# NTSB ANC16LA059: Wight Carbon CUB CCK-1865, N625EX, Wasilla, AK, August 13, 2016 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: August 12, 2016, 18:00 local (Aug 13, 2016, 02:00 UTC) - Place: Wasilla, AK - Coordinates: 61.500556, -149.6725 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=61.5006&lon=-149.6725&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Loss of control on ground](https://openairdocs.org/ntsb-events/230) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report July 26, 2017 - Report: Approved by Office Director - NTSB office: Alaska Regional Office - Parties: Federal Aviation Administration; ANC FSDO - NTSB case key (mKey): 93846 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC16LA059 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/93846/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=93846 - Page: https://openairdocs.org/ntsb/ANC16LA059 ## Probable cause The failure of the tailwheel suspension assembly during landing due to preexisting fatigue fractures in the suspension system, which resulted in a loss of directional control. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: nose/tail landing gear](https://openairdocs.org/ntsb-findings/01023220): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [Wight Richard J CARBON CUB CCK-1865, 1 case](https://openairdocs.org/ntsb-findings/01023220/cases.md?model=05634HF), [All aircraft, 185 cases](https://openairdocs.org/ntsb-findings/01023220/cases.md) - [Performance/control parameters: directional control](https://openairdocs.org/ntsb-findings/01062020): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Wight Richard J CARBON CUB CCK-1865, 1 case](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=05634HF), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330); cases with it: [Wight Richard J CARBON CUB CCK-1865, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=05634HF), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-flare/touchdown: Loss of control on ground](https://openairdocs.org/ntsb-events/230) (defining event); cases with it: [Wight Richard J CARBON CUB CCK-1865, 1 case](https://openairdocs.org/ntsb-events/230/sequence.md?model=05634HF), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Dragged wing/rotor/float/other](https://openairdocs.org/ntsb-events/093); cases with it: [Wight Richard J CARBON CUB CCK-1865, 1 case](https://openairdocs.org/ntsb-events/093/sequence.md?model=05634HF), [All aircraft, 319 cases](https://openairdocs.org/ntsb-events/093/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Wight Richard J CARBON CUB CCK-1865, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05634HF), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The airline transport pilot was conducting a personal cross-country flight in the experimental amateur-built, tailwheel-equipped airplane. The pilot reported that, while landing on a turf and gravel airstrip, the airplane veered sharply left as the tailwheel touched down. Despite applying full right rudder and brake controls, the pilot was unable to correct the airplane's track, and the right wing and horizontal stabilizer impacted the ground. The pilot stated that, after the airplane stopped, he was unable to straighten the tailwheel with the rudder control inputs because the tailwheel was bent. Postaccident metallurgical examination of the tailwheel suspension system revealed fractures within the welds of the assembly and a fatigue fracture at the bolt hole for mounting the tailwheel. The crack fracture surfaces exhibited orange and dark red corrosion, suggesting that the cracks were preexisting, and the fracture surfaces were consistent with overstress. The assembly also exhibited general twisting deformation, primarily as the result of deformation in the pivot bracket. ## Factual narrative On August 12, 2016, about 1800 Alaska daylight time, a tundra tire-equipped, amateur-built, experimental, Wight (Cub Crafters) Carbon Cub CCK-1865 airplane, N625EX, sustained substantial damage while landing on runway 7 at Todds Strip Airport, a private airstrip situated near Wasilla, Alaska. The airline transport pilot and one passenger onboard were uninjured. The airplane was registered to, and operated by, the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight that was not operating on a flight plan. Visual meteorological conditions prevailed at the time of the accident for the flight that originated from Summit Airport, Summit, Alaska, about 1630, and was destined to Todds Strip Airport. The pilot reported that his flight to the Todds Strip Airport, a 1,500-feet-long by 60-feet-wide turf and gravel-covered airstrip was uneventful. He added that while landing, during touchdown in a wheel landing configuration, the airplane veered sharply to the left as the tailwheel touched down. The pilot said he applied a "full deflection" of the right rudder and right brake controls in an attempt to correct the veer, but the airplane continued to veer left. The right wing and right horizontal stabilizer subsequently struck the ground, sustaining substantial