Bell 206L-3 N17592

Summary

On 23 April 2024 at about 17:50 local time, a Bell 206L-3 registered N17592, operated by Premier Rotors LLC, was involved in an accident near Tracy, California, 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

23 April 2024 at 17:50

Classification

Accident

Location

Tracy, California, United States

Nearest airport

New Jerusalem (1Q4)

Coordinates

37.0000, -121.0000

Aircraft

Bell 206L-3

Registration

N17592

Category

Helicopter

Engines

1

Operator

Premier Rotors LLC

Operating rule

Part 91: General Aviation

Purpose of flight

Aerial Observation

Phase of flight

Not recorded

Route

Modesto → Tracy

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR24LA134

Nobody was injured.

A loss of collective control authority due to fatigue failure of the collective servo cylinder extension arms from corrosion pitting.

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

Read the full NTSB narrative

During a pipeline inspection flight, the pilot and passenger of the accident helicopter heard a loud noise, followed by a shudder and an uncontrolled descent. The pilot was unable to stop the helicopter’s descent with collective control inputs and he completed a forced landing into an orchard, which resulted in substantial damage to the tailboom. Postaccident examination of the helicopter revealed fractures in the upper and lower arms of the cylinder extension to the collective control servo. All the linkages and securing hardware for the collective control system were in place. Metallurgical examination revealed the collective servo arm fractured due to fatigue cracking that had initiated in the lower cylinder extension arm at corrosion pits along the inside surface. Once the crack had propagated through more than 80% of the arm’s cross section, the remainder carrying the loads fractured from overstress. The upper arm also fractured from fatigue initiating at corrosion pits along the radii at the forward and aft ends of the open section in the middle of the arm. Composition testing determined that the elements in the corrosion pitting were consistent with compounds found in marine environments. The helicopter had been periodically flown about 50 nm from salt water. However, the undamaged cyclic servo had also been installed in the accident helicopter at the same time as the collective servo. It is unclear why the cylinder extension arms of the collective servo failed, and the cyclic servo cylinder extension arms remained intact, both having been exposed to the same environmental conditions; the extension arms for both the collective and cyclic servos were contained within a protective housing above the cockpit. The fracture surfaces were also examined to count the fatigue striations and correlate the fatigue crack growth with the 59 hours that the helicopter operated with newly installed composite blades. However, the number and pattern of crack arrest features could not be linked to any specific loading events, and the linking of the individual striations to the two-vibrations-per-blade revolution was inconsistent with the 59-hour propagation time. Therefore, the fatigue crack initiation or propagation could not be attributed to the blade installation.

Quoted verbatim from the NTSB record.