ALTDEV.

Narrative

THIS ALTDEV OCCURRED ON A FLT FROM GSO-CLT IN A 737-300 ACFT. AFTER LEVELING AT 11000 FT OUTSIDE OF MAGIC INTXN ON THE MAGIC STAR ARR TO CLT; ZTL SAID TO DSND AND MAINTAIN 11000 FT. WE REPLIED THAT WE WERE LEVEL AT 11000 FT. ZTL DID NOT SAY ANYTHING FURTHER TO US FOR ABOUT A MIN THEN AGAIN SAID TO DSND AND MAINTAIN 11000 FT. WE AGAIN LOOKED AT BOTH ALTIMETERS AND THE ALT ALERTER WINDOW AND REPLIED THAT WE WERE LEVEL 11000 FT. THEY SAID THEY SHOWED US LEVEL AT 12000 FT AND POINTED OUT TFC AT 13000 FT AT A RANGE AND DIRECTION I DON'T REMEMBER AND THEN WENT ON TO COM WITH OTHER ACFT. I THOUGHT THERE MIGHT BE A MALFUNCTION WITH THE XPONDER OR THE ENCODING ALTIMETER. ABOUT THAT TIME; WE DISCOVERED THAT THE ALTIMETERS WERE SET TO 28.88 INSTEAD OF THE PROPER SETTING OF 29.88. WE QUICKLY DSNDED TO 11000 FT AND TOLD ZTL THAT WE WERE LEVEL AT 11000 FT AND HAD SWITCHED XPONDERS; WHICH WE HAD. THEY VERIFIED THAT THEY SHOWED US LEVEL AT 11000 FT AND NO FURTHER COMMENTS ABOUT THE ALT DISCREPANCY WERE MADE. THE ACFT WE WERE FLYING HAD BEEN IN MAINT THE NIGHT BEFORE AND FOR WHAT REASON I DON'T KNOW; THE MAINT PERSONNEL HAD DIALED THE ALTIMETERS ON BOTH SIDES OF THE ACFT BACK TO A SEA LEVEL SETTING WHEN THE FIELD ELEVATION AT GSO IS APPROX 1000 FT MSL. WE ACCOMPLISHED ALL CHKLISTS ON THE PREFLT BUT FAILED TO NOTICE THAT THE SECOND DIGIT OF THE ALTIMETER HAD BEEN SET TO AN 8 INSTEAD OF A 9. THIS IS SOMETHING THAT IS EASY TO MISS; AS I HAVE NEVER SEEN A 28 ANYTHING ALTIMETER SETTING. I THINK IT WOULD NOT BE A BAD IDEA TO HAVE THE SECOND DIGIT 8 AND THE 1 COLORED A DIFFERENT COLOR TO PRECLUDE THIS TYPE OF MISTAKE HAPPENING AGAIN. WHEN AIRBORNE WE STILL HAD A HARD TIME PICKING OUT THE ERROR BECAUSE THE 28 AND 29 ALTIMETER SETTING LOOK SO CLOSE AND YOU NEVER SEE A SETTING IN THE 28 RANGE. SUPPLEMENTAL INFO FROM ACN 285629: APCH CTL ADVISED US TO DSND TO 11000 FT INDICATED 11000 FT. APCH RESPONDED WE NEEDED TO DSND TO 11000 FT THEY SHOWED US AT 12000 AND GAVE US ALTIMETER SETTING 29.98. CHKED OURS; WAS SET AT 28.88.