Pilot Debrief

MEYER LEGACY near Lolo Pass, ID — 2014-07-28

Final reportWPR14FA316
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Date
2014-07-28
Location
Lolo Pass, ID, USA
Aircraft
MEYER LEGACY
Registration
N29MM
Category
Airplane
Highest injury
Fatal
Fatalities
1
Phase of flight
Cruise

Probable cause

The fatigue fracture of an engine connecting rod, which resulted in a catastrophic engine failure and a forced landing in unsuitable terrain.

NTSB narrative

The commercial pilot was conducting a personal cross-country flight in an amateur-built, experimental airplane when he transmitted a distress call. Two pilots in other aircraft near the accident airplane's location relayed the pilot's "mayday" call to air traffic control and he was subsequently heard stating that he had low engine oil pressure and that oil was covering the windshield while he was flying over wooded mountainous terrain. The pilot attempted a forced landing, but the airplane struck trees and then impacted the terrain. Postaccident examination of the engine revealed a hole in the top of the engine case near the No. 2 cylinder. An engine teardown revealed that the Nos. 1 and 2 cylinder connecting rods had fractured. The examination of the fracture surfaces determined that the No. 1 connecting rod fracture was initiated by a fatigue crack and was the catalyst for the engine failure. In addition, partial surface decarburization and surface corrosion pits were observed around the surface of the connecting rod shaft. It is likely that the decarburization and corrosion pits decreased the connecting rod's surface hardness, served as fatigue initiation sites, and led to the premature failure of the No. 1 connecting rod. Although some fatigue cracks were observed on the No. 2 connecting rod, most of the facture surfaces exhibited overstress failure; therefore, the No. 2 connecting rod likely failed after the No. 1 connecting rod fractured. Although the cause of the decarburization was not determined based on the available evidence, it typically results from a manufacturing deficiency. Toxicology testing of the pilot detected metoprolol and rosuvastatin in his tissue samples, and he had a history of high blood pressure and cholesterol; however, it is unlikely that the pilot's medical conditions or the medications he was using to treat them impaired his ability to safely operate the airplane.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have diverted for landing after reporting low oil pressure.

NTSB coding

Evidence available

  • 14 docket documents
View NTSB final reportView NTSB docket

Docket documents14

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