Piper PA-32-300 N1953H accident near Sanford, North Carolina

Probable cause

The installation of an incorrect length of cotter pin on the throttle linkage clevis pin by maintenance personnel at an undetermined time, which resulted in the pin coming loose and the loss of throttle control.

NTSB analysis

The private pilot was in the traffic pattern at the intended destination airport when the airplane experienced a loss of engine throttle control. Unable to reach the runway, he elected to perform a forced landing in a nearby field. During the landing, the airplane struck a fence post, which resulted in substantial damage to the left wing of the airplane.

Postaccident examination revealed that the throttle lever clevis and throttle cable became separated from the throttle arm, which resulted in the engine being unresponsive to throttle input; thus, the pilot could not apply power to the engine from the idle position. No evidence of metal deformation existed on either the throttle lever clevis or on the throttle cable; however, examination of the cotter pin revealed that one prong was separated and unable to be located. Examination of the remaining portion of the cotter pin revealed that it was twice as long as manufacturer-approved guidance required. Examination of the clevis for the propeller cable linkage revealed that the cotter pin prongs exceeded Federal Aviation Administration Advisory Circular 43-13-1B guidance by allowing the prong to exceed the pin diameter and the cotter pin prongs were not seated firmly against the shank. A review of maintenance records did not reveal when the cotter pin was replaced. The hardware was likely installed using the incorrect safetying technique and the improper length of cotter pin. This allowed the prong to become caught and subsequently fracture on nearby hardware, which resulted in the cotter pin becoming unsecured and separating from the linkage pin. Subsequently, the linkage pin detached, which allowed the throttle lever clevis and cable to separate from each other. The last annual inspection occurred 2 weeks and less than 1 flight hour before the accident. It is likely that the mechanic did not detect the incorrect cotter pin and safetying technique due to its location; the location was such that it would have been difficult for the mechanic to see.

Text from the NTSB. Open the NTSB docket for ERA13LA148 for the full record.