Narrative:

On taxi out from freeport ramp, we performed 'before takeoff' checklist. When first officer attempted to cycle controls to check freedom of movement, we discovered that the stick pusher had activated and was holding the yoke full forward. We checked all switch position and indicators, and found nothing abnormal. We had no indication of stall, visual or aural. We returned to the gate and the flight was canceled. After a mechanic was flown in to disconnect the stall avoidance system, we ferried home uneventfully (with no stall warning or stick pusher functioning). The small transport has a history of stick pusher activation during normal flight. I am familiar with one such case at our airline where, if not for the heroic efforts of the crew, the aircraft would have been destroyed. Supposedly, the manufacturer and the users had developed procedures to deal with, and a mechanic fix to prevent inadvertent stick pusher activation. Our situation would have been very grave had this happened while airborne. Neither the first officer nor I were able to overpwr the pusher force. Supposedly, a clutch is built into the system to limit pusher force. Obviously it was not functioning properly. The fact that the small transport is allowed to continue to operate with severe design deficiencies in its stall warning, electrical, nose steering and other system is a travesty! We all know what the ultimate outcome will be if this aircraft is allowed to continue to operate without a comprehensive design review, and mandated modification program. Callback conversation with reporter revealed the following information: the reporting captain states that this popular type of commuter aircraft has had a problem with its stall avoidance system (sas) stick pusher for quite some time. He referenced an article in the current issue of a pilot's union magazine where this problem is addressed and where the NTSB 'probable cause' was changed several yrs after a fatal accident. The reporter has talked at length with his chief pilot and will call the FAA safety hot line. His air carrier's maintenance section found that the sas computer was working properly, but the clutch had disintegrated and the parts jammed the clutch in the actuate position forcing the nose down.

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Original NASA ASRS Text

Title: AN ACR SMT CREW RPTS THAT THEY HAD A FAILED STICK PUSHER ON THE GND, FORTUNATELY.

Narrative: ON TAXI OUT FROM FREEPORT RAMP, WE PERFORMED 'BEFORE TKOF' CHKLIST. WHEN FO ATTEMPTED TO CYCLE CTLS TO CHK FREEDOM OF MOVEMENT, WE DISCOVERED THAT THE STICK PUSHER HAD ACTIVATED AND WAS HOLDING THE YOKE FULL FORWARD. WE CHKED ALL SWITCH POS AND INDICATORS, AND FOUND NOTHING ABNORMAL. WE HAD NO INDICATION OF STALL, VISUAL OR AURAL. WE RETURNED TO THE GATE AND THE FLT WAS CANCELED. AFTER A MECH WAS FLOWN IN TO DISCONNECT THE STALL AVOIDANCE SYS, WE FERRIED HOME UNEVENTFULLY (WITH NO STALL WARNING OR STICK PUSHER FUNCTIONING). THE SMT HAS A HISTORY OF STICK PUSHER ACTIVATION DURING NORMAL FLT. I AM FAMILIAR WITH ONE SUCH CASE AT OUR AIRLINE WHERE, IF NOT FOR THE HEROIC EFFORTS OF THE CREW, THE ACFT WOULD HAVE BEEN DESTROYED. SUPPOSEDLY, THE MANUFACTURER AND THE USERS HAD DEVELOPED PROCS TO DEAL WITH, AND A MECH FIX TO PREVENT INADVERTENT STICK PUSHER ACTIVATION. OUR SIT WOULD HAVE BEEN VERY GRAVE HAD THIS HAPPENED WHILE AIRBORNE. NEITHER THE FO NOR I WERE ABLE TO OVERPWR THE PUSHER FORCE. SUPPOSEDLY, A CLUTCH IS BUILT INTO THE SYS TO LIMIT PUSHER FORCE. OBVIOUSLY IT WAS NOT FUNCTIONING PROPERLY. THE FACT THAT THE SMT IS ALLOWED TO CONTINUE TO OPERATE WITH SEVERE DESIGN DEFICIENCIES IN ITS STALL WARNING, ELECTRICAL, NOSE STEERING AND OTHER SYS IS A TRAVESTY! WE ALL KNOW WHAT THE ULTIMATE OUTCOME WILL BE IF THIS ACFT IS ALLOWED TO CONTINUE TO OPERATE WITHOUT A COMPREHENSIVE DESIGN REVIEW, AND MANDATED MODIFICATION PROGRAM. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTING CAPT STATES THAT THIS POPULAR TYPE OF COMMUTER ACFT HAS HAD A PROB WITH ITS STALL AVOIDANCE SYS (SAS) STICK PUSHER FOR QUITE SOME TIME. HE REFED AN ARTICLE IN THE CURRENT ISSUE OF A PLT'S UNION MAGAZINE WHERE THIS PROB IS ADDRESSED AND WHERE THE NTSB 'PROBABLE CAUSE' WAS CHANGED SEVERAL YRS AFTER A FATAL ACCIDENT. THE RPTR HAS TALKED AT LENGTH WITH HIS CHIEF PLT AND WILL CALL THE FAA SAFETY HOT LINE. HIS ACR'S MAINT SECTION FOUND THAT THE SAS COMPUTER WAS WORKING PROPERLY, BUT THE CLUTCH HAD DISINTEGRATED AND THE PARTS JAMMED THE CLUTCH IN THE ACTUATE POS FORCING THE NOSE DOWN.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.