FLC OF AN MDT DECLARED AN EMER AND RETURNED TO LAND AFTER LOSING THE PWR OF 1 ENG IN ICING CONDITIONS.

Narrative

ENG ANTI-ICE SYS PERFORMED NORMALLY ON FO'S TKOF AND CLBOUT FROM CINCINNATI/NORTHERN KENTUCKY INTL ARPT (CVG). OUTSIDE AIR TEMP INCREASED AS WE CLBED THROUGH CLOUDS. ENG ANTI-ICE WAS TURNED OFF AT APPROX 4000 FT MSL AND PLUS 8 DEGS C OUTSIDE AIR TEMP. ENG ANTI-ICE WAS SELECTED ON AT APPROX 5000 FT MSL AS OUTSIDE AIR TEMP WAS DECREASING FROM PLUS 10 DEGS TO PLUS 8 DEGS C. 'ICE PROTECTION' CENTRAL WARNING PANEL LIGHT ILLUMINATED WITH 'L AIR VALVE' LIGHT ON OVERHEAD PANEL. CAPT RECYCLED L ENG ANTI-ICE SWITCH; WHICH DID NOT SOLVE THE PROB. CAPT THEN RETARDED L PWR LEVER TO APPROX 50 PERCENT TORQUE TO MANUALLY OPEN THE ANTI-ICE/START BLEED VALVE; PER THE ABNORMAL PROCS CHKLIST. 'L AIR VALVE' LIGHT WENT OUT ON OVERHEAD PANEL. CAPT BEGAN SMOOTHLY REAPPLYING CLB TORQUE TO L ENG. TORQUE; PROP AND GAS GENERATOR RPM INDICATIONS FLUCTUATED WILDLY FOR APPROX 3 SECONDS. CAPT MOVED L CONDITION LEVER TO 'T/M LOCKOUT' (TORQUE MOTOR LOCKOUT) POS IN RESPONSE TO UNCOMMANDED POWER PLANT INDICATIONS; PER ABNORMAL PROCS CHKLIST. ALL INDICATIONS FOR L ENG WERE NOW DECREASING TOWARD ZERO AS 'L ENG OIL PRESSURE' CENTRAL WARNING PANEL LIGHT ILLUMINATED. CAPT SECURED L CONDITION LEVER TO 'FUEL OFF' POS AND REQUESTED CTL OF ACFT. CTLS WERE TRANSFERRED FROM FO TO CAPT. FO COMPLETED 'ENG FIRE/FAILURE IN FLT' EMER CHKLIST. AN EMER WAS DECLARED TO ATC; AND WE RETURNED TO CVG. FO COMPLETED CLB; CRUISE; DSCNT; APCH; AND BEFORE LNDG 'SINGLE ENG OPS' ABNORMAL PROCS CHKLIST. A SUCCESSFUL SINGLE ENG LNDG WAS MADE AT CVG.