ANC14CA042

NTSB accident investigation · Robinson Helicopter R44 II · Coldfoot, AK · June 18, 2014

Accident · No injuriesData collectionFinal report
Date
June 18, 2014, 09:45 local (17:45 UTC)
Place
Coldfoot, AK
Injuries
3 uninjured
Damage
Substantial damage
Phase of flight
Maneuvering
Aircraft
N74713Robinson Helicopter R44 II
Defining event
Maneuvering-hover: Settling with power/vortex ring state
Weather
Visual (VMC) · Day
Status
Completed · report August 14, 2014
Report
Approved by Office Director
NTSB office
Alaska Regional Office
Parties
FAA Fairbanks FSDO
FAA report
20140618011719A
Case key
89480

From the NTSB’s public API. By law, NTSB reports can’t be used as evidence in lawsuits over the accident.

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Probable cause

The pilot's failure to maintain adequate main rotor rpm while maneuvering at a low altitude, which resulted in an emergency landing on uneven terrain.

Findings · 3

NTSB’s coded findings. Those marked are part of the probable cause; the rest are factors or other findings. Under each, the cases with the same finding.

Performance/control parameters: prop/rotor parametersAircraft › Aircraft oper/perf/capability · Not attained/maintainedRobinson Helicopter R44 II: 17 casesAll aircraft: 182 casesProbable cause
Terrain: sloped/uneven terrainEnvironmental issues › Physical environment · Contributed to outcomeRobinson Helicopter R44 II: 10 casesAll aircraft: 270 cases

Sequence of events

The events NTSB coded, in order, by phase of flight. The defining event is the one that best describes the accident. Under each, the cases with the same event anywhere in their sequence.

Analysis

The commercial helicopter pilot reported that the purpose of the flight was to transport two technicians to a remote site in an area of mountainous terrain. The pilot fueled the helicopter and flew approximately 30 minutes to a staging area. After loading the two passengers and their gear, he flew to the planned landing zone (LZ), in a narrow box-valley at about 2,550 feet MSL. The proposed LZ was evaluated while performing an out-of-ground-effect hover, but the pilot determined the LZ was unsuitable. A second LZ was evaluated using the same process and also found unsuitable. While hovering out of ground effect, above a third potential LZ, the helicopter began to descend and the pilot added collective pitch to stop the descent. He said the low rotor annunciator horn then sounded and the helicopter continued to descend. In an attempt to avoid landing in an area of uneven terrain, the pilot said he opted to turn the helicopter to the right and downslope, while trying to override the engine governor to attain additional engine power. The helicopter's skids subsequently struck an area of uneven, down sloping terrain. During touchdown, the helicopter nosed down, pivoted to the left, and rolled onto its left side. The helicopter sustained substantial damage to the fuselage, tail boom and main rotor drive system. The pilot reported no preaccident mechanical anomalies with the helicopter that would have precluded normal operation. The pilot characterized the down sloping wind conditions as light and variable.

Factual narrative

The commercial helicopter pilot reported that the purpose of the flight was to transport two technicians to a remote site in an area of mountainous terrain. The pilot fueled the helicopter and flew approximately 30 minutes to a staging area. After loading the two passengers and their gear, he flew to the planned landing zone (LZ), in a narrow box-valley at about 2,550 feet MSL. The proposed LZ was evaluated while performing an out-of-ground-effect hover, but the pilot determined the LZ was unsuitable. A second LZ was evaluated using the same process and also found unsuitable. While hovering out of ground effect, above a third potential LZ, the helicopter began to descend and the pilot added collective pitch to stop the descent. He said the low rotor annunciator horn then sounded and the helicopter continued to descend. In an attempt to avoid landing in an area of uneven terrain, the pilot said he opted to turn the helicopter to the right and downslope, while trying to override the engine governor to attain additional engine power. The helicopter's skids subsequently struck an area of uneven, down sloping terrain. During touchdown, the helicopter nosed down, pivoted to the left, and rolled onto its left side. The helicopter sustained substantial damage to the fuselage, tail boom and main rotor drive system. The pilot reported no preaccident mechanical anomalies with the helicopter that would have precluded normal operation. The pilot characterized the down sloping wind conditions as light and variable.

Aircraft

Registration
N74713
Reported as
Robinson Helicopter R44 II (Raven II)
Category
Helicopter
Serial number
11220
Built
2006
Airframe hours
3,175
Engine
Lycoming IO-540 SER, 245 horsepower, reciprocating
Damage
Substantial damage
Flight
Part 135
Operator
Quicksilver Air Inc
Registered owner
Quicksilver Air Inc
Airworthiness certificate
Standard, Normal
Last inspection
100 hour · June 5, 2014
Departed
CXF · Coldfoot, AK
Destination
Coldfoot, AK
Flight plan
Company VFR
Equipment
Stall warning system

Matched to the registry by N-number and the event date; the registry’s history has gaps, so older matches can be wrong. Compare the reported make and model.

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
46
Injuries
None
Certificates
Flight instructor, Commercial
Instrument ratings
Helicopter
Medical
Class 2, With waivers/limitations
Last flight review
May 13, 2014
Seat
Right
Restraint
3-point
Flight hours
3,700 total · 2,700 in this make and model · 3,600 as pilot in command · 160 in the last 90 days · 110 in the last 30 days · 3 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
30° at 3 knots
Visibility
10 statute miles
Lowest ceiling
13,000 ft overcast
Temperature
57 °F, dew point 52 °F
Altimeter
29.43 inHg
Observed at
PABT, 83 nm away

Docket · 1

The files NTSB released with the investigation on August 6, 2014, on NTSB’s docket system: statements, records, photos and specialists’ reports. 852 KB in all.

FAA reports on this event · 1

The FAA’s own accident and incident reports, matched to the aircraft by N-number and date.