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NTSB Final Report: Preston, Georgia

Location:

Preston, Georgia

Accident Number:

ERA20LA071

Date & Time:

January 8, 2020, 13:39 Local

Registration:

N6186U

Aircraft:

Hughes OH 6A

Aircraft Damage:

Substantial

Defining Event:

Loss of engine power (partial)

Injuries:

2 Minor

Flight Conducted Under: Public aircraft

Analysis

During the flight to observe feral swine invading farm fields, the pilot noted a loss of engine power and rotor rpm. He maneuvered the helicopter away from trees for an autorotation to an open, plowed cornfield. During the landing on rough terrain, the helicopter nosed forward and the main rotor blades contacted the ground, resulting in substantial damage to the helicopter.

A postaccident examination of the flight controls, drive train, fuel system, main rotor system, and tail rotor system did not reveal evidence of a preexisting mechanical malfunction or anomaly. The engine was removed and placed on a test stand; it ran normally for about 2 minutes before the run was concluded. A laboratory test of a fuel sample was unremarkable. The reason for the loss of engine power could not be determined.

Probable Cause and Findings

The National Transportation Safety Board determines the probable cause(s) of this accident to be: A partial loss of engine power for reasons that could not be determined based on the available information.

Findings

Not determined                            (general) - Unknown/Not determined

Factual Information

On January 8, 2020, about 1339 eastern standard time, a Hughes OH-6A, N6186U, was substantially damaged when it was involved in an accident near Preston, Georgia. The commercial pilot and one crewmember sustained minor injuries. The helicopter was registered to the U.S. Department of Agriculture and was operated as a public aerial observation flight.

The pilot reported that the purpose of the flight was to conduct aerial wildlife damage management operations. A feral swine was located and the pilot informed the ground crew via radio of its location. Shortly thereafter, the pilot noted a loss of engine power and rotor rpm. The pilot maneuvered the helicopter away from trees for an autorotation to an open, plowed cornfield. During the landing on rough terrain, the helicopter nosed forward and the main rotor blades contacted the ground. The engine appeared to be running at the time of impact.

A Federal Aviation Administration inspector responded to the accident site and examined the wreckage. The tail boom was separated from the helicopter and three of the four main rotor blades were separated from the hub. The fuselage sustained structural damage.

The operator reported that the N2 (power turbine) governor was changed before the flight due to a problem on a previous flight. The wreckage was retained for further examination, and examination of the flight control system, drive train, main rotor system, and tail rotor system did not reveal evidence of a preexisting mechanical malfunction or anomaly.

The engine was removed from the airframe and sent to a factory-authorized overhaul facility for further examination. Continuity was established for the N1 (gas producer turbine) and N2 rotors. The rotors moved freely without binding or noise. Control continuity was confirmed from the collective twist grip to the fuel control unit. The control linkage to the power turbine governor was fractured at the engine firewall due to impact forces.

The engine was installed on a test stand and prepared for a test run. The engine performed satisfactorily at takeoff power for 2 minutes as well as two lower power test points over a test period totaling about 20 minutes.

Following the test run, the power turbine governor, fuel control unit, fuel nozzle, and fuel pump were bench-tested. The power turbine governor that was removed and replaced before the accident flight was also tested. All units tested satisfactorily and within the manufacturers' specifications.

Examination of the fuel system revealed no anomalies, and the fuel lines and filters were free of contamination and obstructions. A fuel sample was tested in a laboratory with normal results.

History of Flight

Maneuvering Autorotation

Landing-flare/touchdown

Loss of engine power (partial) (Defining event) Off-field or emergency landing

Nose over/nose down

Pilot Information

Certificate:

Commercial; Flight instructor; Private

Age:

62,Male

Airplane Rating(s):

Single-engine land

Seat Occupied:

Right

Other Aircraft Rating(s):

Helicopter

Restraint Used:

4-point

Instrument Rating(s):

Helicopter

Second Pilot Present:

No

Instructor Rating(s):

Helicopter

Toxicology Performed:

No

Medical Certification:

Class 2 With waivers/limitations

Last FAA Medical Exam:

February 26, 2019

Occupational Pilot:

Yes

Last Flight Review or Equivalent:

July 31, 2019

Flight Time:

10175 hours (Total, all aircraft), 8229 hours (Total, this make and model), 10047 hours (Pilot In Command, all aircraft), 93 hours (Last 90 days, all aircraft), 36 hours (Last 30 days, all aircraft), 3 hours (Last 24 hours, all aircraft)

 Aircraft and Owner/Operator Information

Aircraft Make:

Hughes

Registration:

N6186U

Model/Series:

OH 6A No Series

Aircraft Category:

Helicopter

Year of Manufacture:

1969

Amateur Built:

 

Airworthiness Certificate:

None

Serial Number:

69-16048

Landing Gear Type:

High skid

Seats:

4

Date/Type of Last Inspection:

October 10, 2019 100 hour

Certified Max Gross Wt.:

2550 lbs

Time Since Last Inspection:

14 Hrs

Engines:

1 Turbo shaft

Airframe Total Time:

12987 Hrs as of last inspection

Engine Manufacturer:

Allison

ELT:

C126 installed, not activated

Engine Model/Series:

250-C20B

Registered Owner:

 

Rated Power:

420 Horsepower

Operator:

 

Operating Certificate(s) Held:

None

Meteorological Information and Flight Plan

Conditions at Accident Site:

Visual (VMC)

Condition of Light:

Day

Observation Facility, Elevation:

KCSG,392 ft msl

Distance from Accident Site:

39 Nautical Miles

Observation Time:

13:51 Local

Direction from Accident Site:

328°

Lowest Cloud Condition:

Clear

Visibility

10 miles

Lowest Ceiling:

None

Visibility (RVR):

 

Wind Speed/Gusts:

/                                            Turbulence Type

Forecast/Actual:

None / None

Wind Direction:

Turbulence Severity Forecast/Actual:

N/A / N/A

Altimeter Setting:

30.43 inches Hg

Temperature/Dew Point:

16°C / -6°C

Precipitation and Obscuration:

No Obscuration; No Precipitation

 

Departure Point:

Preston, GA

Type of Flight Plan Filed:

None

Destination:

Albany, GA (ABY )

Type of Clearance:

None

Departure Time:

12:40 Local

Type of Airspace:

Class G

Wreckage and Impact Information

Crew Injuries:

2 Minor

Aircraft Damage:

Substantial

Passenger Injuries:

 

Aircraft Fire:

None

Ground Injuries:

N/A

Aircraft Explosion:

None

Total Injuries:

2 Minor

Latitude, Longitude:

31.962499,-84.527496(est)

Administrative Information

Investigator In Charge (IIC):

Hicks, Ralph

 

Additional Participating Persons:

Robert Lohr; FAA/FSDO; College Park, GA Thomas McLeary; USDA; Cedar City, UT Joan Gregoire; MD Helicopters; Mesa, AZ Nick Shepler; Rolls-Royce; Indianapolis, IN

Barry Holt; Thoroughbred Aviation Maintenance; Georgetown, KY

 

Original Publish Date:

March 23, 2022                                                                  Investigation Class:

3

Note:

The NTSB did not travel to the scene of this accident.

 

Investigation Docket:

https://data.ntsb.gov/Docket?ProjectID=100789

 





Created 140 days ago
by Admin

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