# NTSB WPR24LA061: Glasair SH2, N29TT, Prescott, AZ, December 26, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: December 26, 2023, 12:21 local (19:21 UTC) - Place: Prescott, AZ · Runway 21L - Coordinates: 34.65483, -112.41922 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.6548&lon=-112.4192&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing-flare/touchdown: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: FAA FSDO - NTSB case key (mKey): 193576 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR24LA061 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193576/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193576 - Page: https://openairdocs.org/ntsb/WPR24LA061 ## Probable cause Loss of directional control during landing due to an improperly constructed and maintained tailwheel locking assembly. ## 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 · Fatigue/wear/corrosion (probable cause); cases with it: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-findings/01023220/cases.md?model=05655WR), [All aircraft, 185 cases](https://openairdocs.org/ntsb-findings/01023220/cases.md) - [Landing gear system: nose/tail landing gear](https://openairdocs.org/ntsb-findings/01023220): Aircraft › Aircraft systems · Incorrect service/maintenance (probable cause); cases with it: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-findings/01023220/cases.md?model=05655WR), [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: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-findings/01062020/cases.md?model=05655WR), [All aircraft, 3,958 cases](https://openairdocs.org/ntsb-findings/01062020/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=05655WR), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=05655WR), [All aircraft, 371 cases](https://openairdocs.org/ntsb-findings/02062035/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) (defining event); cases with it: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=05655WR), [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: [Tuttle Bruce C TUTTLE-GLASAIR, 1 case](https://openairdocs.org/ntsb-events/230/sequence.md?model=05655WR), [All aircraft, 4,585 cases](https://openairdocs.org/ntsb-events/230/sequence.md) ## Analysis When the airplane’s tailwheel touched the ground during landing, the airplane immediately swerved and ground looped, causing substantial damage to the fuselage due to sideloads on the landing gear. The weather conditions were not a factor, and examination revealed that the tailwheel was jammed 45° relative to the direction of travel. Further examination revealed that the tailwheel assembly locking mechanism was significantly worn and had been incorrectly constructed, so a positive lock was not possible. Under this condition, with light side loads as are often encountered during landing, the tailwheel could unlock and be pushed into an over center position. This resulted in the airplane aggressively swerving as observed. ## Factual narrative On December 26, 2023, about 1221 mountain standard time, an experimental amateur-built Glasair SH2, N29TT, was substantially damaged when it was involved in an accident near Prescott, Arizona. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, after an uneventful wheel landing, he held the tail off the ground until the airplane had decelerated to about 30 mph. As soon as the tailwheel touched the ground, the airplane swung hard to the right, ground looped, and came to rest on the runway edge. The airplane sustained substantial damage to the forward left fuselage, which had buckled and delaminated behind the firewall and just above the left main landing gear leg. Postaccident examination revealed that the tailwheel was jammed at a 45° angle to the left. The airplane was equipped with a free-castering tailwheel, designed to be locked in the straight position during takeoff and landing. It was controlled by a lever in the cabin that was connected via a cable to a spring-loaded locking arm in the tailwheel assembly. The locking arm, when activated, dropped down into a slot cut into the upper plate of the tailwheel trailing arm. The plate was a steel segment of about 90° arc and welded to the tailwheel arms. The pilot reported that, in accordance with the airplane’s operating instructions, he locked the tailwheel straight during takeoff with the cabin control and confirmed it was locked before landing. Postaccident examination revealed that both the cabin control and locking arm were in the locked position, but the tailwheel was jammed about the 45° to the left, rather than straight. Further examination revealed that the locking arm and associated plate slot were worn, and the locking spring had limited tension, such that with light force the tailwheel could be moved out of the straight position and jammed over center as the locking arm dropped down against the outer edges of the locking plate (see figure 1). Figure 1. Tailwheel in the overcenter position. Arrow indicates where the locking arm has dropped down against the outer edges of the locking plate. The construction plans specified that the control cable should be routed directly from the locking arm to a phenolic guide in the vertical fin shear web. However, the cable was routed from the locking arm down to a set of four cable ties mounted to the tailwheel strut (see figure 2). Figure 2. Tailwheel in the straight position; note the cable ties in top left restricting free movement of the locking cable. ## Aircraft - Registration: [N29TT](https://openairdocs.org/deregistered/N29TT-2024-05-30), registration cancelled 2024-05-30, S/N 451, built 1986 (OpenAirDocs) - Reported make and model: Glasair SH2 - Registry model: [Tuttle Bruce C TUTTLE-GLASAIR](https://openairdocs.org/model/tuttle-bruce-c-tuttle-glasair) (registry code 05655WR) (OpenAirDocs) - Registry engine: [Lycoming IO-320 series](https://openairdocs.org/engine/lycoming-io-320-series) (registry code 41509, reciprocating) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: 451 - Year built: 1986 - Airframe hours: 1134.1 - Engines: Lycoming IO-320-E2A 150 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, October 5, 2023, 7 hours before - Departed: SAD, Safford, AZ - Destination: Same as departure - Airport: PRC, Prescott Rgnl - Ernest A Love Fld, runway 03R/21L, 7,619 × 150 ft, asphalt - Equipment: Electronic flight bag or handheld device, Data recorder, Auto-pilot, ADS-B, Onboard weather, Electronic primary flight display, Electronic multifunction display ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 53; injuries: none; commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 3, with waivers/limitations; last flight review December 9, 2023; seat: left; restraint: 4-point; flight hours: 2,991 total, 33 in this make and model, 2,930 as pilot in command, 20 in the last 90 days, 7 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 320° at 7 knots - Visibility: 10 statute miles - Temperature: 46 °F, dew point 10 °F - Altimeter: 30.17 inHg - Observed at: KPRC - METAR: KPRC 261938Z 32007KT 290V360 10SM CLR 08/M12 A3017 RMK AO2 AIRCRAFT INCIDENT T00831117= ## 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 20231226019379A](https://openairdocs.org/incident/20231226019379A), Dec 26, 2023: Tuttle Bruce C TUTTLE-GLASAIR, Prescott, AZ, Substantial damage. The pilot reported that after an uneventful wheel landing in the tailwheel equipped airplane on R21L, he held the airplane’s tail off the ground until it had… ## Docket (4 files) The files NTSB released with the investigation on July 24, 2024, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193576. 9.5 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 11 pages, 4.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16534123&FileExtension=pdf&FileName=r_6120_Redacted-Rel.pdf - Examination report (item 2, PDF, 6 pages, 5 photos, 1.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16534244&FileExtension=pdf&FileName=Exam%20report-Rel.pdf - Examination report attachment 1 (item 3, PDF, 4 pages, 1.5 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16534133&FileExtension=pdf&FileName=Attachment%201-Rel.pdf - Maintenance logbook excerpts (item 4, PDF, 2 pages, 2.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=16534351&FileExtension=pdf&FileName=r_Logbook%20Excerpts_Redacted-Rel.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.