Pilot Debrief

ROBINSON HELICOPTER R22 near Palmer, AK — 2016-12-18

Final reportANC17LA013
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Date
2016-12-18
Location
Palmer, AK, USA
Aircraft
ROBINSON HELICOPTER R22
Registration
N121MR
Category
Helicopter
Highest injury
Minor
Fatalities
0
Phase of flight
Approach

Probable cause

The pilot's failure to maintain main rotor revolutions per minute (RPM) during a pinnacle landing, which resulted in a main rotor stall condition, a loss of control, and a subsequent impact with terrain. A contributing factor was the flight instructor's failure to monitor the main rotor RPM during the pinnacle landing.

NTSB narrative

The flight instructor stated that he was providing flight instruction to the private pilot, practicing pinnacle landings to an area of remote, snow-covered mountainous terrain. The flight instructor said that just before the accident, the private pilot accomplished two successful pinnacle landings. After a third pinnacle landing site was selected, a gravel-covered site on a mountain ridgeline, the private pilot circled the site several times for reconnaissance. He reported that as the helicopter neared the site, about 10 to 20 feet above the surface, he realized that it had a steep uphill grade making the site unsuitable for landing. He explained that, as he was getting ready to tell the private pilot to initiate a go-around, the low rotor revolutions per minute (RPM) warning light and horn activated. The private pilot reported that when the low rotor RPM warning light and horn activated, he observed the gauge indicated about 90 percent RPM. The flight instructor then took control of the helicopter, attempting to maneuver it to the right and towards the predetermined escape route, but it descended and the skids subsequently struck the uneven terrain. He said that after the initial collision, he increased collective pitch and applied right cyclic, but it began to spin to the right, while descending. The helicopter continued to spin, while descending, and it subsequently struck an area of steep, snow-covered terrain. The helicopter then rolled downhill multiple times before coming to rest in an area of steep, snow-covered terrain.

Analysis

Primary failure mode
Controlled flight into terrain
First missed decision gate
Instructor should have aborted approach when site was deemed unsuitable.

NTSB coding

Evidence available

  • Photos
  • 3 docket documents
View NTSB final reportView NTSB docket

Docket documents3

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