A HAWKER 800 ON TOUCHDOWN ACFT EXITED THE RWY STRIKING THE RWY SIGN AND LIGHTS AND INCURRING ACFT DAMAGE. CAUSED BY A CHRONIC BRAKE ANTISKID FAILURE.

Narrative

PLTS DISCOVERED 3 FLAT SPOTTED TIRES DURING A POSTFLT INSPECTION AT ZZA AND NOTIFIED OUR MAINT PERSONNEL IN ZZZ. SINCE THIS ACFT HAD EXPERIENCED APPROX 4 FLAT SPOTTED TIRE EVENTS PREVIOUS TO THIS ONE AND HAVING RULED OUT PLT ERROR BECAUSE OF THE NUMBER OF EVENTS AND THE PLT'S AWARENESS OF THE SIT; IT WAS SUSPECTED THAT AN INTERMITTENT PROB IN THE BRAKE/ANTISKID SYS MAY EXIST. 2 OF OUR TECHNICIANS WERE DISPATCHED TO ZZA WHERE THEY REPLACED THE #1 AND #2 TIRE AND WHEEL ASSEMBLIES; PERFORMED OPERATIONAL TESTS OF THE BRAKE AND ANTISKID SYS AND RETURNED WITH THE ACFT TO OUR HANGAR AT ZZB. THE #3 TIRE FLAT SPOT WAS WITHIN LIMITS AND WAS NOT REPLACED AT THIS TIME. IN CLOSE COLLABORATION WITH ENGINEERS AND TECHNICAL REPRESENTATIVES; A DETAILED INSPECTION OF THE BRAKE SYS WAS CARRIED OUT. FIRST; A HYD FLUID SAMPLE WAS OBTAINED FROM THE BRAKE SYS AND SENT FOR ANALYSIS. NUMEROUS OPERATIONAL AND FUNCTIONAL TESTS OF THE BRAKE AND ANTISKID SYS WERE PERFORMED WITH NORMAL RESULTS. THE BRAKE CTL VALVE WAS THEN INSPECTED AND CHKED FOR PROPER RIGGING. THE MAXARETS [WHEEL SPIN SENSORS] AND MODULATORS WERE REMOVED AND DETAIL INSPECTED. EVIDENCE OF CONTAMINATION WAS FOUND ON BOTH SIDES OF THE L MODULATOR INLET FILTER AND AT THE R MODULATOR PISTON O-RING SEAL. BECAUSE OF THE CONTAMINATION FOUND IT WAS DECIDED TO REPLACE THE BRAKE CTL VALVE AND BOTH MODULATORS AND FLUSH THE LINES CLEAN IN BTWN. AFTER THIS WAS ACCOMPLISHED AND 4 NEW TIRES WERE INSTALLED; FUNCTIONAL TESTS WERE AGAIN PERFORMED OF THE BRAKE/ANTISKID SYS AND TAXI CHKS AND A TEST FLT WERE COMPLETED BEFORE RETURNING THE ACFT TO SVC. THE CONTAMINATION FOUND IN THE SYS WAS CONSIDERED TO BE THE ROOT CAUSE OF THE LOCKED BRAKES IN THIS CASE AND THEREFORE REMOVING IT SHOULD ELIMINATE ANY FUTURE FLAT SPOTTING INCIDENTS. ON APR/XA/01; 67 HRS AND 37 LNDGS LATER; HOWEVER; ANOTHER INCIDENT OF THIS NATURE OCCURRED UPON LNDG AT ZZC. WHEN THE ACFT TOUCHED DOWN; IT PULLED HARD L. THE ACFT EXITED THE RWY STRIKING AN ARPT SIGN AND SEVERAL RWY LIGHTS BEFORE THE PLT GAINED CTL AND BROUGHT THE ACFT BACK ON THE RWY. THE PLT THEN COMPLETED HIS ROLLOUT AND TAXIED CLR OF THE RWY. AT THIS POINT; THE PLT'S WALKAROUND INSPECTION REVEALED THE 2 L MAIN TIRES FLAP-SPOTTED WITH LOSS OF AIR PRESSURE; AND DAMAGE TO THE L FLAP AND GEAR DOOR. AGAIN; WE ARE WORKING CLOSELY WITH TECHNICAL REPRESENTATIVES TO DETERMINE THE CAUSE OF THE L BRAKES BEING LOCKED AT TOUCHDOWN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE HAS A CHRONIC ANTISKID PROB AND AFTER THE RWY EXCURSION WAS MAINT FERRIED TO THE MANUFACTURER'S REPAIR STATION. THE RPTR SAID ALL BRAKE ANTISKID COMPONENTS WERE REMOVED AND SENT TO THE COMPONENT MANUFACTURER FOR TESTING. THE RPTR SAID AS OF THIS DATE THE AIRPLANE IS STILL OTS AT THE MANUFACTURER'S REPAIR STATION. THE RPTR STATED THE OTHER HAWKER 800 OWNED BY THE COMPANY HAS HAD 1 RPTED BRAKE ANTISKID PROB AND IT WAS A HARD MAXARET FAILURE.