Accident Details
On December 18, 2016, at approximately 1100 Alaska standard time, a Robinson R-22 Alpha helicopter, registration N121MR, collided with mountainous, snow-covered terrain about 12 miles north of Palmer, Alaska. The helicopter was registered to and operated by Castor Aviation Ltd. of Wasilla, Alaska, as a visual flight rules (VFR) instructional flight under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed. The flight originated from Wolf Lake Airport, Palmer, at 1002.
Pilot Statements
The flight instructor reported that he was providing instruction to a private pilot working toward a commercial helicopter certificate. At the time of the accident, they were practicing pinnacle landings in the Hatcher Pass Management Area. The private pilot had completed two successful pinnacle landings at sites about 4,200 and 4,600 feet mean sea level. A third site, a gravel-covered ridgeline at about 4,300 feet msl, was selected. After circling for reconnaissance, the pair discussed the approach, including a preplanned escape route to the right of the site.
During the final approach, the private pilot was manipulating the controls. Cockpit indications were in the green, no warning lights illuminated, manifold pressure was 20-21 inches, and descent rate was 150 feet per minute. As the helicopter neared the site about 10-20 feet above the surface, the instructor realized the site had a steep uphill grade, making it unsuitable for landing. As he prepared to call for a go-around, the low rotor RPM warning light and horn activated. The private pilot observed the gauge indicating about 90% RPM.
The instructor took control and attempted to maneuver right toward the escape route, but the helicopter descended and the skids struck uneven terrain. After initial contact, he increased collective and applied right cyclic, but the helicopter began to spin right while descending. It struck steep, snow-covered terrain and rolled downhill multiple times before coming to rest. Both occupants egressed and used a cellular phone to request rescue. They were extracted by a helicopter from a separate company.
Aircraft Damage and Mechanical Status
The helicopter sustained substantial damage to the main rotor system, fuselage, tail boom, and tail rotor system. The flight instructor reported no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.
Meteorological Information
The closest official weather observation station was at Palmer Airport, about 12 miles south of the accident site. At 1053, a METAR reported wind 20 degrees true at 18 knots gusting 24 knots; visibility 10 statute miles; scattered clouds at 8,000 feet and broken clouds at 14,000 feet; temperature 34°F; dew point 14°F; altimeter 28.86 inHg.
Survival and Equipment
The accident helicopter was not equipped with, nor required to have, an emergency locator transmitter. The occupants were not wearing flight helmets. The helicopter had 3-point restraint systems for both seats.
Additional Factors
According to the Robinson R-22 Pilot's Operating Handbook (2016), the low RPM light and horn activate at 97% rotor RPM or below.