Newberg, OR, USA
N2096W
SCHWEIZER 269C
The instructor and student were conducting a night orientation flight. According to a witnesses who worked for the operator, about 15 minutes after the helicopter departed, he heard what sounded like an engine rollback and the helicopter making an autorotation. This was followed by the sound of an increase in engine rpm and the drive belts squealing, culminating with the sound of the helicopter making a loud thud-type noise. Another witness stated that the engine sounded rough and that the helicopter was making a high pitch whining/squealing sound, after which it went silent. A third witness also heard the helicopter making high pitch noise just before the accident. The helicopter was subsequently located in an open field near the departure airport; a postcrash fire erupted, which consumed the helicopter. A postaccident examination of the lower coupling drive shaft showed evidence of severe wear completely around the forward spline that extended beyond the root of the spline teeth. Severe wear of the forward spline teeth could have been caused by a loss of alignment between the engine and the drive shaft or an inflight loss of lubrication in the rubber boot. The rubber boot that retains grease for the forward spline portion of the drive shaft was not recovered and was presumed missing. Loss of grease coverage for the forward spline, either from a rupture of the rubber boot or a loss of the clamp for the rubber boot, could cause sudden inflight wear and overheating of the spline teeth. Severe wear of the forward spline portion of the lower coupling drive shaft most likely led to sudden and complete loss of translational/rotational power between the engine and the transmission. The reason for the severe wear of the forward spline could not be definitively determined due to fire damage and the loss of associated components, which were not located during the investigation.
HISTORY OF FLIGHTOn July 1, 2015, about 2215 Pacific daylight time, a Schweizer 269C helicopter, N2096W, was destroyed by impact forces and a postcrash fire as a result of a hard landing during an emergency autorotation near the Chelaham Airpark (17S), Newberg, Oregon. The certified flight instructor (CFI) and student pilot received fatal injuries. The helicopter was owned by Precision Flight Training Incorporated, of Newberg, and operated by Precision Aviation Training, LLC, also of Newberg. Visual meteorological conditions prevailed at the time of the accident. The local instructional flight was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The operator reported the flight departed 17S about 2200. During the postaccident investigation, the company's Director of Operations revealed to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), that the purpose of the instructional flight was for student night orientation. In a statement provided by a mechanic/witness who had worked for the operator for about three years, the witness reported that he observed the helicopter take off about 15 minutes prior to the accident. It then departed to the northwest, and when it was about 500 feet above ground level he heard the engine roll back, followed by the helicopter making an autorotation. The witness stated the he heard the engine rpm increase and the drive belts squeal, then heard the helicopter make a loud thud. The witness opined that he knew the helicopter was in trouble because of how low it was. Further, he recalled that the engine sounded normal during the flight, including the autorotation, and that the only thing he heard before the crash that raised his concern was the squealing belts. In a telephone interview with the NTSB IIC, a second witness reported that at the time of the accident he was in his home with the windows open, and the helicopter passed his residence very, very low. He said the engine sounded rough, somewhat like the sound cards make in bicycle spokes, and that it went by very fast toward the south. He further stated that the helicopter was making a high pitch whining/squealing sound, after which it went silent. He heard it hit, and then called 911. The witness added that he drove to the accident site, which was just a short distance away, and said that the fire started right away, right after it hit the ground. It a written statement submitted to the NTSB IIC, a third witness, also an employee of the operator, reported that at about the same time as the accident, he heard a high-pitched noise like ungreased belts on a car, followed by a loud sound similar to a backfire. About five minutes later he was advised of the accident. A postaccident examination of the accident site by the NTSB IIC and a Federal Aviation Administration (FAA) aviation safety inspector, revealed that while the helicopter was on a left downwind leg for the departure airport, the flight crew experienced an inflight anomaly, which was followed by an emergency descent and a hard landing. The helicopter impacted a harvested wheat field on a magnetic heading of about 173 degrees, and came to rest on a magnetic heading of about 355 degrees, and about .75 nautical miles northwest of the departure airport. The first point of impact was located about 27 feet north of the main wreckage site. A postcrash fire subsequently erupted, which consumed the helicopter. The helicopter was recovered to a secured location for further examination. PERSONNEL INFORMATIONCertified Flight Instructor (CFI) The CFI, age 31, possessed a commercial pilot certificate with rotorcraft-helicopter, and instrument helicopter ratings. He also possessed a flight instructor certificate with rotorcraft-helicopter, and instrument rotorcraft ratings. The CFI's most recent flight review was successfully accomplished on March 13, 2015, and his most recent second-class airman medical certificate was awarded on August 28, 2014, with the stated limitation, "Must wear corrective lenses for near and distant vision." A review of the CFI's personal flight records revealed that he had accumulated a total flight time of 354.6 hours, 278.1 hours in the same make and model as the accident helicopter, and 123.7 hours of flight instruction