Robinson R44 N7162R

Summary

On 19 September 2015 at about 01:00 local time, a Robinson R44 registered N7162R, operated by Bering Pacific Ranches, Ltd., was involved in an accident near Fort Glenn, Alaska, United States. One person was 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

19 September 2015 at 01:00

Classification

Accident

Location

Fort Glenn, Alaska, United States

Coordinates

53.1667, -168.3833

Aircraft

Robinson R44

Registration

N7162R

Category

Helicopter

Year built

1999

Engines

1

Operator

Bering Pacific Ranches, Ltd.

Operating rule

Part 91: General Aviation

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Fort Glenn → Fort Glenn

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC15LA073

Nobody was injured.

The separation of the tail rotor gearbox from the tailboom attachment point due to overstress loads imposed by a tail rotor blade imbalance as the result of impact with an undetermined object during low-level flight operations.

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

Read the full NTSB narrative

The commercial helicopter pilot was conducting an aerial mustering flight with cattle on a remote island. The pilot reported that, while in a hover, he heard "metallic grinding noises" from behind his position in the front right seat; however, the helicopter was "stable with engine power," the rotor rpm was within normal limitations, and the had "normal responding controls and tail rotor authority." The pilot immediately landed the helicopter on a sandbar, completed the shutdown process, and exited from the helicopter without further incident. While conducting a postflight inspection, the pilot observed that the tail rotor gearbox had separated from the tailboom mounting assembly and was lying on the ground. An examination of the tail rotor gearbox mounting flange bolts and the tail rotor blades revealed signatures consistent with overstress. No signatures of pre-existing damage were observed during the examination. During the low-level profile flown during the aerial mustering operation, it is likely that the tail rotor blades impacted an object which resulted in a severe imbalance of the blades and subsequent separation of the tail rotor gearbox. During the impact and separation sequence, the tail rotor blades likely impacted the vertical stabilizer where the red tail rotor blade "danger" decal is mounted. An examination of the components could not determine what object was impacted. No evidence of impact with foreign objects such as birds, vegetation, or cattle was observed, although such an impact could not entirely be ruled out since neither of the tail rotor blade tips was recovered.

Quoted verbatim from the NTSB record.