Fayetteville, NC, USA
N3241N
RAYTHEON AIRCRAFT COMPANY A36
During a cross-country flight at night, the airplane experienced a total loss of engine power. The private pilot's attempts to restart the engine were unsuccessful. The pilot attempted to glide the airplane to a diversionary airport, but when he realized the airplane would not reach the airport, he conducted a forced landing into wooded terrain. Teardown examination of the engine revealed that the No. 1 cylinder and No. 3 connecting rod had fractured. Metallurgical examination revealed that there was a gray rubbery substance on the case halves, through bolts, and main bearing saddle faces, which could have restricted oil flow. The engine manufacturer's overhaul manual and a service bulletin and service information letter (SIL) listed only one approved sealant for use between case halves, which was similar in color and texture to grape jelly not to the rubbery gray sealant found in the engine, which was not an approved sealant. Further, the SIL stated that the use of an incorrect sealant "on mating threads and between mating surfaces can cause incorrect torque application and subsequent engine damage or failure." Further, the No. 3 connecting rod journal exhibited heat damage and deformation, and the No. 3 connecting rod fracture was consistent with a lack of lubrication. Additionally, the No. 4 main bearing saddle boss exhibited fretting damage, consistent with bearing shift due to lack of torque on the through bolts and blockage of its oil port, which also would have restricted oil flow. Review of maintenance records revealed that the engine was overhauled about 20 months before the accident. The engine had been operated for about 300 hours during that time. It is likely that maintenance personnel applied the unapproved sealant to the engine case halves during the engine overhaul, which ultimately resulted in the total loss of engine power.
On December 11, 2015, at 1931 eastern standard time, a Beechcraft A36, N3241N, was substantially damaged during a forced landing to a wooded area after a total loss of engine power near Fayetteville, North Carolina. The private pilot and two passengers received minor injuries, and one passenger received serious injuries. Nighttime visual meteorological conditions prevailed and an instrument flight rules flight plan was filed. The personal flight departed Bay Bridge Airport (W29), Stevensville, Maryland about 1730 destined for Charleston Executive Airport (JZI), Charleston, South Carolina. The airplane was operated by the private pilot under the provisions of Title 14 Code of Federal Regulations Part 91.According to the pilot, about 2 hours after takeoff the airplane was in cruise flight at 8,000 feet when the engine suddenly lost power. Engine power was restored for a few seconds, and then the airplane lost engine power again as the propeller "windmilled." The pilot turned the airplane toward Fayetteville Regional Airport (FAY) for a forced landing, and the propeller stopped turning during the descent. Attempts to restart the engine were unsuccessful. As the airplane approached FAY, the pilot determined that he was below the visual approach slope indicator lighting glidepath and that the airplane would not reach the airport and performed a forced landing to wooded terrain. Examination of the wreckage at the accident site by a Federal Aviation Administration (FAA) inspector revealed that the airplane came to rest upright on the floor of a pine forest area. The engine and mounts separated from the firewall. The left wing was crushed and curled upward from about mid-span to the wing tip. A portion of the right wing was separated outboard of the flap and was located in the debris path about 25 yards prior to the main wreckage. The landing gear and flaps were found in the retracted position. The airframe and engine were subsequently examined at a recovery facility under the supervision of a National Transportation Safety Board (NTSB) investigator. Fuel was present in both main tanks and both tip tanks, the fuel selector valve functioned normally, and the auxiliary pump switch was in the on position. Teardown examination of the engine revealed metal fragments from the No. 1 cylinder in the oil sump and internal damage including one connecting rod separated from the crankshaft, and two other connecting rods exhibiting discoloration consistent with heat damage. Additionally, a gray colored rubbery substance was observed on the mating surfaces of the crankcase halves. Engine components were forwarded to the NTSB Materials Laboratory, Washington, DC, for further examination. Metallurgical examination revealed beads of gray sealant on the through bolts and on the main bearing saddle faces, which can restrict oil flow. The No. 3 connecting rod journal exhibited heat damage and deformation and the No. 3 connecting rod was fractured, consistent with a lack of lubrication. Additionally, the No. 4 main bearing saddle boss exhibited fretting damage, consistent with bearing shift and blockage of its oil port, restricting oil flow. Review of maintenance records revealed that the airplane's most recent annual inspection was completed on October 15, 2015. At that time, the engine had accumulated 300.6 hours since major overhaul. The engine was overhauled by Aero Engines of Winchester, Inc. on April 21, 2014. Teledyne Continental Motors (TCM) Service Information Letter (SIL)99-2B, published October 17, 2005, related to current authorized sealants, lubricants, and adhesives. The SIL did not list any sealant on the mating surfaces of the crankcase halves except Gasket Maker P/N 646942 – or Loctite 515 Gasket Eliminator Sealant (or its predecessor, Permatex Aviation Grade 3D). Additionally, review of the overhaul manual revealed instructions to apply only TCM Sealant P/N 654663, which was Loctite 515, and silk thread P/N 641543 to the crankcase halves. According to the Manager of Air Safety at Continental Motors Inc., the gray rubber sealant found in the engine was not consistent with Loctite 515, which appears in color and texture like grape jelly. Additionally, review of TCM Service Bulletin (SB)96-7C, published February 8, 2005, which related to torque values for fasteners on all TCM engines, stated: "WARNING THE USE OF SEALANTS OR LUBRICANTS OTHER THAN THOSE SPECIFIED BY TCM ON MATING THREADS AND BETWEEN MATING SURFACES CAN CAUSE INCORRECT TORQUE APPLICATION AND SUBSEQUENT ENGINE DAMAGE OR FAILURE." The FAA Subsequently published Special Airworthiness Information Bulletin (SAIB) NE-16-13, "Powerplant – Prohibited use of sealant" on March 8, 2016. According to the FAA principle maintenance inspector of Aero Engines LLC. (formerly Aero Engines of Winchester, Inc.), he performed a compliance action after the accident for Aero Engines to use only the specific sealant part number and product name (not MIL-SPEC [military standard]) specified by the engine manufacturer when overhauling their respective make and model engine. Additionally, Aero Engines reviewed all their overhauls for unapproved sealants and did not find any other subsequent cases. As of the publication of this report, there have been no further similar engine failures that were overhauled by Aero Engines. There was one previous case (NTSB ID No. ERA14FA313) of a similar failure of an engine overhauled by Aero Engines.
Maintenance personnel's application of an unapproved sealant to the engine case halves during engine overhaul, contrary to manufacturer's instructions, which resulted in lubrication restriction due to a bearing shift and the subsequent internal failure of the engine due to the loss of case through-bolt torque.
Source: NTSB Aviation Accident Database
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