Agusta A109 N109EX

Summary

On 6 November 2020 at about 23:00 local time, a Agusta A109 registered N109EX, operated by Helinet Aviation Services, was involved in an accident near Los Angeles, California, United States. 3 people were on board and 2 were seriously injured, 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

6 November 2020 at 23:00

Classification

Accident

Location

Los Angeles, California, United States

Nearest airport

USC University Hospital (KECK (CL00)

Coordinates

34.0580, -118.2081

Aircraft

Agusta A109

Registration

N109EX

Category

Helicopter

Year built

2009

Engines

2

Operator

Helinet Aviation Services

Operating rule

Part 135: Air Taxi & Commuter

Phase of flight

Not recorded

Route

La Mesa → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR21LA039

2 people were seriously injured.

The loss of tail rotor control due to the separation of the tail rotor duplex bearing ring nut from the thrust sleeve, which resulted in the loss of helicopter control.

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

Read the full NTSB narrative

The pilot established the helicopter in an approach to land on a rooftop helipad. During the approach, as the helicopter was about 40 ft above the helipad, the helicopter began to yaw to the right despite the pilot’s control inputs. As the pilot continued the approach, he experienced a loss of tail rotor control and attempted to land on the helipad as the helicopter’s right yaw increased. A witness videoed the accident sequence which showed the helicopter rotating clockwise about the vertical axis and rolling to the left before it impacted the helipad. Postaccident examination of the helicopter revealed that the ring nut for the tail rotor duplex bearing was backed out of the sleeve, which resulted in the loss of tail rotor control. During the investigation, the manufacturer provided historical records of four previous cases that involved ring nut failures. These cases resulted in the manufacturer developing changes to maintenance practices, issuance of European Union Aviation Safety Agency Emergency Airworthiness Directive 2012-0195E in September 2012, and the issuance of Federal Aviation Administration Airworthiness Directive (AD) 2014-02-08, in March 2014, which was superseded by AD 2015-11-08, in June 2015, as a result of a fourth occurrence. The AD added, in part, a daily pilot check to enhance detection of an impending failure of a tail rotor duplex bearing ring nut installation. The accident pilot and the previous pilot who was assigned to the helicopter reported visually inspecting the two locking wires and signing off on the inspection.

Quoted verbatim from the NTSB record.