North American NAVION A N969TR

Summary

On 5 October 2018 at about 19:45 local time, a North American NAVION A registered N969TR was involved in an accident near Stonewall, Mississippi, United States. One person was on board and nobody was injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

5 October 2018 at 19:45

Classification

Accident

Location

Stonewall, Mississippi, United States

Coordinates

32.1317, -88.7933

Aircraft

North American NAVION A

Registration

N969TR

Category

Airplane

Year built

1946

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Meridian → Gulf Shores

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA19LA008

Nobody was injured.

The fatigue failure of the No. 3 cylinder exhaust valve, which resulted in a fractured camshaft and a total loss of engine power.

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

Read the full NTSB narrative

The pilot stated that, while en route to his destination, the airplane's engine sputtered and then lost total power. During the subsequent forced landing to a highway, the airplane landed hard, and the landing gear collapsed; the airplane sustained substantial damage to the fuselage. A postaccident examination of the engine revealed the No. 3 cylinder exhaust valve fractured where the stem transitioned to the valve head seat. The valve head impacted the No. 3 piston and became lodged between the crankcase and the camshaft, which resulted in the fracture of the camshaft. Fatigue cracking, which initiated at multiple sites, propagated through the valve stem. The presence of a tapered stem near the fracture surface, high temperature oxide deposits, and fatigue striations on the fracture surface suggested that the stem underwent spallation or erosion of the oxides formed during high temperature exposure, which would reduce the stem cross-section over time, increasing the likelihood of initiating fatigue cracking. Additionally, a localized area of wear on the top face of the valve stem was most likely due to the valve not rotating during operation, which could create hot spots or improper thermal dissipation in the hottest parts of the valve and lead to valve damage or failure.

Quoted verbatim from the NTSB record.