Pilot Debrief

ROBINSON HELICOPTER R44 near Seward, AK — 2010-05-15

Final reportANC10CA040
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Date
2010-05-15
Location
Seward, AK, USA
Aircraft
ROBINSON HELICOPTER R44
Registration
N81191
Category
Helicopter
Highest injury
None
Fatalities
0
Phase of flight
Approach

Probable cause

The pilot's failure to maintain clearance from snow-covered terrain while hovering in flat light conditions, which resulted in a dynamic rollover.

NTSB narrative

The commercial helicopter pilot reported that he was on a Title 14, Code of Federal Regulations Part 91, business flight transporting a passenger and seven dogs to a remote camp. As he approached the camp, which was at 3,800 feet mean seal level on a snow-covered glacier, flat light conditions made it difficult to discern topographical features on the glacier, so he elected to land at an alternate landing site at 3,200 feet msl to wait for conditions to improve. During the approach to the alternate site, just before touchdown, the pilot said that the low rotor annunciator horn sounded and that he lowered the collective to regain rotor rpm. The pilot was unable to initiate a go-around so he brought the helicopter to a hover, but due to the prevailing flat light he was unable to discern his height above the site and he unintentionally allowed the helicopter's left skid to touchdown on the uneven, snow-covered terrain. He said that there was an "instantaneous dynamic rollover" as the helicopter rolled to the left, the main rotor blades struck the snow, and the helicopter came to rest inverted. The helicopter sustained substantial damage to the fuselage, tail boom and main rotor drive system. In his written statement to the NTSB, the pilot reported that there were no preaccident mechanical problems with the helicopter, and in the recommendations section of the NTSB 6120.1 form he wrote, in part: "Always keep an 'out' or rejected approach path if conditions are unfavorable on short final." He also noted that he underestimated the difficulties associated with flat light over snow-covered terrain.

Analysis

Primary failure mode
Spatial disorientation
First missed decision gate
Pilot could have aborted the approach earlier due to flat light conditions.

NTSB coding

Evidence available

  • 2 docket documents
View NTSB final reportView NTSB docket

Docket documents2

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