What was found
DURING FLIGHT, THE ENGINE STARTED RUNNING ROUGH AND LOST POWER. EMERGENCY LANDING COMPLETED WITHOUT DAMAGE OR INJURY. MAINT FOUND THE NR 3 EXHAUST VALVE SEIZED IN THE VALVE GUIDE. FURTHER INVESTIGATION FOUND THE GUIDE BROKEN IN THE CYLINDER HEAD. OPERATOR HAS AIRCRAFT WITH THE NEW ROLLER TAPPET ENGINES. HAVE BEEN PERFORMING A SB388C INSPECTION ON THE REST OF THE FLEET AND HAVE FOUND THE MAJORITY OF THE EXHAUST VALVES FOR ALL CYLINDERS TO BE TIGHT IN THE GUIDES. MFG RECOMMENDS A 1000 HOUR INTERVAL FOR THESE ENGINES FOR SB388C INSPECTION. WILL BE INITIATING A 600 HOUR INTERVAL FOR THE SB388C FOR OUR FLEET. HAVE REVISED LEANING PROCEDURES. (K)