Narrative:

Cruise at fl 430/.80 mach on autoplt, stall barrier system suddenly activated with yoke 'shaker' followed almost immediately by yoke 'pusher.' aircraft started descending (autoplt failed). Called for/requested 'emergency descent' with ARTCC who asked how far we wanted to descend. Since we were still troubleshooting, we informed them, 'unsure, we'll let you know when we get there.' stabilized aircraft at FL330 then descended to and maintained FL310 at ARTCC request. Stabilized aircraft by pulling stall computer circuit breaker's (per checklist). Also switched to dadc #2 since dadc #1 failed. After discussing situation with company maintenance via aircraft phone, we diverted to a gulfstream repair facility. Coordinated flight plan change as normal through ARTCC. Callback conversation with reporter revealed the following information: the reporter stated the cause of the stall barrier activation was the incorrect installation of the angle of attack sensors which were both clocked wrong. The reporter said the angle of attack sensors were removed when the aircraft was painted and reinstalled incorrectly after painting. The reporter said the system did not test prior to departure and the flight manual test was tried and the system passed. The reporter stated the flight manual test is to pull the barrier system circuit breakers and wait ten seconds, reset the breakers then test the system which tested ok. The reporter said when the stall barrier system activated at 43000 ft and .80 mach the aircraft started descending and only three methods can be used for disconnecting the stall barrier system. The reporter said the autoplt disconnect and the center pedestal disconnect switch were tried and failed. The last method was pulling the six circuit breakers located over the first officer's overhead which deactivated the system. The reporter stated the failure of the #1 digital air data computer did not play any part in the stall barrier activation and was incidental to the event. The reporter said this aircraft was flight tested twice by the organization that accomplished the maintenance and painting of the aircraft prior to their flight.

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Original NASA ASRS Text

Title: A GULFSTREAM IV IN CRUISE AT FL430 DECLARED AN EMER AND DIVERTED DUE TO STALL BARRIER YOKE SHAKER AND PUSHER ACTIVATION CAUSED BY INCORRECT ANGLE OF ATTACK SENSOR INSTALLATION.

Narrative: CRUISE AT FL 430/.80 MACH ON AUTOPLT, STALL BARRIER SYS SUDDENLY ACTIVATED WITH YOKE 'SHAKER' FOLLOWED ALMOST IMMEDIATELY BY YOKE 'PUSHER.' ACFT STARTED DSNDING (AUTOPLT FAILED). CALLED FOR/REQUESTED 'EMER DSCNT' WITH ARTCC WHO ASKED HOW FAR WE WANTED TO DSND. SINCE WE WERE STILL TROUBLESHOOTING, WE INFORMED THEM, 'UNSURE, WE'LL LET YOU KNOW WHEN WE GET THERE.' STABILIZED ACFT AT FL330 THEN DSNDED TO AND MAINTAINED FL310 AT ARTCC REQUEST. STABILIZED ACFT BY PULLING STALL COMPUTER CB'S (PER CHKLIST). ALSO SWITCHED TO DADC #2 SINCE DADC #1 FAILED. AFTER DISCUSSING SIT WITH COMPANY MAINT VIA ACFT PHONE, WE DIVERTED TO A GULFSTREAM REPAIR FAC. COORDINATED FLT PLAN CHANGE AS NORMAL THROUGH ARTCC. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE CAUSE OF THE STALL BARRIER ACTIVATION WAS THE INCORRECT INSTALLATION OF THE ANGLE OF ATTACK SENSORS WHICH WERE BOTH CLOCKED WRONG. THE RPTR SAID THE ANGLE OF ATTACK SENSORS WERE REMOVED WHEN THE ACFT WAS PAINTED AND REINSTALLED INCORRECTLY AFTER PAINTING. THE RPTR SAID THE SYS DID NOT TEST PRIOR TO DEPARTURE AND THE FLT MANUAL TEST WAS TRIED AND THE SYS PASSED. THE RPTR STATED THE FLT MANUAL TEST IS TO PULL THE BARRIER SYS CIRCUIT BREAKERS AND WAIT TEN SECONDS, RESET THE BREAKERS THEN TEST THE SYS WHICH TESTED OK. THE RPTR SAID WHEN THE STALL BARRIER SYS ACTIVATED AT 43000 FT AND .80 MACH THE ACFT STARTED DESCENDING AND ONLY THREE METHODS CAN BE USED FOR DISCONNECTING THE STALL BARRIER SYS. THE RPTR SAID THE AUTOPLT DISCONNECT AND THE CENTER PEDESTAL DISCONNECT SWITCH WERE TRIED AND FAILED. THE LAST METHOD WAS PULLING THE SIX CIRCUIT BREAKERS LOCATED OVER THE FIRST OFFICER'S OVERHEAD WHICH DEACTIVATED THE SYS. THE RPTR STATED THE FAILURE OF THE #1 DIGITAL AIR DATA COMPUTER DID NOT PLAY ANY PART IN THE STALL BARRIER ACTIVATION AND WAS INCIDENTAL TO THE EVENT. THE RPTR SAID THIS ACFT WAS FLT TESTED TWICE BY THE ORGANIZATION THAT ACCOMPLISHED THE MAINT AND PAINTING OF THE ACFT PRIOR TO THEIR FLT.

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.