As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD/TPA - FLT 6707 - DURING CLIMB ON 4-14-98, AIRCRAFT MADE UNSCHEUDLED LANDING AT IAD DUE TO BOTH STABILIZER TRIMS WILL NOT ENGAGE AND MACH TRIM FALLS OFF-LINE. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED HSTCU COMPUTER. OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (X)