# NTSB LAX07LA078: Republic RC-3, N6248K, Julian, CA, February 2, 2007 - Type: NTSB accident investigation - Classification: Accident · No injuries · Limited investigation · Final report - Date: February 2, 2007, 11:30 local (19:30 UTC) - Place: Julian, CA - Coordinates: 33.066665, -116.633331 - Nearby events: https://openairdocs.org/map.md?lat=33.0667&lon=-116.6333&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Highest injury: No injuries - Injuries: 2 uninjured - Status: Completed, report June 30, 2008 - Report: Approved by Office Director - Parties: Federal Aviation Adminstration - NTSB case key (mKey): 65239 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX07LA078 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/65239/pdf - Page: https://openairdocs.org/ntsb/LAX07LA078 ## Probable cause The failure of the propeller to crankshaft attachment bolts due to fatigue. A contributing factor was the improper installation of the propeller assembly by maintenance personnel. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Propeller failure/malfunction, cruise - normal - maintenance,installation - improper, other maintenance personnel (contributing factor) - propeller system/accessories - fatigue (cause) - Forced landing, descent - emergency - In flight collision with terrain/water, descent - emergency - terrain condition - open field ## Analysis During cruise flight, the propeller assembly departed from the crankshaft flange and fell from the airplane. The pilot executed a forced landing to an open field. The recently overhauled propeller assembly had been installed on the engine for approximately 8 hours prior to the separation. Examination of the airframe revealed the six propeller to crankshaft attachment bolts were fractured, and all failed as a result of fatigue cracking. No chemical composition or other material deficiencies were found on the bolts. Bolt fatigue is most commonly the result of insufficient preload from under torquing the fastener, or improper installation, or from the loss of preload during service. The equal amounts of fatigue on all six bolts suggested that all bolts were equally affected. ## Factual narrative On February 2, 2007, approximately 1130 Pacific standard time, a Republic RC-3 single engine airplane, N6248K, made a forced landing following the separation of the propeller assembly from the crankshaft flange near Julian, California. The commercial pilot and one passenger were not injured. The airplane sustained substantial damage. The owner/pilot was operating the airplane under the provisions of 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan had been filed. The cross-country personal flight departed Gillespie Field Airport (SEE), El Cajon, California, about 1100, with a planned destination of Blythe, California. The pilot reported that during cruise flight, the Hartzell HC-A3VF-3L propeller assembly departed from the crankshaft flange and fell from the airplane. The pilot then executed a forced landing to an open field about 2 miles west of Julian. An examination of the airframe revealed the underside of the fuselage was crushed upward, the left and right horizontal stabilizers were bent, and the six propeller to crankshaft attachment bolts were fractured. The attachment bolts were retained for further examination. Examination of the six attachment bolts by the National Transportation Safety Board Materials Laboratory revealed similar fracture features. The fractures were generally flat and relatively smooth with curved crack arrest marks typical of fatigue progression. Multiple ratchet marks indicated fatigue initiation on opposites side of each bolt indicative of reverse bending loading. However, the majority of the fatigue progression was from one side penetrating an estimated 75 to 85 percent of the cross section. The individual fatigue regions initiated at multiple sites in the root radii of the first fully formed threads. No mechanical damage or corrosion was noted in the thread roots at the origin locations. Measured hardness was consistent with 180,000 pounds per square inch tensile strength steel. A review of the maintenance logbooks revealed the propeller was overhauled and installed on February 5, 2003, at a total airframe time of 802 hours. On January 10, 2007, at a total airframe time of 810 hours, the airframe underwent its most recent annual inspection with no anomalies noted. The pilot reported that at the time of the accident, the propeller assembly had accumulated 8 hours since installation. ## Aircraft - Registration: [N6248K](https://openairdocs.org/deregistered/N6248K-2021-03-06), registration cancelled 2021-03-06, S/N 455, built 1947 (OpenAirDocs) - Reported make and model: Republic RC-3 - Registry model: [Republic RC-3](https://openairdocs.org/model/republic-rc-3) (registry code 3080202) (OpenAirDocs) - Registry engine: [Franklin 6A8 series](https://openairdocs.org/engine/franklin-6a8-series) (registry code 27030, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 455 - Airframe hours: 210 - Engines: Lycoming GO-480-G2D6 250 hp reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Registered owner: Richard L. Essery - Airworthiness certificate: Standard, Normal - Last inspection: Annual, January 1, 2007, 1 hours before - Departed: SEE, El Cajon, CA - Destination: Blythe, CA ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 60; injuries: none; flight instructor, commercial; airplane ratings: multi-engine land, single-engine sea, single-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review October 1, 2006; seat: left; flight hours: 5,000 total, 150 in this make and model, 4,800 as pilot in command, 4 in the last 90 days, 2 in the last 30 days, 1 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 25 statute miles - Lowest ceiling: none - Temperature: 59 °F, dew point 36 °F - Altimeter: 30.13 inHg - Observed at: SEE ## 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 20070202001629A](https://openairdocs.org/incident/20070202001629A), Feb 2, 2007: Stolam RC3, Julian, CA, Substantial damage. (-23) On February 2, 2007, about 1135 pacific standard time, a republic RC-3, N6248K, made a forced landing following the separation of the hub and propeller… 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.