A B737-400 FLC NON ADHERENCE TO ATC CLRNC DURING HEADING TRACK POS ALTDEV. FO IS ON PA SYS WHEN AMENDED CLRNC ALT CHANGE COMES IN TO PIC. PIC IS BUSY DOING OTHER THINGS AND FAILS TO COMPLY WITH COURSE INTERCEPT AND ALT CHANGE.

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AS WE APCHED THE SPA VOR LEVEL AT FL230; I LEFT THE FREQ TO GIVE A PA ANNOUNCEMENT WHICH LASTED APPROX 2-3 MINS. SHORTLY AFTER I RESUMED MY DUTIES WORKING THE RADIO AS THE PNF; ZTL CALLED US AND ASKED IF WE HAD COPIED OUR CLRNC TO CLB TO FL280. I WAS UNAWARE OF SUCH A CLRNC SINCE IT WAS ISSUED WHILE I HAD BEEN OFF THE ATC RADIO GIVING THE PA ANNOUNCEMENTS. BEFORE I COULD KEY MY MIKE TO RESPOND; THE CAPT PICKED UP HIS MIKE AND RESPONDED TO ATC THAT WE WERE IN FACT CLBING TO FL280 (WHICH HE HAD ONLY BEGUN AS THE CTLR BROUGHT IT TO OUR ATTN). THIS SIT CAUGHT ME OFF GUARD HAVING BEEN OUT OF THE LOOP FOR A FEW MINS AND THE CAPT HAD FAILED TO INFORM ME OF THE CLB CLRNC AFTER I HAD COMPLETED THE PA. THE ATC MAN AT THAT POINT BECAME VERY SHORT WITH US AND SAID ARE YOU INTERCEPTING J37? HE SAID SOMETHING SIMILAR TO 'YOU ARE DIVERGING FROM YOUR ROUTING BY 20-30 DEGS TURN L TO A 220 DEG HDG FOR TFC AND CLB NOW AND MAINTAIN FL280; DO YOU COPY?' WHILE ATC AND CAPT WERE COMMUNICATING; I WAS TRYING TO EVALUATE WHAT HAD HAPPENED. I DEDUCED THAT THE FOLLOWING SEQUENCE OF EVENTS HAD OCCURRED: 1) EVERYTHING WAS STABLE WHEN I LEFT THE FREQ TO GIVE THE PA ANNOUNCEMENT. 2) WHILE OFF OF THE RADIO ATC ISSUED US A CLB CLRNC WHICH THE CAPT HAD ACKNOWLEDGED AND DIALED INTO THE MCP ALT WINDOW. THE CAPT NEVER SELECTED A CLB MODE ON THE MCP AFTER SETTING THE NEW ALT IN THE ALT WINDOW; SO THE AIRPLANE REMAINED AT FL230. 3) CONTRARY TO RECOMMENDED PROC; THE CAPT WAS OPERATING THE AUTOPLT IN THE VOR/LOC MODE INSTEAD OF LNAV MODE TO FLY DIRECT TO THE SPA VOR. HAD HE BEEN IN THE LNAV MODE AS RECOMMENDED BY COMPANY PROC; HE WOULD NOT HAVE MISSED THE TURN ONTO J37. 4) WHEN I RETURNED TO THE FREQ HE FAILED TO INFORM ME OF THE CLB CLRNC. 5) THE CTLR'S INQUIRY AS TO OUR STATUS OCCURRED SO SOON AFTER I HAD RETURNED TO THE FREQ; THAT I HAD NOT 'LOOPED IN' AS TO WHAT WAS GOING ON AND I WAS MOMENTARILY CONFUSED. (I DID NOT NOTICE THESE NEXT 2 EVENTS DURING THE PA ANNOUNCEMENT BECAUSE I WAS LOOKING OUT MY SIDE WINDOW.) 6) WE WERE IN AN AIRPLANE WHICH HAD HF RADIOS AND THE CAPT WAS MONITORING IT TO SET HIS WATCH; WHEN; 7) THE CAPT SAYS HE SPILLED A VERY HOT CUP OF COFFEE IN HIS LAP. HE SAYS THAT HE REACTED TO THIS BY TRYING TO REMOVE THE COFFEE FROM THE AFFECTED AREA. WHILE DOING SO HE FAILED TO MONITOR THE AIRPLANE. THE CLB WAS NOT INITIATED NOR THE COURSE INTERCEPTED BECAUSE HE WAS OPERATING IN MANUAL MODES AND WAS DISTRACTED FROM MAKING THE CLB AND COURSE CHANGE AT THE APPROPRIATE TIME. AS IS THE CASE WITH MOST 'SEQUENCE OF EVENTS' TYPE OF INCIDENTS; THE WAY IN WHICH THE CAPT WAS OPERATING THE AUTOPLT WOULD NOT HAVE BEEN A FACTOR HAD HE BEEN ABLE TO CONSTANTLY MONITOR THE AIRPLANE. HE DISTRACTED HIMSELF BY PLAYING WITH THE HF RADIO AND WAS FURTHER DISTRACTED WHEN HE SUPPOSEDLY SPILLED COFFEE ON HIS LAP. ALL OF THIS OCCURRING WHEN HE KNEW THAT I WAS OUT OF THE LOOP. THERE ARE OTHER CONTRIBUTING FACTORS. 1) THIS CAPT IS WHAT I REFER AS 'HIGH MAINT.' HE TENDS TO BE INATTENTIVE AND NEEDS TO BE WATCHED. I KNEW THIS FROM HAVING FLOWN PRIOR TRIPS WITH HIM. 2) THE EVENTS OCCURRED DURING THE FIRST 12 MINS OF MY FIRST FLT FOLLOWING 3 WKS OF VACATION AND MY GUARD WAS DOWN.