GEAR UP LNDG.

Narrative

I WAS PIC OF AN LTT WHICH LANDED WITH ITS GEAR IN THE UP POS IN MANKATO; MN. CONTRIBUTING FACTORS WHICH LED TO THIS INCIDENT INCLUDE ERRATIC OP OF THE COPLT'S AIR DATA COMPUTER WHICH SET OFF THE OVERSPD WARNING ALARM; EVEN THOUGH THERE WAS NOT AN OVERSPD CONDITION. DUE TO THE NOISE LEVEL OF THIS ALARM; I PULLED THE AURAL WARNING CIRCUIT BREAKER -- THE ONLY METHOD AVAILABLE TO SILENCE THE ALARM -- SO THE COPLT AND I COULD CONCENTRATE ON FLYING THE ACFT. THE APPROVED AIRPLANE FLT MANUAL DOES NOT PROVIDE ANY CHKLIST FOR FAILURE OF THE COPLT'S AIR DATA COMPUTER. THE CHKLIST DOES ALLOW AIR DATA REVERSION FROM THE COPLT'S TO THE PLT'S SIDE; BUT DOES NOT MENTION TRANSFER OF DATA FROM THE PLT'S TO THE COPLT'S SIDE. I WAS UNAWARE THAT THE LNDG GEAR WARNING SYS WAS NOW DISABLED; AND IT GAVE NO INDICATION TO THE FLC OF A GEAR UP CONFIGN. WITH THE ABOVE DETRACTIONS AND ATC GIVING NUMEROUS HDG AND ALT CHANGES; THE GEAR WAS OVERLOOKED; WHICH LED TO THE GEAR UP LNDG. CORRECTIVE ACTIONS SHOULD BE TAKEN IN THE CONFIGN OF THE AURAL WARNING SYS. I RECOMMEND THAT IF AN AIR DATA COMPUTER IS TO FAIL AND CONSEQUENTLY SET OFF THE OVERSPD WARNING; THE PLT OR COPLT SHOULD HAVE THE ABILITY TO CANCEL THEIR RESPECTIVE ALARM WITHOUT JEOPARDIZING A COMPLETELY DIFFERENT SYS; IN THIS CASE THE LNDG GEAR WARNING SYS. IN ADDITION; THERE SHOULD BE A CHKLIST FOR THE FAILURE OF THE COPLT'S AIR DATA COMPUTER AND A FOOTNOTE EXPLAINING THE SERIOUS CONSEQUENCE OF SILENCING THE OVERSPD WARNING BY PULLING THE CIRCUIT BREAKER. SUPPLEMENTAL INFO FROM ACN 219742: UPON FINAL DSCNT FOR LNDG THE CAPT DID NOT CALL FOR THE GEAR TO BE PUT DOWN OR FOR THE BEFORE LNDG CHKLIST. HOWEVER; THE CAPT DID CALL FOR FLAPS TO 10 DEGS; AND FULL FLAPS. ON SHORT FINAL I LOOKED AT THE BEFORE LNDG CHKLIST; AND SINCE THERE WAS NO GEAR WARNING HORN AND FLAPS WERE ALREADY FULL; I ASSUMED THE GEAR WAS DOWN.