NTSB Releases Cause of BCSO Helicopter Crash that Killed 4 First Responders


Chapelle, NM –

On July 16th, 2022, the Bernalillo County Sheriff’s Department helicopter was returning to its home airport at Double Eagle on the west side after firefighting operations. It crashed soon after refueling in Las Vegas NM, at the Las Vegas Municipal Airport (LVS). The crash resulted in the destruction of the aircraft and the loss of all personnel on board.

Today the NTSB (National Transportation Safety Board) released a ten page final report on what caused the crash. An extensive investigation into the accident revealed that the cause was a catastrophic mechanical failure within the helicopter’s engine. Examination of the engine indicated that the starter-generator input (zerol) gear had failed due to fatigue. This failure caused the starter-generator driveshaft to shear, leading to the N1 accessory gearbox seizure and a complete loss of engine power.

The investigation further revealed that about 17 flight hours prior to the accident, an engine chip event had occurred. During this event, a small piece of ferrous metal was discovered on the magnetic chip plug. Following the discovery, the oil system was drained and flushed, and the filter elements were removed, cleaned, and reinstalled. After these maintenance actions, no further engine chip lights were reported before the accident.

The chip and oil samples collected during the maintenance were sent to a laboratory for analysis. However, the results of the lab analysis were not utilized by the operator to troubleshoot the cause of the chip event. It was determined that if the operator had conducted a thorough analysis, the deteriorating component and impending failure could have potentially been identified and addressed, possibly preventing the accident.

The low altitude at which the helicopter was flying during its return leg made the transition from powered flight to autorotation extremely critical after the unexpected loss of engine power. Additionally, the high-density altitude conditions, combined with the helicopter flying directly into the setting sun, may have further complicated the autorotation attempt, contributing to the unsuccessful outcome.

Investigators examined the continuity of the rotor drive and flight control systems and found no anomalies with the hydraulic or fuel systems. A minimal amount of foreign debris, primarily dirt, was observed in various sections of the helicopter, including the intake, compressor, gas producer, power turbine (PT), and exhaust sections. The PT was found to rotate freely with no metal spray, scoring, scuffing, tip rub, or bending of the blades noted.

Further examination revealed that the N1 tachometer-generator was clean but would not rotate. The starter-generator drive shaft and input (zerol) gear were both fractured. The starter-generator could be turned freely by hand via the remains of the input shaft. Additionally, the removal of the N1 accessory gearbox (AGB) magnetic chip detector plug revealed a large quantity of metallic chips on the magnetic tip, with multiple metallic fragments found in the bearing compartment oil return/scavenge lines.

Metallurgical examination of the zerol gear showed multiple fatigue fractures, as well as gouging on both the leading and lagging flanks and lands of the gear teeth. The zerol gear was determined to have failed in fatigue from a crack that formed 90° to the original, progressing across the gear. No material anomalies were observed that would have led to the initiation of the crack.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:
The total loss of engine power due to the fatigue failure of the starter-generator input (zerol)
gear which failed due to poor maintenance. Contributing to the accident was the unsuccessful
autorotation complicated by the setting sun and high density altitude.


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