Robinson R44 II N7512N

Summary

On 26 November 2015 at about 17:45 local time, a Robinson R44 II registered N7512N, operated by Timberview Helicopters, was involved in an accident near Destin, Florida, United States. 4 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

26 November 2015 at 17:45

Classification

Accident

Location

Destin, Florida, United States

Nearest airport

Destin Executive (DTS)

Coordinates

30.4000, -86.4714

Aircraft

Robinson R44 II

Registration

N7512N

Category

Helicopter

Year built

2003

Engines

1

Operator

Timberview Helicopters

Operating rule

Part 91: General Aviation

Purpose of flight

Other Work Use

Phase of flight

Not recorded

Route

Destin → Destin

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ERA16LA054

Nobody was injured.

The overstress fracture between the tail rotor driveshaft and intermediate flex plate for reasons that could not be determined based on the available evidence.

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

Read the full NTSB narrative

The commercial pilot was performing a power check before an air tour flight with three passengers onboard. While raising the collective, he heard a loud "pop." He then immediately lowered the collective and secured the helicopter. Postaccident examination of the helicopter revealed that an overstress fracture existed between the tail rotor driveshaft and intermediate flex plate. Examination revealed that all the hardware was in place except for a washer, which is required at each connection between the clutch shaft yoke and flex plate per a caution in the helicopter's maintenance manual. The maintenance manual also contained measurements to determine proper shimming required at the intermediate flex plate. A review of maintenance records revealed that, about 11 flight hours before the accident, the sprag clutch had been removed and replaced. The mechanic who performed the clutch removal and installation stated that the measurements he took at the intermediate flex plate during and after his repairs were the same. He also indicated that, when they installed new hardware, he obtained the same dimensions. Although a misalignment of the intermediate flex coupling would place significant tension along the entire length of the driveshaft between the main rotor gearbox and tail rotor gearbox and a missing washer both could have caused a fatigue-type failure of the tail rotor drive line, the parts fractured due to overstress, not fatigue; therefore, it is unlikely that the missing hardware contributed to the failure. The reason for the overstress fracture between the tail rotor driveshaft and intermediate flex plate could not be determined based on the available evidence.

Quoted verbatim from the NTSB record.