History of Flight
On July 28, 2014, about 0853 mountain daylight time, an amateur-built experimental Meyer-Lancair Legacy, registration N29MM, sustained substantial damage during a forced landing approximately 41 miles southwest of Missoula, Montana, in Lolo Pass, following a reported loss of engine power during cruise flight. The airplane was operated under Part 91. The commercial pilot, the sole occupant, was fatally injured. The flight departed Richland Airport (RLD), Richland, Washington, about 0755, destined for Baker Municipal Airport (BHK), Baker, Montana, with a visual flight rules flight plan filed. Visual meteorological conditions prevailed.
Air traffic control received information from two other aircraft that the accident pilot made a mayday radio call and stated he had low engine oil pressure. The airplane struck terrain while the pilot was attempting to land in a forested area.
GPS tracking revealed the airplane flew an easterly heading toward the planned destination but, during the final minutes, executed a 90-degree left turn to a northerly heading while over the Clearwater National Forest in Idaho.
Aircraft and Pilot Information
The two-seat, low-wing, retractable tricycle gear airplane (serial number L2K-197) was manufactured in 2009. It was powered by an experimental Performance Aircraft Engines (originally Continental) IO-550-EXP engine, serial number TC-5826, rated at 370 horsepower, equipped with a Hartzell controllable pitch propeller. The most recent conditional inspection was completed on September 8, 2013, at an airframe total time of 248.5 hours.
The 71-year-old pilot held a commercial pilot certificate with airplane single-engine land, single-engine sea, and instrument ratings, as well as a flight instructor certificate for airplane single-engine. He held a special issuance FAA third-class medical certificate issued February 27, 2014, with limitations to wear corrective lenses and validity through January 28, 2015. He reported 1,420 total flight hours and 20 hours in the last six months.
Meteorological Conditions
The 0953 recorded data from the Missoula International Airport automated weather observation station, located about 41 miles from the accident site, indicated calm wind, visibility 10 statute miles, clear sky, temperature 19°C, dew point 7°C, and an altimeter setting of 30.24 inches of mercury.
Wreckage and Impact
An FAA inspector examined the accident site. The first identified point of contact was the left wing impacting a tree about 40 feet above ground level. Shortly after, the right wing struck a tree. During the impact sequence, both wings separated. The main fuselage continued about 280 feet and impacted terrain on a mountain slope of about 30 degrees, at an elevation of about 6,528 feet, oriented 180 degrees magnetic. The debris path was about 400 feet long. The main wreckage came to rest about 200 feet below County Road 581 in Clearwater National Forest, Idaho. All major structural components were accounted for. Flight control continuity was established to the rudder and elevators. The landing gear was extended; oil smearing was observed on windshield fragments. The engine separated from the airplane except for one attached cable and came to rest inverted about 10 feet ahead of the fuselage; the propeller hub separated and was near the start of the debris trail.
Communications and Electronic Data
The accident airplane was not in contact with ATC, but two nearby aircraft relayed his mayday distress call to Salt Lake Air Route Traffic Control Center. The distress call was also heard on 121.5 at 0849, reporting loss of oil pressure and oil covering the windshield. A Garmin GTX 327 transponder indicated a last code selected of 7700 (distress). A Garmin SL30 Nav/Com listed the last navigation frequency as 122.9 and last communication frequency as 121.5. A GRT EIS 6000 engine monitor recorded the last flight time as 58 minutes and accumulated engine time as 248.5 hours. An Apple iPad with ForeFlight showed an active route from RLD to BHK; an image captured at 08:44:54 PDT indicated a vertical speed of -925 feet per minute.
Medical and Pathological Information
The Clearwater County Coroner conducted an autopsy on August 7, 2014, determining the cause of death as blunt force injuries. The FAA's Civil Aeromedical Institute performed toxicology tests, which were positive for Metoprolol and Rosuvastatin. The NTSB Chief Medical Officer noted the pilot used Metoprolol for high blood pressure and Rosuvastatin for cholesterol, both reported to the FAA.
Engine Examination
Further examination of the airframe and engine by the NTSB, FAA, and Continental Motors revealed a large hole in the upper left portion of the crankcase above the number 2 cylinder; visible through the hole was a broken connecting rod for the number 1 cylinder. The number 2 cylinder connecting rod was also broken. No measurable oil was found in the engine. The oil pump and filter had minor metal contamination. The oil sump contained metal debris, including fractured connecting rod bolts and nuts. Cylinder nut torques were within manufacturer specifications. Except for the number 1 and 2 cylinder skirts, all cylinders were unremarkable. Main bearings were intact with no anomalies; no signature of oil starvation or loss of oil pressure was noted. All rods and main journals had normal appearance.
The connecting rods were shipped to the NTSB Materials Laboratory. Examination revealed that both rods fractured along the I-beam shafts. Scanning electron microscopy of the number 1 connecting rod fracture surface showed striations consistent with fatigue crack propagation, initiating at the surface; corrosion pits were also observed. The bolt fracture was consistent with overstress failure. The number 2 connecting rod fracture surface showed signatures of progressive fracture, with faint fatigue striations and multiple crack initiation sites; no corrosion pits. The associated bolt failed in tensile overstress.
Mounted and polished cross-sections of the number 1 connecting rod shaft were tested for hardness; results indicated about 10% lower hardness towards the surface. Metallographic analysis revealed up to 0.03-inch of decarburization on the connecting rod surface, consistent with the lower hardness. Decarburization can result from carbon interaction with the furnace atmosphere during engine operation, potentially reducing surface hardness and strength and facilitating fatigue crack initiation.
Probable Cause
No probable cause was stated in the source.