damage. After the airplane stopped, the pilot unsuccessfully attempted to turn the airplane to the right using rudder, brake, and engine power. The pilot stated that he was unable to straighten the tail wheel with the rudder control inputs because the tail wheel was bent. The pilot reported that the airplane had a total time in service of 96 hours. The airplane tailwheel spring had been replaced with a coil spring assembly that was not part of the original airplane kit manufacturer's assembly, which was a leaf spring. The coil spring was an Alaskan Bushwheels T3 Heavy Duty tailwheel suspension system with a reported total time in service of 30 hours. Alaskan Bushwheels T3 Heavy Duty tailwheel suspension system underwent a post-accident metallurgical examination by the National Transportation Safety Board Materials Laboratory. The examination revealed that the underside of the flange used to mount the suspension to the airframe exhibited compression deformation under the faying surfaces of the bolt head washer. Cracks were observed in weld deposits and at the edge of the bolt hole for mounting the tail wheel. The crack fracture surfaces exhibited orange and dark red corrosion product. The dark red coloration of the corrosion deposits suggested that these cracks were pre-existing to the accident. After removal of the corrosion product, the fracture surfaces were examined with a 5X to 50X stereo-zoom microscope. The fractographic features were consistent with overstress fracture. The crack emanating from the edge of the bolt hole was examined. After removal of superficial orange-colored corrosion product, the fracture surface of the bolt hole crack was examined with a5X to 50X stereo-zoom microscope. The fracture initiated and propagated due to fatigue before transitioning to overstress. The edges of the main side plates of the suspension assembly exhibited deformation and impact wear scars. The location of the scars on the side plates is consistent with contact with the airplane's tail wheel steering arms. The pivot bracket exhibited permanent deformation and edge cracking in the region of the welded-in-place bushing as indicated in the close views. A though-thickness crack on the right side was opened for examination of the fracture surface. After removal of orange-colored corrosion product, the fracture surface of the crack was examined with a 5X to 50X stereo-zoom microscope. The fractographic features were consistent with overstress fracture. A weld along the radiused bend in the pivot bracket exhibited a partial thickness crack in the base metal adjacent to the toe of the weld. The suspension assembly exhibited general twisting deformation, primarily as the result of deformation in the pivot bracket. ## Aircraft - Registration: [N625EX](https://openairdocs.org/aircraft/N625EX), registered now, S/N 0093 (OpenAirDocs) - Reported make and model: WIGHT CARBON CUB CCK-1865 - Registry model: [Wight Richard J CARBON CUB CCK-1865](https://openairdocs.org/model/wight-richard-j-carbon-cub-cck-1865) (registry code 05634HF) (OpenAirDocs) - Registry engine: [Aerosport CC-340](https://openairdocs.org/engine/aerosport-cc-340) (registry code 01320, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 0093 - Year built: 2016 - Airframe hours: 96 - Engines: Aerosport CC-340 180 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Pilot - Registered owner: Pilot - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, May 27, 2016 - Departed: PSAT, Summit, AK - Destination: 5AK5, Wasilla, AK - Airport: 5AK5, Todds Strip Airport, runway 7, 1,500 × 60 ft, grass/turf - Equipment: Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 29; injuries: none; commercial, airline transport, flight instructor; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review January 12, 2016; seat: front; restraint: 3-point; flight hours: 6,116 total, 100 in this make and model, 4,636 as pilot in command, 317 in the last 90 days, 98 in the last 30 days, 4 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: 7,000 ft overcast - Temperature: 59 °F, dew point 55 °F - Altimeter: 29.69 inHg - Observed at: PAWS, 6 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 20160812023019A](https://openairdocs.org/incident/20160812023019A), Aug 12, 2016: 2016 Wight Richard J CARBON CUB CCK-1865, Wasilla, AK, Minor damage. According to the preliminary report, after landing and slowing down the a/c pulled to the left, right rudder was applied and a ground loop occurred. PIC also… ## Docket (2 files) The files NTSB released with the investigation on June 5, 2017, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=93846. 4.7 MB in all. - NTSB Materials Laboratory Factual Report (item 1, .PDF, 15 photos, 2.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452839&FileExtension=.PDF&FileName=NTSB%20Materials%20Laboratory%20Factual%20Report-Master.PDF - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 2, .PDF, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40452840&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-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.