Stinson 108 N9366K

Summary

On 17 May 2017 at about 00:30 local time, a Stinson 108 registered N9366K was involved in an accident near West Creek, New Jersey, United States. One person was on board and one 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

17 May 2017 at 00:30

Classification

Accident

Location

West Creek, New Jersey, United States

Nearest airport

Eagles Nest (31E)

Coordinates

39.6589, -74.2997

Aircraft

Stinson 108

Registration

N9366K

Category

Airplane

Year built

1947

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

West Creek → Frederick

Aircraft damage

Substantial

Weather

VMC

Light

Dusk

NTSB number

ERA17LA182

1 person had minor injuries.

A total loss of engine power due to the No. 4 cylinder’s exhaust valve getting stuck and the subsequent fracturing of the valve face stem.

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

Read the full NTSB narrative

The private pilot reported that, while en route on a cross-country flight, the engine began to "shake." The pilot attempted to return to the airport; however, the engine experienced a total loss of power. The pilot subsequently initiated an emergency descent; however, the airplane struck trees and terrain about 1 mile from the approach end of the runway. The crankshaft and remaining cylinders remained intact, and the engine crankshaft rotated smoothly when the propeller was turned by hand. The No. 4 cylinder's exhaust pushrod shroud and exhaust pushrod were both bent. An examination of the engine revealed that the No. 4 cylinder was fracture-separated from the crankcase. The piston, sections of the No. 4 cylinder, and sections of the crankcase were missing. The No. 4 exhaust valve stem was fractured about halfway along its length, and the fracture surface was consistent with reverse bending fatigue crack propagation, which typically results from a stuck valve. The lower half of the stem and face were missing. The No. 4 exhaust valve guide clearance was excessive, and the valve's guide and tip area contained carbon deposits. The cylinder walls contained circular gouges consistent with the exhaust valve face diameter. It is likely that the carbon deposits on the valve stem resulted in the valve getting stuck, which initiated the reverse bending fatigue crack and led to the exhaust valve face stem fracturing and dropping into the cylinder and the subsequent catastrophic engine failure. The engine maintenance records were incomplete and prevented a determination of when the last clearance check of the No. 4 cylinder was performed or when it was last overhauled/replaced.

Quoted verbatim from the NTSB record.