Thursday, December 28, 2017

Bell 47 G2, N975BH, privately registered and operated by the Experimental Aircraft Association (EAA): Accident occurred July 30, 2016 at Wittman Regional Airport (KOSH), Oshkosh, Winnebago County, Wisconsin

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entity:
Federal Aviation Administration / Flight Standards District Office; Milwaukee, Wisconsin

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Location: Oshkosh, WI
Accident Number: CEN16LA294
Date & Time: 07/30/2016, 1505 CDT
Registration: N975BH
Aircraft: BELL 47G 2
Aircraft Damage: Substantial
Defining Event: Powerplant sys/comp malf/fail
Injuries: 3 None
Flight Conducted Under: Part 91: General Aviation - Business - Sightseeing 

On July 30, 2016, about 1500 central daylight time (CDT), a Bell 47 G2, N975BH, experienced a loss of engine power control during descent into Whittman Regional Airport (KOSH), Oshkosh, Wisconsin. The helicopter sustained substantial damage to the main rotor blades and tail. The airline transport-rated pilot and two passengers on-board were not injured. The helicopter was privately registered and operated by the Experimental Aircraft Association (EAA) under the provisions of 14 Code of Federal Regulations Part 136 as a commercial air tour flight. Visual meteorological conditions prevailed for the flight, and no flight plan was filed. The local flight originated at Pioneer Airport (WS17), Oshkosh, Wisconsin.

The pilot explained that tour flights departed from Pioneer Airport (WS17), part of the Oshkosh Airport Complex, and flew over the EAA AirVenture Fly-In grounds then returned to the airport. Upon return to the airport, the pilot entered the downwind leg of the pattern and attempted to reduce power for landing. The power would only decrease to 3100rpm. The throttle was moved 'full travel' with no power change. The pilot explained that he wanted to maintain the collective to avoid over speeding the engine, but was unable to slow or descend. He switched to the right magneto and applied full carburetor heat to reduce the engine power; however, the power did not reduce enough to descend. After flying the traffic pattern "several times" attempting to descend, the pilot described putting the helicopter into a slip with the right pedal. He stated it was the only way to descend because when the pedals were in a neutral position the helicopter would climb with the engine still producing full power. He circled at the end of runway 9 to descend in altitude, getting to approximately 100 feet agl before shutting off the ignition and conducting a low altitude auto rotation. The helicopter impacted the ground "hard" on the back side of the skids, the main rotor blade struck the tail and the tail rotor assembly separated from the tail boom. The helicopter skidded to the left side of the runway and came to rest in the grass.

The pilot stated there were no indications of a flight control problem in prior flights the day of the accident, or during the accident flight until returning to the airport at the completion of the tour.

The pilot indicated a complete overhaul of the helicopter was completed 37.6 hours before the accident flight. An on-scene inspection of the helicopter by the FAA and NTSB personnel revealed the throttle linkage nut had loosened and separated from its fitting, this separation would result in complete loss of throttle control. The maintenance manual for the Bell 47 G-2 did not specify a torque value for this nut given there were no maintenance procedures requiring the nut to be loosened or removed. 

Pilot Information

Certificate: Airline Transport; Commercial; Flight Engineer
Age: 56, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land; Single-engine Sea
Seat Occupied: Left
Other Aircraft Rating(s): Helicopter
Restraint Used: 4-point
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed:
Medical Certification: Class 1 With Waivers/Limitations
Last FAA Medical Exam: 07/05/2016
Occupational Pilot: Yes
Last Flight Review or Equivalent: 07/18/2016
Flight Time:   25000 hours (Total, all aircraft), 970 hours (Total, this make and model), 11000 hours (Pilot In Command, all aircraft), 32 hours (Last 90 days, all aircraft), 27 hours (Last 30 days, all aircraft), 5 hours (Last 24 hours, all aircraft) 

Aircraft and Owner/Operator Information

Aircraft Manufacturer: BELL
Registration: N975BH
Model/Series: 47G 2
Aircraft Category: Helicopter
Year of Manufacture: 1959
Amateur Built: No
Airworthiness Certificate: Normal
Serial Number: 2242
Landing Gear Type: Skid;
Seats: 3
Date/Type of Last Inspection: 06/23/2015, Annual
Certified Max Gross Wt.: 2450 lbs
Time Since Last Inspection:
Engines: 1 Reciprocating
Airframe Total Time: 6866.1 Hours as of last inspection
Engine Manufacturer: Lycoming
ELT: Not installed
Engine Model/Series: VO-435
Registered Owner: MATTHEW L ANDERSON
Rated Power: 260 hp
Operator: Experimental Aircraft Association
Operating Certificate(s) Held:  Commercial Air Tour (136) 

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: KOSH, 782 ft msl
Observation Time:  CDT
Distance from Accident Site: 0 Nautical Miles
Direction from Accident Site: 165°
Lowest Cloud Condition:
Temperature/Dew Point:
Lowest Ceiling: 
Wind Speed/Gusts, Direction:
Visibility (RVR):
Altimeter Setting:
Visibility (RVV):
Precipitation and Obscuration:
Departure Point: Oshkosh, WI (OSH)
Type of Flight Plan Filed: None
Destination: Oshkosh, WI (OSH)
Type of Clearance: VFR
Departure Time: CDT
Type of Airspace: Class D 

Airport Information

Runway Surface Type: Concrete
Airport Elevation: 808 ft
Runway Surface Condition: Dry
Runway Used: 09
IFR Approach: None
Runway Length/Width: 6179 ft / 150 ft
VFR Approach/Landing: Forced Landing; Straight-in; Traffic Pattern 

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: 2 None
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 3 None
Latitude, Longitude: 43.991389, -88.559722 (est)

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