Patterson, LA, USA
N370RL
Bell 206L-1
Approximately 5 minutes after departing on a Title 14, CFR Part 135 air taxi cross-country flight, the helicopter had a loss of engine power while in cruise flight. The commercial helicopter pilot subsequently made a hard forced landing at an off-airport site comprised of tall vegetation and soft terrain. The helicopter came to rest in an upright position, and the two rear seat passengers were able to egress unassisted. Moments later, the helicopter was engulfed in flames. The wreckage path was oriented on a magnetic heading of 225 degrees, and the wind was reported as from 020 degrees at 12 knots. An examination of the engine at the accident site revealed that the fuel line to fuel nozzle "B" nut could be turned by hand, and did not contain a lock wire as required. All other fittings and nuts on the engine were found to be secure. A review of the helicopter's maintenance records revealed that a 50-hour fuel nozzle inspection was performed the evening prior to the accident flight. This inspection required the removal, disassembly, cleaning, inspection, reassembly, and reinstallation of the fuel nozzle. An interview with maintenance personnel revealed that fuel nozzle installation procedures found in the engine manufacturer's maintenance manual had not been followed. A tear down examination of the engine was performed. The engine examination revealed no preimpact anomalies. Investigators conducted operational tests on an engine of the same make and model. The tests were performed in an effort to determine what effect a loose fuel nozzle "B" nut would have on the engine's operation. The test revealed that the engine would experience a substantial loss of power that could conclude in a flame out. Testing further revealed that conditions would have been conducive for an in-flight fire. Investigators could not determine if the fire originated in-flight, or during the ground impact.
HISTORY OF FLIGHT On March 14, 2006, about 0740 central standard time, a single-engine Bell 206L-1 helicopter, N370RL, was destroyed when it impacted terrain following a loss of engine power while in cruise flight near Patterson, Louisiana. The commercial pilot and one passenger were fatally injured and the two remaining passengers sustained minor injuries. The helicopter was registered to and operated by Rotorcraft Leasing Company (RLC), LLC, of Broussard, Louisiana. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 135 on-demand passenger flight. The 75-nautical mile cross-country flight originated from the Harry P Williams Memorial Airport (PTN) near Patterson, Louisiana, at 0735 and was destined for offshore platform Ship Shoal 216, located in the Gulf of Mexico. According to a passenger who had been seated in the left rear seat of the helicopter, the pilot performed a preflight engine check before takeoff. The passenger stated that the takeoff appeared normal and they departed south from the airport at an approximate altitude of 500-700 feet above ground level (agl). The passenger reported that as they began their flight to the south, the helicopter "dropped" several times. Each time the helicopter regained the lost altitude; however, it appeared to do so slowly as if "he, [the pilot], didn't have the power to keep it up." Moments later while over a wooded area, the front seat passenger looked back and said, "brace yourself." The pilot then made a descending right turn, of approximately 90 degrees, towards an open field. As they approached the ground, the pilot brought the nose of the helicopter up as if he was attempting to "slow down." The helicopter impacted the ground on the front left side and came to an abrupt stop in an upright position. The passenger further reported that he unbuckled his lap belt and exited the left aft door of the helicopter into vegetation that was 7-8 feet tall. Once out of the helicopter he observed a small fire by the baggage compartment. A brief time later the helicopter was fully engulfed in flames. The passenger further reported that before ground impact "everything sounded normal and he didn't smell anything unusual." The second surviving passenger was not available for an interview and did not provide a statement to the NTSB investigator-in-charge (IIC). PILOT INFORMATION The pilot held a commercial pilot certificate with ratings for airplane single-engine land, helicopter, instrument airplane, and instrument helicopter ratings. His last Federal Aviation Administration (FAA) second-class medical was issued on September 19, 2005, with the limitation of "MUST HAVE AVAILABLE GLASSES FOR NEAR VISION." The operator submitted a Pilot/Operator Aircraft Accident Report (NTSB Form 6120.1/2). This report indicated the pilot had accumulated a total flight time of 12,545 hours. The pilot accumulated 213 hours in the last 90 days, and 91 hours in the last 30 days. He had 11,070 hours in this make and model of helicopter. His last recorded flight review was completed February 11, 2006. AIRCRAFT INFORMATION The 1980-model Bell 206L-1, serial number 45370, was powered by a 650-shaft horsepower Rolls-Royce Allison 250-C30P turbo shaft engine, serial number CAE 860171, driving a two-bladed main rotor system and a two-bladed tail rotor. There was no flight data recorder, cockpit voice recorder, or fire detection system installed on the helicopter, nor was there a requirement for them. The helicopter was maintained in accordance with Aircraft Type Certificate Data Sheet number H2SW and the appropriate Bell model Maintenance Manual. The Bell model 206 series of RLC's Approved Aircraft Inspection Program (AAIP) requirements were: 1. 