LEMONT, IL, USA
N5070J
Hughes 369D
The helicopter impacted muddy terrain following an auto rotation while conducting power line maintenance. The autorotation was executed from a hover altitude of 100 feet agl. Review of the helicopter's height velocity diagram indicated that the operation was conducted within the "cross hatched" area. Operation within the "cross hatched" area may not allow enough time for the critical transition from powered flight to autorotation. Examination of the airframe, engine and related components revealed no anomalies.
HISTORY OF FLIGHT On April 8, 2000, at 1100 central daylight time, a Hughes 369D, N5070J, operated by Haverfield Incorporated, sustained substantial damage on impact with muddy terrain following an autorotation from approximately 100 feet agl near Lemont, Illinois. The helicopter experienced a total loss of engine power while a platform worker was performing live power line maintenance. The CFR Part 133 external load operation was not operating on a flight plan. The pilot reported no injuries and the platform worker sustained minor injuries. The local flight originated from the Joliet Regional Airport (JOT), Joliet, Illinois at 0830. The pilot reported the following in a written statement, "...At approximately 0830 AM I departed the Joliet airport en route to link up with our ground crew at the LZ (N41 39.20 W88 01.10). I arrived there at approximately 0840 AM and shut down. We then installed the lineman's work platform, all necessary tools and added 25 gallons of fuel". "We then had our tailboard briefing cranked up and departed the LZ for our first work location. There we were to do a repair of the shield wire on structure # 252 which is on line # 1802 wills county to willow springs, which is about 2 miles to the northeast of the LZ." "After about 40 minutes of working on that structure we needed to get some different tools. We returned to the LZ to pick up a bigger hoist, some grips and a few other things. While we were there I took on another 20 gallons a fuel and departed for structure # 252 which is on the same line about 1 mile farther to the east. On structure # 257 we were to replace the insulator and the two dampeners. After 15 minutes of work or about 40 minutes after takeoff the aircraft engine lost power. I executed a autorotation to a swampy area between the powerline and a adjacent railroad track. The helicopter was damaged as a result of this emergency landing. The helicopter ended up sitting on its nose and the engine was NOT running. I pulled the fuel shutoff value handle out to shit the fuel and turned the BATT switch off. The lineman and myself exited the area..." During an interview, the pilot stated that he obtained 25 gallons of fuel prior to departing. The fuel was first sumped from the belly tank and then from the antiice filter with the start pump on. He then landed at a landing zone located 2 to 2-1/2 miles from the accident site where the helicopter was shutdown and the external work platform was attached to the helicopter. He departed to work on the first tower which was located two towers west of the tower nearest the accident location. He then worked the second tower for 15-20 minutes, returned to the LZ and obtained additional tools and 20 gallons of fuel without shutting the engine down. He returned to the second tower to finish and then proceeded to the third tower nearest the accident site. He described the weather when he was at the third tower as being "kind of windy" with a temperature of 25 degrees F. During the flight, he went straight between towers with approximate bank and pitch angles not exceeding 5 degrees with and airspeed of 30-40 knots. He was at the third tower oriented on an easterly heading of 070-080 degrees for 15 minutes when he heard the engine spool down without any banging. He pulled away from the tower and tried to pull collective to ensure it was a loss of power. He rolled right, down and added collective. He saw a patch of brush and then flared "hard" to get on the other side of some brush. The helicopter had some forward airspeed when it contacted terrain. The helicopter then rolled up on its nose during the impact. He stated that the ignition was on. The platform worker stated that the pilot called out that he was coming out. The engine sounded as if it powered down. The helicopter did not touch the power lines and that the blades were still rotating. He curled up in a ball in accordance with his company training. He reported minor injuries, which identified as spasm in his shoulder and back pain. PERSONNEL INFORMATION The 45-year-old pilot held an airline transport pilot certificate with a multi engine land rating and a commercial pilot certificate with single engine land and rotorcraft ratings. He reported a total helicopter time of 6,300 hours of which 3,350 hours were in the accident