What was found
FLIGHT 4427, CREW REPORTED A STRONG ACRID ODOR IN THE CABIN DURING DESCENT. AIRCRAFT LANDED WITHOUT INCIDENT AND REMOVED FROM SERVICE. FOUND OIL LEAKING OUT OF AIR TURBINE STARTER FROM NR 1 ENGINE. REMOVED AND REPLACED THE MAGNETIC CARBON SEAL FROM ACCESSORY DRIVER GEARBOX IAW ROLL ROYCE MM 72-63-10. REPLACED RELEVANT O-RINGS OF SEAL AND STARTER. PERFORMED IDLE ENGINE RUN IAW GHC AND PERFORMED ETN: EM72034R4 FOR ODOR TROUBLESHOOTING. NO ODORS NOTED AT IDLE RUN. PERFORMED HIGH-SPEED ENGINE RUN IAW ETN: NO ENGINE ODOR NOTED. THE OPERATIONAL CHECK WAS GOOD. THE AIRCRAFT WAS RETURNED TO SERVICE.