DFW08LA058

While in cruise flight the airplane's engine lost partial power. Unable to maintain altitude, the pilot executed a forced landing to a clear cut area. During the landing roll, the airplane nosed over and came to rest in an inverted position. The pilot was able to exit the airplane unassisted. During an examination of the engine it was discovered that a brass hex plug, a component of the fuel injector servo, was hanging loose from its safety wire. The investigation revealed that the gasket, found between the brass hex plug and the aluminum regulator cover, had softened due to engine heat. This allowed the brass hex plug to vibrate and eventually fall out. This resulted in the partial loss of engine power. As a result of this investigation, the fuel servo manufacturer issued Mandatory Service Bulletin PRS-107 and the FAA issued Emergency Airworthiness Directive 2008-06-51.

On January 28, 2008, about 0715 central standard time, a single-engine Piper PA32-301FT airplane, N1053F, was substantially damaged during a forced landing following a partial loss of engine power near Wiggins, Mississippi. The private pilot, sole occupant, was not injured. The airplane was registered to and operated by Soarin LLC., of Miami, Florida. Visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 91 personal flight. The 632-nautical mile cross-country flight had originated from the Taylor Municipal Airport (T74), Taylor, Texas, and was destined for a fuel stop at the Marianna Municipal Airport (MAI), Marianna, Florida. The pilot's final destination was to be the Kendall-Tamiami Executive Airport (TMB), located in Miami, Florida.

According to the pilot, while in cruise flight at 7,500-feet mean sea level (MSL), the airplane's engine lost partial power. The pilot turned on the electric fuel pump and switched fuel tanks to no avail. As the airplane descended, the pilot attempted to restore full engine power by cycling the propeller, adjusting the mixture and throttle settings, and by working through the emergency checklist. When engine power could not be restored, the pilot executed a forced landing to a clear cut area. During the landing roll the airplane nosed over and came to rest in an inverted position. The pilot was able to exit the airplane unassisted. The pilot later reported that as the airplane descended the engine made a "pinging" noise.

An inspector from the Federal Aviation Administration (FAA) responded to the accident site. The inspector reported that the airplane's fuselage and wings had sustained structural damage.

The airplane was recovered to Air Salvage of Dallas, located in Lancaster, Texas, for further examination. During an examination of the engine it was discovered that brass hex plug p/n 383493, a component of the fuel injector servo, was hanging loose from its safety wire. This brass hex plug, when installed, seals the fuel servo's regulator access hole. This plug is installed by the manufacturer and is not removed during routine aircraft maintenance.

With a piece of tape placed over the servo regulator access hole, an engine test run was performed. Once started, the engine ran "normally" up to high cruise power. At a power setting similar to that used by the pilot just before the power loss (2400 rpm), the tape was removed and the engine immediately lost power, began "popping," and the rpm's decreased down to about 1600 rpm.

The fuel injector servo, Precision Airmotive Corporation, model number RSA-10ED1, serial number (s/n) 70B82601, was removed and sent to the NTSB materials laboratory for examination. The examination revealed that insufficient torque of the brass hex plug had allowed the plug to vibrate in the fuel injector servo housing. This vibration resulted in the brass threads being worn away until the brass hex plug exited the aluminum regulator cover and hung free from the safety wire.

During the investigation, Precision Airmotive Corporation determined that gasket part number (p/n) 365533, located between the brass hex plug p/n 383493 and the fuel servo regulator cover could shrink from engine heat ,which could result in the hex plug losing its torque against the regulator cover.

As a result of this investigation, Precision Airmotive Corporation issued Mandatory Service Bulletin PRS-107 and the FAA issued Emergency Airworthiness Directive 2008-06-51.