N41411Robinson Helicopter R44 II · 2008

On August 29, 2008, at 1613 central daylight time (CDT), a Robinson R44 II, N41411, was destroyed when it impacted terrain near Ridgedale, Missouri. The flight instructor and the second pilot, who were the only persons on-board, were fatally injured. The helicopter was owned and operated by Central Illinois Air Corp. Visual meteorological conditions (VMC) prevailed at the time of the accident and a company flight plan had been filed for the Title 14 Code of Federal Regulations Part 91 flight. The flight departed Shawnee Regional Airport (SNL), Shawnee, Oklahoma, at approximately 1420 and was destined for West Plains Municipal Airport (UNO), West Plains, Missouri.

The helicopter was on a new aircraft delivery flight from California to the delivery destination in Illinois, and was en route to an intermediate stop to drop off the second pilot. Several witnesses were watching the helicopter in normal cruise flight when it suddenly nosed straight down in a 60 degree dive and impacted trees and terrain. There was an immediate post-impact fire.

A witness in a small boat approximately one mile east of the accident scene was watching the helicopter and said it sounded like the helicopter was in normal cruise. While watching the helicopter she said “it looked to jump back while it was flying” then heard it make a different noise. As the sound got louder the helicopter went out of sight into the trees and all of a sudden the sound got louder and she heard a loud thud. She then saw the explosion. Her group went toward the accident site and helped direct other witnesses to the smoke still coming from the wreckage.

A second witness who was in the same boat said he did not see the helicopter, but he heard the rotor blades making a “soft chop chop chop” sound which he thought was from the rotor blades hitting the trees. As he looked toward the direction of the sound he heard an explosion and saw a “huge plume of smoke” from the accident site.

The third witness was in a small boat approximately 1/2 mile to the southwest of the accident site. He had heard the approaching helicopter and said they were both watching it flying level and straight to the east at about 600 to 700 feet above the ground. It suddenly pitched over and it went straight down at an angle of approximately 60 degrees nose down. During all of this there were no abnormal sounds until after the helicopter went out of sight behind the ridge and he heard a “funky sound” and then the “first boom”.

The fourth witness was in the same boat with the previous witness. He was watching the helicopter when it was about a mile away “flying OK at a normal height”, which he estimated as about 300 yards above the ground. As he was watching the helicopter it pitched over nose first and went down. After it started down “it didn’t turn, it wasn’t spinning, or missing anything, and it wasn’t smoking” as it went down. After it went out of sight he heard the blades “chopping air” and then the noises of impact. He then saw a mushroom shaped cloud of smoke. He quickly called 9-1-1 and his cell phone showed the time of that call was 4:13 pm.

The flight instructor, age 24, held a commercial pilot certificate with a rating in rotorcraft helicopter and a flight instructor certificate with a rating in rotorcraft helicopter. He was not instrument rated. He had completed the Robinson safety course including an evaluation flight in a Robinson 44 helicopter on March 1, 2007. The flight instructor was issued a second-class medical certificate on June 25, 2008, with no limitations. His most recent biennial flight review (BFR) was dated April 23, 2007. The flight instructor had logged 1,565 hours in helicopters, of which 892 hours were in Robinson 44 helicopters. He had logged 393 hours of flight time in helicopters in the preceding 90 days

The second pilot, age 25, held a private pilot certificate with a rating in rotorcraft helicopter. He was not instrument rated. He had completed the Robinson safety course including an evaluation flight in a Robinson 22 helicopter on May 21, 2008. The second pilot was issued a second-class medical certificate on September 5, 2007, with no limitations. His most recent biennial flight review (BFR) was dated April 23, 2008. The second pilot had logged an estimated 137 hours of flight time, of which 133 hours were in helicopters and 10 of those hours were in Robinson 44 helicopters.

N41411 (s.n. 12429), a model 44 II, was manufactured by the Robinson Helicopter Company in 2008. It was a 4-place, helicopter with a 2-blade semi-rigid main rotor and a 2-blade semi-rigid tail rotor. It was powered by a Lycoming IO-540-AE1A5 engine (s.n. L-33031-48E) rated at 245 horsepower.

The helicopter was issued a standard airworthiness certificate on August 18, 2008, in the normal category. The helicopter was sold to the owner on August 19, 2008 and the AC Form 8050-2 was processed by the FAA Aircraft Registration Branch on September 31, 2008. The owner held a dealer’s aircraft registration certificate number D002313, dated May 22, 2008.

Aircraft maintenance documents at the manufacturer's facility showed the helicopter had accumulated 4.0 hours total time on August 18, 2008. At the time of the accident it is estimated the helicopter had accumulated 17 hours total time.

The helicopter was equipped with a Garmin GNS-500W global positioning system (GPS) and a Kannad 406 AF emergency locator transmitter (ELT). The helicopter was not certified for instrument flight.

