Thursday, March 26, 2020

Part(s) Separation from Rotorcraft: Bell 47G-2, N96195; fatal accident occurred July 06, 2018 in Arlington, Rush County, Indiana

Kerry D. Lee
May 8th, 1966 - July 6th, 2018

Main Wreckage

Main Wreckage - Aft Fuselage and Engine

Main Wreckage - Cabin


Instrument Panel

Tail Boom

Tail Rotor

Lower Transmission

Main Rotor and Upper Transmission

Main Rotor Blades

Upper Transmission

Overall views of the main rotor transmission assembly components as-received.

Overall view of main rotor housing assembly attachment bolts, washer (on bolt 4), and nut received separately.

Close views of attachment bolt 2 threads after cleaning and degreasing. 

Close views of attachment bolt 3 threads after cleaning and degreasing.

Close views of attachment bolt 4 threads after cleaning and degreasing.

Close views of attachment bolt 5 threads after cleaning and degreasing. Unlabeled arrows point to circumferential sliding contact marks on pressure flanks of the threads.

Thread profile measurements on intact threads on bolt 2.

Thread profile measurements on intact threads on bolt 3.

Thread profile measurements on intact threads on bolt 4.

Thread profile measurements on intact threads on bolt 5.

Trimble Trim Flight 3 S/N: 4618B07595. 

Lowrance AIRMAP 2000C S/N: 101979244.

Five flight paths from July 6, 2018 on the Trimble Trim Flight 3.

One flight path from July 4, 2018 on the Trimble Trim Flight 3. 

Three flight tracks recorded on Lowrance Airmap 2000c. The dark purple track in the bottom right corner is the accident flight. No times or altitudes are associated with the latitude-longitude tracks.

Accident flight from Lowrance Airmap 2000c data. First (Data Point-0) and last (Data Point-399) data points are shown.

The National Transportation Safety Board traveled to the scene of this accident.

Additional Participating Entities: 

Federal Aviation Administration / Flight Standards District Office; Indianapolis, Indianapolis, Indiana
Lycoming Engines; Williamsport, Pennsylvania

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Location: Arlington, IN
Accident Number: CEN18FA258
Date & Time: 07/06/2018, 1720 EDT
Registration: N96195
Aircraft: Bell 47G
Aircraft Damage: Substantial
Defining Event: Part(s) separation from AC
Injuries: 1 Fatal
Flight Conducted Under: Part 137: Agricultural 

On July 6, 2018, about 1720 eastern daylight time, a Bell 47G-2 helicopter, N96195, was substantially damaged when it impacted a corn field near Arlington, Indiana. A postimpact fire ensued. The commercial pilot was fatally injured. The helicopter was owned and operated by Central Indiana Ag Services, LLC as a Title 14 Code of Federal Regulations Part 137 aerial application flight. Visual meteorological conditions prevailed and no Federal Aviation Administration (FAA) flight plan had been filed for the flight. The local flight departed about 1655 from a loading platform at a farm located 1 mile northwest of the accident location.

According to the co-owner of the helicopter, the pilot had been flying since 0945 that morning and had completed between 10 and 15 spray runs. The pilot was applying a fungicide to corn crops and each run was averaging 20 minutes. When the pilot did not return after 30 minutes, they initiated search operations. The wreckage was located later that evening.

Figure 1 shows the flight track for the accident flight based on GPS latitude and longitude data recovered from a Lowrance AIRMAP 2000c device installed on the helicopter. The device contained data from three flight tracks; one of which was the accident flight. The data did not contain altitude or time data, so the time lengths of the track are not known. The last data point of the final flight recorded was consistent with the wreckage location.

There were no witnesses to the accident.

Figure 1. Accident Flight Track from Lowrance Airmap

Pilot Information

Certificate: Commercial
Age: 52, Male
Airplane Rating(s): Single-engine Land
Seat Occupied: Single
Other Aircraft Rating(s): Helicopter
Restraint Used:
Instrument Rating(s): None
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: Yes
Medical Certification: Class 2 With Waivers/Limitations
Last FAA Medical Exam: 04/24/2018
Occupational Pilot: Yes
Last Flight Review or Equivalent: 02/26/2018
Flight Time:  1865 hours (Total, all aircraft), 27 hours (Total, this make and model) 

