I had a recurring problem with the bracket that clasps the throttle cable at the back of the engine. The bracket is bolted to the intake manifold with a wire saftied screw which goes through a bushing. This arrangement allows a small amount of movement by the bracket. My problem was a loss of throttle control during taxi for takeoff. The screw with safety wire attached pulled out of it’s threads after both the screw and the bushing wore nearly through. In repairing this failure, the mechanic made an error when replacing the screw by tightening to the point that it did not allow the bracket to rotate slightly as intended. This new screw sheared during landing on the next flight. The subsequent repair was done correctly but on the next annual the bushing showed some wear and was replaced with another brass bushing. This bushing also showed wear on a subsequent annual so it was replaced with a steel bushing. In addition, the hole in the bracket was elongated and had to be repaired. The following actions were recommended by Keith Diver: “Power Control cables – including eye bolt joints (throttle and mixture control eyeball fittings): slight looseness. Bolts should be safety tied together. Check tightness and safety-wire on bolts holding standoff brackets on rear of the intake manifold. Pull bolt and check for wear. Lubricate. If hole is worn, drill and ream to 5/16 inch and install bushing and a new bolt. It is recommended putting a spring on the throttle control so it won’t go to idle position if the cable comes off. Do this with a field approved 337 form”. Keith recommends using a generic 1/4 inch OD, 1 5/8 inch long, 030 wire diameter with a 1 1/16 inch stand off from the top aft fuel air valve bolt. I have pictures of the spring and attachments that my mechanic made and will send them if you would like to provide an email address.
