Narrative:

I was the PNF captain on a learjet 25 flight which departed denver, co, for aspen, co. We had been assigned several altitudes during the climb. We were in and out of the tops of the cumulus cloud layer when the deviation occurred and had been encountering light to moderate turbulence. We were assigned to climb to FL210 by ZDV and advised we had traffic at FL220. As we leveled at FL210, the first officer (PF) overshot slightly (100-200 ft). We momentarily broke out of the clouds and simultaneously observed an aircraft which I estimated to be approximately 1 mi ahead of us. The first officer was apparently surprised at sighting the traffic, saw no apparent movement, and believed the traffic was converging on a collision course. He instinctively pulled the nose up, which took our altitude to FL214 (400 ft above assigned altitude). I immediately observed the deviation, took over the controls, retarded power, and pushed the nose down. At the same time, ZDV requested altitude confirmation. I advised center we had overshot our altitude and were correcting. We expeditiously returned to FL210, however, the deviation resulted in a loss of separation by ZDV. At no time did we lose control of the aircraft or deliberately deviate from our clearance. We do not believe the safety of either aircraft was compromised. Our flight continued without further incidence. Supplemental information from acn 557477: as I approached FL210, we went from IMC to VMC, at which time I saw the BAE146 in front of us. I felt I was on a collision course with the BAE146. The time it took for me to recognize I was not on a collision course with the BAE146 is the time we climbed above FL210.

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Original NASA ASRS Text

Title: AN LJ25 CREW, DEPARTING KDEK, OVERSHOT THEIR ASSIGNED ALT.

Narrative: I WAS THE PNF CAPT ON A LEARJET 25 FLT WHICH DEPARTED DENVER, CO, FOR ASPEN, CO. WE HAD BEEN ASSIGNED SEVERAL ALTS DURING THE CLB. WE WERE IN AND OUT OF THE TOPS OF THE CUMULUS CLOUD LAYER WHEN THE DEV OCCURRED AND HAD BEEN ENCOUNTERING LIGHT TO MODERATE TURB. WE WERE ASSIGNED TO CLB TO FL210 BY ZDV AND ADVISED WE HAD TFC AT FL220. AS WE LEVELED AT FL210, THE FO (PF) OVERSHOT SLIGHTLY (100-200 FT). WE MOMENTARILY BROKE OUT OF THE CLOUDS AND SIMULTANEOUSLY OBSERVED AN ACFT WHICH I ESTIMATED TO BE APPROX 1 MI AHEAD OF US. THE FO WAS APPARENTLY SURPRISED AT SIGHTING THE TFC, SAW NO APPARENT MOVEMENT, AND BELIEVED THE TFC WAS CONVERGING ON A COLLISION COURSE. HE INSTINCTIVELY PULLED THE NOSE UP, WHICH TOOK OUR ALT TO FL214 (400 FT ABOVE ASSIGNED ALT). I IMMEDIATELY OBSERVED THE DEV, TOOK OVER THE CTLS, RETARDED PWR, AND PUSHED THE NOSE DOWN. AT THE SAME TIME, ZDV REQUESTED ALT CONFIRMATION. I ADVISED CTR WE HAD OVERSHOT OUR ALT AND WERE CORRECTING. WE EXPEDITIOUSLY RETURNED TO FL210, HOWEVER, THE DEV RESULTED IN A LOSS OF SEPARATION BY ZDV. AT NO TIME DID WE LOSE CTL OF THE ACFT OR DELIBERATELY DEVIATE FROM OUR CLRNC. WE DO NOT BELIEVE THE SAFETY OF EITHER ACFT WAS COMPROMISED. OUR FLT CONTINUED WITHOUT FURTHER INCIDENCE. SUPPLEMENTAL INFO FROM ACN 557477: AS I APCHED FL210, WE WENT FROM IMC TO VMC, AT WHICH TIME I SAW THE BAE146 IN FRONT OF US. I FELT I WAS ON A COLLISION COURSE WITH THE BAE146. THE TIME IT TOOK FOR ME TO RECOGNIZE I WAS NOT ON A COLLISION COURSE WITH THE BAE146 IS THE TIME WE CLBED ABOVE FL210.

Data retrieved from NASA's ASRS site as of July 2007 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.