History of Flight
On August 29, 2008, at 1613 central daylight time, a Robinson R44 II, registration N41411, was destroyed when it impacted terrain near Ridgedale, Missouri. The flight instructor and the second pilot, the only persons on board, were fatally injured. The helicopter, owned and operated by Central Illinois Air Corp., was on a delivery flight from California to Illinois. Visual meteorological conditions prevailed, and a company flight plan had been filed for the Part 91 flight. The helicopter departed Shawnee Regional Airport (SNL), Shawnee, Oklahoma, at approximately 1420, destined for West Plains Municipal Airport (UNO), West Plains, Missouri, with an intermediate stop to drop off the second pilot.
Several witnesses observed the helicopter in normal cruise flight. One witness reported that the helicopter “looked to jump back” and then made a different noise before going out of sight. Another witness, in a boat about half a mile southwest, saw the helicopter flying level and straight to the east at 600 to 700 feet above the ground when it suddenly pitched over and went straight down at an angle of approximately 60 degrees nose down. A fourth witness estimated the helicopter was about 300 yards above ground when it pitched over nose first; after starting down, “it didn’t turn, it wasn’t spinning, or missing anything, and it wasn’t smoking.” The helicopter impacted trees and terrain, and a post-impact fire ensued.
Personnel Information
The flight instructor, age 24, held a commercial pilot certificate with a rotorcraft-helicopter rating and a flight instructor certificate with a rotorcraft-helicopter rating. He was not instrument rated. He had completed the Robinson safety course and an evaluation flight in a Robinson 44 on March 1, 2007. He was issued a second-class medical certificate on June 25, 2008, with no limitations. His most recent biennial flight review was dated April 23, 2007. He had logged 1,565 total helicopter hours, of which 892 were in Robinson 44 helicopters, and 393 hours in the preceding 90 days.
The second pilot, age 25, held a private pilot certificate with a rotorcraft-helicopter rating. He was not instrument rated. He had completed the Robinson safety course and an evaluation flight in a Robinson 22 on May 21, 2008. He was issued a second-class medical certificate on September 5, 2007, with no limitations. His most recent biennial flight review was dated April 23, 2008. He had logged an estimated 137 total flight hours, with 133 in helicopters and 10 in Robinson 44 helicopters.
Aircraft Information
N41411 (serial number 12429) was a Robinson R44 II, a four-place helicopter with a two-blade semi-rigid main rotor and a two-blade semi-rigid tail rotor, powered by a Lycoming IO-540-AE1A5 engine rated at 245 horsepower. It was manufactured in 2008 and issued a standard airworthiness certificate on August 18, 2008. The helicopter had accumulated 4.0 hours total time at delivery and an estimated 17 hours at the time of the accident. It was equipped with a Garmin GNS-500W GPS, a Kannad 406 AF ELT, and a handheld “Spot Personal Tracker” that transmitted position reports every ten minutes.
Meteorological Information
At 1553, the ASOS at Boone County Airport (HRO), Harrison, Arkansas, about 18 miles southeast of the accident site, reported wind from 010 degrees at 6 knots, visibility 10 statute miles, few clouds at 6,000 feet, scattered clouds at 10,000 feet, temperature 30°C, dew point 21°C, and an altimeter setting of 30.01 inches of mercury.
Communications
The FAA Razorback approach controller at Northwest Arkansas Regional Airport (XNA) provided VFR flight following to N41411. Last radio contact was approximately 20 miles east of XNA after flight following was terminated. No contacts with AFSS were reported. The flight instructor sent a text message at 1454 stating the intent to go to West Plains instead. The Spot Personal Tracker reported six positions between 1437 and 1557, with the last position about 34 miles west of the accident location. A cell phone photograph taken at 1612 by the second pilot showed a view of Beaver Lake, approximately 32 miles west of the accident site.
Wreckage and Impact Information
The accident site was at 36°30'00"N, 093°18'53"W, at an estimated elevation of 1,010 feet MSL. Debris was fragmented along 135 feet on a magnetic bearing of approximately 040 degrees, with a debris field width of about 60 feet. An impact crater was 34 feet from the first broken tree. Tree strikes measured angles up to 52 degrees from horizontal. The main wreckage, including the engine, transmission, and main rotor system, was located 15 feet from the impact crater. The cockpit and cabin were mostly consumed by the post-impact fire. The airspeed indicator showed 108 knots. The cockpit mixture control was in the full rich position. The engine was separated from the airframe and sustained impact and thermal damage. The engine cooling fan showed no rotational scoring. The lower sheave and actuator bearings rotated smoothly. The main rotor gearbox and mast sustained thermal and minor impact damage. Most flight control push/pull tubes were broken, with overload or thermal damage.
Medical and Pathological Information
Autopsies were performed on both pilots on September 1, 2008. Ethanol was detected in brain specimens at 0.038 gm percent, below the toxic level of 0.08 percent, and was considered a postmortem artifact from decomposition. Toxicology tests for the flight instructor showed no carbon monoxide, cyanide, or drugs. For the second pilot, ethanol was detected in brain, muscle, and liver, and n-propanol in brain; no drugs were detected.
Engine Examination
The engine was examined at Lycoming facilities on September 23-24, 2008. Accessory drive gears sustained impact damage; the left magneto idler gear had a broken tooth. The crankshaft and camshaft could be rotated by hand. No evidence of bearing distress, overspeed, or valve train distress was found. The crankshaft gear bolt was not broken, but the crankshaft dowel pin was sheared. SEM examination showed overload with no fatigue. No pre-impact anomalies that would have precluded normal operation were observed.