FAIRVIEW, PA, USA
N1944J
Enstrom F-28C
The helicopter was purchased and flown about 1 hour to another airport. The following day the pilot departed on a ferry flight. About 5 minutes after takeoff, the engine lost power when the RPM dropped to 1,900, and the pilot entered autorotation. During the descent the engine continued to idle and the cabin filled with smoke. The helicopter landed hard and the main rotor blades struck the tailboom. The last annual inspection occurred 53 months before the accident. A Special Flight Permit was issued by the FAA for the ferry flight. The helicopter's engine was overhauled 33 months before the accident, and 3.9 hours had been logged on the engine from the date of overhaul, to the date of the helicopter's purchase. At the time of the accident the engine had accumulated a total of 6.7 hours since overhaul. Examination of the engine revealed the forward side of the #2 piston was melted and eroded away, and a hole had melted through the piston. An FAA publication described detonation as spontaneous combustion which can burn a hole completely through a piston.
HISTORY OF FLIGHT On October 24, 1997, at 1335 eastern daylight time, an Enstrom F-28C, N1944J, was substantially damaged during a forced landing to a field near Fairview, Pennsylvania. The certificated commercial pilot and passenger were not injured. Visual meteorological conditions prevailed for the flight that originated at the Capital City Airport (CXY), Harrisburg, Pennsylvania, about 1330, destined for the Westmoreland County Airport, Latrobe, Pennsylvania. No flight plan had been filed for the ferry flight conducted under 14 CFR Part 91. In a written statement, the pilot said that the helicopter was purchased on October 23, 1997, in Hazleton, Pennsylvania, and he flew it to CXY. The following day he departed on the ferry flight. After takeoff, the pilot leveled off at his cruise altitude of 700 feet above the ground, and observed "all instruments to be in the 'green' in normal operating range." The pilot also stated that about 3 miles west of CXY, he noted a "slight drop in engine power." He further stated: "As I looked, the engine lost all power and I saw the needles (engine RPM & rotor RPM) split and the engine RPM dropped to approx. 1,900 RPM..." The pilot then entered an autorotation. The engine continued to idle, but would not "produce power." The pilot stated that the cabin filled with smoke and the helicopter touched down on a sloped area, where the tailboom was struck by the main rotor blades. The accident occurred during the hours of daylight approximately 40 degrees, 13 minutes north latitude, and 76 degrees, 52 minutes west longitude. PERSONNEL INFORMATION The pilot held a commercial pilot certificate with a rating for rotorcraft helicopter, and a private pilot certificate with a rating for airplane single engine land. His most recent Federal Aviation Administration (FAA) Second Class Medical Certificate was issued on October 31, 1996. The pilot stated in the NTSB Form 6120.1/2, that his total flight experience was 1,575 hours, of which 1,300 hours were in helicopters, all in make and model. AIRCRAFT INFORMATION Examination of the helicopter's maintenance records revealed that the last recorded annual inspection occurred during May 1993. In December 1993, the helicopter's Hobbs meter read 1055.7 hours. In January 1995, at a Hobbs meter reading of 1061.0, the engine under went a complete major overhaul. On October 23, 1997, when the helicopter was sold, the Hobbs meter read 1064.9 hours. At the accident site, the Hobbs read 1067.7 hours. A Special Flight Permit was issued by the Harrisburg FAA Office (FSDO 13) on October 22, 1997. The authorization was valid, "...only upon certification in the aircraft log book by an A&P Mechanic..." The helicopter's logbooks revealed that it had been inspected on October 23, 1997, by an airframe and powerplant mechanic. WRECKAGE AND IMPACT INFORMATION The helicopter wreckage was examined at the accident site on October 24 and 25, 1997. According to FAA Inspectors, the examination revealed that all major components of the helicopter were accounted for at the scene. The helicopter was upright and there was damage to the helicopter's main rotor blades. The FAA Inspector's report stated, "...Aircraft received damage on main rotor blade which struck the tailrotor assembly tearing the last 24 to 30 inches of the tailcone and rotor assembly from the aircraft." The Inspector's initial examination of the engine revealed that the #3 cylinder did not have compression, and that it was overheated. Additionally, the oil filter contained metal flakes. The engine was removed for further examination, and shipped to the Textron-Lycoming facility, Williamsport, Pennsylvania. TEST AND RESEARCH On December 11, 1997, the engine was examined at the Textron-Lycoming facility, Williamsport, Pennsylvania, under the supervision of the Safety Board Investigator. The examination revealed rust inside of all of the valve covers. The bolts were loose on the #2 valve cover, and tight on the #1, #3, and #4 valve covers. An observation was made that the #2 cylinder on a Lycoming four cylinder engine, would be the #3 cylinder on a Continental four cylinder engine. The tops of cylinders #1, #3, and #4 were painted blue, indicating nitride cylinders. The top of the #2 cylinder was discolored to a gray color, which indicated a high temperature condition. The timing of the right magneto was measured at 18.5 degrees BTC, and the timing of the left magneto was measured at 17.5 degrees BTC. The specifications for the engine listed 20 degrees as the required setting. The internal timing of the engine was determined to be correct. The engine was disassembled and the forward side of the #2 piston was observed to be melted and eroded away. A melted hole extended through the piston. The #2 cylinder's rings were broken, and the piston pin was warn down on the melted side of the piston. Pieces of the broken rings from the #2 cylinder were found under the valve tappets of other cylinders, with some pieces imbedded in the engine case below the tappets. Half of the #1 cylinder exhaust valve tappet was broken off and imbedded in the inside of the engine case. All cylinder tappets displayed impact damage. The front main bearing displayed heavy scoring with metal imbedded. The center crankshaft bearing displayed significant wear, and the rear bearing displayed scoring from metal debris. The oil suction screen contained metal debris. The fuel injection nozzles were removed and found to be absent of debris. ADDITIONAL INFORMATION An FAA published Powerplant Handbook, AC65-12A, was reviewed. Under the topic of Combustion Process, it stated that detonation, "...is the spontaneous combustion of the unburned charge ahead of the flame fronts after ignition of the charge. The explosive burning during detonation results in an extremely rapid pressure rise. This rapid pressure rise and the high instantaneous temperature, combined with the high turbulence generated, cause a 'scrubbing' action on the cylinder and the piston. This can burn a hole completely through the piston." It further stated, "...the presence of severe detonation during its operation is indicated by dished piston heads, collapsed valve heads, broken ring lands, or eroded portions of valves, pistons, or cylinder heads." The AC described design, cylinder cooling, magneto timing, mixture distribution, and carburetor settings as factors effecting detonation. The helicopter wreckage was released on October 25, 1997. The engine was released on December 11, 1997, and shipped to Robert Dudo, at 7000 Merrill Ave, Chino Airport, Eagle Nest 4, Hangar 14, Chino, California, 91710.
inadequate maintenance, which led to detonation and a melted piston, and subsequent power loss.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
