Narrative:

Flight planned at FL250 to mht. During descent I was PNF and had acquired ATIS for mht. As per the checklist all the ATIS items were briefed, and as I read off the altimeter to the first officer (PF) I held up and pointed to the ATIS number and altimeter reading '29.64.' he looked at the number, repeated it and I watched him dial it in, as I dialed it into my 2 altimeters (normal and standby). The controller wanted a rapid rate of descent. We obliged with 3000 FPM. I cautioned the first officer that the autoplt has been known to disregard the altitude preselected and penetrate set altitudes. Not just this aircraft, problem is fleetwide. He acknowledged this and was ready for it. The assigned altitude was to be 11000 ft. At 13000 ft I cautioned the first officer to expect capture soon and failing that to disengage the autoplt and effect the level off. He said he would. With 3000 FPM descent, I again stated this at 12000 ft. And at 11500 ft said, 'level off it's going to go through it!' ATC wants to know our altitude as we pass through 11000 ft, and as I check his altimeter it reads level at 11000 ft while mine reads 10000 ft. I immediately ask for a current altimeter setting and select TCASII display while the controller tells us to climb immediately to 11000 ft. He also gives traffic a 30 degree turn to avoid us. I found the traffic at 7-6 mi, 1-2 mi higher, and later closest pass was 2 - 2 1/2 and several hundred vertical. I checked all 3 altimeters. My 2 were correctly set. His was incorrectly set to 30.46. I checked the ATIS card, however the writing was clear and large enough not to confuse -- nor could he explain it. He was very apologetic and is otherwise a very dependable and trustworthy crew member. I can only think he might have dialed in part of a frequency he heard during the descent. I will check this through on future flts to mht. Contributing factors: this airplane is dark. Damned dark! All of them are! I'm certain that if more instrument/cockpit illumination existed this would not have occurred, and on the ramp without an engine running it's much worse. I would also vote in favor of an altimeter comparator warning system. If installed it would alert pilots to the potential mis- setting of their altimeters. We have a heading comparator warning annunciator and they do a fine job. The heading comparator shows a 'C' in orange on the eas if headings differ by more than 6 degrees total. In the future I'll have the first officer call out the ATIS number for the altimeter instead of accepting an 'ok' as confirmation that he has correctly set the altimeter. Reading it from my side at night in turbulence might not be any better but at least he will have stated the setting. And I will attempt to read it each time we reset them.

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Original NASA ASRS Text

Title: FLC OF AN LTT OVERSHOT DSCNT ALT DUE TO THE FO'S ALTIMETER BEING MISSET.

Narrative: FLT PLANNED AT FL250 TO MHT. DURING DSCNT I WAS PNF AND HAD ACQUIRED ATIS FOR MHT. AS PER THE CHKLIST ALL THE ATIS ITEMS WERE BRIEFED, AND AS I READ OFF THE ALTIMETER TO THE FO (PF) I HELD UP AND POINTED TO THE ATIS NUMBER AND ALTIMETER READING '29.64.' HE LOOKED AT THE NUMBER, REPEATED IT AND I WATCHED HIM DIAL IT IN, AS I DIALED IT INTO MY 2 ALTIMETERS (NORMAL AND STANDBY). THE CTLR WANTED A RAPID RATE OF DSCNT. WE OBLIGED WITH 3000 FPM. I CAUTIONED THE FO THAT THE AUTOPLT HAS BEEN KNOWN TO DISREGARD THE ALT PRESELECTED AND PENETRATE SET ALTS. NOT JUST THIS ACFT, PROB IS FLEETWIDE. HE ACKNOWLEDGED THIS AND WAS READY FOR IT. THE ASSIGNED ALT WAS TO BE 11000 FT. AT 13000 FT I CAUTIONED THE FO TO EXPECT CAPTURE SOON AND FAILING THAT TO DISENGAGE THE AUTOPLT AND EFFECT THE LEVEL OFF. HE SAID HE WOULD. WITH 3000 FPM DSCNT, I AGAIN STATED THIS AT 12000 FT. AND AT 11500 FT SAID, 'LEVEL OFF IT'S GOING TO GO THROUGH IT!' ATC WANTS TO KNOW OUR ALT AS WE PASS THROUGH 11000 FT, AND AS I CHK HIS ALTIMETER IT READS LEVEL AT 11000 FT WHILE MINE READS 10000 FT. I IMMEDIATELY ASK FOR A CURRENT ALTIMETER SETTING AND SELECT TCASII DISPLAY WHILE THE CTLR TELLS US TO CLB IMMEDIATELY TO 11000 FT. HE ALSO GIVES TFC A 30 DEG TURN TO AVOID US. I FOUND THE TFC AT 7-6 MI, 1-2 MI HIGHER, AND LATER CLOSEST PASS WAS 2 - 2 1/2 AND SEVERAL HUNDRED VERT. I CHKED ALL 3 ALTIMETERS. MY 2 WERE CORRECTLY SET. HIS WAS INCORRECTLY SET TO 30.46. I CHKED THE ATIS CARD, HOWEVER THE WRITING WAS CLR AND LARGE ENOUGH NOT TO CONFUSE -- NOR COULD HE EXPLAIN IT. HE WAS VERY APOLOGETIC AND IS OTHERWISE A VERY DEPENDABLE AND TRUSTWORTHY CREW MEMBER. I CAN ONLY THINK HE MIGHT HAVE DIALED IN PART OF A FREQ HE HEARD DURING THE DSCNT. I WILL CHK THIS THROUGH ON FUTURE FLTS TO MHT. CONTRIBUTING FACTORS: THIS AIRPLANE IS DARK. DAMNED DARK! ALL OF THEM ARE! I'M CERTAIN THAT IF MORE INST/COCKPIT ILLUMINATION EXISTED THIS WOULD NOT HAVE OCCURRED, AND ON THE RAMP WITHOUT AN ENG RUNNING IT'S MUCH WORSE. I WOULD ALSO VOTE IN FAVOR OF AN ALTIMETER COMPARATOR WARNING SYS. IF INSTALLED IT WOULD ALERT PLTS TO THE POTENTIAL MIS- SETTING OF THEIR ALTIMETERS. WE HAVE A HDG COMPARATOR WARNING ANNUNCIATOR AND THEY DO A FINE JOB. THE HDG COMPARATOR SHOWS A 'C' IN ORANGE ON THE EAS IF HDGS DIFFER BY MORE THAN 6 DEGS TOTAL. IN THE FUTURE I'LL HAVE THE FO CALL OUT THE ATIS NUMBER FOR THE ALTIMETER INSTEAD OF ACCEPTING AN 'OK' AS CONFIRMATION THAT HE HAS CORRECTLY SET THE ALTIMETER. READING IT FROM MY SIDE AT NIGHT IN TURB MIGHT NOT BE ANY BETTER BUT AT LEAST HE WILL HAVE STATED THE SETTING. AND I WILL ATTEMPT TO READ IT EACH TIME WE RESET THEM.

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.