# NTSB WPR19LA029: BKF Backcountry Supercub, N59BK, Casper, WY, November 19, 2018 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: November 19, 2018, 14:50 local (21:50 UTC) - Place: Casper, WY - Coordinates: 42.905834, -106.459999 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=42.9058&lon=-106.4600&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Bent Wing Aviation, Casper FSFO - NTSB case key (mKey): 98667 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR19LA029 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/98667/pdf - Page: https://openairdocs.org/ntsb/WPR19LA029 ## Probable cause The seizure of two bearings in the reduction gearbox, resulting in the total loss of engine power. Contributing to the accident was a high descent rate which resulted in a hard landing. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Accessory gear-boxes](https://openairdocs.org/ntsb-findings/01058300): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [BKF BACKCOUNTRY SUPERCUB, 1 case](https://openairdocs.org/ntsb-findings/01058300/cases.md?model=056359R), [All aircraft, 19 cases](https://openairdocs.org/ntsb-findings/01058300/cases.md) - [Use of equip/info: aircraft control](https://openairdocs.org/ntsb-findings/02063040): Personnel issues › Task performance · Pilot (probable cause); cases with it: [BKF BACKCOUNTRY SUPERCUB, 1 case](https://openairdocs.org/ntsb-findings/02063040/cases.md?model=056359R), [All aircraft, 9,295 cases](https://openairdocs.org/ntsb-findings/02063040/cases.md) - [Performance/control parameters: descent rate](https://openairdocs.org/ntsb-findings/01062037): Aircraft › Aircraft oper/perf/capability · Not attained/maintained (probable cause); cases with it: [BKF BACKCOUNTRY SUPERCUB, 1 case](https://openairdocs.org/ntsb-findings/01062037/cases.md?model=056359R), [All aircraft, 242 cases](https://openairdocs.org/ntsb-findings/01062037/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Initial climb: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [BKF BACKCOUNTRY SUPERCUB, 1 case](https://openairdocs.org/ntsb-events/341/sequence.md?model=056359R), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Landing-flare/touchdown: Loss of control in flight](https://openairdocs.org/ntsb-events/240); cases with it: [BKF BACKCOUNTRY SUPERCUB, 1 case](https://openairdocs.org/ntsb-events/240/sequence.md?model=056359R), [All aircraft, 5,002 cases](https://openairdocs.org/ntsb-events/240/sequence.md) - [Landing: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [BKF BACKCOUNTRY SUPERCUB, 1 case](https://openairdocs.org/ntsb-events/092/sequence.md?model=056359R), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) ## Analysis The commercial pilot was flight testing the airplane to evaluate an experimental diesel engine reduction gearbox. During the takeoff, as the airplane climbed above 500 ft above ground level, the pilot increased engine power, but a total loss of engine power occurred shortly afterward. The pilot initiated a left descending turn to return to the runway. During the landing sequence, the airplane had a high descent rate. The airplane touched down hard, resulting in the separation of the left main landing gear axle and substantial damage to the left wing lift strut. Postaccident examination of the engine reduction gearbox found that two propeller shaft bearings inside the reduction gearbox seized, causing the total loss of engine power. ## Factual narrative The owner of Backcountry Cub kit airplanes stated that the inability to bring up the nose during an engine-out landing was "not a characteristic of the airplane." The pilot stated that the airplane's stall speed should have been in the mid-30-knot range. He also stated that, other than a high descent rate, he had no indication that the airplane was near a stall. On November 19, 2018, about 1450 mountain standard time, an experimental amateur-built BKF Backcountry Super Cub airplane, N59BK, was substantially damaged when it was involved in an accident near Casper, Wyoming. The commercial pilot and pilot-rated passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. The airplane was part of an experimental program using a diesel engine and reduction gearbox to transfer power from the engine to the propeller. The pilot reported that when landing during the previous flight, the airplane lacked pitch authority to flare with the engine at idle. The airplane’s elevator was re-rigged to correct the lack of pitch authority. According to the pilot, he initiated the takeoff for the accident flight from runway 21 using full power. After the airplane became airborne, the pilot reduced power slightly. As the airplane climbed above 500 ft above ground level, the pilot increased engine power, but a total loss of engine power occurred shortly afterward. The pilot initiated a left descending turn to return to the runway. During the turn, the pilot realized that he would not be able to completely align with the runway, so he leveled the wings to land on the runway and roll off the runway edge into the grass. The pilot stated, that, during the descent, the airplane’s indicated airspeed was 50 knots, and the airplane had a high descent rate. Subsequently, the airplane landed hard on the right side of runway 21, and the left main landing gear axle separated. The left wing lift strut was substantially damaged. The reduction gearbox was examined at Bent Wing Aviation in Casper, and a Federal Aviation Administration representative from the Casper flight standards field office oversaw the examination. The examination report stated, "both forward and reverse thrust bearings on the main propeller shaft were fused or seized." Additional information regarding the reduction gearbox examination is available in the public docket for this accident. ## Aircraft - Registration: [N59BK](https://openairdocs.org/deregistered/N59BK-2020-08-02), registration cancelled 2020-08-02, S/N BC21115R006, built 2018 (OpenAirDocs) - Reported make and model: BKF Backcountry Supercub - Registry model: [BKF BACKCOUNTRY SUPERCUB](https://openairdocs.org/model/bkf-backcountry-supercub) (registry code 056359R) (OpenAirDocs) - Registry engine: [Amateur-built UNKNOWN ENG](https://openairdocs.org/engine/amateur-built-unknown-eng) (registry code 99999) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: BC21115R006 - Year built: 2018 - Airframe hours: 0.5 - Engines: CKT TD240 240 horsepower reciprocating - Damage: Substantial damage - Flight: Flight test, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Departed: CPR, Casper, WY - Destination: CPR, Casper, WY - Airport: CPR, Casper/Natrona County Intl, runway 21, 10,165 × 150 ft, asphalt - Equipment: ADS-B, Angle of attack indicator, Auto-pilot, Electronic primary flight display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 73; injuries: none; commercial; airplane ratings: multi-engine land, single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review April 20, 2017; seat: front; restraint: 4-point; flight hours: 20,322 total, 1 in this make and model, 28 in the last 90 days, 2 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 220° at 11 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 36 °F, dew point 21 °F - Altimeter: 30.17 inHg - Observed at: KCPR ## 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 20181119023799A](https://openairdocs.org/incident/20181119023799A), Nov 19, 2018: Bkf Aviation Ltd BACKCOUNTRY SUPERCUB, Casper, WY, Substantial damage. Aircraft engine propeller accessary case locked up after takeoff. 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.