Aircraft and Owner/Operator Information

Aircraft Make: Bell 
Registration: N96195
Model/Series: 47G 2
Aircraft Category: Helicopter
Year of Manufacture: 1953
Amateur Built:No 
Airworthiness Certificate: Restricted
Serial Number: 681
Landing Gear Type: Skid
Seats: 1
Date/Type of Last Inspection: 02/15/2018, Annual
Certified Max Gross Wt.:
Time Since Last Inspection: 27 Hours
Engines: 1 Reciprocating
Airframe Total Time: 13948.8 Hours at time of accident
Engine Manufacturer: Lycoming Engines
Engine Model/Series: VO-435-A1F
Registered Owner: Central Indiana AG Services, LLC
Rated Power: 250 hp
Operator: Central Indiana AG Services, LLC
Operating Certificate(s) Held: None

Limited maintenance records were provided to FAA inspectors and subsequently, National Transportation Safety Board (NTSB) investigators. A review of the available maintenance records indicated that an annual inspection had been completed on February 15, 2018, at an airframe total time of 13,922 hours. The Hobbs Meter on scene read 323.8. The helicopter flew approximately 26.8 hours between the last inspection and the accident and had a total airframe time of 13,948.8 hours.

On July 9, 2009, the main rotor transmission was replaced with another transmission. A maintenance release card for the main rotor transmission, dated June 24, 2009, revealed that the fan drive quill and the clutch assembly were repaired with serviceable parts in accordance with Bell 47G-2 maintenance procedures. The transmission was tested and reinstalled "in accordance with the manufacturers publications and FAR part 43." The work orders associated with this replacement confirmed this information.

The maintenance records contained only two entries indicating routine annual/100-hour inspections between July 2009 and January 2014. A maintenance log entry dated November 1, 2014, stated in part "retorqued transmission T adapter plat bolts." This maintenance was performed during a 100-hour inspection at an airframe total time of 13,875.2 hours. The mechanic that performed this work was no longer available to speak to investigators. No other entries in the available maintenance records noted work on the main rotor transmission.

According to the co-owner of the helicopter, on the day before the accident, he and the pilot performed general maintenance on the helicopter. The co-owner's description of the maintenance performed did not include any reference to work on the main rotor transmission.

According to the Illustrated Parts Breakdown (IPB) document for the Bell 47G-2 helicopter as provided by a representative of Scott's Bell, Inc., the attachment bolts holding pieces of the main rotor transmission housing together consist of 6 AN5-37A bolts, 1 AN5-41A bolt, and 1 AN5-44A bolt. The AN5-41A and AN5-44A bolts are located next to each other. Each of the bolts in the IPB has a NAS679A5 nut. The 6 AN5-37A bolts are each installed with 1 AN960-516 washer under the head and 1 AN960-516L washer under the nut. The AN5-41A and AN5-44A bolts are each installed with 1 AN960-516 washer under the head and another AN960-516 washer under the nut.

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KGEZ, 802 ft msl
Distance from Accident Site: 8 Nautical Miles
Observation Time: 2153 UTC
Direction from Accident Site: 250°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling:None 
Visibility (RVR):
Wind Speed/Gusts: 8 knots /
Turbulence Type Forecast/Actual: None / None
Wind Direction: 40°
Turbulence Severity Forecast/Actual: N/A / N/A
Altimeter Setting: 30.24 inches Hg
Temperature/Dew Point: 28°C / 15°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Arlington, IN
Type of Flight Plan Filed: None
Destination: Arlington, IN
Type of Clearance: None
Departure Time: 1655 EDT
Type of Airspace: Class G 

Wreckage and Impact Information

Crew Injuries: 1 Fatal
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None 
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 Fatal
Latitude, Longitude: 39.633056, -85.635833 

The wreckage was located at the south end of a corn field at an elevation of 850 ft. The initial impact point was characterized by damage to the crop, just north of the edge of the field. The initial damage swath/scar was 20 ft long and 6 ft at its widest point. The helicopter impacted on an approximate bearing of 002° and the wreckage came to rest inverted about 20 ft from the initial impact point.

The main wreckage of the helicopter included the fuselage, landing skids, engine and lower transmission assembly, tail rotor, and tail boom. A postimpact fire damaged the left side of the fuselage and engine.

The upper portion of the helicopter, to include both main rotor blades, the mast, collective and cyclic controls, swash plate, and upper portion of the transmission were located about 75 ft north of the main wreckage. The components remained together as an assembly.

The lower portion of the transmission assembly remained attached to the engine. The internal gears of the transmission rotated freely when actuated at the engine and the tail rotor spline. A large scar/witness mark was observed on the inside well of the transmission. The mounting holes on the lower housing of the transmission were labeled Nos. 1 through 8 for identification purposes (Figure 2). The Nos. 1 and 7 holes were torn and partially separated. The Nos. 2 and 3 holes were unremarkable. The Nos. 4 and 5 holes were elongated. The Nos. 6 and 8 holes were elongated, and the hole material exhibited tearing on the outer edge. No fasteners remained in any of the holes.

