As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT - 6282 - IAD-HPN - AIRCRAFT MADE A UNSCHEDULED LANDING AT IAD DUE TO FO'S ASI READING 40 KNOTS LOW. AIRCRAFT RETURNED TO GATE WITH NO FURTHER PROBLEMS. MAINTENANCE INSPECTED AND REMOVED AND REPLACED ASI, OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FRO RETURN TO SERVICE. (M)