LEAR 35 ON THE MILTON STAR LGA DSNDING TO 10000 FT. CAPT SET ALTIMETER TO 30 PT 70; CORRECT 29 PT 70. CTLR QUESTIONED ALT WHEN ERROR WAS DISCOVERED.

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THE INCIDENT INVOLVED THE CAPT ALTIMETER BEING SET INCORRECTLY ON THE APCH. CHKLIST ACCOMPLISHED PASSING THROUGH FL180. THE LCL ALTIMETER AT THE TIME WAS 29.70; THE CAPT'S ALTIMETER WAS SET TO 30.70. THIS PROB WAS DISCOVERED WHEN THE APCH CTLR INQUIRED AS TO WHAT ALT THE PREVIOUS CTR CTLR HAD ISSUED US. THE CONTRIBUTING FACTORS WERE OUR COMPANY PROCS AND POSSIBLY THE LACK OF A STATIC DEFAULT CONNECTION MODULE FOR THE FO SIDE ALTIMETER IN THE LEAR 35. THIS SECOND FACTOR IS IMPORTANT BECAUSE THIS HAS A TENDENCY TO CAUSE THE PLT IN THE R SEAT TO LOOK AT THE CAPT'S ALTIMETER MORE OFTEN THAN THE FO BECAUSE OF THE STATIC ERROR. THE HUMAN PERFORMANCE IN THIS SIT IS VERY CLR. FIRST; OUR PROC CALLS FOR EACH PLT TO SET HIS/HER ALTIMETER; POINT OUT THE NEW SETTING AND READ IT TO THE OTHER PLT OUT LOUD. I FEEL THIS PROC WORKS; EXCEPT IN THIS CASE THE CREW MEMBERS HEARD THE CALLOUTS; BUT DID NOT LISTEN TO THEM. THE COPLT'S ALTIMETER WAS SET CORRECTLY AT 29.70; THE CAPT'S WAS SET AT 30.70. BOTH CREW MEMBERS CALLED THEIR RESPECTIVE SETTINGS OUT LOUD BUT NEITHER CAUGHT THE DIFFERENCE. THE PNF (IN THE R SEAT) FAILED TO XCHK ALTIMETERS BECAUSE OF THE SIT DESCRIBED ABOVE. BECAUSE THIS ALTIMETER (FO SIDE) CAN BE AS MUCH AS 500 FT OFF FROM THE CAPT'S ALTIMETER IT IS IGNORED AND BOTH CREW MEMBERS' ATTN IS FOCUSED ON THE CAPT'S ALTIMETER ONLY. ADDITIONALLY; BECAUSE THE ALT ALERTER IN THIS ACFT IS 'TIED' TO THE CAPT'S ALTIMETER IT DID NOT WARN OF THE DEV. THE QUALITY OF HUMAN PERFORMANCE WAS COMPROMISED I THINK DUE TO THE VERY NICE WX CAUSING SOME COMPLACENCY IN THE COCKPIT AND THE FACT THAT THE ALTIMETERS ARE SET NUMEROUS TIMES PER WK; MONTH; YR. BASICALLY; I THINK THAT IT IS SUCH A REPETITIVE TASK THAT PEOPLE TAKE IT FOR GRANTED. I GUESS I DIDN'T REALLY DESCRIBE THE WHOLE SCENARIO. TO RECAP; THE CAPT'S ALTIMETER INDICATED 10000 FT (AT 30.70); THE FO ALTIMETER 9000 FT (AT 29.70; THE CORRECT SETTING). THE CREW HAD NO CLUE OF THIS DEV UNTIL A CTLR ASKED. WE PASSED ABOUT 2 MI HORIZLY FROM A LIGHT TWIN WITH 0 VERT SEPARATION. THE CREW'S ACTION OF NOT PAYING CLOSE ENOUGH ATTN TO THE OTHER CREW MEMBER'S ACTIONS AND WORDS CLRLY COMPROMISED SAFETY. THE ONLY SUGGESTION I HAVE IS THAT PLTS IN A 2- PLT ENVIRONMENT SHOULD USE THIS RESOURCE TO ITS FULLEST. PLEASE PUBLISH AN ARTICLE IN 'CALLBACK' ON THIS SUBJECT. WE AND EVERYONE ELSE NEED TO BE REMINDED HOW A SIMPLE ACTION CAN LEAD TO DISASTER. THIS EVENT WAS A SIGNIFICANT ONE FOR ME. I HAVE MANY ADDITIONAL COMMENTS AND IDEAS ON THIS PROB. PLEASE FEEL FREE TO CALL ME. SUPPLEMENTAL INFO FROM ACN 365484: THE COPLT'S ALTIMETER IN THE LEAR JET HAS A SUBSTANTIAL STATIC POS ERROR. THE INST OFTEN READS 500-600 FT OFF ALT. IT IS NORMAL FOR THE COPLT TO SEE A CONSIDERABLE DEV ON HIS/HER ALTIMETER.