Delta Junction, AK, USA
N26TC
MCDONNELL DOUGLAS HELICOPTER 369E
The pilot reported that he was in cruise flight when he heard a “pop” and the engine lost all power. He initiated an autorotation to a clearing, but was unable to reach it and had to land in an area with trees. The helicopter struck treetops during the descent and landed hard, sustaining structural damage. A postaccident inspection, including running the engine in a test cell, disclosed ample uncontaminated fuel, and no evidence of any preimpact mechanical problems with the helicopter’s engine or systems.
HISTORY OF FLIGHT On March 6, 2010, about 1255 Alaska standard time, a McDonnell Douglas 369E helicopter, N26TC, registered to and operated by Aurora Aviation Services, Inc., was landed hard during an autorotation landing near Delta Junction, Alaska, following a reported total loss of engine power. Visual meteorological conditions prevailed at the time, and a company visual flight rules (VFR) flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 135 non-scheduled, domestic, passenger flight from a site near Healy, Alaska, to Wingsong Estates Airport, Delta Junction, Alaska. The helicopter sustained substantial damage. The certificated commercial pilot and two of three passengers were not injured; the third passenger sustained serious injuries. The flight originated from Healy about 1220. The pilot stated that earlier that day the flight departed from the Wingsong airport with a full fuel load and flew to Healy, landing uneventfully. He secured the helicopter, and remained on the ground for several hours. On the return flight, while flying between 300 and 400 feet above ground level, at an indicated airspeed of between 110 and 115 knots, he heard a “pop” and then the engine out horn. He verified he had a loss of engine power, and advised the passengers to brace. He initiated a descent for an autorotation landing, and maintained 80 knots with the main rotor rpm at the lower end of the green arc in an effort to reach a nearby river bottom. Realizing that he was unable to reach the intended touchdown location, he continued the descent and aimed for a spot in the trees close to the river edge. When he was close to the tree tops he “flared hard and pulled full collective to slow down [decelerate and] cushion the ground contact.” The helicopter continued 50 feet, then impacted the ground hard, coming to rest upright. The on-board emergency locator transmitter (ELT) did not activate. After establishing that the passengers were safe, he used a cell phone from one of them and called his wife, who called the Federal Aviation Administration (FAA) flight service station, initiating search and rescue efforts. The injured passenger was airlifted to a hospital in Anchorage. The helicopter crashed during daylight conditions. PERSONNEL INFORMATION The pilot, age 52, holds commercial, flight instructor, and mechanic certificates. The ratings listed on his commercial pilot certificate included airplane single engine land, rotorcraft helicopter, instrument airplane and instrument helicopter. His most recent FAA second-class special issuance medical certificate was issued on November 9, 2009, and contained a restriction to possess glasses for near and intermediate vision. The medical was not valid after November 30, 2010. The submitted NTSB Pilot/Operator Aircraft Accident/Incident Report indicated the pilots’ total rotorcraft flight time was 4,150 hours, and he listed having 2,500 hours in the accident make and model helicopter. His last airman competency/proficiency check in accordance with 14 CFR Part 135.293 titled, “Initial and recurrent pilot testing requirements” and Part 135.299 titled, “Pilot in command: Line checks: Routes and airports” was performed in the accident helicopter on May 8, 2009. The flight check included powerplant failure, simulated engine failure, and autorotations. The result of the check was “approved” and all procedures were recorded to be satisfactory. AIRCRAFT INFORMATION The helicopter was manufactured in 1991 by McDonnell Douglas Helicopter Company, as model 369E, and was designated serial number 0489E. It was powered by a Rolls-Royce (formerly Allison Engine Company) 250-C20B engine rated at 420 shaft horsepower (SHP) with 375 SHP usable. Review of the “Daily Log” sheets revealed the helicopter was last inspected in accordance with an annual inspection on February 15, 2010. The helicopter total time at the time of the inspection was recorded to be 10,380.9 hours. On February 18, 2010, an entry in the “Daily Log” indicates that the compressor case halves were removed and serviceable compressor case halves were installed by the accident pilot/mechanic. The entry indicates the total time on the case halves was unknown, but the time since overhaul for the case halves was listed as “0.0.” The helicopter total time at that time was reported to be 10,387.5 hours. Following the case halves replacement, the pilot flew the helicopter and approved it for return to service. The helicopter total time at the time of the accident was reported to be 10,399.7 hours. METEOROLOGICAL INFORMATION The closest weather reporting facility was the Allen Army Airfield Airport, about 6 nautical miles south-southeast from the accident site. A surface observation weather report taken from the airport at 1253, or approximately 2 minutes before the accident, indicates the wind was from 300 degrees at 10 knots, the visibility was 10 statute miles, and few clouds existed at 3,000 feet. Scattered clouds existed at 13,000 and 18,000 feet, and the temperature and dew point were minus 03 and 07, respectively. The altimeter setting was 29.18 inches of Mercury. WRECKAGE AND IMPACT INFORMATION Examination of the accident site revealed the helicopter came to rest upright