SEA96FA130

While in cruise flight over Hood Canal, the rotorcraft began shaking, and a ground witness heard a 'pop' and observed white smoke. The pilot-in-command executed an intentional ditching, but was unable to swim to shore. The passenger survived. Postcrash examination revealed that the Lycoming HIO-360-D1A engine's number two connecting rod assembly had failed when the cap end had separated. Metallurgical examination revealed that the connecting rod cap had failed from fatigue and that both connecting rod bolts had failed in overload. The fatigue was associated with fretting within the rod cap inner face between the face and the bearing surface.

History of flight

On June 19, 1996, approximately 1140 hours Pacific daylight time, a Hughes 269C rotorcraft, N7400F, being flown by a private pilot, sustained substantial damage during a collision with water following a total loss of power and forced ditching in Hood Canal near Eldon, Washington. The pilot and passenger exited the aircraft and the passenger was able to swim to shore with serious injuries. The pilot, who was observed swimming toward the shoreline by the passenger, was not recovered and is presumed to have drowned. Visual meteorological conditions existed and a company flight plan had been filed. The flight, which was personal, was to have been operated under 14CFR91, and originated from Shelton, Washington, approximately 1115.

The passenger reported in an interview with an FAA inspector that while the rotorcraft was cruising approximately 400 feet above the surface of Hood Canal it began a hard and erratic shaking. He stated that the rotorcraft descended toward the water and was unable to reach the shoreline (refer to attached statements). A witness along the shore reported hearing a loud "pop" and seeing white smoke in the vicinity of the rotorcraft (refer to attached statements). A sonar search by the US Navy for the rotorcraft and pilot was unsuccessful.

The rotorcraft was subsequently located by the owner and recovered on July 20, 1996, under the observation of an NTSB investigator. The wreckage was then secured by Mr. Don Hawks at the Shelton airport.

Aircraft information

The Lycoming HIO-360-D1A engine, serial number L-20456-51A, underwent a 100 hour inspection on April 27, 1996, and had a total of approximately 847 hours of operating time since its last major overhaul conducted on August 21, 1987. The engine's time of operation between the 100 hour inspection and the accident was approximately 91 hours and the engine's total time since new was approximately 5776 hours. The engine was installed in N7400F on August 16, 1990, with a total time of 4929.0 hours time since new.

On March 4, 1995, at an engine total time of 5290.1 hours, the rotorcraft was involved in a blade strike/hard landing. No significant engine maintenance was accomplished immediately following that event (refer to ATTACHMENTS I & II). Then, on December 18, 1995, at a total engine time of 5539.3 hours, metal chips were detected in the engine oil. The engine was disassembled and repaired including the installation of new rod cap nuts and new rod bearings (refer to ATTACHMENT III).

An FAA inspector telephonically interviewed the mechanic who performed the above referenced engine maintenance and was told that during the engine disassembly the rod end bolts were not replaced but were re-used, and that all maintenance accomplished on the engine was in accordance with the Lycoming maintenance manual (refer to attached statement).

Tests and research

The engine was removed from the airframe by mechanics from Avstar Aviation, Inc., and was disassembled at the Avstar Aviation facility at the Pierce County airport on the afternoon of July 25, 1996. The Hobbs meter showed a reading of 437.1 hours when the engine was removed. The left engine case half was observed to have a large hole above the number two cylinder. The camshaft was observed to broken in two. The number two connecting rod was observed separated from the crankshaft and was missing the rod cap end (refer to photograph 1). Upon removal of the number two cylinder, fragments of the connecting rod cap end as well as its associated end bolts and nuts were recovered from within the engine.

The pieces of the two connecting rod cap bolts including a section from the rod cap end still attached to one of the bolts, all from the number two connecting rod, were examined at the NTSB's Materials Laboratory. The fracture surface of the connecting rod cap end piece displayed arrest marks, consistent with a fatigue fracture. This was confirmed under examination utilizing a scanning electron microscope. Examination of the bearing (inner) surface of the rod cap end piece revealed fretting features indicating relative movement between the rod cap and the bearing shell. Both rod cap bolt pieces displayed fracture surfaces characteristic of overstress separations (refer to attached Metallurgical Report).

The remainder of the engine was subsequently shipped to Lycoming where, under the control of an NTSB investigator, it was further disassembled and examined on September 27, 1996. The examination revealed evidence of fretting on the numbers one and three connecting rod cap half surfaces and evidence of galling on the inner diameter of the associated connecting rod cap bearing surfaces. Additionally, severe galling was observed on the numbers three and four connecting road bearing surfaces (refer to attached engine disassembly report).

Additional information

The Lycoming HIO-360-D1A engine was removed from the airframe by mechanics from Avstar Aviation, Inc., on the afternoon of July 24, 1996, and transported to the Avstar maintenance facility at Pierce County Airport, Puyallup, Washington. The engine was subsequently shipped to Lycoming for further examination and then shipped by Lycoming directly to Mr. James F. Irvin, Aircraft Engine Reconstruction Specialists, Bullhead City, Arizona. The engine and retained components were released to Mr. James Stiger of Barrus & Stiger on September 22, 1996 (refer to NTSB Form 6120.15 for documentation of retention and subsequent release of the engine, logs, and connecting rod bolts and associated components).