Narrative:

While on an IFR flight from pfn-vrb, ATC cleared us to descend from FL270 to FL260. I acknowledged leaving FL270 to maintain FL260. The PF initiated the descent using the autoplt with a rate of about 450 FPM. About this time I left the center frequency to copy the ATIS at vrb. While listening to the ATIS I noted our altitude descending through FL265. As I finished recording the ATIS I advised the PF that I was back on center frequency. I looked at the altimeter and saw that we had gone back up to FL270. I told the PF and asked him to hurry down to FL260. At this time ATC called and asked our altitude. I said FL270 descending to FL260. He said he thought he saw us descending earlier. I asked if there was any conflict or 'problem' and he said no. The problem was the failure of the PF to maintain vigilance while I had my head down copying the ATIS. (This particular pilot while having 14000 hours plus a type in this aircraft has a very lackadaisical attitude toward flying. Our company only uses him as a copilot, however, he is allowed to fly from the left seat.)

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Original NASA ASRS Text

Title: ALTDEV ALT UNDERSHOT IN DSCNT. PIC CHKS OUT OF AN ALT WITH ATC AND THEN LATER NOTES THE PF HAD CLBED BACK TO DEPARTED ALT.

Narrative: WHILE ON AN IFR FLT FROM PFN-VRB, ATC CLRED US TO DSND FROM FL270 TO FL260. I ACKNOWLEDGED LEAVING FL270 TO MAINTAIN FL260. THE PF INITIATED THE DSCNT USING THE AUTOPLT WITH A RATE OF ABOUT 450 FPM. ABOUT THIS TIME I LEFT THE CTR FREQ TO COPY THE ATIS AT VRB. WHILE LISTENING TO THE ATIS I NOTED OUR ALT DSNDING THROUGH FL265. AS I FINISHED RECORDING THE ATIS I ADVISED THE PF THAT I WAS BACK ON CTR FREQ. I LOOKED AT THE ALTIMETER AND SAW THAT WE HAD GONE BACK UP TO FL270. I TOLD THE PF AND ASKED HIM TO HURRY DOWN TO FL260. AT THIS TIME ATC CALLED AND ASKED OUR ALT. I SAID FL270 DSNDING TO FL260. HE SAID HE THOUGHT HE SAW US DSNDING EARLIER. I ASKED IF THERE WAS ANY CONFLICT OR 'PROB' AND HE SAID NO. THE PROB WAS THE FAILURE OF THE PF TO MAINTAIN VIGILANCE WHILE I HAD MY HEAD DOWN COPYING THE ATIS. (THIS PARTICULAR PLT WHILE HAVING 14000 HRS PLUS A TYPE IN THIS ACFT HAS A VERY LACKADAISICAL ATTITUDE TOWARD FLYING. OUR COMPANY ONLY USES HIM AS A COPLT, HOWEVER, HE IS ALLOWED TO FLY FROM THE L SEAT.)

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.