SINGLE PLT IN A BE20 IS DSNDING TO 13000 FT AND THEN GIVEN DSCNT TO 12000 FT. PLT ACKNOWLEDGED CLRNC AND REALIZES THAT HE HAD ALREADY DSNDED THROUGH 13000 FT. PLT LEVELED AT 12000 FT AND CONFESSES HIS MISTAKE.

Narrative

ZAB CLRED ME TO 13000 FT. SET ALERTER AND CONTINUED DSCNT. IN THE MEANTIME; I WAS GIVEN TFC TO FOLLOW INTO SAF. KEPT LOOKING FOR TFC AND INQUIRING ABOUT ITS POS. WHEN ZAB CLRED ME FOR FURTHER DSCNT TO 12000 FT; I LOOKED AT ALTIMETER TO RPT PASSING ALT ONLY TO REALIZE I HAD PASSED 13000 FT WITHOUT LEVELING. IMMEDIATELY CONFESS MY MISTAKE AND LEVEL AT 12000 FT. IN THE MIDST OF ALL THE COM AND LOOKING FOR TFC I HAD MISSED HEARING ALT ALERT AT 14000 FT AND 12750 FT! IN ADDITION; I HAD FAILED TO ARM ALT SELECT ON AUTOPLT. SINCE WE ARE A SINGLE PLT OP; IT IS NORMAL TO USE THE AUTOPLT TO ITS FULLEST CAPABILITIES. THIS IS ESPECIALLY TRUE IN TERMINAL AREAS. EVEN WITH ACTIVE NOISE CANCELING HEADSET I MISSED THE ALERTER TONE. SPERRY/HONEYWELL HAS ELECTED TO USE A HIGH FREQ BEEP INSTEAD OF A MORE DISTINCTIVE TONE AND WE WILL INVESTIGATE CHANGING THAT. DOES LOSS OF HEARING IN HIGHER FREQ RANGE OVER TIME HAVE ANY EFFECT? WHO KNOWS. THIS IS A HEADS UP CALL TO AVIATE THEN COMMUNICATE. WE WILL INSTALL EGPWS AND TCASII WITHIN 6 MONTHS.