ANC07LA062

NTSB accident investigation · Hiller UH-12E · Skwentna, AK · July 10, 2007

Accident · No injuriesLimited investigationFinal report
Date
July 9, 2007, 16:10 local (Jul 10, 2007, 00:10 UTC)
Place
Skwentna, AK
Injuries
1 uninjured
Damage
Substantial damage
Phase of flight
Landing
Aircraft
N146ETHiller UH-12E
Weather
Visual (VMC) · Day
Status
Completed · report November 29, 2007
Report
Approved by Office Director
NTSB office
Alaska Regional Office
Parties
Anchorage, FSDO-03
FAA report
20070709014499A
Case key
66158

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 clearance from a glacier, which resulted in a tail rotor strike during landing, and damage to the helicopter during an emergency descent/landing on rough/uneven terrain. Factors contributing to the accident were variable and gusty wind conditions.

Sequence of events

NTSB’s coding before 2008: each occurrence and phase of flight, and the causes and factors under it. The codes are defined in NTSB’s coding manual.

In flight collision with terrain/waterLanding
Clearance - not maintainedPilot in commandCause
Rotor system,tail rotor blade - blade strike
Terrain condition - rough/uneven
Terrain condition - snow covered
Weather condition - variable windFactor
Weather condition - gustsFactor
Loss of control - in flightEmergency descent/landing
In flight collision with terrain/waterEmergency descent/landing
Terrain condition - rough/uneven
Terrain condition - snow covered

Analysis

The solo commercial certificated pilot was attempting an off-airport landing on rough/uneven terrain under Title 14, CFR Part 91. The pilot reported that he was attempting a toe-in landing to pickup passengers, and about one foot above the ground he heard a loud bang, and the helicopter yawed to the right. The tail rotor separated from the helicopter, and the helicopter descended uncontrolled, impacting the ground, damaging the tail rotor, tail boom, fuselage, and main rotor system. During a postaccident inspection of the site, the pilot reported finding an area of disturbed snow, where the tail rotor struck the glacier. He described the conditions as wind shifts up to 180 degrees, gusting 10-15 knots, density altitude 7,000 feet, and marginal flat light on a snow-covered glacier. A passenger waiting to be picked up reported that it looked like a gust of wind pushed the tail of the helicopter to the right, and the tail rotor struck a snow bank.

Factual narrative

On July 9, 2007, about 1610 Alaska daylight time, a Hiller UH-12E helicopter, N146ET, sustained substantial damage during an impact with terrain, following a tail rotor strike while attempting to land on a glacier, about 60 miles west of Skwentna, Alaska. The helicopter was being operated by Prism Helicopters, Wasilla, Alaska, as a visual flight rules (VFR) positioning flight under Title 14, CFR Part 91, when the accident occurred. The solo commercial certificated pilot was not injured. Visual meteorological conditions prevailed, and company flight following procedures were in effect.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on July 9, the director of operations for the operator said the helicopter was stationed at Terra Camp, which is a mine site west of Skwentna. She said the helicopter left Terra Camp to pickup passengers at a drill-pad site at the 6,000 foot elevation above the camp. According to a passenger waiting at the drill site for the helicopter, she was told that it looked like a gust of wind pushed the tail of the helicopter to the right, and the tail rotor struck a snow bank. She said the tail rotor separated from the helicopter, and the helicopter descended uncontrolled, impacting the ground. She reported damage to the helicopter's tail rotor, tail boom, fuselage, and main rotor system.

In a written statement to the NTSB dated July 9, the pilot wrote that he was attempting a toe-in landing to pickup passengers. He reported that about one foot above the ground he heard a loud bang, and the helicopter yawed to the right. He landed and secured the helicopter. Inspecting the site, he reported he found an area of disturbed snow where the tail rotor must have struck the glacier. In his statement, the pilot described the conditions as wind shifts up to 180 degrees, gusting 10-15 knots, density altitude 7,000 feet, and marginal flat light on a snow-covered glacier.

Aircraft

Registration
N146ET
Reported as
Hiller UH-12E
Category
Helicopter
Serial number
HA3046
Airframe hours
5,225
Engine
Allison 250C20B, 420 horsepower, turbo shaft
Damage
Substantial damage
Flight
Positioning · Part 91
Operator
Prism Helicopters
Registered owner
Dragonfly Air LLC
Airworthiness certificate
Standard, Normal
Last inspection
Annual · June 1, 2007
Departed
Terra Camp, AK
Flight plan
Company VFR

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
48
Injuries
None
Certificate
Commercial
Instrument ratings
Helicopter
Medical
Class 2, With waivers/limitations
Last flight review
May 1, 2007
Seat
Left
Flight hours
14,300 total · 560 in this make and model · 13,815 as pilot in command · 200 in the last 90 days · 45 in the last 30 days · 4 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Wind
Variable at 10 knots, gusting 15
Visibility
10 statute miles
Temperature
50 °F

FAA reports on this event · 1

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