A CPR TWIN JET FO OVERSHOOTS HIS ASSIGNED ALT WHEN ATTEMPTING A SPD CHANGE USING THE FLT DIRECTOR COMMAND BARS NE OF BRO; TX.

Narrative

DEPARTING BRO; ATC INSTRUCTED 'CANCEL SPD RESTR.' WE HAD NOT BEEN GIVEN A SPD RESTR; SO WE ASKED ATC IF WE HAD BEEN GIVEN ONE. ATC ADVISED US OF A SPECIAL TEST PROGRAM; WHEREBY ACFT OPERATING BELOW 10000 FT MSL WERE ABLE TO OPERATE AT GREATER THAN 250 KTS IF CLRED BY ATC. AT THE TIME OF THE CLRNC; WE WERE CLBING TO 9000 FT ASSIGNED AT 250 KTS USING A PRESET CLB SCHEDULE IN THE FMS. I ATTEMPTED TO INCREASE SPD OF ACFT BY LOWERING NOSE; BUT BECAUSE OF THE PRESET SPDS IN FMS THE COMMAND BARS ON THE PLTS ADI COMMANDED AN INCREASE CLB PITCH TO BRING DOWN THE AIRSPD. INSTINCTIVELY I BROUGHT THE NOSE BACK UP TO MATCH THE COMMAND BARS. AT ABOUT THE SAME TIME I MATCHED PITCH WITH COMMAND BARS; THEY SUDDENLY DROPPED. BECAUSE THE ALT SELECT FEATURE WAS TRIPPED ON BY RAPIDLY APCHING OUR ASSIGNED ALT OF 9000 FT; I WAS UNABLE TO MATCH THE NEW POS OF THE COMMAND BARS BECAUSE OF EXCESSIVE NEGATIVE 'G' LOADS. BY THE TIME I HAD COMPLETED THE RECOVERY MANEUVER; THE ACFT HAD GONE THROUGH THE ASSIGNED ALT BY 600 FT (9600 FT). WE RETURNED TO OUR ASSIGNED ALT. ATC DID NOT SEEM TO NOTICE.