# NTSB WPR11CA358: Mcdonald Lynn B Avid Flyer Mark IV, N30456, Yamhill, OR, July 31, 2011 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: July 31, 2011, 08:30 local (15:30 UTC) - Place: Yamhill, OR - Coordinates: 45.361389, -123.353057 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=45.3614&lon=-123.3531&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-landing roll: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report October 17, 2011 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 81358 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR11CA358 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/81358/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=81358 - Page: https://openairdocs.org/ntsb/WPR11CA358 ## Probable cause The pilot’s loss of directional control during landing rollout due to an unlocked tail wheel that was caused by a degradation of the tailwheel assembly mounting angle. ## 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 · Damaged/degraded (probable cause); cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-findings/01023220/cases.md?model=05624ZD), [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 · Not attained/maintained (probable cause); cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=05624ZD), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Runway/land/takeoff/taxi surface](https://openairdocs.org/ntsb-findings/03023000): Environmental issues › Physical environment · Contributed to outcome; cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-findings/03023000/cases.md?model=05624ZD), [All aircraft, 253 cases](https://openairdocs.org/ntsb-findings/03023000/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Landing-landing roll: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=05624ZD), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) - [Landing-landing roll: Loss of control on ground](https://openairdocs.org/ntsb-events/230); cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-events/230/sequence.md?model=05624ZD), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) - [Landing-landing roll: Runway excursion](https://openairdocs.org/ntsb-events/300); cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-events/300/sequence.md?model=05624ZD), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) - [Landing-landing roll: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Mcdonald Lynn B AVID FLYER MARK IV, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05624ZD), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot reported that his approach to, and landing on, the private airstrip in his amateur-built, experimental, conventional gear airplane were normal. During rollout in the calm wind condition, the airplane began an uncommanded right turn. The pilot attempted to correct his loss of directional control by application of rudder and engine power. However, the tail wheel had unlocked and was evidently in a castoring mode. Despite his efforts to straighten the airplane’s path, the airplane veered off the runway and impacted a ditch. During the impact sequence one propeller blade broke, and the left wingtip and a wing rib were broken. The pilot reported that he built and maintained the experimental airplane. He opined that the accident could have been prevented had the angle of the tail wheel assembly been correct. After years of use, the tail wheel spring-to-empennage attachment assembly flattened. The incorrect angle altered the tail wheel’s pivot point. This event, combined with the vibration induced during rollout on the gravel runway, allowed the tail wheel to unlock. ## Factual narrative The pilot reported that his approach to, and landing on, the private airstrip in his homebuilt, experimental, conventional gear airplane were normal. During rollout in the calm wind condition, the airplane began an uncommanded right turn. The pilot stated that he attempted to correct his loss of directional control by application of rudder and engine power. However, the tail wheel had unlocked and was evidently in a castoring mode. Despite his efforts to straighten the airplane’s path, the airplane veered off the runway. It rolled over brush and went into a ditch. During the impact sequence one propeller blade broke, and the left wingtip and a wing rib were broken. The pilot reported that he built and maintained the experimental airplane. He opined that the accident could have been prevented had the angle of the tail wheel assembly been correct. After years of use, the tail wheel spring-to-empennage attachment assembly flattened. The incorrect angle altered the tail wheel’s pivot point. This event, combined with the vibration induced during rollout on the gravel runway, allowed the tail wheel to unlock. ## Aircraft - Registration: [N30456](https://openairdocs.org/aircraft/N30456), registered now, S/N 1279D, built 1994 (OpenAirDocs) - Reported make and model: MCDONALD LYNN B AVID FLYER MARK IV - Registry model: [Mcdonald Lynn B AVID FLYER MARK IV](https://openairdocs.org/model/mcdonald-lynn-b-avid-flyer-mark-iv) (registry code 05624ZD) (OpenAirDocs) - Registry engine: [Bombardier ROTAX (ALL)](https://openairdocs.org/engine/bombardier-rotax-all) (registry code 09050, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 1279D - Airframe hours: 1541 - Engines: BOMBARDIER ROTAX (ALL) 65 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, August 22, 2010, 14 hours before - Departed: S75, Independence, OR - Destination: OR05, Yamhill, OR - Airport: OR05, Flying M, runway 07, 1,200 × 40 ft, gravel ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 76; injuries: none; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review June 18, 2011; seat: left; flight hours: 2,413 total, 1,540 in this make and model, 14 in the last 90 days, 6 in the last 30 days, 0 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 64 °F - Altimeter: 30.04 inHg ## Docket (1 files) The files NTSB released with the investigation on September 13, 2011, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=81358. 527 KB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 527 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40352445&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.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.