ERA17LA169

While the airplane was in cruise flight, the airline transport pilot noticed a drop in manifold pressure; he advanced the throttle to regain power. After several unsuccessful attempts to regain full power, he made a forced landing and the airplane collided with a ditch, which resulted in damage to the right wing spar. Postaccident examination of the throttle body fuel injection servo revealed the throttle cable linkage was loose at the attachment point of the throttle body fuel injection servo. Further examination revealed the throttle cable linkage had slipped because the gear teeth did not make full contact locking together. Some of the gear teeth on the throttle linkage and on the throttle body servo were worn with flat spots. It is likely that this condition ultimately resulted in the pilot's inability to control the power setting of the engine.

On April 30, 2017, about 1330 eastern daylight time, a Piper PA32RT-300, N31678, was substantially damaged during a forced landing near Coral Springs, Florida. The airline transport pilot and pilot-rated passenger were not injured. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight.According to the pilot, during cruise flight he noticed that the engine manifold pressure dropped. He advanced the throttle forward to regain engine power, with no response from the engine. The engine continued to run smoothly at a reduced power setting; however, he was unable to maintain altitude. After several additional unsuccessful attempts to increase engine power, the pilot declared an emergency, and subsequently performed a forced landing on a levy. During the landing roll, the airplane veered off the side of the levy and collided with a ditch. Examination of the wreckage by a Federal Aviation Administration inspector revealed that the aft right wing spar was damaged. An examination of the throttle body fuel injection servo revealed the throttle cable linkage attachment was disconnected from throttle body. An inspection of the throttle cable revealed the cable operated smoothly without any binding, and it moved freely while opening and closing the throttle position. The fuel injection throttle body servo was removed from aircraft for further inspection and revealed that the throttle linkage was loose at the attachment point of the throttle body fuel injection servo. The castle nut and cotter pin were installed but the castle nut was loose, not allowing the throttle linkage teeth to make full contact with fuel injection throttle body servo linkage teeth that controlled the butterfly valve within the throttle body. Operating the linkage manually revealed that the linkage slipped since the gear teeth were not tightened completely and did not make full contact locking together. The throttle linkage gear teeth were also worn with flat spots on some of the gearing teeth. The throttle body linkage gearing teeth also had flat spots on the assembly. According to the airplane's maintenance records, the engine was most recently overhauled in June 2014. At that time an overhauled throttle body fuel injection servo was installed onto the engine. The engine had since undergone annual inspections in August 2015 and September 2016, and both of the maintenance log entries documenting those inspections did not explicitly mention inspection or maintenance of the throttle body fuel injection servo.