Chatham, NJ, USA
N44EK
ROBINSON HELICOPTER R44
The private pilot was on the second leg of a cross-country flight in the helicopter. After about 45 minutes and while in cruise flight at 1,800 ft mean sea level, the engine lost total power; the low rpm warning sounded, and the pilot initiated an autorotation in the congested area during nighttime conditions. During the autorotation, the helicopter struck a building, which resulted in substantial damage to the fuselage. Postaccident examination of the engine revealed that the crankshaft gear bolt was about 3/16 inch from the seated position. The safety lockplate washer was worn, the back of the bolt head displayed rotational scoring, the bottom threads of the bolt were damaged, and the alignment dowel had sheared. The engine had accumulated 5.9 hours total time since undergoing major overhaul about 1 year before the accident. It is likely that, when the engine was overhauled, the crankshaft gear bolt was not properly seated against the gear, which resulted in the crankshaft gear disengaging from the accessory gears and a subsequent total loss of engine power.
On February 24, 2017, at 1823 eastern standard time, a Robinson R-44 helicopter, N44EK, collided with buildings and terrain after performing a forced autorotation landing near Chatham, New Jersey. The private pilot received minor injuries and the passenger was seriously injured. The helicopter was registered to N44EK Inc. and operated under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Night visual flight rules conditions prevailed near the accident site at the time of the accident and no flight plan was filed for the flight that originated at Millville Municipal Airport (MIV), Millville, New Jersey, about 1745. The pilot and passenger departed in the afternoon on the day of the accident from Richmond Executive Airport-Chesterfield County (FCI), Richmond, Virginia, then flew to MIV where they requested a fuel "top-off." The pilot purchased 24.1 gallons of 100 low-lead aviation fuel about 1730, and then departed enroute to Lincoln Park Airport (N07), Lincoln Park, New Jersey, which was about 101 nautical miles away. The pilot reported that during cruise flight from MIV to N07, he was transitioning the area near Morristown Municipal Airport (MMU) Morristown, New Jersey about 1,800 mean sea level, when the engine stopped producing power. The low RPM warning horn sounded, and he lowered the collective and entered an autorotation. The area was congested, and it was during nighttime conditions. The pilot spotted a clear area between two long single-story buildings (garages) but struck one of the buildings during the forced landing and subsequently lost control. The passenger stated that immediately before the accident, he heard a "whoosh" followed by the engine losing power. The MMU airport tower controller was in communication with the pilot during the transition through the MMU airspace; according to the air traffic control transcripts, at 1819:24, the pilot reported, "two thousand three hundred, we're on the way down to eighteen hundred, four four echo kilo", which was acknowledged by the controller. At 1823:37 the pilot reported, "uh Morristown, helicopter four four echo kilo, we are going to make an autorotation, we don't know where we are." The pilot repeated "we're making an autorotation" several times, then reported "emergency going down." A witness in the nearby apartment building stated he heard the helicopter and described the "engine missing or sputtering." He heard it pass over the roof, then heard the collision. PERSONNEL INFORMATION According to Federal Aviation Administration (FAA) airman records, the pilot held a private pilot certificate with a rating for rotorcraft-helicopter. At the time of the accident, he had accumulated about 1,600 hours of flight experience, of which 1,100 hours were in the helicopter make and model. AIRCRAFT INFORMATION According to FAA and the helicopter's maintenance records, the helicopter received a standard airworthiness certificate in the normal category on December 7, 1999. It was a four place, two blade helicopter that was powered by a 225 HP, six cylinder, Lycoming O-540 series engine. The engine had accumulated 5.9 hours total time since undergoing major overhaul, that was completed on March 7, 2016. The airframe, with the newly overhauled engine installed, was overhauled and inspected on January 16, 2017, and had accrued about 2,000 total airframe hours at the time of overhaul. The helicopter was recently purchased on December 15, 2016. METEOROLOGICAL INFORMATION At 1845, the weather reported at MMU, located about 4 miles north northwest of the accident site, included wind from 180° at 7 knots, visibility 15 statute miles, few clouds at 6,000 ft, temperature 20° C, dew point 12° C, and an altimeter setting of 28.84 inches of mercury. WRECKAGE AND IMPACT INFORMATION The helicopter struck the roof of a single-story garage on the forward down slope of the roof and came to rest on an asphalt access road perpendicular to the garages. The tail rotor separated about 5 ft in from the tail rotor and the main rotor blades were bent down span wise. There were multiple buckles in the