given. Additionally, the CFI had accumulated 122.5 hours, 66.8 hours, and 3.8 hours in the last 90 days, 30 days, and 24 hours respectively. The CFI was given a company evaluation flight by the operator on February 9, 2015, and a company Federal Aviation Regulation Part 141 check ride on March 13, 2015. The CFI began performing flight instructor duties for the operator on April 22, 2015. This was the CFI's initial employment as a flight instructor. Pilot Undergoing Instruction (PUI) According to records provided by the operator, the PUI, age 29, received his student pilot certificate concurrent with his airman third-class airman medical certificate on April 17, 2015, with no limitations. According to the PUI's personal flight logbook, he had logged a total of 41.6 hours of flight time, of which 38.4 hours were in helicopters, 6.0 hours was as pilot in commend/solo flight time, and 35.8 hours were in the same make and model as the accident helicopter. Additionally, the PUI had flown 32.0 hours and 19.1 hours in the preceding 90 days and 30 days respectively. AIRCRAFT INFORMATIONThe helicopter, N2096W, serial number S1865, was manufactured in 2004. It was powered by a Lycoming HIO-360-D1A reciprocating engine, serial number RL-7497-51A, rated at 190 horsepower. According to the operator, the engine had accumulated a total time of 3,729.2 hours, 21.9 hours since its most recent inspection, which was performed on June 22, 2015, and 849.8 hours since its last major overhaul. Additionally, the most recent 100-hour inspection was performed on June 2, 2015, at an airframe total time of 3,757.5 hours. It was also noted that the engine lower coupling drive shaft, part number 269A5559, serial number S345, was installed on this date with a total time of 5,199 hours. METEOROLOGICAL INFORMATIONAt 2253, the weather reporting facility at the McMinnville Municipal Airport (MVV), McMinnville, Oregon, which is located about 8.5 nautical miles south-southwest of the accident site, reported wind 260° at 4 knots, visibility 7 miles, sky clear, temperature 22°C, dew point 14°C, and an altimeter setting of 29.94 inches of mercury. AIRPORT INFORMATIONThe helicopter, N2096W, serial number S1865, was manufactured in 2004. It was powered by a Lycoming HIO-360-D1A reciprocating engine, serial number RL-7497-51A, rated at 190 horsepower. According to the operator, the engine had accumulated a total time of 3,729.2 hours, 21.9 hours since its most recent inspection, which was performed on June 22, 2015, and 849.8 hours since its last major overhaul. Additionally, the most recent 100-hour inspection was performed on June 2, 2015, at an airframe total time of 3,757.5 hours. It was also noted that the engine lower coupling drive shaft, part number 269A5559, serial number S345, was installed on this date with a total time of 5,199 hours. WRECKAGE AND IMPACT INFORMATIONThe aircraft and engine were examined at the facilities of Nu Venture Air Service, Dallas, Oregon, on August 20, 2015, under the supervision of the NTSB IIC and FAA inspectors. Participants to the examination included representatives from Sikorsky Aircraft and Lycoming Engines. The results of the examinations revealed the following. Airframe Photos of the site provided by a Portland Flight Standards District Office aviation safety inspector revealed that the helicopter was severely damaged by a postcrash fire. All components appeared to be closely located to the main fuselage. The frame tubing exhibited multiple fractures, kinks and bends. It also showed it had been exposed to the fire, with all paint burned away. Both forward cluster fittings that attach the cross beam were separated from the frame tubing. Other portions of the frame were separated by fractures of the tubing or welds. The aft mast support strut was intact. The right support strut exhibited minor mid span bending, and the left strut appeared straight. All exhibited thermal damage. The tail boom was separated from the fuselage, appeared intact with minor damage, with no blade strikes apparent. The forward bulkhead attachment lug was fractured and was consistent with overload separation. There was minor fire damage to the paint on the forward end, and oily soot deposits further aft. The tail gear box adapter remained in the boom with several attach bolt holes deformed. The tail stinger was separated at the adapter. Both tail boom support struts exhibited a compression buckle at mid-span, and separated attach fittings at the center attachment to the tail boom. The horizontal stabilizer forward attach fitting was fractured. The vertical stabilizer was crushed and bent aft with vegetation remaining in the folded sheet metal. The landing gear and crossbeams were severely damaged. The aft crossbeam was largely intact, separated from the frame, and exhibited significant bending, and was fractured and separated at the right side cluster fitting; additionally, the right outboard end was burned away. All landing gear dampers were separated at one or both ends and several were burned. The left skid was fractured and separated just forward of the forward skid strut. The right skid appears to have been intact but suffered melting and burning. The support struts were separated at the crossbeam attach areas, and several suffered significant fire damage and burning. The root ends of all three main rotor blades remained attached to the main rotor head; the outer airfoils were cut away to facilitate recovery. Each blade was relatively intact, and exhibited minor impact damage. Two blades exhibited thermal damage, with some of the aluminum airfoil consumed. The main rotor head was intact and remained attached to the drive shaft. The swashplate and rotating scissor links were intact. The rotor head turned freely in the mast bearing. Both tail rotor blades were intact, with one having remained attached to the hub via the strap pack. The opposite blade had separated thru a fracture at the inboard end of the hub spindle and fractured the strap pack also. Tip damage and some airfoil compression damage was present with the separated blade tip cap gone. The pitch change links were attached, although the