ALT EXCURSION DURING HIGH ALT CRUISE BY FLC OF AN MD11.

Narrative

I WAS ACTING AS PNF WHILE RECEIVING MY IOE ON THE MD11. THE CHK CAPT WAS FLYING IN THE R SEAT AND WAS THE PF. AFTER DEPARTING CVG FOR EUROPE; WE WERE AT CRUISE ALT OF 33000 FT MSL NEAR SYRACUSE; NY. THE WX WAS DETERIORATING RAPIDLY WITH MULTIPLE TSTMS; EXTREME TURB; STRONG WINDS; AND ACCORDING TO THE CTR; TORNADIC ACTIVITY. IT WAS NECESSARY TO MAKE MANY LATERAL DEVS TO AVOID THE WX; AND WE WERE BOTH CONCENTRATING ON THE WX RADAR WHILE BEING GIVEN SEVERAL CHANGES TO OUR CLRNC BY ZNY. I WAS VERY BUSY TALKING ON THE RADIO AND ATTEMPTING TO CHK OUR RTE ON THE CHARTS AND MAPS. CTR CALLED AND ASKED OUR ALT; AT WHICH POINT WE BOTH REALIZED THAT THE AIRPLANE (WHICH WAS ON AUTOPLT AT ALL TIMES) WAS LEVEL AT 32000 FT. THE PF IMMEDIATELY CLBED BACK TO 33000 FT. THERE WAS NEVER AN ALT WARNING FROM THE AUTOPLT OR ALTIMETER SYS; AND NEITHER OF US CAN EXPLAIN HOW THE ALT CHANGED. IT IS POSSIBLE THAT IN ALL THE CONFUSION TAKING PLACE; THAT THE PF TURNED THE ALT CTL KNOB INSTEAD OF THE HEADING KNOB TO ATTEMPT A WX DEV. THE 2 KNOBS ARE NEXT TO EACH OTHER AND ARE ALMOST IDENTICAL ON THIS AIRPLANE. THE CTLR SAID THAT THERE WAS NO CONFLICT AND 'NO PROB.'