DC8 CARGO FLT IN A NIGHT OP SUFFERS ALT EXCURSIONS ABOVE AND BELOW ASSIGNED ALT. PIC FORGOT TO SET CRUISE PWR. FO OUT OF SEAT; IN THE LAVATORY.

Narrative

WHILE CLBING OUT OF FL320; FO ASKED ME IF HE COULD GO TO THE HEAD; I SAID ALL RIGHT. AS HE LEFT THE FLT DECK AND AS I WAS DONNING MY OXYGEN MASK THE AUTOPLT WAS SLUGGISH WITH THE PITCH WHEEL; SO I DISENGAGED IT; REVERTING TO MANUAL CTL. NEXT; AS I WAS LEVELING AT FL330; CTR RPTED TFC AHEAD AND ABOVE US (BEING NIGHT-VMC). I BEGAN SCANNING FOR THIS TFC (AND FAILED TO CALL FOR 'CRUISE PWR'). ACFT THEN BALLOONED 200-290 FT HIGH (NO ALT ALERT DEVICE; WARNING CHIME; OR LIGHT). SIMULTANEOUSLY; THE FE SAID; 'OUT OF FL332 FOR FL330' AND CTR ASKED; 'ACR X; WHAT IS YOUR ALT?' WHILE I WAS APPLYING FORWARD PRESSURE TO STOP AND REVERSE EXCURSION I TRIED TO BE SMOOTH NOT TO INJURE MY FO (WHO WAS IN THE HEAD). WHILE NOTICING THE UNUSUAL FORWARD PRESSURE ON YOKE TO PITCH DOWN WITH THE ALT EXCURSION; I WAS THINKING 'MOUNTAIN WAVE' AND SAID THIS OVER RADIO AS KNEE JERK REACTION (NO TIME FOR SMALL WORDS LIKE; 'THIS 'FEELS' LIKE MOUNTAIN WAVE.') NEXT I OVERSHOT MY ALT (BECAUSE I FORGOT I STILL HAD CLB PWR) GOING BELOW MY ASSIGNED ALT TO 300 FT BELOW. (THIS TIME I GOT THE ALT ALERT DEVICE WARNING LIGHT AND CHIME.) THEN; RETURNING IMMEDIATELY (BUT SMOOTHLY) TO MY ASSIGNED ALT AND HAD 'CRUISE PWR SET.' FO RETURNED TO FLT DECK (HE OBVIOUSLY THOUGHT I WAS 'PLAYING AROUND' WHEN THAT WAS NOT THE CASE AT ALL). NEXT ZID ASKED ME TO CONTACT IND QUALITY ASSURANCE. I CALLED THEM ASAP AND GOT ANSWERING MACHINE SATURDAY AND SUNDAY. BUT MONDAY MORNING; TALKED WITH THEM. I SINCERELY BELIEVE THIS ALL COMES DOWN TO ME (THE CAPT) BEING FATIGUED. (CREW DUTY STARTED DB45 AM EST IN IAD; SO AT TIME OF OCCURRENCE I WAS AT 14 HRS 45 MINS INTO MY DAY ON TOP OF MANY DELAYS; CHANGES AND DISTRS AND INCREASED WORKLOAD.) SUPPLEMENTAL INFO FROM ACN 355420: 14 HRS 45 MINS INTO THE CREW DUTY PERIOD. PRIOR TO DEP; THE CREW REMAINED IN THE ACFT IN EXCESS OF 3 HRS AWAITING ACFT UPLOAD. AFTER DEP AND PRIOR TO LEVELOFF; I HAD TO LEAVE MY SEAT TO SATISFY PHYSIOLOGICAL NEEDS. THIS NEED AROSE BECAUSE OF THE LONG PERIOD PRIOR TO DEP WHERE PROPER FACILITIES AND PRIVACY CONDITIONS WERE NOT AVAILABLE.