separated blade link was badly bent. Both blades exhibited thermal damage to the paint. The tail rotor fork and teetering bolt were intact, and the assembly teetered properly. The fork was equipped with the elastomeric bearings. The pitch control unit was intact, rotated freely, slid in and out on the pinion, and was attached to the pitch links. The control bell crank was engaged in the pitch control housing and attached to the tail gear box and the control rod. The inboard rubber boot was consumed by fire. The tail rotor gear box (TGB) remained attached to the tail boom with elongation of several of the attachment bolt holes. The TRG was rotated and exhibited continuity from the input to the TGB output. The chip detector was not examined. The tail rotor drive shaft (TRDS) was separated at the forward end from the main gear box (MGB) pinion drive spline. The retention nut exhibited damage to the flange. MGB drive adapter splines were intact. The forward TRDS splines were intact, and the cup contained grease. The forward end of the TRDS exhibited no torsional buckling with some minor tearing and flattening, and was fractured and separated at the point where it passed through the forward bulkhead. The aft spline joint at the TGB was intact, remained assembled and exhibited continuity through the TGB. The main gearbox (MGB) housing was consumed by fire. The pinion and pinion shaft bearings survived. The ring gear and support structure survived and were engaged on the lower drive splines of the main rotor drive shaft. All gear teeth were intact with no indications of breakage. The lower portion of the mast was consumed by fire. The belt drive assembly was largely gone, having been consumed by the fire. The lower pulley was intact and thermally damaged, with both bearings in proper location, and complete except for seals. The linear actuator was in the fully engaged position. The idler pulley tension cable was separated mid-span. Subsequent to an examination with a magnifying glass, it exhibited clean fresh cut marks which occurred during recovery operations. The upper pulley internal wheel was consumed by fire, while the outer ring remained intact. The over- running clutch in the upper pulley functioned properly, engaged counterclockwise (looking forward), and rotated freely clockwise when mounted on the pinion. The engine coupling shaft (short shaft) was located in the lower pulley, and was separated from the engine. The shaft was removed from the pulley, found to be intact, and appeared to be straight. The aft splined end appeared intact with no obvious damage to the teeth. The rubber grease retention boot was melted. The forward splines exhibited severe damage to the extent that they were not visibly discernable. The rubber boot was not present, although the snap ring and safety wire retention hardware remained on the shaft. The engine mounted spline adapter exhibited an external strike with minor deformation. The rubber grease boot retention clamp was observed in place. The engine mounted adapter splines were present with little damage, although there was a hard metallic deposit in the spline groove covering through about a third of the circumference It was about a quarter of an inch long, positioned about the mid-point longitudinally in the spline. The forward end of the pulley hollow shaft exhibited a deformation from internal contact with the drive shaft, bending the outer wall outboard. Several parts were retained by the NTSB IIC to be sent to the NTSB Materials Laboratory, located in Washington, D.C. The engine driveshaft, the engine mounted drive adapter, and a bag of sample grease and debris from the Impeller were retained. The helicopter was equipped with the optional 60-gallon fuel system, which is made up of an additional fuel tank mounted on the left aft of the cabin wall; plumbing is connected to the standard right side mounted tank. The tanks were breached, and exhibited significant burning. Due to impact forces and thermal damage, the throttle and mixture cables were not able to be examined. No investigation of rotation, timing or compression was possible due to the extensive postcrash thermal damage. The majority of the flight control system, which is comprised of aluminum and magnesium, was consumed in the postcrash fire. Control continuity was established for the MR swashplate input control rods to the pitch housings. The input rods ended in melted aluminum at about the same point that the mast was consumed. The steel TR pedal torque tube survived the fire, with the TR pedal arms incurring a varying degree of thermal damage. TR control continuity was established from the TR blades through the TGB mounted bell crank and control rod in the tail boom, to the forward bulkhead where the rod was fractured. The electric cyclic trim system was not located, and was presumed to have been consumed in the postcrash fire. Engine The engine was separated from the airframe and sitting upside down on a tarp for the examination. The number 1 and 3 cylinder heads and oil sump were consumed by fire. The rear accessory case was deformed and partially consumed by fire. The engine case was deformed by heat. Both magnetos were partially consumed by fire and deformed. The fuel servo was also consumed by fire. The starter ring gear support center was broken apart. The attached fan blades were separated. The edge of the fan blade disk revealed signs of rotation at impact. The engine to airframe drive coupler shaft splines were found sheared off and ground down on the engine side. The engine drive adapter splines contained the sheared off spline from the shaft, and also had damaged splines. The cooling fan disk with the starter ring gear
The loss of translation/rotational power between the engine and the transmission due to the severe wear of the forward spline portion of the lower coupling drive shaft. The reason for the severe wear of the forward spline could not be definitively determined due to fire damage and the loss of associated components, which were not located during the investigation.
Source: NTSB Aviation Accident Database
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