The helicopter was carrying a handheld GPS “Spot Personal Tracker” that gave position reports to a website accessible to the owner. Those position reports were transmitted approximately every ten minutes and gave the time, latitude and longitude.

The U. S. Surface Analysis chart at 1600 showed that high pressure systems were located over northeastern Texas, northern Kansas and eastern Iowa. A low pressure system was located over central Kentucky with a cold front extending to the south through Tennessee then extending to the west through Arkansas to northern Oklahoma. The accident site was located north of and behind the retreating cold front with nearby station models indicating VFR conditions.

At 1553, the automated surface observing system (ASOS) at Boone County Airport (HRO), Harrison, Arkansas, located approximately 18 miles southeast of the accident site, reported the 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 degrees Celsius, dew point 21 degrees Celsius, and an altimeter setting of 30.01 inches of Mercury.

The Federal Aviation Administration (FAA) air route traffic control tower (ATCT), Razorback approach controller, at Northwest Arkansas Regional Airport (XNA), Fayetteville/Springdale, Arkansas provided VFR flight following to N41411. The controller’s last radio contact with the N41411 was approximately 20 miles east of the XNA airport after N41411 had terminated flight following.

The FAA reported that the automated flight service Station (AFSS) had no contacts with N41411 on the day of the accident.

The owner’s flight locating records show that they had their last cell phone conversation with the flight instructor at 1356 during a lunch stop at the SNL airport. Then, at 1454 the flight instructor sent the following text message:

“Going to head to west plains instead...drop him off n Farmington and head back...bout same distance”

The handheld GPS “Spot Personal Tracker” reported six position reports between 1437 and 1557. The last position reported at 1557 was approximately 34 miles west of the accident location.

Several family members received a cell phone photograph at 1612 from the second pilot with the text message “random lake in arkansas”. The cell phone photograph matches a view to the southeast of the “Big Clifty” branch of Beaver Lake in Arkansas, approximately 32 miles west of the accident location.

There were no other reported communications with N41411 during the flight from the SNL airport.

The accident site was located in a wooded area at a location of 36 degrees, 30 minutes, 00 seconds north latitude, and 093 degrees, 18 minutes, 53 seconds west longitude, at an estimated elevation of 1,010 feet MSL.

Investigators from the Safety Board, the FAA, Robinson, and Lycoming examined the wreckage at the accident scene on August 30 and 31, 2008.

Debris from the wreckage was fragmented along the ground approximately 135 feet from the initial tree strike on a magnetic bearing of approximately 040 degrees. The width of the debris field was approximately 60 feet.

An impact crater was located 34 feet from the first broken tree on a 042 degree magnetic bearing. The angle from the fractured base of the first broken tree to the impact crater was measured with an inclinometer as level.

Another tree top contacted by the helicopter was located 33 feet on a bearing of 064 degrees to the impact crater. The angle from the fractured surface of the second broken tree top to the impact crater was measured with an inclinometer as 33 degrees from the horizontal. Other tree tops located from 9 feet to 21 feet from the impact crater had fractured surfaces that measured with an inclinometer as much as 52 degrees from the horizontal.

The main wreckage was located 15 feet on a bearing of 045 degrees from the impact crater and consisted of the engine, transmission, main rotor system and other fuselage parts. The tail rotor hub and gear box, main rotor tips, both tail rotor tips, all four doors, the baggage door, and all parts of the helicopter were accounted for and examined.

The cockpit and cabin was mostly consumed by the post-impact fire with the exception of some items recovered from the debris field, the majority of which sustained varying degrees of thermal damage. Most cockpit instruments were destroyed by impact or fire. The airspeed indicator showed 108 knots, the mixture control was in the full rich position with the mixture guard in place.

The main fuel tank sustained impact and thermal damage. The fuel cap was observed secured to the filler neck and the finger strainer, outlet flitting and crossover fitting were located and examined. The auxiliary fuel tank sustained impact and thermal damage. The fuel cap and finger strainer were examined. The entire fuel tank vent system, the aluminum fuel lines and the fuel valve were consumed by fire. All fuel hose fittings were observed disconnected with the exception of the inlet hose to the fuel distribution block.

The gascolator sustained impact damage and was separated from the firewall. The housing, screen and mounting bracket were recovered from beneath the surface of the impact crater. The fuel lines and bowl were separated from the housing and the gascolator screen was torn and deformed. The auxiliary fuel pump sustained impact damage, was separated from the motor and the fittings were disconnected. The throttle control system sustained impact and thermal damage and had numerous disconnects. Throttle position at the collective lever could not be determined. The butterfly valve inside the fuel control unit was observed in a fully open position.

The engine was completely separated from the airframe. It came to rest inverted and partially covered with cabin debris. The engine was subjected to the post-impact fire and sustained thermal damage. The accessory housing, fuel pump, magnetos, cooling panels and scroll received the most severe thermal damage. There was severe impact damage to the sump, starter, alternator, intake manifold, exhaust manifolds, and muffler. The engine-cooling fan sustained one impact mark at the 6 o’clock position. There was no rotational scoring on the edges of the fan. There were no score marks on the oil cooler or the cooling panels adjacent to the starter ring gear.