200-hour tail rotor gearbox and transmission oil change. 2. 600-hour hydraulic and facet filter bypass. 3. 7-day airframe inspection. 4. 3-month emergency equipment inspection. 5. 6-month float inspection. 6. 12-month main rotor mast internal inspection. 7. 24-month flight control bolt inspection. In addition, the following airframe inspections were to be accomplished on RLC's Bell 206L-1: 1. Daily preflight inspection. 2. 100-hour airframe inspection. 3. 300-hour airframe inspection. 4. 1200-hour airframe inspection. The AAIP further required that the Allison Model 250-C30P engine be maintained in accordance with Engine Type Certificate Data Sheet number E1GL, and engine life-limited parts be replaced in accordance with Allison Operation and Maintenance Manual 16W2. Engines parts that require overhaul were to be overhauled in accordance with Allison Overhaul Manual 14W3. The engine inspections consisted of the following: 1. 50-hour fuel nozzle inspection 2. 150-hour engine inspection 3. 300-hour engine inspection 4. 300-hour engine oil change. The maintenance records for N370RL were reviewed by the accident investigation team. No anomalies or unusual events were noted, and no open discrepancies or deferred items were listed in maintenance records at the time of the accident. From maintenance records, the airframe was estimated to have accumulated a total of 10,622 hours at the time of the accident, and the engine had accumulated a total of 20,614 hours. The weight and balance was computed for the NTSB's investigator-in-charge (IIC), with estimated weight for crew, cargo, and fuel for determining center of gravity (CG). The result of the computation was that the aft, forward, and lateral CG ranges were within the limits. Fueling records at Harry P Williams Memorial Airport established that the helicopter was last fueled on March 14, 2006, with the addition of 25 gallons of Jet A aviation fuel. A fuel sample was taken from the helicopter before the accident flight. Investigators found the fuel to be clear and bright with no anomalies noted. The fuel tested negative for water. METEOROLOGICAL INFORMATION At 0755, the weather observation facility at PTN, reported wind from 020 degrees at 12 knots, visibility 10 statute miles, clear of clouds, temperature 61 degrees Fahrenheit, dew point 37 degrees Fahrenheit, and a barometric pressure of 30.16 inches of Mercury. COMMUNICATIONS There were no reported radio communications from the pilot after he departed PTN. WRECKAGE AND IMPACT INFORMATION On site documentation of the wreckage was conducted by investigators from the National Transportation Safety Board, Federal Aviation Administration, Bell Helicopter, Rolls Royce, and Rotorcraft Leasing Company. The wreckage was located in a soft field of tall "Roosevelt Cane", approximately three miles south of PTN. The Global Positioning System (GPS) coordinates recorded at the accident site were 29 degrees 39.625 minutes north latitude and 091 degrees 19.473 minutes west longitude, at a field elevation of approximately -12 feet mean sea level (msl). All major components were accounted for at the accident site. The wreckage path was about 125 feet long, approximately 20 feet wide, and oriented along a measured heading of 225 degrees. The first point of ground impact was about 150 feet west of a line of deciduous trees. About five feet beyond the first impact scar was a six inch deep ground imprint, which resembled the shape of the helicopter's lower fuselage. Within this imprint were stubs of cane that were pushed over in the westerly direction. The partially burned remains of a landing gear cross tube and the right skid tube were found in this area. The tail rotor blades, tail rotor gear box, tail cone, vertical stabilizer and various small pieces were found along the wreckage path in the area between the first ground impact and the main wreckage. The main wreckage, consisting of the fuselage, engine, main rotor head, mast, transmission pylon, and the surviving sections of the main rotor blades, came to rest about 80 feet beyond the first point of ground contact. The main wreckage, which had been nearly consumed by the post impact fire, was found oriented on a heading of 310 degrees. The main rotor (M/R) head was found attached to the mast and sections of both main rotor blades were found attached to the M/R head. The horizontal stabilizer came to rest about 45 feet west, and sections of the tail rotor drive train and aft tail boom were located approximately 90 feet north, from the main wreckage. Due to the extent of thermal damage to the helicopter, flight control continuity could not be established. The engine exhibited thermal damage. An examination of the engine at the accident site revealed that the fuel line to the fuel nozzle "B" nut could be turned by hand and did not contain a lockwire. All other fittings and nuts on the engine were found to be secure. An off site tear down examination of the engine was performed. The detailed engine tear down examination revealed