As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAD/BUF - FLT 7486 - DURING TAKEOFF, MADE AN UNSCHEDULED LANDING DUE TO CAPTAIN'S HSI FLAGGED. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND RE-RACKED CAPTAIN'S HSI. OPS CHECK OK. AIRCRAFT RELEASED AND RETURNED TO SERVICE. (X)