ALT BUST.

Narrative

WHILE CRUISING AT FL330; WITH LIVE HORSES AS CARGO; WE EXPERIENCED MODERATE TURB. THE FO (PNF) WAS IN THE LAVATORY. THE CAPT RECEIVED CLRNC TO CLB TO FL350. APCHING FL350; THE CAPT CANCELED THE ALT CAPTURE MODE AND SELECTED VERT SPD IN AN EFFORT TO SMOOTH THE LEVEL OFF FOR THE HORSES. I WAS UNAWARE THAT HE HAD DESELECTED ALT CAPTURE. AT APPROX FL360; CTR QUERIED US ON OUR CLRNC; THEN ASKED IF WE WOULD LIKE TO CONTINUE TO FL370. THE CAPT DECLINED AND DSNDED TO FL350. THE FOLLOWING APPEAR TO BE FACTORS IN THIS INCIDENT: NONSTANDARD CARGO: HORSES; NONSTANDARD PROC BY THE CAPT IN AN ATTEMPT TO PROTECT THE CARGO; DISTRACTED ATTN BY CAPT AND SO DURING LEVEL OFF; FMS DESIGN IN DC-10 THAT GIVES NO ALERT OF ALTDEV IN THE VERT SPD MODE. SUPPLEMENTAL INFO FROM ACN 272490: I BELIEVE THAT A LIGHT SHOULD BLINK OR A HORN SHOULD BE ACTIVATED IN THE EVENT OF EXCEEDING THE ALT ALERTER RATHER THAN JUST BLINDLY BEING ABLE TO CLB RIGHT OUT OF THE SKY UNTIL NOTICED. (IN FACT; IF YOU LEAVE A SELECTED ALT; A LIGHT DOES BLINK UNTIL MANUALLY CANCELED.) IF A MANUAL VERT SPD CLB CAN CANCEL THE AUTOMATIC LEVELOFF PORTION OF THE AUTOPLT; I FEEL IT IS EXTREMELY IMPORTANT TO INVESTIGATE ADDING A FEATURE TO THE AUTOFLT SYS THAT SHOULD TELL YOU WHEN THE ACFT HAS EXCEEDED WHAT YOU HAVE SET IN THE WINDOWS. I ALSO BELIEVE THAT FLT DEPTS SHOULD TRAIN THEIR PLTS TO BRING IN THE 3RD CREW MEMBER OF A 3-MAN COCKPIT INTO THE 'FRONT END' PICTURE WHEN A FRONT END PLT HAS TO EXCUSE HIMSELF FROM THE COCKPIT FOR PHYSIOLOGICAL REASONS.