AN A300 CLBING IN CTL WHEEL STEERING (CWS) MODE FAILED TO CAPTURE AN MCP ALT WHILE INDICATING A FUNCTIONAL CAPTURE.

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WE WERE CRUISING AT FL340 WITH THE #2 AUTOPLT ENGAGED FOR FO'S LEG. ATC HAD REQUESTED BEST FORWARD SPD FOR TFC SEQUENCE PRIOR TO PRESENT CTLR. WE HAD MACH .81 SELECTED IN THE SPD WINDOW AND 'ALT HOLD' ON THE FCP; ALL WITH CAPT'S CONSENT. THE CAPT REQUESTED AND WAS GRANTED A CLB TO FL360 AS PER THE FLT PLAN RELEASE SCHEDULED CLB. DURING THE CLB; OUR SELECTED SPD OF MACH .81 WAS BEGINNING TO PUT US OVER VMO. THE CAPT REACHED UP TO DIAL THE SPD BACK TO MACH .80 BUT OVER SPD WARBLE HAD ALREADY BEEN SET OFF. AT THE SAME TIME THE FO INITIATED A DIFFERENT SOLUTION. THE FO SIMULTANEOUSLY SELECTED 'CTL WHEEL STEERING' (CWS) AND APPLIED BACK PRESSURE TO THE YOKE. THE ACFT'S FORWARD SPD WAS SLOWED AND THE OVER SPD WARNING STOPPED; BUT THE ACFT'S VERTICAL SPD WAS INCREASED. APCHING OUR ASSIGNED ALT; THE FO ANNOUNCED 'ALT STAR' (ALT*); SIGNIFYING THAT THE ALT CAPTURE MODE WAS ENGAGED. BOTH CREW MEMBERS MONITORED THE AUTOPLT AS THE ACFT APCHED FL360 EXPECTING A SMOOTH LEVELOFF; SINCE BOTH FMA'S INDICATED ALT*. AT 36100 FT; BOTH CREW MEMBERS GRABBED THE YOKE; DISCONNECTED THE AUTOPLT; AND MANUALLY LEVELED THE ACFT BACK TO FL360. DURING THE LEVELOFF; BOTH CREW MEMBERS SAW A MAX ALT OF 36250 FT ON THEIR RESPECTIVE ALTIMETERS. SOMETIME DURING THE MANUAL LEVELOFF THE TCAS ALERTED WITH A TA (ADVISORY ONLY). AT THIS TIME; THE FO GLANCED AT THE VSI/TCAS DISPLAY; AND DID NOT SEE ANY TARGETS. WITHIN A FEW SECONDS; THE ACFT WAS BACK AT FL360; AND THE AUTOPLT WAS BACK ON. AFTER THE AUTOPLT WAS BACK ON; WE WERE QUERIED BY CTR; 'ARE YOU LEVEL AT FL360?' WE WERE; AND WE REPLIED IN THE AFFIRMATIVE. AFTER THAT QUERY; A TARGET APPEARED ON THE TCAS THREE O'CLOCK POSITION TRANSITING OUR TCAS DISPLAY TOWARD THE TWELVE O'CLOCK POSITION; 1000 FT ABOUT OUR FLT LEVEL. OUR TCAS WAS IN THE 12 MILE RANGE. AT NO TIME DURING THIS EVENT WAS MINIMAL TFC SEPARATION EFFECTED; HOWEVER; THE POTENTIAL EXISTED. THE FO BELIEVED HE HAD RESELECTED THE AUTOPLT BACK TO 'COMMAND' (CMD) SINCE ALT* HAD ANNUNCIATED ON THE FMA DISPLAY; BUT APPARENTLY IT DID NOT REVERT TO CMD MODE WHEN SELECTED. THE CAPT DID NOT NOTICE CWS2 ON HIS FMA AUTOPLT MODE WINDOW AND THAT THE FO HAD