# NTSB WPR13LA191: Ercoupe 415-C, N87114, Mesquite, NV, April 14, 2013 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Limited investigation · Final report - Date: April 14, 2013, 10:20 local (17:20 UTC) - Place: Mesquite, NV - Coordinates: 36.89611, -114.049446 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.8961&lon=-114.0494&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Defining event: [Initial climb: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: Minor injuries - Injuries: 1 minor - Status: Completed, report June 2, 2014 - Report: Approved by Office Director - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration FSDO - NTSB case key (mKey): 86645 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR13LA191 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/86645/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=86645 - Page: https://openairdocs.org/ntsb/WPR13LA191 ## Probable cause Separation of the propeller from the engine during initial climb due to the incorrect torque applied to the propeller hub nut during maintenance. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Propeller system: propeller assembly](https://openairdocs.org/ntsb-findings/01046110): Aircraft › Aircraft propeller/rotor · Incorrect service/maintenance (probable cause); cases with it: [Engineering & Research 415-C, 1 case](https://openairdocs.org/ntsb-findings/01046110/cases.md?model=0420302), [All aircraft, 29 cases](https://openairdocs.org/ntsb-findings/01046110/cases.md) - [Maintenance: installation](https://openairdocs.org/ntsb-findings/02062035): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Engineering & Research 415-C, 1 case](https://openairdocs.org/ntsb-findings/02062035/cases.md?model=0420302), [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. - [Initial climb: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Engineering & Research 415-C, 1 case](https://openairdocs.org/ntsb-events/338/sequence.md?model=0420302), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) - [Emergency descent: Collision with terr/obj (non-CFIT) ](https://openairdocs.org/ntsb-events/470); cases with it: [Engineering & Research 415-C, 8 cases](https://openairdocs.org/ntsb-events/470/sequence.md?model=0420302), [All aircraft, 10,189 cases](https://openairdocs.org/ntsb-events/470/sequence.md) ## Analysis The propeller departed the airplane during the initial climb following takeoff, and the pilot performed a forced landing into a rocky field. The airplane sustained substantial damage to the right wing and firewall during the accident sequence; the pilot was not injured. The propeller and its associated hub mounting hardware were not recovered. The threaded portion of the crankshaft had been flattened by the propeller's hub, indicating that the hub nut was in place but had backed off during the flight. The nut had backed off most likely because the incorrect torque had been applied during its reinstallation, about 40 flight hours before the accident flight. ## Factual narrative On April 14, 2013, about 1020 Pacific daylight time, an Engineering and Research Corporation (Ercoupe) 415-C, N87114, landed hard during a forced landing shortly after takeoff from Mesquite Airport, Mesquite, Nevada. The pilot was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The private pilot sustained minor injuries; the airplane sustained substantial damage to the right wing and firewall during the accident sequence. The cross-country personal flight departed Mesquite about 1015, with a planned destination of Ely Airport, Ely, Nevada. Visual meteorological conditions prevailed, and a visual flight rules flight plan had been filed. The pilot reported that the ground run-up, takeoff, and initial climb were uneventful, with the airplane maintaining a climb rate of 500 feet per minute, at an engine speed of 2,300 rpm. About 5 minutes later, he felt a low frequency vibration, and assuming it was an engine speed related harmonic, reached forward to adjust the throttle. Just as he reached forward, the engine speed surged to 4,000 rpm, and he immediately retarded the throttle. The pilot could not see any propeller movement, and the engine did not appear to be producing thrust. In an attempt to diagnose the problem, he advanced the throttle again, and the engine surged to 4,200 rpm. The pilot realized that the propeller had separated from the engine, and began to configure the airplane for a forced landing. He stated that due to the altered center of gravity with the propeller missing, he was unable to maintain positive airplane control at any airspeed below 85 mph. He subsequently performed a forced landing into rocky desert scrub, about 5 miles from the airport. The airplane had undergone an annual inspection on August 6, 2012, at a tachometer time of 264.2 hours. Maintenance records indicated that at the time of inspection, the Continental C85-12 engine, serial number 27027-7-12, had accrued 320.2 hours since overhaul in July 1996. An entry dated July 27, 2012, indicated that the propeller was removed to facilitate the installation of the crankshaft oil seal at a tachometer time of 252.3 hours. The tachometer on the airplane at the accident