ANC11CA056

NTSB accident investigation · Hughes 500D · Ambler, AK · June 27, 2011

Accident · No injuriesData collectionFinal report
Date
June 27, 2011, 09:25 local (17:25 UTC)
Place
Ambler, AK
Injuries
1 uninjured
Damage
Substantial damage
Phase of flight
Standing
Aircraft
C-GLHQHughes 500D
Defining event
Standing-engine(s) operating: Loss of control on ground
Weather
Visual (VMC) · Day
Status
Completed · report October 4, 2011
Report
Approved by Office Director
NTSB office
Alaska Regional Office
Parties
Federal Aviation Administration (Operations)
Case key
80946

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

On this page

Probable cause

The pilot's misalignment of the helicopter on the landing structure.

Findings · 2

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.

Runway/land/takeoff/taxi surfaceEnvironmental issues › Physical environment · Contributed to outcomeAll aircraft: 253 cases
Personnel issuesPersonnel issues › Task performance · PilotAll aircraft: 137 casesProbable cause

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 helicopter pilot landed a high skid, turbine-powered helicopter at a remote drilling site, and the three passengers disembarked. The remote landing site was constructed of 6-inch by 6-inch wooden beams, which required that the pilot land perpendicular to and on the beams with the helicopter's skids. The pilot reported that after landing he retarded the engine throttle to flight idle to begin the mandatory 2 minute engine cool down procedure. He then got out of the helicopter to check the placement of the helicopter's skids on the beams, and it subsequently tipped backwards, with the tail rotor striking terrain. A postaccident inspection revealed that while landing, the pilot inadvertently placed the helicopter's skids behind the aft wooden beam, and the helicopter tipped backwards once the pilot exited the helicopter. The pilot said there were no preimpact mechanical problems with the helicopter. The helicopter sustained substantial damage to the tail boom, tail rotor drive system, and tail rotor gearbox.

Factual narrative

The helicopter pilot landed a high skid, turbine-powered helicopter at a remote drilling site, and the three passengers disembarked. The remote landing site was constructed of 6-inch by 6-inch wooden beams, which required that the pilot land perpendicular to and on the beams with the helicopter's skids. The pilot reported that after landing he retarded the engine throttle to flight idle to begin the mandatory 2 minute engine cool down procedure. He then got out of the helicopter to check the placement of the helicopter's skids on the beams, and it subsequently tipped backwards, with the tail rotor striking terrain. In his written statement to the NTSB, the pilot wrote, in part: "While waiting, I stepped out of the helicopter to look under the helicopter to verify that my bear paws were both securely placed on the supporting timber. Within a moment of stepping out, I noticed movement and watched as the helicopter tipped backwards until it came to rest on the tail rotor and stinger." A postaccident inspection revealed that while landing, the pilot inadvertently placed the helicopter's skids behind the aft wooden beam, and the helicopter tipped backwards once the pilot exited the helicopter. The pilot said there were no preimpact mechanical problems with the helicopter. The helicopter sustained substantial damage to the tail boom, tail rotor drive system, and tail rotor gearbox.

Aircraft

Registration
C-GLHQ
Reported as
Hughes 500D
Category
Helicopter
Serial number
200662D
Airframe hours
18,753
Engine
Allison 250-C20B, 420 horsepower, turbo shaft
Damage
Substantial damage
Flight
Part 135
Operator
Prism Helicopters
Registered owner
Prism Helicopters
Airworthiness certificate
Standard, Normal
Departed
Ambler, AK
Destination
Ambler, AK
Flight plan
Unknown

Flight crew

As NTSB recorded them. NTSB leaves out names.

Role
Pilot
Age
36
Injuries
None
Certificate
Commercial
Instrument ratings
Helicopter
Medical
Class 2, With waivers/limitations
Last flight review
May 2, 2011
Seat
Left
Flight hours
4,975 total · 87 in this make and model · 4,857 as pilot in command · 88 in the last 90 days · 78 in the last 30 days · 2 in the last 24 hours

Weather

Conditions
Visual (VMC) · Day
Visibility
30 statute miles
Lowest ceiling
None

Docket · 2

The files NTSB released with the investigation on August 5, 2011, on NTSB’s docket system: statements, records, photos and specialists’ reports. 497 KB in all.