rotational scoring on the compressor shroud and correlating rub on the compressor impeller. All four turbine wheels were found complete and could be rotated by hand. All bearings were found to be complete and each engine shaft to spline adapter was found connected. The engine's accessory gearbox case, fuel pump, fuel control unit, and the power turbine governor were consumed by the post impact fire. All gears from the accessory gearbox were found complete. The engine examination did not reveal any pre impact anomalies. A review of the helicopters maintenance records revealed that a 50-hour fuel nozzle inspection was performed the evening prior to the accident flight. This inspection required the removal, disassembly, cleaning, inspection, reassembly, and reinstallation of the fuel nozzle. The 50-hour fuel nozzle inspection was performed by a certificated airframe and powerplant (A&P) mechanic. Once completed, the fuel nozzle installation was inspected by an inspector and the appropriate logbook entries were made. Training records for the mechanic and inspector were reviewed, and no discrepancies were noted. A representative from the Safety Board conducted separate telephone interviews with the mechanic who performed the 50-hour fuel nozzle inspection and the inspector. The mechanic stated that following the fuel nozzle inspection, he reinstalled the fuel nozzle into the engine combustion chamber, torque it with a special tool, and lockwired it. He then attached the fuel nozzle hose and tightened it with a 9/16 inch wrench. He then asked an inspector to inspect the installation. The mechanic further stated that an engine run-up was not performed upon the completion of the inspection. The inspector stated that he performed a visual inspection of the fuel nozzle installation. During the inspection the inspector asked the mechanic "did you tighten the line?" to which the mechanic responded in the affirmative. According to Rolls-Royce 250-C30 Series Operation and Maintenance Manual, dated December 15, 1997, section 73-10-03, PARA 1.B, (4), (5), the following procedure should be followed once the fuel nozzle has been installed: "(4) Connect the fuel nozzle hose. Tighten hose coupling to 80-120 lb in. (9.0-13.6 N.m). Secure with lockwire. NOTE: Early production fuel nozzle hoses do not incorporate means to accommodate installation of lockwire. These early hoses do not require lockwire. [The fuel nozzle hose installed on N370RL did incorporate a means to lockwire.] (5) Check run the engine after fuel nozzle replacement." Additionally, the following warning was given: "WARNING: FAILURE TO PROPERLY INSTALL, ALIGN, AND TORQUE FUEL, OIL, AND AIR FITTINGS AND TUBES COULD RESULT IN AN ENGINE FAILURE." MEDICAL AND PATHOLOGICAL INFORMATION The Jefferson Parish Forensic Center, located in Harvey, Louisiana, performed an autopsy on the pilot on March 15, 2006. The FAA, Toxicology Accident Research Laboratory, located in Oklahoma City, Oklahoma, conducted toxicological testing on the pilot. The results of analysis of the specimens were negative for carbon monoxide, cyanide, volatiles, and tested drugs. TESTS AND RESEARCH On December 12, 2006, at the facilities of Rolls Royce, the NTSB IIC with representatives from Rolls Royce and Bell Helicopter conducted tests on a new 250-C30P turbo shaft engine. The tests were performed in an effort to determine what effect a loose fuel nozzle "B" nut would have on the engine's operation. Initial testing was performed by placing a "T" fitting and ball valve in the fuel supply line upstream of the fuel line to fuel nozzle "B" nut. The ball valve allowed a controlled test to simulate a leak at the fuel nozzle "B" nut. The engine was then started and allowed to stabilize at idle. When the ball valve was opened to simulate a small leak at the "B" nut, the engine immediately flamed out. Investigators then removed the "T" fitting and ball valve and connected the fuel line in a typical installation configuration. The engine was started, and while at idle, the fuel nozzle "B" nut was loosened to simulate how the fuel nozzle "B" nut was found at the accident site. The engine continued to run; however, fuel began to leak out at a steady drip. As the engine power was increased, the fuel began to run and then spray in a steady stream aft of the engine to a distance of approximately seven feet. The fuel flow and N1 (gas producer) rpm from this test were compared to values obtained from an engine run without a fuel leak. The comparison revealed that as a result of the fuel leak, a fuel flow of 35 pph greater then the allowable limit for the Bell 206 produced a N1 rpm that was 3,200 less then what the engine would produce at takeoff power. The test further revealed that conditions would have been conducive for an inflight fire. ADDITIONAL INFORMATION The wreckage of the helicopter was released on March 17, 2006, and the engine was released on July 15, 2006, to a representative of the operator.
The improper installation of an engine fuel line fitting by other maintenance personnel, which resulted in a loose fitting and a loss of engine power during cruise flight. Factors associated with the accident are a tailwind, and the lack of a suitable site for a forced landing.
Source: NTSB Aviation Accident Database
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