BE1900 WAS USING THE #2 XPONDER TO SHOW CLRED ALT 6000 FT. AFTER DEP ADVISED NO XPONDER; IN CHKING SAW SWITCH WAS OFF. HAD CHANGED ACTIVE XPONDER TO #2 ACCOUNT DAY OF THE MONTH AND PUT IN 6000 ON #1 VERSUS CLRED ALT 1600 FT. NO CONFLICT; BUT CTLR UPSET.

Narrative

ON TKOF FROM TPA; XB07 LCL ON MAY/XX/97; THE FLC OF FLT TPA-MIA CLBED ON HDG 310 DEGS TO 6000 FT. THE TWR CTLR ADVISED THAT HE WAS NOT RECEIVING A XPONDER RETURN. IT WAS DISCOVERED THAT THE XPONDER 1/2 SELECT TOGGLE SWITCH WAS SET TO THE STANDBY XPONDER. THIS WAS READJUSTED AND WE WERE HANDED OFF TO DEP CTL. THE COPLT (PNF) CHKED IN ADVISING WE WERE HDG 310 DEGS; CLBING THROUGH 4500 FT FOR 6000 FT. THE CTLR RESPONDED 'ROGER' THEN QUERIED '...THEY GAVE YOU 6000 FT EH?...' TO WHICH THE FO RESPONDED AFFIRMATIVE. APPROX 5 MINS LATER; THE FLC WAS ASKED BY TPA DEP CTL TO WRITE DOWN THE NUMBER OF THE DEP CTL FACILITY AND CALL THE WATCH SUPVR UPON ARR IN MIA. UPON ARR IN MIA; I PERSONALLY CALLED THE WATCH COMMANDER; WHO INFORMED ME THAT THEY HAD PLAYED THE TAPE BACK AND DISCOVERED THAT THE ASSIGNED ALT ON INITIAL DEP WAS IN FACT 1600 FT; NOT 6000 FT AS WE HAD PROCEEDED TO DO. WE HAD A DISCUSSION ABOUT THE EVENT; AND SINCE THERE WAS NO CONFLICT; AND THE WX WAS CLR VMC; THE WATCH SUPVR CONSIDERED THE ISSUE RESOLVED. I RECEIVED THE CLRNC; AND PROCEEDED TO SET UP THE RADIOS FOR THE FLT. I RECALL SETTING THE XPONDER CODE IN XPONDER #1; THEN THE ALT AS 0016 WITH THE DIGITS OF THE XPONDER #2; REPRESENTING 1600 FT. IT IS COMMON PRACTICE TO USE THE SPARE XPONDER AS AN 'ALT SELECT DISPLAY;' SINCE SOME BUT NOT ALL OF OUR FLEET OF BE1900'S ARE EQUIPPED WITH ALT SELECT DISPLAY/WARNING DEVICES; AND THIS PARTICULAR ACFT WAS NOT EQUIPPED AS SUCH. I THEN NOTED THAT IT WAS A DAY NUMBER DIVISIBLE BY 2. OUR OPERATING PRACTICE REQUIRES US TO ALTERNATE XPONDER #1 ODD DAYS; AND XPONDER #2 EVEN DAYS. I THEN SWITCHED THE XPONDERS; SETTING THE SQUAWK CODE IN XPONDER #2; AND APPARENTLY RESETTING 0060 INSTEAD OF 0016 IN THE DIGITS OF THE STANDBY XPONDER. WE THUS BELIEVED ON DEP THAT WE WERE TO CLB TO 6000 FT. THE CTLR; ON DEP; DID NOT SEE A XPONDER REPLY AND ADVISED US. WE DISCOVERED THAT THE XPONDER SELECT SWITCH WAS NOT TOGGLED TO THE #2 XPONDER. THIS SEEMS TO HAVE BEEN AN OMISSION ON MY PART; LIKELY OMITTED BECAUSE THE SMALL SELECT SWITCH IS LOCATED AWAY FROM THE XPONDERS ON THIS ACFT ON THE UPPER MIDDLE INST PANEL; RATHER THAN BTWN THE XPONDERS. HAD THE TOGGLE SWITCH BEEN MOUNTED BY THE XPONDERS; NOT AWAY FROM THEM; I AM CERTAIN I WOULD NOT HAVE MISSED THIS ITEM. THE WATCH SUPVR AT TPA LATER ADVISED ME THAT ALL DEPS ON THE 310 DEG HDG WERE ASSIGNED 1600 FT. THE INADVERTENT SELECTION OF 6000 FT DID NOT SEEM ODD AT FIRST; I HAD NOT FLOWN THIS DEP FREQUENTLY; AT LEAST RECENTLY; AND IT WAS THUS NOT 'COMMITTED TO MEMORY' AS MANY FREQUENT CLRNCS ARE FAMILIAR. IN CONCLUSION; I BELIEVE THE MISUNDERSTANDING OF ASSIGNED ALT WAS CAUSED FIRST BY THE LACK OF FLEET UNIFORMITY IN HAVING ALT SELECT/WARNING DISPLAYS; AND ON THE CREW HAVING TO RELY ON THE 'STOP-GAP' MEASURE OF RELYING ON THE SPARE XPONDER DISPLAY DIGITS FOR USE AS AN 'ALT BUG.' ALSO; THE INST PANEL ERGONOMICS COULD HAVE PREVENTED THE OMISSION.