Background
On September 20, 2009, at approximately 1309 Pacific daylight time, a Robinson R22 Beta helicopter, registration N956SH, collided with terrain near Forest Grove, Oregon. Hillsboro Aviation, Inc. operated the helicopter under 14 CFR Part 91. The certified flight instructor (CFI) and the commercial pilot under instruction (PUI) sustained fatal injuries. The helicopter sustained substantial damage from impact forces and a post-crash fire. Visual meteorological conditions prevailed, and no flight plan had been filed.
Flight History
The local instructional flight departed Hillsboro, Oregon, at 1204. The operator reported that the PUI was preparing for a CFI check ride and occupied the left seat. The two airmen intended to practice autorotations with power recoveries. A witness with helicopter experience observed several uneventful autorotations before stopping watching. Another witness reported hearing a bang, then observed the helicopter descending upright with the left skid low. A third witness observed the helicopter flying overhead and appearing out of control; the front dropped toward the ground, and it seemed to tumble or flip before disappearing behind trees, followed by a large fireball.
Personnel Information
The 34-year-old CFI held a commercial pilot certificate with rotorcraft-helicopter and instrument helicopter ratings, along with a CFI certificate. He held a second-class medical certificate issued December 1, 2008, with no limitations. Family members reported over 1,000 total flight hours; company records indicated 1,012.5 hours in helicopters, with 1,010 in the R22.
The 32-year-old PUI held a commercial pilot certificate with a rotorcraft-helicopter rating. He held a second-class medical certificate issued October 17, 2008, requiring corrective lenses. Family members reported over 200 hours in helicopters; company records indicated 205.5 hours, with 202 in the R22.
Aircraft Information
The helicopter was a Robinson R22 Beta, serial number 0956. Total airframe time at the last 100-hour inspection (August 21, 2009) was 10,147 hours. The engine was a Textron Lycoming O-320-B2C, serial number L-16024-39A, with 10,402 hours at the same inspection.
Meteorological Information
The nearest official weather station was Hillsboro (KHIO), 6 nautical miles northeast of the accident site, elevation 208 feet msl. A METAR at 1253 PDT reported winds from 350 degrees at 5 knots, visibility 10 miles, clear skies, temperature 20°C, dew point 8°C, altimeter 30.35 inches of mercury.
Wreckage and Impact Information
An FAA inspector examined the wreckage on scene. The helicopter was upright and extensively burned; no ground scars led to the wreckage. Skids were spread outward, the fuel tank ruptured. The tail boom was intact with no rotational damage to the tail rotor. Main rotor grips were bent up, and blades coned upward beginning about 18 inches from the hub.
Medical and Pathological Information
Autopsies ruled cause of death as blunt force trauma for both pilots. Toxicological testing for the CFI showed no volatiles or tested drugs; tests for carbon monoxide or cyanide were not performed. For the PUI, tests for carbon monoxide or cyanide were not performed; quinine was detected in the liver, and 22 mg/dL ethanol was detected in muscle but not in the brain. The report stated the ethanol was from sources other than ingestion.
Additional Information
Robinson Safety Notice SN-24 (revised June 1994) notes that main rotor blade stall due to low main rotor rpm causes a high percentage of helicopter accidents, leading to an immediate uncontrolled descent and potential fatal outcome above 40-50 feet.