A DC9 CREW FAILS TO MAKE AN ALT XING WHEN THEY HAVE USED THE WRONG ALTIMETER SETTING FROM THE DEP ARPT FOR DSCNT. THE PIC ASSUMED THE DEP ARPT'S SETTING WAS CORRECT BECAUSE THE CARD WASN'T LABELED AS TO ARPT NAME.

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ROCKET ONE ARR TO HOU HOBBY ARPT (I WAS THE PF). ON DSCNT PASSING FL180 WE SET ALTIMETER SETTING OF 29.57 INCHES (ACTUAL HOU ALTIMETER WAS APPROX 30.16 INCHES). WE WERE TOLD TO CROSS SSLAM INTXN AT 10000 FT (WE DID). SHORTLY THEREAFTER THE CTLR ASKED US WHAT OUR ALT WAS AND WE SAID 10000 FT. (HIS RADAR SCREEN WAS SHOWING US AT APPROX 10600-10700 FT; MY ESTIMATE.) THE CTLR THEN GAVE US THE HOU ALTIMETER SETTING OF 30.16 INCHES. REALIZING OUR MISTAKE WE SET THE CORRECT ALTIMETER SETTING AND OUR ALTIMETERS SHOWED US 600-700 FT HIGH. WE THEN WENT DOWN TO 10000 FT. WE APOLOGIZED FOR THE ERROR AND NOTHING ELSE WAS SAID. (THERE WERE NO TFC CONFLICTS.) MY PARTNER RECORDED THE HOU ATIS ON OUR ATIS SLIP AND WHEN HE DISPLAYED IT DURING DSCNT HE DISPLAYED THE WRONG SIDE OF THE SLIP (THE DEP SIDE; THUS THE DEP ALTIMETER SETTING OF 29.75 INCHES WAS SET IN OUR ALTIMETER DURING DSCNT INTO HOU). THERE IS A STATION LINE ON EACH SIDE OF THE SLIP (DEP AND ARR SIDES) AND THE DEP STATION WAS NOT WRITTEN ON THE SLIP SO WHEN WE WENT THROUGH 18000 FT I ASSUMED THAT 29.75 INCHES WAS THE CORRECT HOU ALTIMETER SETTING. I WILL NO LONGER ASSUME AS MUCH ANYMORE. IT WAS AN EASY MISTAKE TO MAKE AND IT GOT BY BOTH OF US FOR A WHILE.