Accident Overview
On December 11, 2015, at 1931 eastern standard time, a Beechcraft A36, registration 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 14 CFR Part 91.
Pilot's Account
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, then lost again as the propeller windmilled. The pilot turned 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 he was below the visual approach slope indicator lighting glidepath and that the airplane would not reach the airport, so he performed a forced landing to wooded terrain.
Wreckage Examination
Examination of the wreckage by a Federal Aviation Administration (FAA) inspector revealed the airplane came to rest upright on the floor of a pine forest. 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.
Engine and Maintenance Findings
The airframe and engine were subsequently examined at a recovery facility under NTSB supervision. Fuel was present in both main and tip tanks; the fuel selector valve functioned normally, and the auxiliary pump switch was on. Teardown of the engine revealed metal fragments from the No. 1 cylinder in the oil sump and internal damage: one connecting rod separated from the crankshaft, and two others showed heat damage. A gray rubbery substance was observed on the mating surfaces of the crankcase halves. Metallurgical examination found beads of gray sealant on through bolts and main bearing saddle faces, which can restrict oil flow. The No. 3 connecting rod journal exhibited heat damage and deformation, and the No. 3 rod was fractured, consistent with lack of lubrication. The No. 4 main bearing saddle boss showed fretting damage consistent with bearing shift and oil port blockage.
Maintenance records showed the most recent annual inspection was completed on October 15, 2015, at which time the engine had 300.6 hours since major overhaul. The engine was overhauled by Aero Engines of Winchester, Inc. on April 21, 2014.
Sealant Issues
Teledyne Continental Motors (TCM) Service Information Letter (SIL) 99-2B, published October 17, 2005, related to authorized sealants, lubricants, and adhesives. The SIL did not list any sealant on crankcase halves except Gasket Maker P/N 646942 or Loctite 515 Gasket Eliminator Sealant (or its predecessor, Permatex Aviation Grade 3D). The overhaul manual instructed use of TCM Sealant P/N 654663 (Loctite 515) and silk thread P/N 641543.
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 like grape jelly.
TCM Service Bulletin (SB) 96-7C, published February 8, 2005, related to torque values and warned: "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."
Post-Accident Actions
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 principal maintenance inspector for Aero Engines LLC (formerly Aero Engines of Winchester, Inc.), he performed a compliance action for Aero Engines to use only the specific sealant part number and product name specified by the engine manufacturer when overhauling their engines. Aero Engines reviewed all their overhauls for unapproved sealants and did not find any other subsequent cases. As of the report's publication, there have been no further similar engine failures from Aero Engines. There was one previous case (NTSB ID No. ERA14FA313) of a similar failure of an engine overhauled by Aero Engines.