A B737 CREW; DEPARTING SEA; NEGLECTED TO NOTICE THEIR ALTIMETERS HAD DEFAULTED TO QNH 29 PT 92; RESULTING IN A 500 FT ERROR AT LEVELOFF.

Narrative

DURING PREFLT; COCKPIT ALTIMETERS WERE SET TO 30.43. BEFORE START; AN ANOMALY WAS NOTICED ON THE ENG AND SYS ELECTRONIC DISPLAY. THIS REQUIRED SOME ENTRIES ON THE MAINT PORTION OF THE FMC TO RESET. THIS PROC IS IN THE AMPLIFIED PORTION OF OUR FLT HANDBOOK BUT I ELECTED TO USE MY SHORT-HAND NOTES WRITTEN IN MY LOGBOOK. AS I READ ALOUD; THE FO TYPED IN THE APPROPRIATE COMMANDS. THE DISPLAY RESET TO THE NORMAL MODE AND WE CONTINUED PREPARING FOR PUSHBACK. AFTER TKOF; WE WERE CLRED TO 9000 FT THEN CLRNC WAS CHANGED TO 4000 FT AND THEN 5000 FT BY ATC. AFTER LEVELOFF AT 5000 FT; ATC ASKED OUR ALT LIMIT. NOT KNOWING WHAT HE MEANT; I THOUGHT HE WAS ASKING THE CEILING OF THE ACFT; I TOLD THE COPLT TO SAY FL410. WE WERE EVENTUALLY CLRED TO OUR CRUISING ALT; BUT I SENSED THERE WAS SOME CONFUSION BTWN US AND ATC. WE LATER REALIZED THAT WHEN WE RESET OUR DISPLAY; THE ALTIMETERS DEFAULT TO 29.92. WE DID NOT NOTICE THIS; SO WHEN WE LEVELED OFF AT 5000 FT WE WERE APPROX 500 FT OFF. AFTER LNDG; THE COPLT TALKED TO ATC BY TELEPHONE TO EXPLAIN THE SIT. IF WE HAD LOOKED AT THE FLT HANDBOOK INSTEAD OF USING MY NOTES; WE WOULD HAVE BEEN WARNED THAT THE ALTIMETER DEFAULTS TO 29.92 AND MUST BE RESET TO LCL SETTING. WX WAS GOOD AND WE WEREN'T BEING RUSHED; JUST A MAJOR OVERSIGHT. SUPPLEMENTAL INFO FROM ACN 545676: WE RAN PROC TO RECOVER THE COMPASS DISPLAY. WE DIDN'T NOTICE THIS CAUSED OUR ALTIMETERS TO REVERT TO 29 PT 92. THEY HAD PREVIOUSLY BEEN SET AT 30.43. THERE WAS SOME CONFUSION FROM THE DEP CTLR ABOUT WHAT ALT WE WERE GIVEN AND WHAT WE WENT TO. AT THIS POINT; I NOTICED OUR ALTIMETERS WERE SET AT 29.92. THIS WOULD MAKE US ABOUT 500 FT OFF. WE RESET TO 30.43 AND CONTINUED WITHOUT FURTHER DISCUSSION. AFTER LNDG; WE CALLED THE CTLR AND EXPLAINED WHAT HAPPENED.