ABRUPT AND UNEXPLAINED YAW APPROACHING 100K ON THE TAKE OFF ROLL RESULTS IN HIGH SPEED REJECTED TAKE OFF FOR B737-800 FLIGHT CREW.

Narrative

THE EVENT WAS A HIGH SPD REJECTED TKOF. TKOF CONDITIONS WERE CLR SKIES; TEMP OF 84 DEGS; AND WIND 140 DEGS AT 5-10 KTS. I WAS THE PLT MONITORING. DURING THE TKOF ROLL; SHORTLY AFTER I STATED; '87 KTS; THROTTLE HOLD; ENG INSTS CHKED;' THE ACFT MADE AN ABRUPT YAW TO THE L. I LOOKED UP TO CHK THE ACFT'S TRACK DOWN THE RWY AND IN THE TRANSITION FROM THE ENG INSTS TO OUTSIDE REFS; THE FO STATED 'ENG FAIL.' I TOOK CTL; REJECTED THE TKOF AT ABOUT 95 KTS. AFTER STOPPING THE ACFT AND EXAMINING THE ENG INST; IT WAS APPARENT THAT WE DID NOT HAVE AN ENG FAILURE. THE 'ENG FAILURE' CALL WAS BASED ON THE YAW AND A NEED FOR AN UNUSUAL AMOUNT OF COUNTERACTING RUDDER. THE REJECTED TKOF WAS BASED ON THE ENG FAILURE CALL. SUPPLEMENTAL INFO FROM ACN 801562: THE CAPT INSTRUCTED ME TO CHK THE OPS MANUAL FOR THE APPLICABLE BRAKE COOLING SCHEDULE WHILE HE MADE A PA TO THE CABIN. THE CAPT HAD DETERMINED THAT THE RTO WAS INITIATED AT APPROX 95 KTS. LATER THE FDR SHOWED 103 KTS. THE CAPT CONSULTED THE COMPANY'S FOM AND COMPLIED WITH THE RTO OPERATIONAL POLICY BY FIRST CONTACTING THE OP'S CTR DUTY PLT. WE DISCUSSED THE POSSIBLE CAUSES OF THE ABNORMAL YAW AND CONCLUDED WE HAD EXPERIENCED A LARGE ROGUE WIND GUST AND WITH NO APPARENT INDICATIONS OF A MECHANICAL FAILURE; THE CAPT DETERMINED IT WAS SAFE TO CONTINUE. APPROX 45 MINS AFTER THE RTO; AND WITH APPROVAL FROM THE FLT OPS GENERAL MGR; WE CONTINUED THE OP TO DEST. THE AIR CREW COMPLIED WITH THE COMPANY'S RTO POLICY AND DEEMED IT SAFE TO CONTINUE.