site indicated 294.5 hours. The crankshaft was of the tapered type, with the propeller hub and flange assembly being held in place with a single hub nut. The tapered portion of the crankshaft was keyed to accept the propeller hub assembly. The crankshaft tip, propeller hub, and hub nut all contained four "safety holes" drilled 90 degrees apart radially. The design was such that a flat-head pin was installed through one of these holes once they were aligned, after the correct hub nut torque was applied. A cotter pin was utilized to retain the flat-head pin. According to representatives from Continental Motors, once the correct hub nut torque was applied, the flat-head and cotter pins should be loose within the assembly, a tight fit indicating that the propeller hub nut hadbacked off. Neither the propeller nor its associated hub hardware forward of the crankshaft seal was recovered. The crankshaft was removed from the engine to facilitate inspection. Its threaded portion exhibited flattening and peening damage to about 45 percent of its surface. Three of the four safety holes were round and appeared undamaged, with the fourth exhibiting elongation in the plane of rotation, and material smear of its outer lip. The owner stated that the crankshaft oil seal was replaced due to an oil leak. He did not recall seeing a cotter pin ever installed on the hub nut, noting instead the use of a cadmium plated bolt and "Nyloc" nut. ## Aircraft - Registration: [N87114](https://openairdocs.org/deregistered/N87114-2018-06-04), registration cancelled 2018-06-04, S/N 287, built 1946 (OpenAirDocs) - Reported make and model: ERCOUPE 415-C - Registry model: [Engineering & Research 415-C](https://openairdocs.org/model/engineering-research-415-c) (registry code 0420302) (OpenAirDocs) - Registry engine: [Continental C85 series](https://openairdocs.org/engine/continental-c85-series) (registry code 17008, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 287 - Year built: 1946 - Airframe hours: 1800 - Engines: Continental Motors C85 75 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, August 6, 2012, 42.2 hours before - Departed: 67L, Mesquite, NV - Destination: KELY, Ely, NV - Flight plan: VFR - Airport: 67L, Mesquite, runway 01, 5,121 × 75 ft, asphalt - Equipment: Handheld GPS ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 66; injuries: minor; private; airplane ratings: single-engine land; medical: class 3, with waivers/limitations; last flight review August 27, 2012; seat: left; restraint: lap only; flight hours: 1,674 total, 100 in this make and model, 1,589 as pilot in command, 7 in the last 90 days, 7 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 70° at 10 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 72 °F, dew point 25 °F - Altimeter: 29.65 inHg - Observed at: KLAS, 69 nm away ## Docket (10 files) The files NTSB released with the investigation on April 25, 2014, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=86645. 12.2 MB in all. - Pilot/Operator Aircraft Accident Report, NTSB Form 6120.1 (item 1, .PDF, 1.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40391367&FileExtension=.PDF&FileName=Pilot%2FOperator%20Aircraft%20Accident%20Report,%20NTSB%20Form%206120.1-Redacted.PDF - Photo 1 - Airplane at Accident Site (item 2, .PDF, 158 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411542&FileExtension=.PDF&FileName=Photo%201%20-%20Airplane%20at%20Accident%20Site%0D%0A-Master.PDF - Photo 2 - Engine Crankshaft at Accident Site (item 3, .PDF, 143 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411543&FileExtension=.PDF&FileName=Photo%202%20-%20Engine%20Crankshaft%20at%20Accident%20Site%0D%0A-Master.PDF - Photo 3 - Engine Crankshaft (item 4, .PDF, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411544&FileExtension=.PDF&FileName=Photo%203%20-%20Engine%20Crankshaft%0D%0A-Master.PDF - Photo 4 - Engine Crankshaft, Flattened Thread (item 5, .PDF, 3.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411545&FileExtension=.PDF&FileName=Photo%204%20-%20Engine%20Crankshaft,%20Flattened%20Thread%0D%0A-Master.PDF - Photo 5 - Engine Crankshaft, Safety Hole (item 6, .PDF, 3.2 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411546&FileExtension=.PDF&FileName=Photo%205%20-%20Engine%20Crankshaft,%20Safety%20Hole%0D%0A-Master.PDF - Statement of Party Representatives to NTSB Investigation (item 7, .PDF, 247 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411547&FileExtension=.PDF&FileName=Statement%20of%20Party%20Representatives%20to%20NTSB%20Investigation-Redacted.PDF - Engine Logbook Excerpts (item 8, .PDF, 382 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411548&FileExtension=.PDF&FileName=Engine%20Logbook%20Excerpts-Redacted.PDF - C85 Maintenance Manual Excerpts (item 9, .PDF, 218 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411549&FileExtension=.PDF&FileName=C85%20Maintenance%20Manual%20Excerpts-Master.PDF - Release of Aircraft Wreckage, NTSB Form 6120.15 (item 10, .PDF, 134 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=40411550&FileExtension=.PDF&FileName=Release%20of%20Aircraft%20Wreckage,%20NTSB%20Form%206120.15-Redacted.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.