History of Flight
On October 15, 2010, at 1110 central daylight time, a Bell 206B helicopter, registration N96MP, operated by the Missouri State Highway Patrol (MSHP), impacted terrain near Clarkson Valley, Missouri. Visual meteorological conditions prevailed. The flight was conducted under 14 CFR Part 91 without a flight plan. The private pilot, the sole occupant, was fatally injured. The flight had departed from Arnold, Missouri, about 1053 and was en route to Spirit of St. Louis Airport (SUS), St. Louis, Missouri.
Earlier that day, two MSHP troopers arrived at the Arnold Police Department about 0845 to join the pilot for a speed enforcement operation. The helicopter landed in a field near the police department shortly before 0900. After takeoff around 0900, the front-seat trooper noted the fuel gauge read "slightly above 25." The pilot mentioned he would need to obtain fuel before a next flight at 1200. After over an hour of flying, the pilot performed an additional speed enforcement. Upon returning to the Arnold Police Department, the front-seat trooper observed the fuel gauge indicated "half way between E and 25." The pilot shut down, and the troopers exited. The trooper reported no unusual noises or actions during the takeoff for SUS.
A witness near the accident site reported hearing the engine "sputter" then "stop." The rotor separated from the helicopter, and both descended. The fuselage was "gyrating wildly" and appeared out of control.
Personnel Information
The pilot, age 47, joined the MSHP on August 1, 1993. He held a private pilot certificate with single-engine airplane and helicopter ratings, among others. His total flight time was 2,607 hours, including 820 hours in the accident helicopter model. His last flight review was in April 2009, and his last Bell 206B training was at Bell Helicopter Training Academy in June 2010, which included emergency procedures. He had no prior accidents, incidents, or enforcement actions on record.
Aircraft Information
The 1981 Bell 206B, serial number 3377, was powered by an Allison 250-C20B engine. The last 100-hour/300-hour/annual inspection occurred on May 7, 2010, at a total airframe time of 11,185.4 hours. At the time of the accident, total airframe time was 11,254.5 hours.
Meteorological Information
At 1054, the automated weather system at SUS reported wind from 240 degrees at 8 knots, visibility 10 statute miles, clear skies, temperature 16°C, dew point 3°C, and altimeter setting 30.11 inches of mercury.
Wreckage and Impact Information
The accident site was located about 3 nautical miles southeast of SUS at an elevation of about 632 feet. The debris path was about 600 feet long, oriented south-southeast to north-northwest. Blue and white paint chips consistent with the helicopter's exterior were found near the southern end. The main rotor with hub was about 50 feet south-southeast of the fuselage, which lay on its left side with tail boom and tail rotor attached. No fuel spillage was evident.
Examination of the main rotor showed one blade with blue marks spanning about 13 feet from the hub. Pitch change link separations were consistent with overstress. The tail boom was twisted with gouging near the horizontal stabilizer. The short shaft was deformed into the engine exhaust. No circumferential scoring was found on the tail rotor drive shaft.
Fuel system examination revealed about 3 quarts of Jet A fuel in the tank bladder. The fuel shutoff valve was open and functional. The low fuel switch and float arm operated normally. The airframe fuel filter contained about 1 ounce of Jet A. The fuel line to the engine-driven fuel pump had 2 drops of Jet A. Fuel lines were intact. Flight control continuity was confirmed.
Medical and Pathological Information
The pilot's medical records were reviewed. His last FAA second-class medical certificate was issued on May 27, 2010. He reported no medications or mental disorders. An autopsy attributed death to multiple blunt injuries. Toxicology tests detected alprazolam (in urine only), desmethylvenlafaxine, venlafaxine, and naproxen in blood or urine. Ethanol was not detected.
Tests and Research
Engine examination at Rolls Royce found compressor rub marks and blade bending consistent with impact rotation. The turbine section showed crush damage but no rotational marks on blade paths. Fuel lines from fuel control to nozzle contained little or no fuel.
Component examination at Bell Helicopter revealed the mast was fractured above the shoulder with elongation and twisting. The yoke and straps had no anomalies. The sprag clutch functioned normally. The coupling was bound due to impact damage.
The Rotorcraft Flying Handbook discusses low G conditions and mast bumping, noting that abrupt forward cyclic input can lead to low G conditions and possible rotor mast contact, potentially causing mast damage or rotor separation.
The MSHP standard operating procedures prohibit flying while under the influence of drugs that affect performance. The pilot's chain of command had no knowledge of his medication use.