FLT CREW OF C500 EXPERIENCE INADVERTENT AUTOPLT DISCONNECT. MOMENTARY LOSS OF CTL RESULTS.

Narrative

WE WERE ON A ROUTINE IFR FLT FROM HOU TO CNW. WE WERE IN SOLID IFR CONDITIONS AT 16000 FT. AS THE PNF IN THE R SEAT; I HAD JUST TURNED IN THE ASOS AND WAS IN THE PROCESS OF COPYING IT WHEN WE RECEIVED AN INSTRUCTION FROM ZHU TO GO DIRECT TO DEST. ALTHOUGH I HAVE MORE THAN 6000 HRS IN CE550 AND 560 ACFT; WE WERE IN AN OLDER CE500 WHICH I HAVE FLOWN SEVERAL TIMES. IN RECONSTRUCTING WHAT TOOK PLACE; IT APPEARS THAT I INADVERTENTLY DISCONNECTED THE AUTOPLT WHILE ATTEMPTING TO ANSWER ATC WITHOUT EITHER PLT BEING AWARE OF IT. THE PF WAS LOOKING AT THE APCH PLATE AND I WAS COPYING THE ASOS INFO WHEN THE PF REALIZED THAT THE AIRPLANE WAS ROLLING INTO A STEEP BANK. HE IMMEDIATELY INITIATED CORRECTIVE ACTION; THEN CONTACTED ATC AND INFORMED THEM THAT WE HAD HAD AN AUTOPLT PROB. THE FLT WAS CONTINUED WITHOUT FURTHER INCIDENT. THERE WAS NO TFC CONFLICT. THE MAIN PROB IS THE LOCATION OF THE AUTOPLT DISCONNECT SWITCH ON THIS AIRPLANE; COUPLED WITH THE LACK OF AN 'AUTOPLT DISCONNECTED' WARNING. THE SWITCH IS ABOVE AND BEHIND THE RADIO XMIT SWITCH ON THE R SIDE OF THE COPLT'S YOKE AND IT IS EASY TO CONFUSE THE TWO. ALTHOUGH THIS IN ITSELF IS NOT A PROB; THAT THERE EITHER IS NO WARNING TO THE PLT THAT THE AUTOPLT HAS BEEN DISCONNECTED; OR THAT IT WAS NOT WORKING PROPERLY WAS THE MAJOR CONTRIBUTOR TO THIS POTENTIALLY SERIOUS INCIDENT. THE ROLL APPARENTLY OCCURRED BECAUSE THE AIRPLANE WAS IN A TURN WHEN THE AUTOPLT DISCONNECTED. THAT BOTH PLTS WERE PERFORMING OTHER TASKS AT THE TIME WAS ALSO A FACTOR; ALTHOUGH THIS PARTICULAR AIRPLANE IS CERTIFIED FOR SINGLE-PLT OP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: A PHONE DISCUSSION WITH THE RPTR REVEALED THE FOLLOWING. THIS OLDER ACFT APPARENTLY HAS HAD A VARIETY OF AFTER MARKET MODIFICATIONS INCLUDING THE AUTOPLT. THE RPTR IS UNSURE AS TO THE CONFIGN AS COMPARED TO NEW. IN ADDITION; HE NOTED THAT A LOGBOOK WRITE-UP REGARDING THE INCIDENT RESULTED IN THE REPLACEMENT OF THE 'AUTOPLT CTLR' SO HE IS NOW UNCERTAIN WHETHER THE ACTUAL INCIDENT RESULTED FROM AN INADVERTENT DISCONNECT OR AN AUTOPLT MALFUNCTION.