The lower sheave was examined and the lower actuator support bearing rotated smoothly. The lower section of the actuator remained attached to the lower support bearing. The actuator motor was disconnected from the gear portion which remained attached to the upper actuator housing. The upper support bearing rotated smoothly. The aft V-belt was not recovered. The remaining three V-belts were separated by a sharp cut and remained between the frame and the upper sheave. The upper sheave rotated smoothly and correctly on the driveshaft. The sprag clutch operated properly.

The main rotor gearbox, mast and main rotor hub sustained thermal damage and minor impact damage. The majority of the main rotor blade sections were observed with the main wreckage. Evidence of main rotor blade coning was not observed. Both elastomeric teeter stops were consumed by fire. The teeter stop brackets remained in place and were undamaged. The droop stops and spindle tusks were undamaged. The clutch driveshaft was disconnected forward of the aft yoke with jagged and angular edges. The tail rotor driveshaft had two disconnects forward of the damper bearing and two disconnects aft of the bearing. All four disconnects were flat and bent with jagged and angular edges. The tail rotor driveshaft damper bearing remained in place and rotated smoothly. The tail rotor gearbox housing was separated into several pieces. The input gear and housing remained attached to the rear of the tail boom at the bulkhead. The output gear driveshaft, output gear, and outboard bearing were undamaged. The inboard driveshaft bearing was demolished. Blue gear oil was observed on all tail rotor gearbox components. The tail rotor blade hub was undamaged. Both tail rotor blades were disconnected and had several leading edge impact marks along the blades. The tail rotor pitch change slider was free to slide along the tail rotor gearbox output shaft.

Many of the flight control push/pull tubes were broken between rod ends with evidence of overload failure and/or thermal damage. All flight control rod ends were accounted for and were secured to their appropriate attaching points. The top clevis and actuator shaft were observed connected to the aft servo. All flight control components in the swash plate area were observed securely attached with the exception of one pitch change link rod end which exhibited evidence of overload fracture features.

An autopsy was performed on the flight instructor on September 1, 2008 by Southwest Missouri Forensics in Nixa, Missouri. The autopsy findings also reported that the presence of ethanol "at 0.038 gm percent in the brain, is below the toxic level (0.08 percent) and is probably a post mortem artifact and the result of decompositional changes."

Forensic toxicology was performed on specimens from the flight instructor by the FAA, Civil Aerospace Medical Institute, Oklahoma City, Oklahoma. The toxicology report stated: NO CARBON MONOXIDE detected in Blood; NO CYANIDE detected in Blood; ETHANOL detected in Blood; ETHANOL detected in Liver; NO ETHANOL detected in Muscle; NO DRUGS LISTED ABOVE DETECTED in Blood.

An autopsy was performed on the second pilot on September 1, 2008 by Southwest Missouri Forensics in Nixa, Missouri. The autopsy findings also reported that the presence of ethanol "at 0.038 gm percent in the brain, is below the toxic level (0.08 percent) and is probably a postmortem artifact and the result of decompositional changes."

Forensic toxicology was performed on specimens from the second pilot by the FAA Civil Aerospace Medical Institute, Oklahoma City, Oklahoma. The toxicology report stated: Tests for CARBON MONOXIDE were not performed; Tests for CYANIDE were not performed; ETHANOL detected in Brain; ETHANOL detected in Muscle; ETHANOL detected in Liver; N-PROPANOL detected in Brain; NO DRUGS LISTED ABOVE DETECTED in Liver.

Investigators from the Safety Board, the FAA, and Lycoming examined the engine at the Lycoming Engine facilities in Williamsport, Pennsylvania on September 23 and 24, 2008.

The accessory drive gears sustained impact damage and the magneto drive gears were displaced. The left magneto idler drive gear was found with a broken tooth and the cushion retainer was broken. The left magneto was fragmented in small pieces. The rotating magnet shaft and gear assembly was not located or recovered. Fragmented remains of the right magneto were recovered. The right magneto idler gear shaft was broken. Disassembly of the engine revealed that the crankshaft and camshaft could be easily rotated by Hand. No evidence of bearing distress, engine over speed, or valve train distress was found.

The initial on-scene examination had previously found possible evidence of a broken crankshaft gear bolt. After disassembly, the crankshaft gear (P/N 13S19647), crankshaft gear bolt (P/N STD-2247), lock plate (P/N LW-18638) and crankshaft dowel pin (P/N STD-1065) were examined by non-destructive means. The crankshaft gear and bolt were not broken, but the dowel pin had been sheared. A scanning electron microscope (SEM) examination of the crankshaft dowel revealed a damaged fracture surface with evidence of overload. The SEM examination did not show evidence of fatigue.

No pre-impact anomalies of the engine were observed that would have precluded normal operation.