SELECTED CWS ON THE FCP. HAD HE KNOWN; HOWEVER; IT PROBABLY WOULD NOT HAVE PREVENTED THE OCCURRENCE. THE CAPT WAS NOT IN THE HABIT OF USING THE CWS MODE; AND HE WAS NOT AWARE THAT THE A300/A310 AUTOPLT WILL NOT CAPTURE ALT WHEN IN CWS MODE. OUR COMPANY FLT MANUAL (CFM) DOES NOT SPELL THIS OUT VERY WELL. WHAT OUR CFM DOES SAY IS; 'ONE AP ENGAGED IN CTL WHEEL STEERING (CWS). THE AP MAINTAINS PITCH ATTITUDE AND BANK ANGLE EXISTING AT THE MOMENT OF ENGAGEMENT.' ALSO; ONE PAGE STATES; 'AP ENGAGED IN CWS OPERATES INDEPENDENT FD'S.' IF OUR CFM FURTHER ELABORATES ON THE FUNCTIONAL CAPABILITIES OF THE A300/A310 AUTOPLT 'CWS' MODE WITH RESPECT TO ALT CAPTURE I AM UNAWARE OF WHERE THE INFO IS LOCATED. I (THE FO) DISCUSSED THE SCENARIO WITH ANOTHER CAPT. THE CAPT SUGGESTED TRYING TO SEE WHAT IT WILL ACTUALLY DO. WE PURPOSELY SELECTED A CRUISE ALT 2000 FT BELOW AN ALT CLRED TO (SO AS TO PREVENT A PROB WITH ATC) AND SELECTED CWS TO WATCH WHAT WILL HAPPEN. WE WERE SURPRISED TO SEE THAT THE FMA DISPLAYED ALT*; AND THEN IT EVEN DISPLAYED ALT; WHILE THE ACFT KEPT CLBING! THUS THE AP ENGAGED IN CWS OPERATES INDEPENDENT OF FD'S; AS PER CFM. IN RETROSPECT; THE CAPT AND I BELIEVE THERE SHOULD BE A CAUTION OR WARNING INSERTED INTO OUR CFM STATING THE INABILITY OF THE A300/A310 AUTOPLT TO CAPTURE ALT WHEN IN THE CWS MODE. ALSO; IF THE USE OF CWS IS GOING TO BE TAUGHT IN TRAINING TO PUT EMPHASIS ON WHAT THIS AUTOPLT MODE WILL AND WILL NOT DO FOR THE FLT CREW. WE BELIEVE THIS TO BE A CRITICAL ITEM IN THE AGE OF WORLDWIDE RVSM AIRSPACE. LESSONS LEARNED: CAPT: IF ATC REQUESTS A CERTAIN SPD AND YOU GIVE IT TO THEM; YOU MAY NOT BE ABLE TO MAINTAIN THAT SAME SPD AT A HIGHER FLT LEVEL. DO NOT USE CTL WHEEL STEERING (CWS) UNLESS YOU ARE TOTALLY FAMILIAR WITH WHAT IT WILL AND WILL NOT DO FOR YOU. FO: JUST BECAUSE YOU SEE 'ALT*' DOES NOT MEAN YOU WILL ACTUALLY CAPTURE THE ALT! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR'S A300 FLEET SAFETY MANAGER IS PUBLISHING AN ARTICLE ADDRESSING THIS INCIDENT. AT LEAST ONE OTHER CREW HAS RPTED THIS SAME BEHAVIOR. THE PLT'S USE OF CTL WHEEL STEERING (CWS) IS NOT TAUGHT AS A NORMAL PROC; BUT USED BY SOME PLTS IN SPECIFIC CIRCUMSTANCES TO SLOW THE ACFT OR CTL A CLB OR DSCNT. HE AGAIN EMPHASIZED THAT THIS MODE'S INABILITY TO CAPTURE AN ALT IS NOT DOCUMENTED IN THE PLT'S HANDBOOK.