# NTSB CEN18LA059: American Champion 7GCAA, N519MA, Longmont, CO, December 20, 2017 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: December 20, 2017, 08:50 local (15:50 UTC) - Place: Longmont, CO - Coordinates: 40.165832, -105.166114 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=40.1658&lon=-105.1661&mi=10 - Phase of flight: [Landing](https://openairdocs.org/ntsb-phases/550) (OpenAirDocs' grouping) - Defining event: [Landing: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report July 5, 2018 - Report: Approved by Office Director - NTSB office: Central Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 96525 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN18LA059 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/96525/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=96525 - Page: https://openairdocs.org/ntsb/CEN18LA059 ## Probable cause The failure of the landing gear through bolt primarily due to fatigue during a hard landing, which resulted in a landing gear collapse and runway excursion. Contributing to the accident was noncompliance with the manufacturer service letter. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Failure (probable cause); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=2121002), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Fatigue/wear/corrosion (probable cause); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=2121002), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Not serviced/maintained (probable cause); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=2121002), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Landing gear system: main gear strut/axle/truck](https://openairdocs.org/ntsb-findings/01023213): Aircraft › Aircraft systems · Not inspected (probable cause); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-findings/01023213/cases.md?model=2121002), [All aircraft, 86 cases](https://openairdocs.org/ntsb-findings/01023213/cases.md) - [Maintenance/inspections: scheduled maint checks](https://openairdocs.org/ntsb-findings/01010520): Aircraft › Aircraft handling/service · Not inspected (probable cause); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-findings/01010520/cases.md?model=2121002), [All aircraft, 76 cases](https://openairdocs.org/ntsb-findings/01010520/cases.md) - [Inspection: scheduled/routine inspection](https://openairdocs.org/ntsb-findings/02061520): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-findings/02061520/cases.md?model=2121002), [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. - [Landing: Hard landing](https://openairdocs.org/ntsb-events/092); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-events/092/sequence.md?model=2121002), [All aircraft, 2,102 cases](https://openairdocs.org/ntsb-events/092/sequence.md) - [Landing: Dragged wing/rotor/float/other](https://openairdocs.org/ntsb-events/093); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-events/093/sequence.md?model=2121002), [All aircraft, 319 cases](https://openairdocs.org/ntsb-events/093/sequence.md) - [Landing: Nose over/nose down](https://openairdocs.org/ntsb-events/096); cases with it: [American Champion 7GCAA, 2 cases](https://openairdocs.org/ntsb-events/096/sequence.md?model=2121002), [All aircraft, 2,287 cases](https://openairdocs.org/ntsb-events/096/sequence.md) - [Landing: Landing gear collapse](https://openairdocs.org/ntsb-events/094); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-events/094/sequence.md?model=2121002), [All aircraft, 1,787 cases](https://openairdocs.org/ntsb-events/094/sequence.md) - [Landing: Sys/Comp malf/fail (non-power)](https://openairdocs.org/ntsb-events/330) (defining event); cases with it: [American Champion 7GCAA, 1 case](https://openairdocs.org/ntsb-events/330/sequence.md?model=2121002), [All aircraft, 994 cases](https://openairdocs.org/ntsb-events/330/sequence.md) ## Analysis The flight instructor and private pilot were conducting an instructional flight when the private pilot made a hard landing and the airplane bounced. The flight instructor heard a "snapping" sound during the landing and subsequently took over the flight controls. He increased engine power to compensate for the bounced landing then landed the airplane on the runway. Upon touchdown, the left landing gear collapsed up and aft. The airplane continued forward on its nose and left wing, then departed the left side of the runway. The left landing gear through bolt was found fractured. A metallurgical examination of the landing gear through bolt fracture revealed two opposing regions of fatigue comprising 80-90% of the cross-sectional area of the bolt. These were separated by a narrow region of overstress, consistent with reverse bending fatigue crack propagation, which likely grew under low stress as evidenced by the length of the fatigue cracks. The airplane was subject to a manufacturer service letter for inspection of the landing gear through bolts due to previous instances of cracking and failure. The service letter recommended that the inspections be performed on or before the next 100-hour inspection and at 100-hour intervals thereafter, and at more frequent intervals if the aircraft is used in soft or rough runway operations. The owner of the airplane was unaware of the service letter and stated that the airplane had not received the recommended inspection. Although not required, it is likely that had the service letter been complied with and the through bolt been regularly inspected, the fatigued bolt would have been replaced and the accident would have been prevented. ## Factual narrative On December 20, 2017, about 0850 mountain standard time, an American Champion Aircraft 7GCAA, N519MA, landed hard and departed the