AN MU300 FLC IS CONFUSED WHEN ATC QUERIES THEM ABOUT THE ALT ASSIGNMENT AND THEIR PRESENT ALT. ZJX; FL.

Narrative

THIS WAS THE LAST LEG OF A PART 91 CPR TRIP. I USED TO FLY REGULARLY WITH THIS COMPANY BUT HAD NOT BEEN FLYING IN THIS ACFT WITH THIS CAPT FOR 2 MONTHS PRIOR TO THIS TRIP. WE HAD HAD 2 MALFUNCTIONS ON THE ACFT THIS DAY. ON A PREVIOUS LEG; THE #1 RADIO HAD FAILED. THIS WAS THE ONE THAT HAS THE FLIP-FLOP (STANDBY) FUNCTION. WE HAD TO USE OUR STANDBY #2 COM RADIO FOR XMITTING. THEN; WE HAD A THRUST REVERSER STICK OPEN (FAIL TO STOW) AFTER LNDG. FORTUNATELY; A MAINT FACILITY WAS ABLE TO FIX THE REVERSER AND SWAP OUR MALFUNCTIONING RADIO SO THAT WE COULD USE THE FLIP-FLOP FEATURE ON #2. AFTER A 2 HR DELAY; WE FINALLY HEADED HOME. I WAS FLYING AND USING THE AUTOPLT. IT WAS GETTING DARK AND WE WERE EATING DINNER THAT WE PICKED UP DURING OUR DELAY. I HAD FLT PLANNED FOR FL270. WE WERE LEVEL AT FL250. CTR GAVE A CALL TO CLB TO FL290. ALTHOUGH RADIO AND ALT PRESELECT WERE THE PNF DUTIES; HE WAS EATING AND SO I ACKNOWLEDGED AND SET THE ALT AND STARTED THE CLB. I DID THINK FL290 WAS ODD SINCE I FILED FOR FL270 BUT THE CAPT SAID NO PROB SO WE ACCEPTED IT. AS WE CLBED THROUGH FL277; CTR QUERIED OUR ALT. WE SAID FL277 TO WHICH HE ASKED WHAT WE WERE ASSIGNED. WE SAID FL290 AND THERE WAS A PAUSE; AFTER WHICH HE SAID SOMETHING LIKE 'ROGER.' MY THOUGHT WAS IMMEDIATELY THAT PERHAPS I HEARD FL270 AND ACKNOWLEDGED IT; BUT DIALED IN FL290. I DON'T THINK THAT IS THE CASE SINCE I REMEMBER THINKING IT WAS ODD THAT THEY ASSIGNED IT WHEN WE HAD PLANNED FOR FL270. IN ANY EVENT; IF WE HAD NOT BEEN DISTRACTED BY FATIGUE; RADIO PROBS; EATING; LACK OF CLR DELINEATION OF 'WHO IS DOING WHAT' IN THE COCKPIT; THEN WE WOULD BOTH HAVE KNOWN IF WE HAD BEEN ASSIGNED SOMETHING OTHER THAN FL290. I FEEL CONFIDENT WE WERE RIGHT; AND THE CTLR NEVER QUERIED US ABOUT IT AGAIN; BUT THERE IS THE NAGGING UNCERTAINTY THAT CAUSES ME TO WRITE THIS RPT.