make and model and 60 hours were on the last 30 days. He received a second-class medical certificate with no limitations or waivers on March 31, 2000. AIRCRAFT INFORMATION The helicopter, serial number 121096D, was operated by the Haverfield Corporation under a restricted category airworthiness certificate. The helicopter was manufactured in 1981 and accumulated a total airframe time of 1,244.30 hours. It was powered by a 420-shaft horsepower Rolls-Royce 250-C20B engine, serial number CAE 823361F. The operator reported a total engine time of 8,677.30 hours. The airframe was last inspected by the operator during a 100-hour inspection completed on March 16, 2000 at a total airframe time of 1,208.1 hours. The engine was last inspected during a 200-hour inspection completed on March 16, 2000 at a total engine time of 8,641.10 hours. The helicopter was involved in accident involving a partial loss of engine power for undetermined reasons on February 9, 1999 (The National Transportation Safety Board (NTSB) accident number NYC99LA055). Following the accident on February 9, 1999, the engine was replaced with serial number CAE 823361F. The only engine accessory involved in both accidents was the fuel pump, serial number 4076. The Hughes 369D fuel system consists of a suction type system (nongravity vertical feed of approximately 15 inches) with two interconnected main fuel cells located beneath the passenger floor. The total fuel capacity is 64 U.S. gallons or 416.0 lbs, with 62 gallons or 408.0 lbs of usable fuel. The fuel vent system consists of a forward and aft vent to provide for the elimination of vapor fume hazard, equalization of cell pressure, prevention of fore and aft cell pressurizing during helicopter operation, a rapid servicing rate without blowback and prevention of fuel spillage. The forward and aft vent systems are both coupled to a vapor riser tube, which incorporated an emergency shutoff vent valve. The operation of the valve is an automatic function and the valve will remain open as long as the helicopter is within 30 degrees of normal attitude in any direction. METEOROLOGICAL INFORMATION Weather recorded 22 nm on a magnetic heading of 289 degrees from the accident site, at 1053, reported: wind 341 degrees at 16 knots gusting to 22 knots, visibility of 10 sm, clear sky conditions, temperature of -1 degree C, dew point of -7 degree C, and an altimeter of 30.19 inches of mercury. WRECKAGE AND IMPACT INFORMATION The helicopter was resting in a wet marsh grass area and beneath power lines. The helicopter was oriented on a magnetic heading of 016 degrees (from tail to nose). The tail boom was severed at approximately 12 inches aft of the engine compartment (fuselage station 197.78) and approximately forward of the aft end of the tail boom (fuselage station 264.32). The tail rotor drive shaft was fractured into 6 sections and exhibited lateral deformation fracturing consistent with overstress at each of the fracture points. Continuity of the tail rotor gearbox, which remained attached to the tail boom, was confirmed. The operator had removed the communication radios, navigation radios, main rotor blades and tail boom. The helicopter's fuel tank contained approximately 110-120 lbs of fuel. Approximately 0.2 oz of fuel was drained from the fuel line connecting the check valve to the fuel nozzle. The fuel line was then reattached. The airframe anti-ice filter was removed and was full of fuel. The engine driven fuel pump cover contained approximately 3/4 fuel upon its removal and the 5 micron fuel filter did not exhibit any contaminates. The engine driven pump cover was then reattached. The start pump and fuel shut off valve were operated from the cockpit; no anomalies were noted. A utility truck containing power line parts and tools was used to fuel the helicopter. The utility truck was equipped with a Jet A fuel tank and a Velcon Filters VF-61EP fuel filter. Inspection of fuel from the fuel dispensing nozzle and sumps did not reveal any contaminants. Further examination of the helicopters fuel system, anti-ice filter and engine driven pump fuel bowl and fuel nozzle screen, which was noted to be intact also did not display solid contaminates. The fuel samples were tested and found to contain less than 5 ppm of water. Inspection of the fuel vents did not reveal any obstructions. Borescope inspection, under the supervision of an FAA inspector, of the fuel line from the fuel tank to the firewall did not reveal any obstructions. A vacuum check through the upper fuel pump's filter cover drain port was performed using a handheld vacuum gauge. An 8 and 20 inch Hg differential vacuum was applied. The vacuum was unable to maintain 8 inch Hg of differential pressure for two minutes but was able to maintain 20 inch Hg of differential pressure for greater than two minutes. Engine control continuity through