Narrative:

We were cruising at FL340 with the #2 autoplt engaged for first officer's leg. ATC had requested best forward speed for traffic sequence prior to present controller. We had mach .81 selected in the speed window and 'altitude hold' on the fcp; all with captain's consent. The captain requested and was granted a climb to FL360 as per the flight plan release scheduled climb. During the climb; our selected speed of mach .81 was beginning to put us over vmo. The captain reached up to dial the speed back to mach .80 but over speed warble had already been set off. At the same time the first officer initiated a different solution. The first officer simultaneously selected 'control wheel steering' (cws) and applied back pressure to the yoke. The aircraft's forward speed was slowed and the over speed warning stopped; but the aircraft's vertical speed was increased. Approaching our assigned altitude; the first officer announced 'altitude STAR' (altitude*); signifying that the altitude capture mode was engaged. Both crew members monitored the autoplt as the aircraft approached FL360 expecting a smooth leveloff; since both FMA's indicated altitude*. At 36100 ft; both crew members grabbed the yoke; disconnected the autoplt; and manually leveled the aircraft back to FL360. During the leveloff; both crew members saw a maximum altitude of 36250 ft on their respective altimeters. Sometime during the manual leveloff the TCAS alerted with a TA (advisory only). At this time; the first officer glanced at the vsi/TCAS display; and did not see any targets. Within a few seconds; the aircraft was back at FL360; and the autoplt was back on. After the autoplt was back on; we were queried by center; '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 flight level. Our TCAS was in the 12 mile range. At no time during this event was minimal traffic separation effected; however; the potential existed. The first officer believed he had reselected the autoplt back to 'command' (cmd) since altitude* had annunciated on the FMA display; but apparently it did not revert to cmd mode when selected. The captain did not notice CWS2 on his FMA autoplt mode window and that the first officer had selected cws on the fcp. Had he known; however; it probably would not have prevented the occurrence. The captain was not in the habit of using the cws mode; and he was not aware that the A300/A310 autoplt will not capture altitude when in cws mode. Our company flight manual (cfm) does not spell this out very well. What our cfm does say is; 'one ap engaged in control 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 altitude capture I am unaware of where the information is located. I (the first officer) discussed the scenario with another captain. The captain suggested trying to see what it will actually do. We purposely selected a cruise altitude 2000 ft below an altitude cleared to (so as to prevent a problem with ATC) and selected cws to watch what will happen. We were surprised to see that the FMA displayed altitude*; and then it even displayed altitude; while the aircraft kept climbing! Thus the ap engaged in cws operates independent of FD's; as per cfm. In retrospect; the captain and I believe there should be a caution or warning inserted into our cfm stating the inability of the A300/A310 autoplt to capture altitude 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 flight crew. We believe this to be a critical item in the age of worldwide rvsm airspace. Lessons learned: captain: if ATC requests a certain speed and you give it to them; you may not be able to maintain that same speed at a higher flight level. Do not use control wheel steering (cws) unless you are totally familiar with what it will and will not do for you. First officer: just because you see 'altitude*' does not mean you will actually capture the altitude! Callback conversation with reporter revealed the following information: the reporter's A300 fleet safety manager is publishing an article addressing this incident. At least one other crew has reported this same behavior. The pilot's use of control wheel steering (cws) is not taught as a normal procedure; but used by some pilots in specific circumstances to slow the aircraft or control a climb or descent. He again emphasized that this mode's inability to capture an altitude is not documented in the pilot's handbook.

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Original NASA ASRS Text

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

Narrative: 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.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.