ALTDEV ALT UNDERSHOT IN A FAILED ALT XING RESTRICTION SITUATION. ALERT ARTCC RADAR CTLR CAUGHT ERROR AS TCASII TA RA CHIMED IN TO ANNOUNCE A PROBLEM WITH OPPOSITE DIRECTION TFC.

Narrative

AT CRUISE FL350 RECEIVED CLRNC TO CROSS IMP VOR AT OR BELOW FL280 DSND TO FL240; WE WERE APPROX 40-60 MI FROM THE VOR WBOUND. I WAS FLYING AND STARTED A SLOW DSCNT. THE FO WAS OCCUPIED IN A CONVERSATION WITH A FLT ATTENDANT WHO HAD BROUGHT COFFEE TO THE COCKPIT. DURING DSCNT I UNKNOWINGLY FORGOT THE XING ALT AND UNKNOWINGLY STARTED PLANNING ON XING AT FL290 INSTEAD OF FL280. I LEVELED AT FL290 APPROX 10 DME PRIOR; BUT DID NOT ENGAGE ALT HOLD. (NO KEY INDICATOR FOR THE FO TO ASK WHY I LEVELED OFF 1000 FT HIGH.) RIGHT OVER THE VOR CENTER QUESTIONED OUR ALT AND NOTIFIED US OF HEAD-ON TFC AT FL290. I RAPIDLY DSNDED AND COULD SEE TFC AT 11 O'CLOCK. TCASII ALERTED JUST AS WE STARTED THE DSCNT. I THINK IT (TCASII) WOULD HAVE PREVENTED A MISHAP IF CENTER OR RADIO PROBLEMS HAD PRECLUDED A WARNING. WHY IT HAPPENED: 1) NIGHT; DID NOT WRITE DOWN THE CLRNC. 2) STARTED DOWN VERY EARLY WITHOUT CALCULATING A DSCNT RATE OR PLAN TO MAKE RESTRICTION. 3) HAD TOO MUCH TIME AND NO SENSE OF URGENCY TO KEY MEMORY. 4) DID NOT REVERIFY WITH FO BECAUSE HE WAS BUSY AND DISTRACTED. TO HIM IT LOOKED LIKE WE WOULD HAVE PLENTY OF TIME TO MAKE A SIMPLE XING RESTRICTION. HUMAN FACTORS (COCKPIT RESOURCE MGMNT): FO WAS VERY COMPETENT AND EXPERIENCED. BUT THERE I WAS; FLYING SINGLE PLT BECAUSE HE WAS BUSY. I HAD NOT ACCEPTED THIS ROLE (AS A SINGLE PLT). HAD I; I WOULD HAVE RECORDED THE CLRNC OR TAKEN EXTRA MEASURES TO INSURE MEMORY LAPSES OR DISTRS WOULD HAVE BEEN COVERED. CORRECTIVE ACTION: RECORD CLRNCS. ADVANCED ACFT HAVE VIDEO SCREENS THAT CAN BE USED AT NIGHT WHEN COCKPIT LIGHTING MAKES PEN AND INK A PROBLEM. BE AWARE OF UNUSUAL ALTS LIKE FL290 WBOUND. CONSIDER USING THE ALT REMINDER FOR XING RESTRICTION; THEN RESETTING FOR FINAL ALT. THE PNF (CAPT) OR FO (OTHER PLT) HAS RESPONSIBILITY TO MONITOR CLRNCS AND RESTRICTIONS; ALSO; WHETHER CTLING THE AIRPLANE OR GETTING THE ATIS OR A CUP OF COFFEE. NOT ALL CAPTS ARE INFALLIBLE.