# NTSB CEN12LA655: TL Ultralight Sro Stingsport, N898N, Longmont, CO, September 1, 2012 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: September 1, 2012, 11:30 local (17:30 UTC) - Place: Longmont, CO - Coordinates: 40.217777, -105.010276 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.2178&lon=-105.0103&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report April 10, 2014 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 85136 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN12LA655 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/85136/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=85136 - Page: https://openairdocs.org/ntsb/CEN12LA655 ## Probable cause The failure of the wood propeller blades in flight. Contributing to the accident was the owner/operator’s failure to complete required inspections on the propeller within the specified interval, which reduced the likelihood of detecting the cracks and may have contributed to the crack growth. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Propeller system: propeller blade section](https://openairdocs.org/ntsb-findings/01046111): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [TL Ultralight Sro STINGSPORT, 2 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md?model=060001R), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md) - [Propeller system: propeller blade section](https://openairdocs.org/ntsb-findings/01046111): Aircraft › Aircraft propeller/rotor · Fatigue/wear/corrosion (probable cause); cases with it: [TL Ultralight Sro STINGSPORT, 2 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md?model=060001R), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md) - [Propeller system: propeller blade section](https://openairdocs.org/ntsb-findings/01046111): Aircraft › Aircraft propeller/rotor · Inadequate inspection (probable cause); cases with it: [TL Ultralight Sro STINGSPORT, 2 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md?model=060001R), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md) - [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Pilot (probable cause); cases with it: [TL Ultralight Sro STINGSPORT, 1 case](https://openairdocs.org/ntsb-findings/02061520/cases.md?model=060001R), [All aircraft, 167 cases](https://openairdocs.org/ntsb-findings/02061520/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [TL Ultralight Sro STINGSPORT, 1 case](https://openairdocs.org/ntsb-events/340/sequence.md?model=060001R), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) ## Analysis While conducting maneuvers at 2,500 feet, the airplane began to vibrate violently. The pilot aborted the maneuver and retarded the throttle to idle; the engine experienced a total loss of power. The pilot executed a forced landing into a field. After the landing, the pilot and the designated pilot examiner noticed that two of the propeller blades had separated from the propeller hub. An examination of the fractured blades and blade sleeves revealed that blade A likely fractured due to progressive cracking at laminate bonds at the interface between the wood blade and the metal sleeve. The powdery wood observed in the slots and at the root end of the blade shank were indicative of rubbing wood as the cracks progressed. The blade B fracture was likely secondary and occurred due to the vibrations associated with the imbalance created by the blade A fracture and subsequent separation. The propeller log indicated that manufacturer-specified visual inspections and torque checks were not conducted at the specified interval of 150 hours but at intervals of about 203, 320, and 250 hours. The delayed visual inspections reduced the likelihood of detecting the cracks and the delayed torque checks might have contributed to crack growth in the blade. ## Factual narrative The airplane was a TL Ultralight SRO Stingsport, two-place, high wing, fixed gear, light sport airplane manufactured in 2006. An airworthiness certificate was issued for N889N on March 10, 2006. It was powered by a Bombardier Rotax engine and equipped with a 3 bladed WoodComp wooden propeller. Visual inspections of the propeller and propeller hub and bolt torques were checked per the TL Ultralight SRO and WoodComp instructions. The inspections were completed on: August 1, 2009 at a total time of 158.4; August 3, 2009 at a total time of 361.2; August 12, 2010 at a total time of 680.9; and September 1, 2011 at a total time of 924.8. According to WoodComp, the propeller inspections were required at 150 hour intervals. On September 1, 2012, about 1130 mountain daylight time, a TL Ultralight SRO Stingsport airplane, N898N, conducted a forced landing after two of the propeller blades separated inflight near Longmont, Colorado. The airplane sustained substantial damage. The sport pilot and the designated pilot examiner (DPE) on board were not injured. The aircraft was registered to STING4FUN