# NTSB WPR14CA390: William M Oprendek Pitts S1S, N93DB, Sedona, AZ, September 25, 2014 - Type: NTSB accident investigation - Classification: Accident · No injuries · Data collection · Final report - Date: September 25, 2014, 08:30 local (15:30 UTC) - Place: Sedona, AZ - Coordinates: 34.848609, -111.78833 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.8486&lon=-111.7883&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report December 5, 2014 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration FSDO - NTSB case key (mKey): 90158 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR14CA390 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/90158/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=90158 - Page: https://openairdocs.org/ntsb/WPR14CA390 ## Probable cause Failure of the tailwheel steering assembly during maneuvering flight, which resulted in a loss of directional control during the landing roll. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [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: [William M Oprendek PITTS S1S, 1 case](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=05632LV), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Landing gear system: landing gear steering system](https://openairdocs.org/ntsb-findings/01023250): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [William M Oprendek PITTS S1S, 1 case](https://openairdocs.org/ntsb-findings/01023250/cases.md?model=05632LV), [All aircraft, 32 cases](https://openairdocs.org/ntsb-findings/01023250/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [William M Oprendek PITTS S1S, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=05632LV), [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); cases with it: [William M Oprendek PITTS S1S, 1 case](https://openairdocs.org/ntsb-events/230/sequence.md?model=05632LV), [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: [William M Oprendek PITTS S1S, 1 case](https://openairdocs.org/ntsb-events/300/sequence.md?model=05632LV), [All aircraft, 3,643 cases](https://openairdocs.org/ntsb-events/300/sequence.md) ## Analysis The pilot/builder of the experimental amateur-built, tailwheel-equipped airplane had just completed a flight as part of phase one flight testing. He reported an uneventful approach to landing, with the main landing gear touching down first. However, as soon as the tailwheel made contact with the runway, the airplane yawed violently to the right. The pilot applied full left rudder and brake control input, but the airplane did not respond, and departed the runway descending down an embankment. The airplane sustained substantial damage to the upper wing spar and fuselage structure at the landing gear attach points. Postaccident examination revealed that the tailwheel was locked 90 degrees to the right. The tailwheel assembly was disassembled, and the steering arm cam spring appeared jammed between the shaft and housing. The inner surface of the housing exhibited scoring marks, consistent with a pre-existing failure of the spring. The pilot reported that he had purchased the tailwheel assembly used, and that he did not have any records indicating its manufacturer or serial number. ## Factual narrative The pilot/builder of the experimental amateur-built, tailwheel-equipped airplane had just completed a flight as part of phase one flight testing. He reported an uneventful approach to landing, with the main landing gear touching down first. However, as soon as the tailwheel made contact with the runway, the airplane yawed violently to the right. The pilot applied full left rudder and brake control input, but the airplane did not respond, and departed the runway descending down an embankment. The airplane sustained substantial damage to the upper wing spar and fuselage structure at the landing gear attach points. Postaccident examination revealed that the tailwheel was locked 90 degrees to the right. The tailwheel assembly was disassembled, and the steering arm cam spring appeared jammed between the shaft and housing. The inner surface of the housing exhibited scoring marks, consistent with a pre-existing failure of the spring. The pilot reported that he had purchased the tailwheel assembly used, and that he did not have any records indicating its manufacturer or serial number. ## Aircraft - Registration: [N93DB](https://openairdocs.org/deregistered/N93DB-2017-01-05), registration cancelled 2017-01-05, S/N PITTS S1SS-3, built 2013 (OpenAirDocs) - Reported make and model: WILLIAM M OPRENDEK PITTS S1S (NO SERIES) - Registry model: [William M Oprendek PITTS S1S](https://openairdocs.org/model/william-m-oprendek-pitts-s1s) (registry code 05632LV) (OpenAirDocs) - Registry engine: [Superior IO-360 series](https://openairdocs.org/engine/superior-io-360-series) (registry code 59251, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: PITTS S1SS-3 - Year built: 2013 - Airframe hours: 53.1 - Engines: SUPERIOR XP-IO-360-E1D 185 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, July 3, 2014, 43.2 hours before - Departed: SEZ, Sedona, AZ - Destination: SEZ, Sedona, AZ - Airport: SEZ, Sedona, runway 03, 5,132 × 100 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 70; injuries: none; commercial, flight engineer, airline transport; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 3, waiver time limited special; last flight review June 12, 2013; seat: single; restraint: 5-point; flight hours: 31,293 total, 690 in this make and model, 23,909 as pilot in command, 14.1 in the last 90 days, 3.9 in the last 30 days ## Weather - Conditions: Visual (VMC), Day - Wind: 80° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 75 °F, dew point 48 °F - Altimeter: 30.22 inHg - Observed at: KSEZ ## 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 20140925019389A](https://openairdocs.org/incident/20140925019389A), Sep 25, 2014: William M Oprendek PITTS S1S, Sedona, AZ, Substantial damage. The aircraft was conducting a phase 1 flight for experimental amateur built operating limitations out of the Sedona Airport area. The pilot stated the aircraft… ## Docket (6 files) The files NTSB released with the investigation on November 25, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=90158. 1.9 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40419437&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Builder-Mechanic Statement (item 2, .PDF, 41 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40419438&FileExtension=.PDF&FileName=Builder-Mechanic%20Statement-Redacted.PDF - Photo 1 - Tailwheel (item 3, .PDF, 176 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40419439&FileExtension=.PDF&FileName=Photo%201%20-%20Tailwheel-Master.PDF - Photo 2 - Tailwheel Assembly (item 4, .PDF, 156 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40419440&FileExtension=.PDF&FileName=Photo%202%20-%20Tailwheel%20Assembly-Master.PDF - Photo 3 - Tailwheel Assembly (item 5, .PDF, 135 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40419441&FileExtension=.PDF&FileName=Photo%203%20-%20Tailwheel%20Assembly-Master.PDF - Photo 4 - Tailwheel Cam and Spring (item 6, .PDF, 123 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40419442&FileExtension=.PDF&FileName=Photo%204%20-%20Tailwheel%20Cam%20and%20Spring-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.