TWO MECHANICS ARE INFORMED THE LEFT AND RIGHT COWLINGS ON THE #2 TAIL ENGINE OF A DASSAULT FALCON JET WERE FOUND DAMAGED AT THEIR UPPER HINGE POINTS; AFTER A HIGH POWER RUN AND REVERSER CHECKS WERE ACCOMPLISHED.

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I WAS INFORMED ON OCT/XA/08 THAT MY COMPANY WAS CONSIDERING THE FOLLOWING INCIDENT A SAFETY OF FLT ISSUE. ON THE NIGHT OF SEP/XB/08 WHILE WORKING OVER FROM FIRST SHIFT TO SECOND SHIFT; THE #2 ENG COWLINGS WERE BLOWN OPEN AND DAMAGED A FALCON. THE ACFT HAD A CLR WATER WASH PERFORMED ON ALL ENGS THAT REQUIRED A MOTOR; THEN AN 80% PWR RUN. I WAS IN THE COCKPIT OBSERVING A SECOND SHIFT PERSON PERFORM THE WASH; MOTOR AND RUN AS THIS WAS HIS FIRST RUN AFTER SIMULATOR TRAINING. THE WASH AND MOTOR WENT NORMAL. FOR THE RUN; #2 ENG WAS STARTED FIRST AND THEN THE APU WAS SHUT DOWN SO #2 ENG COWLING COULD BE OPENED AND A LEAK OF BLEED AIR DUCTS; THAT HAD BEEN CAPPED FOR THE WASH; COULD BE DONE. IT IS AT THIS POINT I DO NOT KNOW WHAT HAPPENED WITH REGARDS TO THE COWLINGS. I DO KNOW WE IN THE COCKPIT; WERE CLRED TO START THE OTHER ENGS BY A GND OBSERVER; SO WE ASSUMED THE #2 ENG COWLINGS HAD BEEN CLOSED AT THAT TIME. AFTER THE OTHER ENGS WERE STARTED AND LEAK CHKED; WE TAXIED TO TXWY E RUN-UP AREA AT THE ARPT. DURING TAXI; REVERSE ENG THRUST WAS USED WITH NO PROB NOTED. DURING RUN-UP OF THE FIRST ENG; A DIP/MOVEMENT OF THE NOSE WAS NOTED; BUT THIS WAS NO MORE THAN USUALLY NOTED ON A RUN TO PWR ON OTHER ACFT. DUE TO LOW LIGHT IN RUN-UP AREA AND BECAUSE IT WAS CLOSE TO XB30; THE TAXI LIGHT WAS TURNED ON TO ENSURE WE WERE NOT AND HAD NOT MOVED. AFTER ENSURING WE WERE NOT MOVING; THE RUN-UP WAS FINISHED AND WE TAXIED BACK TO THE HANGAR WITH NO PROB NOTED. AFTER RETURNING TO THE HANGAR; I WENT HOME LEAVING SECOND SHIFT TO FINISH WITH THE ACFT AND DO DEP CHKS. THE DAMAGE TO THE ACFT WAS NOT NOTED UNTIL THE ACFT HAD ARRIVED AT ITS HOME STATION. SUPPLEMENTAL INFO FROM ACN 808410: I WAS NOT MADE AWARE THAT THIS WAS A SAFETY OF FLT ISSUE UNTIL THE DAY I WAS DISCHARGED OCT/XA/08. AT XA00 THE DAY OF THE INCIDENT; I WAS TOLD THE FALCON NEEDED A COMPRESSOR WASH; AND THAT IT WOULD BE LEAVING AFTER IT WAS DONE; AND THE CREW WAS WAITING FOR IT. WE COMPLIED WITH THE ASH. ENG AND MAINT SHOPS MADE THE ACFT READY FOR THE ENG RUNS. WHILE THAT WAS IN WORK; I WAS TASKED WITH RUNNING ENG. APPROX XA00 WHEN THE ACFT WAS READY; A DRY MOTOR WAS PERFORMED ON EACH ENG. I STARTED #2 ENG AND A LEAK CHK WAS PERFORMED; COWLINGS WERE CLOSED. #1 AND #3 ENGS WERE STARTED AND LEAK CHKED. WE WERE CLRED TO TAXI AND PROCEED TO TXWY E RUN AREA. ACFT HAD LIGHT FUEL LOAD SO THE THRUST REVERSER WAS DEPLOYED DURING THE TAXI. AT TXWY E; I BROUGHT UP #3 AND FELT THE ACFT SETTLE; REDUCED #3 TO IDLE AND CHKED THE SCREENS -- NO FAULTS NOTED. I BROUGHT UP #2 TO 80% FOR 3 MINS; REDUCED #2 TO IDLE. SAME PROC WAS DONE ON #1 AND #3 ENGS -- NO FAULTS NOTED. TAXI BACK TO HANGAR. INSTALLED #1 AND #3 ENG COWLINGS. STARTED THE DEP CHKS; FOUND #2 COWLING OPEN; SO I CLOSED THEM AND COMPLETED THE CHK. ACFT DEPARTED APPROX XE00. A FEW DAYS LATER WE FOUND OUT THAT #2 COWLINGS WERE DAMAGED FROM NOT BEING LATCHED BEFORE WE TAXIED TO THE TXWY E RUN-UP AREA. CALLBACK CONVERSATION WITH RPTR ACN #807896 REVEALED THE FOLLOWING INFO: REPORTER STATED THE DASSAULT FALCON JET IS A FLY BY WIRE AIRCRAFT WITHOUT ANY TILLER OR YOKE AND ALL STEERING IS DONE THROUGH THE RUDDER PEDALS. STEERING RATIOS CHANGE DEPENDING ON THE AMOUNT OF RUDDER PEDAL INPUT DURING AN ATTEMPTED TURN. REPORTER STATED THEY WERE INFORMED THE #2 ENGINE COWLINGS WERE DAMAGED AT THEIR UPPER HINGE POINTS WITH ASSOCIATED DAMAGE TO THE SURROUNDING TAIL SKIN AND TAIL STRUCTURE. THE AREA FOUND DAMAGED; COULD NOT BE SEEN FROM THE GROUND WHILE PERFORMING A NORMAL WALKAROUND.