Figure 2. Lower Transmission With Labels 1 through 8

The upper portion of the transmission assembly remained attached to the main rotor assembly. The attachment locations where the upper portion separated from the lower portion were labeled Nos. 1 through 8 for identification purposes and corresponded with the lower portion of the transmission. Bolt Nos. 1 and 7 remained inserted and both the metal from the adjacent mounting surface and the nut remained attached. Bolts Nos. 2 and 3 remained inserted and neither bolt remained attached to a nut. Bolts Nos. 4, 5, and 6 remained partially inserted and neither bolt remained attached to a nut. Bolt No. 8 remained inserted and was bent at the thread end and no nut was attached.

The upper portion of the main rotor transmission assembly and the eight attachment bolts were sent to the NTSB Materials Laboratory in Washington, DC, for further examination.

A washer was observed under the head of each of the attachment bolts Nos. 1, 2, 7, and 8. A washer was also included with attachment bolt No. 4, but not with bolt Nos. 3 and 5. Bolts Nos. 1 and 7 had nuts remaining in place on the threaded end of the bolt, and 2 washers were observed under the nut on each bolt. The thickness of all remaining washers except for the one under the head of attachment bolt No. 7 was approximately 0.060 inch, consistent with an AN960-516 washer. The washer under the head of attachment bolt No. 7 was about one-half the thickness of the other washers, consistent with an AN960-516L washer.

On the lower surface of the freewheeling gear where it mated to the lower transmission housing, areas of slight fretting damage and material transfer were observed near attachment bolt holes Nos. 3 through 8. The lower edge of attachment bolt hole No. 5 was deformed inward consistent with contact with the attachment bolt grip.

The attachment bolts had varying numbers of intact and sheared threads. On bolts Nos. 1 and 7, all threads were intact. Bolts Nos. 2 through 6 and 8 had between one and five intact threads adjacent to the bolt grip, but the thread peaks were at least partially flattened and smeared, consistent with contact with the corresponding lower housing attachment hole bore. The remainder of the threads in bolts Nos. 2 through 6 and 8 were fractured near the thread roots, and the fracture surfaces were smeared, consistent with shear fracture from contact with the corresponding threads of the nut. Sheared bolt threads remained trapped within the separated nut.

Closer views of the threaded ends of bolts Nos. 2 and 3 illustrated intact but damaged threads between the shank and the completely sheared threads. The pressure flanks of some of the mostly intact threads were deformed and missing with a profile shape corresponding to the nut thread peak profile. Circumferential sliding contact marks were observed in the contact surfaces of the damaged pressure flanks where the deformed and missing bolt thread was observed.

The pressure flanks on several intact threads on bolt No. 5 had circumferential contact marks but appeared without substantial deformation or missing material. The pressure flanks of the intact threads on bolt No. 4 had no circumferential contact marks or circumferential contact damage.

Dimensional measurements on the intact portions of threads for attachment bolts Nos. 2 through 5 found that the major diameters of threads in bolts Nos. 2, 3, and 5 were less than the minimum specified diameter for a new bolt and the major diameter of the threads for bolt No. 4 was close to the lower limit.

Bolts Nos. 3 through 5 had thread profile measurements that were generally comparable to the thread specification. Measured values for bolt No. 2 showed larger deviations from the specified thread profile. The average flank angle for bolt No. 2 was about 11° less than the specified angle of 60° and the average thread depth for bolt No. 2 was 0.0055 inch less than the specified value of 0.02481 inch. The average width of the thread peaks in bolt No. 2 was about double the maximum thread peak width calculated from the thread form at the minimum major diameter of 0.3053 inch. The thread peaks for bolt No. 2 had a gold hue consistent with the original plating, indicating variations in thread depth and peak width were not due to wear or damage to the thread peak. 

Medical And Pathological Information

The Central Indiana Forensic Associates, LLC, performed the autopsy on the pilot on December 12, 2008, as requested by the Shelby County Coroner's Office. The cause of death was "positional asphyxia and left-sided rib fractures" and the manner of death was ruled an accident.

The FAA Forensic Sciences Laboratory, Oklahoma City, Oklahoma, performed toxicological tests on specimens that were collected during the autopsy. Results were negative for all tests conducted. 

Tests And Research

A performance study was conducted by the NTSB Office of Research and Engineering using the data recovered from the two onboard recording devices to understand the pilot's flying technique on previous flights. During the five flights, the helicopter stayed between 100 and 150 ft above ground level and the groundspeeds varied between 40 and 60 knots. The calculated load factors for these flights varied from about 1.20 g's to 1.45 g's, which were within the normal flight load factors of between 2 and 2.5 g's for most helicopters.

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