Pilot Debrief

VANS RV7 - UNDESIGNAT near Belfair, WA — 2015-02-10

Final reportWPR15LA101
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Date
2015-02-10
Location
Belfair, WA, USA
Aircraft
VANS RV7 - UNDESIGNAT
Registration
N513BW
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Cruise

Probable cause

A total loss of engine power during cruise flight due to the fatigue failure of the engine crankshaft. Contributing to the accident was the unapproved repair and improper inspection of the engine crankshaft.

NTSB narrative

The pilot reported that the airplane was at 1,500 ft mean sea level as he was returning to the departure airport when the engine "abruptly quit." When all attempts to restart the engine failed, the pilot chose to land on a gravelly split. During the landing roll, the airplane's small tires sunk into the gravel, which resulted in the airplane nosing over. A postaccident examination of the engine revealed that the crankshaft had fractured adjacent to the aft radius of the No. 3 rod journal. Examination of the crankshaft revealed that it failed due to fatigue cracking that had initiated at locations on either side of a preexisting longitudinal crack. The radius also contained several circumferential cracks, including ones in the region corresponding to the relative location of the fatigue origins of the fracture. Examination also revealed that the No. 3 rod journal had been chromium-plated to regain lost material; however, according to the engine manufacturer, chromium plating on bearing journals was not an approved repair. Although the fatigue did not initiate in the plating, it did start near the edge of the replating in an area likely reworked (ground) following the unapproved plating. The multiple circumferential cracks noted in the radius likely resulted from the repair grinding and may have contributed to the fatigue initiation. A review of the engine logbooks revealed that the engine had been overhauled and subsequently inspected by the "magnaflux method" three times in a 14-month period about 15 years before the accident, during which the extensive cracking would have been present, indicating that the magnaflux inspections of the crankshaft were not effectively performed.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have conducted a thorough preflight engine inspection.

NTSB coding

Evidence available

  • Photos
  • 9 docket documents
View NTSB final reportView NTSB docket

Docket documents9

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