Kaman HH-43F N559D

Summary

On 18 August 2006 at about 23:00 local time, a Kaman HH-43F registered N559D, operated by Horizon Helicopters, was involved in an accident near Metaline Falls, 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

18 August 2006 at 23:00

Classification

Accident

Location

Metaline Falls, Washington, United States

Coordinates

48.8272, -117.2967

Aircraft

Kaman HH-43F

Registration

N559D

Category

Helicopter

Engines

1

Operator

Horizon Helicopters

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

External Load

Phase of flight

Not recorded

Route

Metaline Falls → Metaline Falls

Aircraft damage

Destroyed

Weather

VMC

Light

Day

NTSB number

SEA06LA162

1 person died.

The failure of the left-hand cross-shaft input internal spline while the helicopter was in a hover, which resulted in the loss of gear box timing, in-flight blade contact and separation, and the subsequent loss of control and impact with a log deck.

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

Read the full NTSB narrative

The pilot was about to release a load of logs onto a log pile from an altitude between 150 to 200 feet when ground crewmen heard an explosion, then observed the helicopter descend in a nose down attitude before impacting the log deck. An examination of the accident site by an FAA inspector revealed that all major portions of the helicopter were accounted for. A subsequent examination of the wreckage revealed a failure of the transmission's left-hand cross-shaft internal spline, which resulted in the loss of gearbox timing and subsequent in-flight blade contact and separation. Maintenance records revealed that the helicopter's transmission was overhauled on May 1, 2006; the time between the overhaul and the accident was 409.4 hours. An examination of the fractured transmission center housing was caused by two fatigue cracks, which were probably caused by severe cyclic stresses that resulted from repeated loading and unloading of logs.

Quoted verbatim from the NTSB record.