Narrative:

My second entry into an airport that gives the altimeter in hectopascals, the first time being 6 months ago. The captain flying, and an old hand, and me relatively new on the aircraft and to international flying. Approach control gave the altimeters as '998 hectopascals.' I read back '29.98.' he repeated his original statement. Forgetting that our altimeter has settings for both millibars and hectopascals (I had only used it once in my career and that was 6 months ago), I asked the captain where the conversion chart was. The captain told me that approach control meant 29.98. Assuming he knew what he was doing, I believed him. The altimeter issue was soon forgotten, as this was near the end of a long flight. The airport area is peppered with hills, and I was constantly monitoring the captain's airspeed and altitude. Soon after resetting the altimeters at 11000', he went low 100-200' and slow 10 KTS a couple of times. At the OM he again was 10 KTS slow and 200' low. Combined with our altimeter error (998 hectopascals = 29.46) of 500' and plus 200' deviation, we were 700' low at the OM, causing the altitude alert system to activate. I knew we were awfully close to the hill at the outer, but it was not until we landed and our altimeters read 500' did I realize what happened. The WX was VFR, scattered clouds, hazy and turning to dusk. We both made a serious error and don't want to put the blame elsewhere, but there was a contributing factor. In preparation for our arrival, I looked through our flight operations manual, but it is so fragmented and disorganized that I must have missed the section about the way this airport issues altimeter settings.

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Original NASA ASRS Text

Title: ALT DEVIATION. OVERSHOOT ON DESCENT. WRONG ALTIMETER SETTING.

Narrative: MY SECOND ENTRY INTO AN ARPT THAT GIVES THE ALTIMETER IN HECTOPASCALS, THE FIRST TIME BEING 6 MONTHS AGO. THE CAPT FLYING, AND AN OLD HAND, AND ME RELATIVELY NEW ON THE ACFT AND TO INTL FLYING. APCH CTL GAVE THE ALTIMETERS AS '998 HECTOPASCALS.' I READ BACK '29.98.' HE REPEATED HIS ORIGINAL STATEMENT. FORGETTING THAT OUR ALTIMETER HAS SETTINGS FOR BOTH MILLIBARS AND HECTOPASCALS (I HAD ONLY USED IT ONCE IN MY CAREER AND THAT WAS 6 MONTHS AGO), I ASKED THE CAPT WHERE THE CONVERSION CHART WAS. THE CAPT TOLD ME THAT APCH CTL MEANT 29.98. ASSUMING HE KNEW WHAT HE WAS DOING, I BELIEVED HIM. THE ALTIMETER ISSUE WAS SOON FORGOTTEN, AS THIS WAS NEAR THE END OF A LONG FLT. THE ARPT AREA IS PEPPERED WITH HILLS, AND I WAS CONSTANTLY MONITORING THE CAPT'S AIRSPD AND ALT. SOON AFTER RESETTING THE ALTIMETERS AT 11000', HE WENT LOW 100-200' AND SLOW 10 KTS A COUPLE OF TIMES. AT THE OM HE AGAIN WAS 10 KTS SLOW AND 200' LOW. COMBINED WITH OUR ALTIMETER ERROR (998 HECTOPASCALS = 29.46) OF 500' AND PLUS 200' DEVIATION, WE WERE 700' LOW AT THE OM, CAUSING THE ALT ALERT SYS TO ACTIVATE. I KNEW WE WERE AWFULLY CLOSE TO THE HILL AT THE OUTER, BUT IT WAS NOT UNTIL WE LANDED AND OUR ALTIMETERS READ 500' DID I REALIZE WHAT HAPPENED. THE WX WAS VFR, SCATTERED CLOUDS, HAZY AND TURNING TO DUSK. WE BOTH MADE A SERIOUS ERROR AND DON'T WANT TO PUT THE BLAME ELSEWHERE, BUT THERE WAS A CONTRIBUTING FACTOR. IN PREPARATION FOR OUR ARR, I LOOKED THROUGH OUR FLT OPS MANUAL, BUT IT IS SO FRAGMENTED AND DISORGANIZED THAT I MUST HAVE MISSED THE SECTION ABOUT THE WAY THIS ARPT ISSUES ALTIMETER SETTINGS.

Data retrieved from NASA's ASRS site as of August 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.