplt and flew the aircraft back down. The altitude alerter chime sounded (300 ft) and our TCAS advisory gave us 'traffic; traffic.' as we were descending; ZHU asked us about our altitude. We told him we were leveling at FL390. When we got to FL390; ZHU asked us to confirm that we were at FL390. We confirmed it and about 20 seconds later we were abeam the traffic. I'm sure the other aircraft got a TCAS advisory. Our maximum altitude reached FL393. I anticipate and watch for altitude capture when using the afcs. It has always captured altitude when it was armed. I was distraction by watching the aircraft I was supposed to avoid getting closer to than 1000 ft vertically; and the acfs did not capture the altitude.

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Original NASA ASRS Text

Title: LEAR 45XR FLT CREW HAS AN ALT EXCURSION DURING LEVELOFF AT CRUISE ALT.

Narrative: WE WERE CLBING OUT SAT ON THE ALAMO 6 SID AND IN THE VICINITY OF SEEDS INTXN WE WERE GIVEN DIRECT TO LFK VOR AND AN INTERIM LEVELOFF OF FL390 FOR OPPOSITE DIRECTION TFC AT FL400. WE WERE SOMEWHERE SW OF BRENHAM AS OUR ALT APCHED FL390 WITH THE AUTOPLT ON AND THE FLT LEVEL CHANGE MODE ENGAGED. THE AUTOPLT ALT WINDOW WAS SET FOR FL390. IMMEDIATELY PRIOR TO ME WATCHING FOR ALT CAPTURE BY THE AUTOMATIC FLT CTL SYS; ZHU CALLED OUT THE OPPOSITE DIRECTION TFC TO US WHICH WE HAD BEEN LOOKING AT ON TCAS. WE HAD AN EASY VISUAL SIGHTING OF THE OTHER JET. THE MORNING WAS SO CLR THAT IT WAS HARD NOT TO WATCH THE CONTRAILS OF IT EVEN THOUGH IT WAS NEARLY 20 MI AWAY. ANYWAY; AFTER STARING AT THE TFC A FEW SECONDS TOO LONG; I LOOKED AT OUR ALT AND SAW THAT WE WERE FL391 AND CLBING. I HIT THE AFCS VERT SPD MODE AND DIALED IN A DSCNT. OUR INERTIA CARRIED US UP TOWARDS FL393. I DISCONNECTED THE AUTOPLT AND FLEW THE ACFT BACK DOWN. THE ALT ALERTER CHIME SOUNDED (300 FT) AND OUR TCAS ADVISORY GAVE US 'TFC; TFC.' AS WE WERE DSNDING; ZHU ASKED US ABOUT OUR ALT. WE TOLD HIM WE WERE LEVELING AT FL390. WHEN WE GOT TO FL390; ZHU ASKED US TO CONFIRM THAT WE WERE AT FL390. WE CONFIRMED IT AND ABOUT 20 SECONDS LATER WE WERE ABEAM THE TFC. I'M SURE THE OTHER ACFT GOT A TCAS ADVISORY. OUR MAX ALT REACHED FL393. I ANTICIPATE AND WATCH FOR ALT CAPTURE WHEN USING THE AFCS. IT HAS ALWAYS CAPTURED ALT WHEN IT WAS ARMED. I WAS DISTR BY WATCHING THE ACFT I WAS SUPPOSED TO AVOID GETTING CLOSER TO THAN 1000 FT VERTLY; AND THE ACFS DID NOT CAPTURE THE ALT.

Data retrieved from NASA's ASRS site as of January 2009 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.