from the cockpit controls to the engine was confirmed. Flight control continuity was also confirmed. TESTS AND RESEARCH Haverfield Corporation conducts aerial live-line maintenance and inspection of lines ranging from 39-Kv - 765-Kv with a skid-mounted external work platform (supplemental type certificate SH1861SO) and external crewmember. Repairs include conductor repair, marker ball installation or replacement and aerial washing of insulators. Haverfield operated 16 helicopters under 14 CFR Part 133 rotorcraft external load operations. Six of the aircraft were Hughes 500 series helicopters. A search of FAA service difficulty reports from 1995 for the Hughes 369 model under the category of power loss yielded 37 results. The number of reports with respect to a component part was as follows: Bearing 1 Bleed Air Valve Line 1 Bleed Air Valve 3 Carbon Vane 1 Combustion Case 1 Compressor Case 1 Compressor 1 Diffuser Assembly 1 Drive Splice 1 Engine 2 Fuel Bypass 1 Fuel Control 2 Fuel Nozzle 6 Gear Shaft 1 Governor 5 P3 Line 1 PC Air Filter 1 Pc Air Tube 1 Rotor Assembly 1 Spline Shaft 1 Throttle Bell Crank Support 1 Tube Assembly 2 Turbine Assembly 1 The engine was shipped to Rolls-Royce Allison for an engine run. Prior to the engine run, a 45-psi pneumatic air source was used to perform a pneumatic leak test. An additional vacuum check was performed, which exhibited a 6.5 inch Hg of differential pressure loss within 2 minutes. The fuel inlet fitting was then tightened, and the vacuum check repeated; a 0.5 inch Hg loss in 2 minutes was noted. The chip detectors were removed and did not exhibit contaminants. The fuel nozzle's inlet screen was intact and not collapsed and did not contain contaminants. The engine was placed on a test stand and run for 1 hour and 24 minutes through a series of accelerations, decelerations and static test points that were recorded and included in this report as the "Allison Engine Company Data Reduction Report". The mechanical driven fuel pump was tested under the supervision of the FAA at Argo-Corporation. Test results were within the certification standards of the pump. The test was then followed by a disassembly examination, which revealed no anomalies. The power turbine governor alters the fuel schedule determined by the gas producer fuel control to maintain desired power turbine speed under load conditions. The gas producer fuel control is a hydromechanical unit that schedules fuel flow delivered to the engine during starting and load conditions. The fuel control and governor were also removed and subsequently tested under the supervision of the NTSB at Honeywell. During testing of the governor a leak test was performed and at 25 psi a leak at the compressor discharge pressure (Pc) inlet fitting was noted. The tests results were within the manufacturers service limits. Both units were then disassembled and inspected; no mechanical anomalies were noted. The compressor bleed air valve, serial number FF32011, was removed from the engine and tested at Rolls-Royce Allinson. The test indicated that the bleed air valve did not meet the manufacturer's new production specifications but met in service production specifications. The fuel vapor riser lab was examined at the NTSB's Material Laboratory. The Material's Laboratory factual report stated that, "...The valve repeatedly opened when the pressure was reduce to a little below 0.5 inch WC (WC referred to water column height of a water manometer to measure line pressure). With no pressure applied the valve was heard to open between 20 and 25 degrees from the vertical position in all four axes". According to the Rotorcraft Flying Handbook, "A height/velocity diagram, published by the manufacturer for each model of helicopter, depicts the critical combinations of airspeed and altitude should and engine failure occur. Operating at the altitudes and airspeeds shown within the crosshatched or shaded areas of the H/V diagram may not allow enough time for the critical transition from powered flight to autorotation". The height/velocity diagram for the MD369D shows that at a height of 100 feet and an indicated airspeed of 0 knots, the phase of flight would be in the crosshatched area. ADDITIONAL INFORMATION Following the accident Haverfield has placed into effect a standard operating policy of operating the helicopter's start pump continuously on Hughes 500 helicopters. The FAA, Haverfield Incorporated, Boeing, Honeywell, Rolls-Royce Allison, Argo-Tech, and Standard Aero were parties to the investigation. The wreckage and all component parts were released to the operator.
the loss of engine power for undetermined reasons. A factor was the operation within the cross "hatched area" of the helicopter's height/velocity curve by the company.
Source: NTSB Aviation Accident Database
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