Garlick UH-1H N1577

Summary

On 7 October 2012 at about 22:13 local time, a Garlick UH-1H registered N1577, operated by McCarty David M, was involved in an accident near Shady Cove, Oregon, United States. One person was on board and one had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

7 October 2012 at 22:13

Classification

Accident

Location

Shady Cove, Oregon, United States

Coordinates

42.5689, -122.8844

Aircraft

Garlick UH-1H

Registration

N1577

Category

Helicopter

Year built

1965

Engines

1

Operator

McCarty David M

Operating rule

Part 133: Rotorcraft Ext. Load

Purpose of flight

External Load

Phase of flight

Not recorded

Route

Grants Pass → Grants Pass

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR13FA006

1 person had minor injuries.

The separation of the tail rotor gearbox and tail rotor assembly as a result of fatigue to the tail rotor gearbox input quill assembly attachment studs.

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

Read the full NTSB narrative

The pilot reported that he was in straight and level flight over mountainous, tree-covered terrain when he heard a loud noise followed by an abrupt jolt and right yaw. The pilot initiated a descent into a valley when he heard a second loud noise followed by severe vibrations and activation of the low rotor RPM horn. The helicopter continued to descend before it impacted the trees and ground below. During an on-scene examination, control continuity was established throughout the helicopter with the exception of the 90-degree gearbox and tail rotor assembly, which were separated from the helicopter and not found. The gear box is positioned in between the tail rotor drive shaft and tail rotor assembly; it takes the input from the tail rotor drive shaft (through a quill assembly), and adjusts and transfers the energy to the tail rotor assembly. Because the gearbox and tail rotor separated in flight, the investigation was not able to examine them to determine their condition or their proper installation. However, the tail rotor gearbox input quill assembly, vertical driveshaft clamp, and two remaining gearbox attachment studs were removed for additional examination. Fatigue damage was noted along the fracture surface of the two gearbox attachment studs that were still attached to the vertical fin side of the mounting flange. The remaining four attachment holes were empty; however, helical rubbing marks were found around their perimeter along with an adjacent lip of deformed material, which is indicative of the studs being present at one point. Postaccident examination and a test run of the helicopter's engine revealed no anomalies that would have precluded normal operation. The helicopter's most recent tail rotor gearbox inspection occurred about one month prior to the accident; however, the investigation could not determine if the fatigued area would have been included in the inspection, or whether any evidence of fatigue would have been detectable at the time of the inspection.

Quoted verbatim from the NTSB record.