Robinson R44 II N25WH

Summary

On 27 July 2013 at about 18:55 local time, a Robinson R44 II registered N25WH, operated by Rocky Mountain Rotors, was involved in an accident near Thompson Falls, Montana, United States. 3 people were on board and one died, one was 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

27 July 2013 at 18:55

Classification

Accident

Location

Thompson Falls, Montana, United States

Coordinates

47.5467, -115.5203

Aircraft

Robinson R44 II

Registration

N25WH

Category

Helicopter

Year built

2004

Engines

1

Operator

Rocky Mountain Rotors

Operating rule

Part 91: General Aviation

Purpose of flight

Aerial Observation

Phase of flight

Not recorded

Route

Polson → Thompson Fall

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR13FA343

1 person died.

The pilot's failure to maintain helicopter control while operating in conditions conducive to a loss of tail rotor effectiveness.

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

Read the full NTSB narrative

The helicopter was flying northeast following a line of utility poles for the aerial survey flight. A surviving passenger, who occupied the left rear seat, reported that the helicopter began to rotate in a clockwise direction just before impact. A second surviving passenger, who occupied the left front seat, stated that the helicopter was flying straight and level before it began to spin. He added that, before impact, he heard the low rotor rpm warning horn. The helicopter impacted heavily forested terrain in a steep nose-down, right-bank attitude. At the time of the accident, the helicopter was about 200 lbs below its maximum gross weight. Wind was calculated to be between 2 and 16 knots from the southwest with maximum gusts of about 20 knots near the accident site, which would have resulted in a tailwind condition. Examination of the helicopter did not reveal any anomalies that would have precluded normal operation.   Video footage recorded by a passenger showed the helicopter traveling about 39 knots on a northeasterly heading and at an altitude of about 200 ft above ground level. The groundspeed then began to decay to about 30 knots over a period of about 30 seconds. The helicopter then yawed right, and the groundspeed dropped to 22.6 knots. The helicopter then appeared to develop an uncontrollable right spin, and the video ended with the helicopter crashing into the forest below. It is likely that the combination of the helicopter's high gross weight, the reduction in airspeed, and the tailwind condition led to a loss of tail rotor effectiveness, which resulted in the right yaw from which the pilot did not recover control.

Quoted verbatim from the NTSB record.