Cumberland SKYBOLT N4TZ

Summary

On 8 April 1997 at about 20:30 local time, a Cumberland SKYBOLT registered N4TZ was involved in an accident near Smithfield, North Carolina, United States. 2 people were 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

8 April 1997 at 20:30

Classification

Accident

Location

Smithfield, North Carolina, United States

Nearest airport

Johnston County (JNX)

Coordinates

35.4998, -78.3405

Aircraft

Cumberland SKYBOLT

Registration

N4TZ

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Walterboro → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

MIA97LA123

Nobody was injured.

Installation by a student mechanic of a counterweight retaining washer that did not meet engine manufacturers specifications resulting in partial separation of the counterweight, failure of the No.5 connecting rod adjacent to the counterweight, and seizure of the engine. Contributing to the accident was improper supervision of the student mechanic by aviation school personnel.

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

Read the full NTSB narrative

The engine failed and seized as the flight approached the airport for landing. During a forced landing in a field the aircraft nosed over. Post crash examination of the engine showed a counterweight retaining clip, washer, and pivot pin had separated allowing the counterweight to move around on the remaining pivot pin. The counterweight struck the No. 5 piston connecting rod causing it to fail and seize the engine. The counterweight retaining washer was found to have been ground and to not meet the manufacturers specified dimensions. Two pieces of the washer had separated. The engine had been taken by the owner to a community college aircraft maintenance school for overhaul. The engine was returned and installed on the aircraft 83 flight hours before failure. No logbook records were found to show the engine had been overhauled. Representatives of the aircraft maintenance school stated the work performed on the engine was a repair not an overhaul and that the original counterweight retaining washers and clips had been reused.

Quoted verbatim from the NTSB record.