Eurocopter EC120B N88HA

Summary

On 16 November 2015 at about 15:40 local time, a Eurocopter EC120B registered N88HA, operated by Hanscopter LLC, was involved in an accident near Goshen, Indiana, United States. 2 people were 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

16 November 2015 at 15:40

Classification

Accident

Location

Goshen, Indiana, United States

Nearest airport

Goshen Municipal (GSH)

Coordinates

41.5267, -85.7933

Aircraft

Eurocopter EC120B

Registration

N88HA

Category

Helicopter

Year built

2010

Engines

1

Operator

Hanscopter LLC

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

Elkhart → Elkhart

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

CEN16LA047

Nobody was injured.

The failure of the Thomas coupling at the interface with the main gear box tail rotor output shaft, which resulted in the helicopter's loss of tail rotor control.

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

Read the full NTSB narrative

The flight instructor and helicopter-rated pilot were returning from an instructional flight in the helicopter. The flight instructor reported they heard a noise come from somewhere in the helicopter. They diverted to a nearby airport for a precautionary landing. As they approached the airport, the noise level increased. The instructor took the controls, and, about 15 ft above ground level and 25 knots, the helicopter began an uncommanded left yaw. The instructor responded with corresponding right pedal input; however, it did not stop the left yaw. The instructor immediately reduced engine power and initiated a hovering autorotation. A postaccident examination revealed the tail rotor drive system's Thomas coupling interface with the main gear box tail rotor output shaft failed. The Thomas coupling was part of the installation of an after-market air conditioning system approved under a supplemental type certificate (STC). Laboratory examinations revealed that while the pulley within the tail rotor drive system was made to the STC holder's requirements, those requirements deviated significantly from the original equipment output flange. Changes were made to the spline profile, manufacturing method, and lubrication regimen. Any of these changes, either independently or collectively, likely contributed to the increased wear and failure of the Thomas coupling. After the accident, the manufacturer issued a service bulletin and the Federal Aviation Administration issued an emergency airworthiness directive that called for an immediate and repetitive inspection of the coupling every 25 flight hours or deactivating the air conditioning system by removing the STC's Thomas coupling and reinstalling the original equipment manufacturer's Thomas coupling half.

Quoted verbatim from the NTSB record.