LLC and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed for the flight, which operated without a flight plan. The flight originated from Erie Municipal Airport (KEIK), Erie, Colorado at 1100. The DPE stated that while the pilot was conducting a steep turn demonstration at 2,500 feet above the ground, the engine began vibrating violently. The pilot aborted the maneuver and retarded the throttle to idle when the engine experienced a total loss of power. The pilot made an emergency landing in a nearby field. After the landing, the pilot and DPE noticed that two of the three propeller blades had separated from the propeller hub. The airplane sustained substantial damage to the firewall and engine mount. An automated weather report at Erie, Colorado, 14 miles north of the accident site, was issued at 1134 and reported: wind from 020 degrees and 3 knots, 10 miles visibility, sky clear, temperature 29 degrees Celsius (C), dewpoint 3 degrees C, and pressure 30.12 inches of mercury. The pilot, age 43, held a sport pilot certificate at the time of the accident. He received his private pilot certificate after the conclusion of the accident flight. The remaining propeller blade and all three propeller sleeves were examined by the NTSB Materials Laboratory, Washington, DC. Each of the propeller blades and corresponding blades sleeves were labeled A, B, and C for identification purposes. Blade A consisted of an entire blade sleeve and a small amount of fractured wood inside the sleeve. A tan powdery substance was noted in the sleeve and in the slots of the sleeve. The substance was tested and matched that of the wood propeller. Progressive cracks were evident in blade A between the blade and the metal sleeve. Blade B consisted of an entire blade sleeve and a section ofwood which remained attached to the sleeve and also extended out of the sleeve. The blade exhibited cracks in the wood that corresponded to the interface between the blade and the sleeve. Blade C consisted of an entire blade sleeve and an entire wood blade and exhibited kinked fibers in the composite layer and crack features at the blade root near the metal sleeve. The airplane came to rest upright in a field. The engine mounts and firewall were bent during the forced landing. The rest of the airplane was otherwise unremarkable. ## Aircraft - Registration: [N898N](https://openairdocs.org/aircraft/N898N), registered now, S/N TLUSA129, built 2006 (OpenAirDocs) - Reported make and model: TL ULTRALIGHT SRO STINGSPORT - Registry model: [TL Ultralight Sro STINGSPORT](https://openairdocs.org/model/tl-ultralight-sro-stingsport) (registry code 060001R) (OpenAirDocs) - Registry engine: [Bombardier ROTAX (ALL)](https://openairdocs.org/engine/bombardier-rotax-all) (registry code 09050, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: TLUSA129 - Year built: 2006 - Engines: Rotax reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Sting4fun LLC - Registered owner: Sting4fun LLC - Airworthiness certificate: Special, Special light-sport (Special) - Departed: EIK, ERIE, CO - Destination: EIK, ERIE, CO ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 43; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; seat: left - Check pilot; injuries: none; airline transport, flight instructor; airplane ratings: single-engine land, single-engine sea; seat: right ## Weather - Conditions: Visual (VMC), Day - Wind: 20° at 3 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 84 °F, dew point 37 °F - Altimeter: 30.12 inHg - Observed at: KEIK, 14 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). - [Incident 20120901021719I](https://openairdocs.org/incident/20120901021719I), Sep 1, 2012: Tl Ultralight Sro STINGSPORT, Erie, CO, Minor damage. On 9-1-2012, aircraft N898N, a light sport aircraft, experienced major damage when one propeller blade separated from the hub during cruise flight. Flight… ## Docket (4 files) The files NTSB released with the investigation on March 26, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=85136. 3.7 MB in all. - Miscellaneous - Accident Report (item 1, .PDF, 1.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40410340&FileExtension=.PDF&FileName=Miscellaneous%20-%20Accident%20Report-Redacted.PDF - Maintenance Records - Propeller Inspections (item 2, .PDF, 873 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40410353&FileExtension=.PDF&FileName=Maintenance%20Records%20-%20Propeller%20Inspections-Redacted.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 3, .PDF, 56 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40410348&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.PDF - Materials Laboratory 15 - Factual Report 13-103 (item 4, .PDF, 1.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40409789&FileExtension=.PDF&FileName=Materials%20Laboratory%2015%20-%20Factual%20Report%2013-103-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.