Robinson R22 N121MR

Summary

On 18 December 2016 at about 20:00 local time, a Robinson R22 registered N121MR, operated by Castor Aviation Ltd, was involved in an accident near Palmer, Alaska, United States. 2 people were on board and 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

18 December 2016 at 20:00

Classification

Accident

Location

Palmer, Alaska, United States

Coordinates

61.7672, -149.1378

Aircraft

Robinson R22

Registration

N121MR

Category

Helicopter

Year built

1985

Engines

1

Operator

Castor Aviation Ltd

Operating rule

Part 91: General Aviation

Purpose of flight

Instructional

Phase of flight

Not recorded

Route

Palmer → Palmer

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

ANC17LA013

2 people had minor injuries.

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.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full 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. 

Quoted verbatim from the NTSB record.