What was found
NEWLY OVERHAULED PROPS, HARTZELL PN HC-B4MP-3C, ON KING AIR B300. INFLIGHT, WHEN POWER WAS REDUCED FOR LANDING, THE PROPS S/N FWA4217 AND FWA4213 WENT FLATTER THAN THE FLIGHT LOW PITCH SYSTEM, CAUSING DANGEROUS DRAG, SIGNIFICANT REDUCTION IN AIRSPEED AND ALTITUDE AS THE NOSE IS PITCHED DOWN TO AVOID A STALL. ON ANOTHER OCCASION, ONLY ONE PROP WENT TOO FLAT, UNABLE TO COUNTER WITH FULL RUDDER. PLEASE NOTE THIS SITUATION WAS NOT CAUSED BY THE AIRFRAME LOW PITCH TORQUE SYSTEM WHICH IS ELECTRICALLY CONTROLLED. CIRCUIT BREAKER POWER WAS REMOVED FROM THE AIRFRAME FLIGHT LOW PITCH SYSTEM DURING TROUBLESHOOTING TEST FLIGHTS, AND PROBLEM REMAINED BOTH PROPELLERS HAD HARTZELL HC-SB-61-394 (GUIDE BLOCK/PITCH ROD CLEARANCE) COMPLETED DURING OVERHAUL. FOUND PROPELLER PITCH LINKS GALLING SLIGHTLY ON DOME AT NEAR LINK ATTACH PINS, AND NO LUBRICATION ON PITCH LINKS OR PITCH RODS. NOTE: HARTZELL’S MAINTENANCE/OVERHAUL MANUAL DOES NOT REQUIRE THE LOW PITCH STOP ROD LUBRICATION, WHILE BEECH MAINTENANCE MANUAL CHAPTER 12-20-01 REQUIRES PITCH ROD LUBRICATION AT 200 HRS. AFTER PITCH LINKS AND RODS WERE LUBRICATED, SUBSEQUENT FLIGHT SHOWED THE PROPS TO BE OPERATING NORMALLY – NO BINDING AND PROPER OPERATION AT THE FLIGHT LOW PITCH SYSTEM.