Cessna A185 N5806J

Summary

On 3 August 2019 at about 14:00 local time, a Cessna A185 registered N5806J was involved in an accident near Saginaw, Michigan, United States. 4 people were on board and 4 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

3 August 2019 at 14:00

Classification

Accident

Location

Saginaw, Michigan, United States

Coordinates

43.4042, -83.9800

Aircraft

Cessna A185

Registration

N5806J

Category

Airplane

Year built

1970

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Flint → Beaver Island

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN19LA249

4 people had minor injuries.

Maintenance personnel’s failure to properly align the crankshaft during an engine reassembly which led to a fatigue failure of the crankshaft and the loss of all engine power.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The pilot was in cruise flight in a single-engine airplane when the engine lost power. He selected a road for the forced landing, during which the airplane impacted a power pole and electrical wires. The airplane came to rest inverted and incurred substantial damage to the airplane’s fuselage and wings. Postaccident examination revealed that the engine’s crankshaft had failed due to fatigue. The accident crankshaft was subject to a mandatory service bulletin (MSB) and subsequent Federal Aviation Administration airworthiness directive (AD) requiring inspection of the crankshaft material for metallurgical anomalies; however, this inspection was not performed on the accident airplane’s crankshaft. A detailed metallurgical examination of the crankshaft revealed that a fatigue crack had progressed through most of the crankshaft web cross section, consistent with relatively low-stress, high cycle fatigue. Because no indications of intergranular fracture or large areas of overstress fracture with the planar dimpled rupture features indicative of thermal damage on the fracture surface were noted, it is unlikely that manufacturing issues resulted in the fatigue cracking even though metallurgical testing revealed that the crankshaft material did not meet specification. Rather, the cracking likely initiated due to stray or excessive wear to the forward journal to web radius. It is further likely that a misalignment during a previous reassembly of the engine that occurred about two years prior when two cylinders were replaced resulted in the failure. Given this information, it is likely that maintenance personnel’s failure to properly align the affected crankshaft during the reassembly resulted in a low-stress high cycle fatigue failure of the crankshaft and the subsequent loss of all engine power.

Quoted verbatim from the NTSB record.