# NTSB CEN18LA249: Air Tractor AT502, N502S, Tappen, ND, June 28, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: June 27, 2018, 20:00 local (Jun 28, 2018, 01:00 UTC) - Place: Tappen, ND - Coordinates: 46.869541, -99.625095 - Nearby events: https://openairdocs.org/map.md?lat=46.8695&lon=-99.6251&mi=10 - Phase of flight: [Takeoff](https://openairdocs.org/ntsb-phases/300) (OpenAirDocs' grouping) - Defining event: [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report June 3, 2020 - Report: Approved by Office Director - NTSB office: Central Region - Parties: FAA - Fargo FSDO - NTSB case key (mKey): 97666 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA249 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/97666/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=97666 - Page: https://openairdocs.org/ntsb/CEN18LA249 ## Probable cause The partial loss of engine power for reasons that could not be determined based on the available evidence. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Not determined](https://openairdocs.org/ntsb-findings/05000000): Not determined › Not determined · Unknown/Not determined (probable cause); cases with it: [Air Tractor AT-502B, 7 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md?model=0390307), [All aircraft, 2,247 cases](https://openairdocs.org/ntsb-findings/05000000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Takeoff: Loss of engine power (partial)](https://openairdocs.org/ntsb-events/342) (defining event); cases with it: [Air Tractor AT-502B, 7 cases](https://openairdocs.org/ntsb-events/342/sequence.md?model=0390307), [All aircraft, 1,858 cases](https://openairdocs.org/ntsb-events/342/sequence.md) - [Takeoff: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Air Tractor AT-502B, 6 cases](https://openairdocs.org/ntsb-events/300/sequence.md?model=0390307), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) - [Takeoff: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [Air Tractor AT-502B, 4 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=0390307), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) ## Analysis The pilot reported that he noticed degraded engine performance when the airplane was about halfway down the runway during takeoff for the aerial application flight. Specifically, the engine torque decreased from 1,700 ft-lbs at the start of the takeoff to 1,500 ft-lbs. He determined that there was not enough runway to abort the takeoff and stop the airplane, so he applied full power and dumped the product load. The engine continued to lose power, and the airplane subsequently continued off the end of the runway and nosed over in high vegetation. Postaccident examination of the airplane and engine, including individual testing of several engine components, confirmed that the engine was producing power during the impact sequence, but no determination could be made as to how much power the engine produced. The examination did not reveal any mechanical malfunctions or failures that would have precluded normal operation. ## Factual narrative 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. ## Aircraft - Registration: [N502S](https://openairdocs.org/deregistered/N502S-2020-01-30), registration cancelled 2020-01-30, S/N 502B-0456, built 1997 (OpenAirDocs) - Reported make and model: Air Tractor AT502 (B) - Registry model: [Air Tractor AT-502B](https://openairdocs.org/model/air-tractor-at-502b) (registry code 0390307) (OpenAirDocs) - Registry engine: [Pratt & Whitney PT6A series](https://openairdocs.org/engine/pratt-whitney-pt6a-series) (registry code 52034, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 502B-0456 - Year built: 1997 - Engines: Pratt & Whitney Canada PT-6A-34AG 750 horsepower turbo prop - Damage: Substantial damage - Flight: Aerial application, Part 137 - Operator: Ross Seed Co Inc Dba - Registered owner: Ross Seed Co Inc Dba - Airworthiness certificate: Special, Restricted (Special) - Departed: PVT, Tappen, ND - Destination: PVT, Tappen, ND - Airport: PVT, Private, runway 27, 2,500 × 100 ft, grass/turf ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 54; injuries: none; commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; seat: single; restraint: 5-point; flight hours: 13,000 total ## Weather - Conditions: Visual (VMC), Day - Wind: 260° at 6 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 52 °F - Altimeter: 29.81 inHg - Observed at: BIS, 46 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 20180627022449A](https://openairdocs.org/incident/20180627022449A), Jun 27, 2018: Air Tractor Inc AT-502B, Tappen, ND, Substantial damage. On takeoff roll the aircraft seemed to suffer a partial loss of power. The pilot jettisoned the load and moved the power lever all the way forward. The… ## Other investigations on N502S (1) From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. - [NTSB FTW99LA005](https://openairdocs.org/ntsb/FTW99LA005), Oct 8, 1998: Air Tractor AT-502B (N502S), Ringling, OK, substantial damage. Probable cause: The pilot's failure to maintain obstacle clearance. A factor was the sun glare which impaired the pilot's vision. ## Docket (2 files) The files NTSB released with the investigation on December 5, 2019, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=97666. 8.8 MB in all. - Pilot Statement (item 1, .PDF, 170 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40478638&FileExtension=.PDF&FileName=Pilot%20Statement-Master.PDF - Pratt & Whitney Examination Report (item 2, .PDF, 8.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40483789&FileExtension=.PDF&FileName=Pratt%20%26%20Whitney%20Examination%20Report-Master.PDF From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.