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.)