Sunday, April 12, 2020

Loss of Engine Power (Partial): Air Tractor AT-502B, N502S; accident occurred June 27, 2018 in Tappen, Kidder County, North Dakota

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

Additional Participating Entity:

Federal Aviation Administration / Flight Standards District Office; Fargo, North Dakota

Aviation Accident Factual Report - National Transportation Safety Board:

Investigation Docket - National Transportation Safety Board:

Location:Tappen, ND
Accident Number: CEN18LA249
Date & Time:06/27/2018, 2000 CDT
Registration: N502S
Aircraft:Air Tractor AT502
Aircraft Damage: Substantial
Defining Event: Loss of engine power (partial)
Injuries: 1 None
Flight Conducted Under: Part 137: Agricultural

On June 27, 2018, about 2000 central daylight time, an Air Tractor 502B, N502S, impacted vegetation and the terrain following a reported partial loss of engine power during takeoff from a private airstrip near Tappen, North Dakota. The pilot was not injured, and the airplane was destroyed. The airplane was registered to and operated by Ross Seed Company, Inc. under the provisions of Title 14 Code of Federal Regulations Part 137 as an aerial application flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan The local flight was originating at the time of the accident.

The pilot reported that he had performed a full day of spraying in the accident airplane, which had performed normally all day with no abnormal sounds, vibrations, or indications. He stated that during the accident takeoff, the engine torque was initially set to 1,700 ft-lbs. When the airplane was just past the halfway point of the runway, he noticed that the tail of the airplane was not coming up as expected. He looked at the torque indicator and it was reading 1,500 ft-lbs of torque. He determined that he would not be able to abort the takeoff and stop the airplane on the remaining runway, so he elected to push the power lever full forward and dump the chemical load. He said that he believed the engine continued to lose power. The airplane continued off the end of the runway into a cattail patch and nosed over.

The airplane engine was examined by Federal Aviation Administration inspectors and a representative of Pratt & Whitney Canada, the engine manufacturer. The exhaust duct was impact fractured adjacent to the exhaust duct ports. This separated the majority of the power section components and the propeller from the engine and the aircraft. The rotational signatures that were found on the compressor turbine vane, compressor turbine, power turbine vane, and the power turbine were consistent with the engine producing power during the impact with the terrain. Static impact marks were noted on downstream side of the power turbine vane baffle from contact with the power turbine. The power turbine had static impact marks on the downstream side from contact with the power turbine shaft housing. The static impact marks indicated that the power turbine stopped rotating during the impact sequence. There were no indications of any pre-impact distress found to any of the examined components. The starting flow control unit (SFCU), fuel pump, fuel control unit (FCU), propeller governor (CSU), and over-speed governor (OSG) were removed for independent testing. Observations recorded during testing of the SFCU, CSU, FCU and OSG were consistent with field adjustments or impact damage. There were no defects or damage evident that would have prevented normal operation prior to the accident. 

Pilot Information

Certificate: Commercial
Age: 54, Male
Airplane Rating(s): Multi-engine Land; Single-engine Land; Single-engine Sea
Seat Occupied: Single
Other Aircraft Rating(s): Glider; Helicopter
Restraint Used:
Instrument Rating(s): Airplane
Second Pilot Present: No
Instructor Rating(s): None
Toxicology Performed: No
Medical Certification: Class 2 Without Waivers/Limitations
Last FAA Medical Exam: 03/19/2018
Occupational Pilot: Yes
Last Flight Review or Equivalent:
Flight Time: 13000 hours (Total, all aircraft)

Aircraft and Owner/Operator Information

Aircraft Make: Air Tractor
Registration: N502S
Model/Series: AT502 B
Aircraft Category: Airplane
Year of Manufacture: 1997
Amateur Built: No
Airworthiness Certificate: Restricted
Serial Number: 502B-0456
Landing Gear Type: Tailwheel
Seats: 1
Date/Type of Last Inspection:  Unknown
Certified Max Gross Wt.: 8000 lbs
Time Since Last Inspection:
Engines:  Turbo Prop
Airframe Total Time:
Engine Manufacturer: Pratt & Whitney Canada
Engine Model/Series: PT-6A-34AG
Registered Owner: Ross Seed Co Inc Dba
Rated Power: 750 hp
Operator: Ross Seed Co Inc Dba
Operating Certificate(s) Held: Agricultural Aircraft (137)

Meteorological Information and Flight Plan

Conditions at Accident Site: Visual Conditions
Condition of Light: Day
Observation Facility, Elevation: BIS, 1661 ft msl
Distance from Accident Site: 46 Nautical Miles
Observation Time: 1952 CDT
Direction from Accident Site: 260°
Lowest Cloud Condition: Clear
Visibility:  10 Miles
Lowest Ceiling: None
Visibility (RVR):
Wind Speed/Gusts: 6 knots /
Turbulence Type Forecast/Actual:
Wind Direction: 260°
Turbulence Severity Forecast/Actual:
Altimeter Setting: 29.82 inches Hg
Temperature/Dew Point: 29°C / 11°C
Precipitation and Obscuration: No Obscuration; No Precipitation
Departure Point: Tappen, ND (PVT)
Type of Flight Plan Filed: None
Destination: Tappen, ND (PVT)
Type of Clearance:None 
Departure Time: 2000 CDT
Type of Airspace: Class G

Airport Information

Airport: Private (PVT)
Runway Surface Type: Dirt; Grass/turf
Airport Elevation: 1740 ft
Runway Surface Condition: Dry
Runway Used: 27
IFR Approach:None 
Runway Length/Width: 2500 ft / 100 ft
VFR Approach/Landing: None

Wreckage and Impact Information

Crew Injuries: 1 None
Aircraft Damage: Substantial
Passenger Injuries: N/A
Aircraft Fire: None
Ground Injuries: N/A
Aircraft Explosion: None
Total Injuries: 1 None
Latitude, Longitude: 45.875000, -99.636389

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