Narrative:

This has to be one of the most shocking NASA forms I've filled out. I cannot believe it happened. So here it is. The first officer was off getting ATIS, talking to company, and all that good stuff. I was given a late descent clearance from about FL240 to 15000 ft at jaybo intersection. The radios were a little busy as they always are in the northeast corridor. When I realized how much time I had to make the crossing restr I noticed the VNAV telling me I must descend at 2900 FPM. So, I started down. I was given 30.54 on the altimeter setting -- so I thought. The first officer came back off the radios at about 16000 ft. He said to me, 'the aft is not capturing the altitude.' I said 'yes it is.' my side was capturing what it thought was 15000 ft. His side had descended 1000 ft below. The altimeter was actually 29.54. It took us a couple of moments to determine the cause of confusion. I immediately disconnected the autoplt and climbed to the true 15000 ft. ATC never said a word. In fact, they told us we were cleared down to 11000 ft almost right away. I never have had this happen before. I was shocked and a little startled too. This should not happen. We debriefed and decided it was lack of crew communication and possibly last min task saturation. This will hopefully never ever happen to me again -- yikes! Supplemental information from acn 504280: we debriefed and determined the descent was probably a little too rushed and maybe we were both a little task saturated.

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Original NASA ASRS Text

Title: A CL65 PIC DSNDS OVER 500 FT BELOW HIS ASSIGNED ALT WHEN HE HAD RESET HIS LCL QNH TO A HIGHER SETTING THAN ISSUED PASSING JAYBO INTXN, MD.

Narrative: THIS HAS TO BE ONE OF THE MOST SHOCKING NASA FORMS I'VE FILLED OUT. I CANNOT BELIEVE IT HAPPENED. SO HERE IT IS. THE FO WAS OFF GETTING ATIS, TALKING TO COMPANY, AND ALL THAT GOOD STUFF. I WAS GIVEN A LATE DSCNT CLRNC FROM ABOUT FL240 TO 15000 FT AT JAYBO INTXN. THE RADIOS WERE A LITTLE BUSY AS THEY ALWAYS ARE IN THE NE CORRIDOR. WHEN I REALIZED HOW MUCH TIME I HAD TO MAKE THE XING RESTR I NOTICED THE VNAV TELLING ME I MUST DSND AT 2900 FPM. SO, I STARTED DOWN. I WAS GIVEN 30.54 ON THE ALTIMETER SETTING -- SO I THOUGHT. THE FO CAME BACK OFF THE RADIOS AT ABOUT 16000 FT. HE SAID TO ME, 'THE AFT IS NOT CAPTURING THE ALT.' I SAID 'YES IT IS.' MY SIDE WAS CAPTURING WHAT IT THOUGHT WAS 15000 FT. HIS SIDE HAD DSNDED 1000 FT BELOW. THE ALTIMETER WAS ACTUALLY 29.54. IT TOOK US A COUPLE OF MOMENTS TO DETERMINE THE CAUSE OF CONFUSION. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND CLBED TO THE TRUE 15000 FT. ATC NEVER SAID A WORD. IN FACT, THEY TOLD US WE WERE CLRED DOWN TO 11000 FT ALMOST RIGHT AWAY. I NEVER HAVE HAD THIS HAPPEN BEFORE. I WAS SHOCKED AND A LITTLE STARTLED TOO. THIS SHOULD NOT HAPPEN. WE DEBRIEFED AND DECIDED IT WAS LACK OF CREW COM AND POSSIBLY LAST MIN TASK SATURATION. THIS WILL HOPEFULLY NEVER EVER HAPPEN TO ME AGAIN -- YIKES! SUPPLEMENTAL INFO FROM ACN 504280: WE DEBRIEFED AND DETERMINED THE DSCNT WAS PROBABLY A LITTLE TOO RUSHED AND MAYBE WE WERE BOTH A LITTLE TASK SATURATED.

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.