# NTSB ERA24LA258: Clapp Saberwing, N120SW, Valdosta, GA, June 11, 2024 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Class 3 · Limited · Final report - Date: June 10, 2024, 20:00 local (Jun 11, 2024, 00:00 UTC) - Place: Valdosta, GA · near 2589 Old Clyattville Rd, Valdosta, GA - Coordinates: 30.76759, -83.3028 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=30.7676&lon=-83.3028&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report April 29, 2026 - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Eastern Region Aviation - Parties: FAA/FSDO - NTSB case key (mKey): 194462 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ERA24LA258 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194462/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=194462 - Page: https://openairdocs.org/ntsb/ERA24LA258 ## Probable cause The total loss of engine power due to the shearing of the woodruff key that indexed the crankshaft gear and hub assembly to the crankshaft, which resulted in the gear and hub rotating from their indexed position and caused the crankshaft-to-camshaft timing to become misaligned. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Engine (reciprocating): recip eng front section](https://openairdocs.org/ntsb-findings/01058510): Aircraft › Aircraft power plant · Failure (probable cause); cases with it: [William M Clapp CLAPP-SABERWING, 1 case](https://openairdocs.org/ntsb-findings/01058510/cases.md?model=05633X7), [All aircraft, 13 cases](https://openairdocs.org/ntsb-findings/01058510/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute: Loss of engine power (total)](https://openairdocs.org/ntsb-events/341) (defining event); cases with it: [William M Clapp CLAPP-SABERWING, 1 case](https://openairdocs.org/ntsb-events/341/sequence.md?model=05633X7), [All aircraft, 3,820 cases](https://openairdocs.org/ntsb-events/341/sequence.md) - [Approach: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [William M Clapp CLAPP-SABERWING, 1 case](https://openairdocs.org/ntsb-events/470/sequence.md?model=05633X7), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The pilot departed the airport on a local flight to perform system checks of the experimental amateur-built airplane. During a functional check of the ignition system, while the pilot was selecting between the points and electronic ignition at a high engine power setting, the engine lost all power about 8 miles away from the airport. After multiple unsuccessful attempts to restart the engine, the pilot declared an emergency and executed a forced landing to a field. The airplane subsequently impacted a utility line and came to rest inverted in a field about 2 miles from the airport. The right wing, fuselage, and empennage sustained substantial damage. Postaccident examination of the automotive conversion engine revealed that the woodruff key that indexed the crankshaft gear and hub assembly to the crankshaft was sheared. The gear and hub assembly had rotated about 30° from its indexed position, resulting in the crankshaft-to-camshaft timing being out of alignment and a subsequent total loss of engine power. According to the pilot, who had built the engine about 17 years and 20 flight hours before the accident, when switching from points to electronic ignition sources, there was a small interval for the electronics to power up, resulting in a jolt across the engine when power was restored. The jolt, at a high power setting, was likely enough to rotate the gear and shear the woodruff key. ## Factual narrative On June 10, 2024, about 2000 eastern daylight time, an experimental amateur-built Clapp Saberwing airplane, N120SW, was substantially damaged when it was involved in an accident near Valdosta, Georgia. The pilot sustained serious injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 test flight. The pilot reported that he departed Valdosta Regional Airport (VLD), Valdosta, Georgia, on a local flight to perform system checks of the airplane. During a functional check of the ignition system, while selecting between points and electronic ignition at a high engine power setting, the engine lost all power about 8 miles southwest of VLD. After multiple unsuccessful attempts to restart the engine, the pilot declared an emergency and executed a forced landing to a field. During the landing, the airplane impacted a utility line and came to rest inverted in a field about 2 miles from the airport. The right wing, fuselage, and empennage sustained substantial damage. Postaccident examination of the Corvair automotive conversion engine by an FAA inspector and the pilot (who also built the engine) revealed that the timing marks on the crankshaft gear and hub assembly were not aligned with the crankshaft position. Further examination revealed that the woodruff key that indexed the crankshaft gear and hub assembly to the crankshaft was sheared and the assembly was rotated about 30° from its indexed position on the crankshaft. According to the pilot, when switching from points to electronic there was a small interval for the electronics to power up, resulting in a jolt across the engine when power was restored. The pilot reported that the accident engine was assembled as a test engine in 2007 and accrued about 20 flight hours. Since 2007, the interference fit between the crankshaft and the crankshaft gear and hub assembly increased from 0.002 inches to .004 inches, and hardened woodruff keys replaced standard woodruff keys to improve durability. ## Aircraft - Registration: [N120SW](https://openairdocs.org/aircraft/N120SW), registered now, S/N CLAPP04, built 2014 (OpenAirDocs) - Reported make and model: Clapp Saberwing - Registry model: [William M Clapp CLAPP-SABERWING](https://openairdocs.org/model/william-m-clapp-clapp-saberwing) (registry code 05633X7) (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: CLAPP04 - Year built: 2014 - Airframe hours: 551 - Engines: Spyder Engines 120HP1FB 100 horsepower reciprocating - Damage: Substantial damage - Flight: Flight test, Part 91 - Airworthiness certificate: Special, Experimental (Special) - Last inspection: Condition, March 30, 2024, 20 hours before - Departed: VLD, Valdosta, GA - Airport: VLD, Valdosta Rgnl, runway 4, 5,598 × 100 ft, asphalt - Equipment: Handheld GPS, Electronic primary flight display, Auto-pilot ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 55; injuries: serious; private, commercial, flight instructor; airplane ratings: single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review September 23, 2023; seat: left; restraint: 4-point; flight hours: 2,166 total, 436 in this make and model, 2,029 as pilot in command, 18 in the last 90 days, 9 in the last 30 days, 3 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 210° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 88 °F, dew point 73 °F - Altimeter: 29.75 inHg - Observed at: VLD, 1.5 nm away - METAR: KVLD 102353Z 21003KT 10SM CLR 31/23 A2975 RMK AO2 SLP081 T03060228 10367 20306 52003 ## 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 20240610015799A](https://openairdocs.org/incident/20240610015799A), Jun 10, 2024: William M Clapp CLAPP-SABERWING, Valdosta, GA, Destroyed. The Valdosta regional airport air traffic control tower received an emergency declaration due to an engine failure. Pilot reported engine failure eight miles… ## Docket (5 files) The files NTSB released with the investigation on April 22, 2026, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=194462. 94.0 MB in all. - NTSB 6120 1 form (item 1, PDF, 9 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19942558&FileExtension=pdf&FileName=NTSB%206120%201%20Form_Redacted-Rel.pdf - Photo array (item 2, PDF, 3 pages, 789 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19942652&FileExtension=pdf&FileName=Photo%20Array-Rel.pdf - Mor pilot statement and engine examination summary (item 3, PDF, 7 pages, 414 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19942786&FileExtension=pdf&FileName=MOR%20Pilot%20Statement%20and%20Engine%20Examination%20Summary%20_Redacted-Rel.pdf - Maintenance records (item 4, PDF, 3 pages, 89.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19942374&FileExtension=pdf&FileName=Maintenance%20Records_Redacted-Rel.pdf - Wreckage release form (item 5, PDF, 1 page, 947 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=20179427&FileExtension=pdf&FileName=Wreckage%20Release_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.