As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE A VERY STRONG ACRID ODOR WAS NOTED, ACCOMPANIED BY A BURNING SENSATION IN NOSE AND THROAT. ODOR SEEMED STRONGEST AT CAPTAINS SIDE. UNSCHEDULED LANDING. FOUND NR 1 PACK TURBINE BYPASS VALVE STUCK IN THE OPEN POS. REMVOED AND REPLACED BYPASS, RAN ENGINES AND CHECKED OK. (M)