fuselage and the landing skids were flattened out to both sides of the fuselage. The fuel tanks remained intact, were capped and fuel was visible, about six inches below fuel filler neck. Fuel samples were taken; it was blue in color, with a fuel odor and no contaminants. All major components of the helicopter were accounted for at the scene and all components remained attached to the engine, gear box, rotor blade and tail rotor. The examination of the wreckage was conducted at a secured facility. The rocker box covers were removed, and no anomalies were noted. However, when the crankshaft was rotated, there was no movement noted on any of the rocker arms. Thumb compression and suction were observed on cylinder No. 5 when the crankshaft was rotated. However, no compression was observed on any other cylinders. The cylinders were examined using a lighted borescope and no anomalies were noted. The engine was removed from the helicopter to facilitate further examination. The accessory section of the engine was removed. The crankshaft gear bolt was about 3/16 inches from the seated position. The safety lockplate washer was present; however, the washer exhibited wear. Rotational scoring was noted on the crankshaft gear bolt head. The crankshaft gear bolt was removed, and the bottom threads of the bolt were damaged. The crankshaft gear was removed, and the alignment dowel was sheared. For more information about the engine examination, the report can be found in the public docket for this case. Figure 1: Left and right photographs of the crankshaft gear bolt.ADDITIONAL INFORMATION According to the Textron Lycoming Direct Drive Overhaul Manual, Section 7-65, Crankshaft Gear; "Assemble the gear to the crankshaft using both a new lockplate and bolt. Refer to Figure 7-12F. The correct bolt, lockplate and dowel for each gear are shown in Table 7-4. Tighten the bolt to 125 inch lbs. torque, then with a hammer and brass drift, tap lightly around the pilot flange of the gear and listen for sharp solid sounds from the hammer blows that would indicate that the gear is seated against the crankshaft. As a check on seating against the crankshaft, attempt to insert a pointed .001 inch thick feeler gage or shim stock between the gear and crankshaft at each of the three scallops. The .001 feeler gage, or any smaller feeler gage, must fit between the two surfaces at any location. (.001 feeler gage is used as an indicator, however there must be no clearance between crankshaft and gear.) Retighten the gear attaching bolt to the proper tor que. Tighten the 5/16 inch bolt to 204 inch-pound torque or the 1/2 inch bolt to 660 inch-pound torque. Measure the clearance between the O.D. of the gear flange and the pilot I.D. of the crankshaft. There should not be more than .0005 inch clearance at any point. Bend the lockplate against the bolt head." On January 23, 2003, Lycoming issued a mandatory service bulletin (SB475C) for crankshaft gear modification and assembly procedures which in part states; "Damage to the crankshaft gear and the counterbored recess in the rear of the crankshaft, as well as badly worn or broken gear alignment dowels are the result of improper assembly techniques or the reuse of worn or damaged parts during reassembly. Since a failure of the gear or the gear attaching parts would result in complete engine stoppage, the proper inspection and reassembly of these parts is very important." Step 6 of the procedures described the assembly of the gear to the crankshaft using a new lockplate and bolt; "Assemble the gear to the crankshaft using both a new lockplate and bolt. Refer to Figure 6. The correct bolt, lockplate and dowel for each gear are shown in Table 2. Tighten the bolt to 125 in.-lbs. torque, then with a hammer and brass drift, tap lightly around the pilot flange of the gear and listen for sharp solid sounds from the hammer blows that would indicate that the gear is seated against the crankshaft. As a check on the seating against the crankshaft, attempt to insert a pointed .001 inch thick feeler gage or shim stock between the gear and crankshaft at each of the three scallops. The .001 feeler gage, or any smaller feeler gage, must NOT fit between the two surfaces at any location. (.001 feeler gage is used as an indicator, however, there must be no clearance between crankshaft and gear.) Retighten the gear attaching bolt to the proper torque. Tighten the 5/16 inch bolt to 204 in.-lbs. torque or the 1 1/2 inch bolt to 660 in.-lbs. torque. Measure the clearance between the O.D. of the gear flange and the pilot I.D. of the crankshaft. There should not be more than .0005 inch clearance at any point." On September 12, 2016, Lycoming issued supplement No. 1 to the mandatory service bulletin that provided an alternate method of compliance to Service Bulletin No. 475C if the crankshaft gear is replaced rather than modified.
Maintenance personnel's improper installation and inspection of the crankshaft gear bolt during major overhaul, which resulted in the crankshaft gear disengaging from the accessory gears of the engine and a subsequent loss of power.
Source: NTSB Aviation Accident Database
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