left side runway at Vance Brand Airport (LMO), Longmont, Colorado. The flight instructor and private pilot were not injured and the airplane sustained substantial damage during the runway excursion. The airplane was registered to CAG International Inc., and operated by Fly Elite Aviation, under the provisions of 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed at the time of the accident and no flight pan had been filed. The local flight departed about 0845. The flight instructor reported that private pilot made a hard landing during an instructional flight. The flight instructor heard a "snapping" sound during the landing so he took over the flight controls. He increased the throttle to compensate for the bounced landing and then landed the airplane on the runway. The left landing gear collapsed upward and aft damaging the left wing strut. The airplane continued forward on its nose and left wing as it departed the left side of the runway near taxiway A2 (figure 1). Figure 1 – Accident airplane The responding Federal Aviation Administration (FAA) inspector reported that the left landing gear thru-bolt was fractured. The left wing was bent upward, and the bottom and left side of the fuselage was damaged. A metallurgical examination of the landing gear thru-bolt fracture revealed a primary fatigue fracture that initiated at the shank surface and propagated through about 60% of the bolt diameter (figure 2). A second fatigue crack initiated on the shank surface about 180° from the primary crack and propagated through 20% to 30% of the bolt diameter. The fracture surface exhibited a narrow region of overstress fracture between the two fatigue crack regions. Figure 2 – Bolt fracture surface with notation On December 13, 1978, Bellanca Aircraft Corporation issued FAA approved service letter C-135 for the purposes of inspecting landing gear thru-bolts and U-bolts. The service letter applied to the accident airplane and was issued due to reports of cracked and failed thru-bolts and U-bolts which were used to attach the landing gear to the fuselage frame. The service letter stated that these problems were due to one or more of the following: (1) excessive loads during soft or rough runway operations; (2) improper torque; (3) corrosion. The service letter recommended the inspections be performed on or before the next 100-hour inspection and at 100-hour intervals thereafter, and at more frequent intervals if the aircraft is used in soft or rough runway operations. The airplane owner stated that the Bellanca service letter C-135 had not been complied with, nor was it required under the FAA regulations. The owner provided documentation that on September 7, 2017, an airframe annual inspection and engine 100-hour inspection were completed at tachometer time 1,817.5 hours. ## Aircraft - Registration: [N519MA](https://openairdocs.org/aircraft/N519MA), registered now, S/N 489-2004, built 2004 (OpenAirDocs) - Reported make and model: AMERICAN CHAMPION AIRCRAFT 7GCAA (NO SERIES) - Registry model: [American Champion 7GCAA](https://openairdocs.org/model/american-champion-7gcaa) (registry code 2121002) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 489-2004 - Year built: 2004 - Airframe hours: 1847 - Engines: Lycoming O-320-B2B 160 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Operator: Fly Elite Aviation - Registered owner: Cag International Inc DBA - Airworthiness certificate: Standard, Aerobatic; Standard, Normal - Last inspection: Annual, September 7, 2017 - Departed: LMO, Longmont, CO - Destination: LMO, Longmont, CO - Airport: LMO, Vance Brand, runway 29, 4,799 × 75 ft, concrete ## Flight crew As NTSB recorded them. NTSB leaves out names. - Flight instructor; age 56; injuries: none; flight instructor, commercial; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, with waivers/limitations; last flight review November 10, 2017; seat: rear; restraint: 5-point; flight hours: 3,200 total, 118 in this make and model, 45 in the last 90 days, 16 in the last 30 days, 2 in the last 24 hours - Pilot; age 38; injuries: none; private; airplane ratings: single-engine land; medical: class 3, without waivers/limitations; last flight review May 20, 2017; seat: front; restraint: 4-point; flight hours: 144 total, 8 in this make and model, 8 in the last 90 days, 6 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 340° at 4 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 43 °F, dew point 25 °F - Altimeter: 29.80 inHg - Observed at: KLMO ## 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 20171220023359A](https://openairdocs.org/incident/20171220023359A), Dec 20, 2017: American Champion Aircraft 7GCAA, Longmont, CO, Substantial damage. The left hand landing gear, inboard retaining bolt failed during landing on runway 29 at klmo airport. During landing phase of an instructional flight for… ## Docket (4 files) The files NTSB released with the investigation on January 19, 2018, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=96525. 3.2 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.6 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40459474&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Master.PDF - Maintenance Records (item 2, .PDF, 542 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40459475&FileExtension=.PDF&FileName=Maintenance%20Records-Master.PDF - Manufacturer Service Letter C-135 (item 3, .PDF, 855 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40459476&FileExtension=.PDF&FileName=Manufacturer%20Service%20Letter%20C-135-Master.PDF - Photos (item 4, .PDF, 200 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40459477&FileExtension=.PDF&FileName=Photos-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.