Robinson R22 BETA N8331F

Summary

On 27 April 1998 at about 20:00 local time, a Robinson R22 BETA registered N8331F was involved in an incident near Franklin, Wisconsin, United States. 2 people were on board and nobody was injured. The aircraft was slightly damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

27 April 1998 at 20:00

Classification

Incident

Location

Franklin, Wisconsin, United States

Coordinates

42.8808, -88.0008

Aircraft

Robinson R22 BETA

Registration

N8331F

Category

Helicopter

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Unknown

Phase of flight

Not recorded

Route

Milwaukee → Unknown

Aircraft damage

Minor

Weather

VMC

Light

Dawn

NTSB number

CHI98IA136

Nobody was injured.

The mechanic's failure to follow the manufacturer's maintenance rebuilding instructions.

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

Read the full NTSB narrative

The pilot said he felt an abnormal vibration in his helicopter during cruise flight. He said he reduced power and made a partial power auto-rotation to a normal landing in an open field. The on-scene investigation revealed that the tail rotor's hub bolt had fractured completely. The hub bolt attaches the tail rotor assembly to its drive shaft. Examination of the bolt revealed it had failed due to fatigue. Maintenance records showed the bolt had 168.3-hours on it since had been examined. It had been removed from the hub assembly so that new teeter bearings could be installed in the hub. The mechanic said he visually examined the bolt and believed it could be returned to service. The mechanic said he did not use the required teeter bearing alignment tool to reinstall the new bearings because the fit was not tight. He said he did not re-balance the tail rotor assembly afer the work had been done. Re-balancing is a required process according to the manufacturer's maintenance procedures. The mechanic said he told the customer to have it checked if he felt any vibration.

Quoted verbatim from the NTSB record.