What was found
AFTER DOING A NORMAL START AND MAGNETO DROP CHECK, THE A/C WAS IN A 20 FT HOVER PREPARING TO TAKEOFF FROM A REMOTE OIL PLANT SITE, WHEN A CHANGE IN ENGINE NOISE AND AN INCREASE IN MANIFOLD PRESSURE WAS NOTICED. THERE WAS NOT ENOUGH ENGINE POWER TO SUSTAIN A HOVER AND THE PILOT WAS FORCED TO LAND THE A/C. DURING GROUND RUN CHECKS, IT WAS NOTICED THAT THE ENGINE WOULD STALL WHEN THE RT MAG WAS SELECTED. BOTH MAGS WERE REPLACED AND THE A/C RETURNED TO SERVICE. THE SUSPECT MAGS ARE BEING SENT FOR OVERHAUL.