AN SMA PLT SWEARS THAT HE WAS ASSIGNED THE SAME ALT AS ANOTHER ACFT.

Narrative

THE DEP CLRNC FROM MARTIN STATE ARPT CONTAINED AN INITIAL CLB ALT OF 3000 FT; EXPECT 7000 FT 10 MINS AFTER DEP. AFTER TKOF; MTN TWR HANDED US OFF TO BWI DEP WHO TURNED US NBOUND AND CONTINUED OUR CLB TO 5000 FT. I ACKNOWLEDGED THE CLRNC AND DIALED THE NEW ALT INTO THE ACFT'S 'POOR MAN'S ALT ALERTER' (AN INEXPENSIVE ITEM WHICH INSTALLS ON THE FACE OF THE ALTIMETER). SHORTLY AFTERWARD; I WAS SWITCHED TO ANOTHER BWI CTLR. I CHKED IN AS I NORMALLY DO '...WITH YOU IN THE CLB THROUGH XXXX FOR 5000 FT.' THE CTLR ACKNOWLEDGED THIS AND (ALMOST APOLOGETICALLY) PROMISED US HIGHER IN A FEW MI. AS WE CONTINUED THE CLB TO 5000 FT; I HEARD THE CTLR ISSUE ANOTHER ACFT AN IMMEDIATE TURN AND THEN INSTRUCT US TO TURN IMMEDIATELY AND CLB TO 6000 FT. I COMPLIED INSTANTLY; SENSING THE URGENCY IN HIS VOICE. A FEW MOMENTS LATER THE CTLR QUESTIONED OUR ASSIGNED ALT AS HE EXPECTED US TO LEVEL OFF AT 4000 FT. THE PAX IN THE R PLT SEAT; A PLT HIMSELF; WAS WEARING A HEADSET AND MONITORING COMS AND THE FLT'S PROGRESS. HE STATES THAT HE HEARD US CLRED TO 5000 FT; MY ACKNOWLEDGEMENT AND OBSERVED ME CHANGE THE ALT BUG ON THE ALTIMETER TO 5000 FT. I STATED TO THE CTLR THAT I WAS SURE THE PREVIOUS CTLR HAD CLRED US TO 5000 FT AND HIS REPLY WAS 'NO PROB; WE WORKED IT OUT ON THIS END.' THE FLT CONTINUED WITHOUT FURTHER INCIDENT. I DO NOT BELIEVE THAT I WAS AT FAULT IN THIS SIT. ANYONE; INCLUDING MYSELF; CAN MAKE A MISTAKE. IN THIS CASE; HOWEVER; I WOULD HAVE HAD TO HEAR THE WRONG ALT FROM THE FIRST DEP CTLR; DIAL IT INTO THE ALTIMETER; AND RPT THAT ALT TO 2 CTLRS WITHOUT EITHER ONE (OR THE PLT SEATED NEXT TO ME) CATCHING THE ERROR. POSSIBLE; I SUPPOSE; BUT NOT VERY LIKELY. IN ANY CASE; I DO NOT KNOW ANY WAY IN WHICH I COULD HAVE PREVENTED THIS SIT AND AM THANKFUL THAT IT DID NOT BECOME MORE SERIOUS.