Bell UH1B N64RA

Summary

On 8 March 2019 at about 15:05 local time, a Bell UH1B registered N64RA was involved in an accident near Forks, Washington, United States. One person was on board and one died. The aircraft was destroyed. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

8 March 2019 at 15:05

Classification

Accident

Location

Forks, Washington, United States

Coordinates

48.1011, -124.0950

Aircraft

Bell UH1B

Registration

N64RA

Category

Helicopter

Year built

1965

Engines

1

Operator

Not recorded

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

External Load

Phase of flight

Not recorded

Route

Forks → Forks

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

WPR19FA091

1 person died.

A total loss of engine power due to the failure of the gas generator sealing disk as a result of the operator’s exceedance of the sealing disk life limits at too low an altitude for the pilot to accomplish a successful autorotation which resulted in the collision with terrain.

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

Read the full NTSB narrative

The pilot departed on his first external load flight of the day; shortly thereafter, employees heard a mayday call over the company radio. The helicopter was found inverted in the designated logging area, with the cargo line attached to the cargo hook and the grapple attached to a log. Examination of the airframe and cargo hook revealed no anomalies or mechanical failures that would have precluded normal operation. Examination of the engine revealed that the gas generator first stage sealing disk had fractured and separated into three major pieces. Multiple internal components of the engine were subsequently damaged as a result, including all four turbine rotors and nozzles. An examination of the first stage sealing disk revealed fracture features consistent with low cycle fatigue. The overhauled engine was installed into the accident helicopter about 8 months before the accident. The sealing disk was installed into the engine at the time of overhaul and had previously accrued 1,067.3 hours and 2,134.6 cycles. The operator had not kept an accurate documentation of engine cycles, and it was unknown who was responsible for documenting the engine cycles into the daily flight logs. A review of maintenance records and the helicopter's electronic cycle counter revealed that the sealing disk had exceeded the published life limit of 6,900 cycles. The last documented cycle value was 9,023.13. The cycle counter had recorded 12,023.19 cycles. Following the sealing disk separation, and subsequent internal damage, the engine lost all power, necessitating a forced landing via autorotation. Due to the low altitude and densely tree covered terrain, it is unlikely that the pilot had reaction time to release the load which became entangled in the trees as he was attempting autorotation.

Quoted verbatim from the NTSB record.