Bell 212 N512TA

Summary

On 25 August 2018 at about 22:45 local time, a Bell 212 registered N512TA was involved in an accident near Dardanelle, California, United States. One person was on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

25 August 2018 at 22:45

Classification

Accident

Location

Dardanelle, California, United States

Coordinates

38.3558, -119.8425

Aircraft

Bell 212

Registration

N512TA

Category

Helicopter

Year built

1977

Engines

2

Operator

Not recorded

Operating rule

Public Use

Purpose of flight

Fire Fighting

Phase of flight

Not recorded

Route

Bald Mountain Helibase → Donnell Fire

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR18LA242

1 person was seriously injured.

An in-flight failure of the trunnion bearing and subsequent failure of the drive link and swashplate support, which resulted in the loss of helicopter control.

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

Read the full NTSB narrative

The pilot was conducting water bucket operations when he heard a one-per-revolution whispering sound emanating from the helicopter. He elected to return to the helibase and accepted the Air Attack controller’s offer to escort him back. While en route to the helibase, at an airspeed about 60 knots, the whispering sound evolved into a vibration that progressively worsened. The pilot then elected to land as soon as possible at a nearby location. Upon arrival to the precautionary landing site, the vibration momentarily stopped and was followed by a loud bang, an aggressive vertical vibration, and a loss of control. The helicopter impacted steep mountainous terrain and rolled once onto its left side. The occupants of the escort helicopter observed the accident helicopter nose over about 20° to 30°, followed by a 360° flat turn before it impacted the terrain. Examination of the wreckage revealed that multiple components of the main rotor control system had failed along with a span-wise failure of one of the main rotor blades. The drive link associated with the failed rotor blade had failed in overload at its lower lug and swashplate trunnion bearing. The outer race of the trunnion bearing exhibited brinelling consistent with axial movement of the inner section of the bearing. The inner section of the trunnion bearing separated from the rotating swashplate along with the lower lug of the drive link. Gouges and impact marks found on the arms of the non-rotating swashplate were likely made from the lower lug of the drive link as the inner section of the trunnion bearing began to pull out of the outer race. Contact of the lower lug with one of the arms of the non-rotating swashplate likely resulted in the overload failure of the drive link. These liberated components were not recovered. The in-flight failure of the swashplate drive link resulted in the loss of control of the associated main rotor blade. The uncontrolled blade, free to move out of track with the other controlled blade, resulted in at least a partial loss of control of the main rotor system. The associated vibrations from the out-of-track rotors likely resulted in the failure of the swashplate support and the total loss of control of the helicopter.

Quoted verbatim from the NTSB record.