among a stand of small diameter trees. The helicopter which was listing to the right was recovered for further examination. Examination of the helicopter and engine following recovery was performed by representatives of the airframe and engine manufacturer with FAA oversight. Examination of the airframe revealed the fuselage appeared slightly twisted however there was no visual damage to the fuselage station (FS) 78.50 frame, FS 124 canted frame, keel beam or mast support. The lower left and right sides and the underside of the fuselage displayed the most damage. The right and underside portions of the forward fuselage back to FS 85 exhibited deformed structure, dents and tears. The damage extended upward to almost level with the crew and cabin floors. The area in the vicinity of the gear struts on both sides of the fuselage was damaged consistent from gear strut flexing upward on ground contact. The lower right forward strut area was the most severely damaged. The left and right upper boom fairing had some warping and oil canning of the skin panels. The composite air inlet fairing displayed some wrinkling to the surface layer on both sides of the fuselage. The horseshoe shaped FS 137.50 frame exhibited minor distortion damage at the bottom (6 o’clock position). The tail boom remained securely mounted to the aft fuselage. The FS 197.78 frame tail boom attaching points and mounting bolts appeared undamaged. The tubular monocoque structure was mostly intact but exhibited visible damage at approximately FS 252. There was no visual evidence of rotor blade strikes to the tail boom. The tail empennage including the vertical stabilizer, horizontal stabilizer, and tail rotor assembly was in place although heavily damaged. Damage to the main rotor blades varied in severity and included bent spars, chord-wise wrinkling, leading edge damage and trailing edge bending and separation. Three of the blades exhibited large bends from 35 to 90 degrees just past the blade root at the end of the doubler, and one blade had partially separated and nearly fractured through. There was no evidence of blade contact to the fuselage or tail boom. Examination of the cockpit revealed the crew and passenger seats displayed some deformation to their frames. The seat pan on the left and right crew seats were depressed approximately 0.250 inch at various locations across the structure. The cockpit restraint system components were examined and no deficiencies were noted. Examination of the fuel system revealed a sufficient quantity of fuel was on-board for the intended flight, though the amount was not drained and quantified. Visual inspection of the fuel system revealed no visible damage to the fuel cells, plumbing, or fittings with the exception of the fuel drain valve which was noted to be damaged as a result of the ground contact. A vacuum check of the fuel system was performed with no air or fuel leaks noted. A sample of fuel from the fuel tank was obtained and although it was not tested, visible inspection revealed it was clear with no evidence of noticeable water or contaminants. Examination of the flight control system revealed cyclic, collective, and anti-torque control continuity. Anti-torque pedal movement was restricted by impingement of the damaged tail boom on the long tail rotor control rod at approximately FS 252. Examination of the engine by a representative of the engine manufacturer with FAA oversight revealed all of the engine mounts were intact as well as both the power turbine governor (PTG) input shaft and the fuel control unit (FCU) throttle linkage. The PTG and FCU rigging was continuous and properly adjusted. The bleed valve was in the open position. The N1 shafting system rotated and was continuous to the starter generator and 1st stage turbine wheel when checked with a borescope. The N2 shafting system was also continuous from the 4th stage turbine wheel to the main rotor and tail rotor. No foreign object damage (FOD) was noted on the compressor or compressor inlet. The magnetic chip detector plugs were clean and oil wetted with an appropriate amount of oil (approximately 1/2 liter) remaining in the gearbox. All external air, fuel, and oil line connections were at least finger tight and a pneumatic system leak check was conducted using shop air with no leaks detected. The fourth stage turbine wheel was undamaged and the first stage turbine nozzle, nozzle shield, and wheel displayed no discrepancies when checked using a borescope. The aircraft was equipped with a scavenge oil filter which was not removed as the pending bypass indicator was not extended. The engine mounted fuel filter element was inspected and it was free of debris while the filter bowl was full of fuel. The fuel nozzle displayed carbon formation on the air shroud and trace amounts were noted in the secondary fuel orifice. The engine was removed from the helicopter and shipped to the manufacturer’s facility for an attempted run in a test cell. The engine was placed in a test cell as received and was operationally tested with FAA oversight. The engine started and passed power calibration and droop checks. Several acceleration checks were performed and were unsuccessful in inducing power loss, surge, or flameout. No anomalies were observed during the testing. MEDICAL AND PATHOLOGICAL INFORMATION The pilot submitted urine and saliva specimens on the date of the accident for post accident drug and alcohol testing, respectively. The results were negative for tested drugs consisting of amphetamines, cocaine, marijuana, phencyclidine (PCP), and opiates. The results were also negative for alcohol.
A total loss of engine power in flight for undetermined reasons.
Source: NTSB Aviation Accident Database
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