# NTSB WPR20LA062: Cessna 172H, N1658F, El Monte, CA, January 6, 2020 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: January 6, 2020, 13:09 local (21:09 UTC) - Place: El Monte, CA - Coordinates: 34.085556, -118.035003 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=34.0856&lon=-118.0350&mi=10 - Phase of flight: [Maneuvering](https://openairdocs.org/ntsb-phases/450) (OpenAirDocs' grouping) - Defining event: [Maneuvering: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Western Pacific Region - Parties: Federal Aviation Administration - NTSB case key (mKey): 100785 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=WPR20LA062 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/100785/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=100785 - Page: https://openairdocs.org/ntsb/WPR20LA062 ## Probable cause The inflight separation of a section of a propeller blade due to a fatigue crack which resulted in a forced landing. ## 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 · Fatigue/wear/corrosion (probable cause); cases with it: [Cessna 172H, 1 case](https://openairdocs.org/ntsb-findings/01046111/cases.md?model=2072424), [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 · Failure (probable cause); cases with it: [Cessna 172H, 1 case](https://openairdocs.org/ntsb-findings/01046111/cases.md?model=2072424), [All aircraft, 51 cases](https://openairdocs.org/ntsb-findings/01046111/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Maneuvering: Part(s) separation from AC](https://openairdocs.org/ntsb-events/338) (defining event); cases with it: [Cessna 172H, 2 cases](https://openairdocs.org/ntsb-events/338/sequence.md?model=2072424), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) ## Analysis The pilot reported that during the flight, the airplane suddenly vibrated severely followed by a sudden loss of engine power and the appearance of oil on the windscreen. The pilot noticed that the propeller was not rotating along with visible damage to the engine cowling. The pilot initiated a forced landing to a nearby airport and landed uneventfully. Postaccident examination of the airplane revealed that the engine mount was bent, and a portion of one propeller blade had separated in flight. Examination of the propeller revealed that it exhibited a fracture chordwise across the propeller approximately 12 inches outboard of the center of the propeller hub. The leading-edge area of the fracture exhibited an area of darker coloration and smoother surface texture along with fracture features consistent with progressive crack growth on the fracture surface in the area. The signatures were consistent with a fatigue fracture originating at the leading edge of the propeller ## Factual narrative On January 6, 2020, about 1309 Pacific standard time, a Cessna 172H airplane, N1658F, was substantially damaged when it was involved in an accident near El Monte, California. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the purpose of the flight was to break in new engine cylinders while circling the city of El Monte at 3,500 ft mean sea level. During the flight, the airplane suddenly vibrated severely followed by a sudden loss of engine power and the appearance of oil on the windscreen. The pilot noticed that the propeller was not rotating and there was visible damage to the engine cowling. The pilot initiated a forced landing to the San Gabriel Valley Airport (EMT) and landed uneventfully. Examination of the airplane by a Federal Aviation Administration inspector revealed that the engine mount was bent and one of the propeller blades was separated about 1 ft outboard of the blade root. The propeller was retained for further examination. Examination of the propeller by the National Transportation Safety Board Materials Laboratory revealed that the propeller exhibited a chordwise fracture across the propeller approximately 12 inches outboard of the center of the propeller hub. The fracture surface was relatively flat in the area, including the leading edge of the propeller, and transitioned to a slant type fracture toward the trailing edge. The leading edge exhibited an area of darker coloration and smoother surface texture, which was evident when exposed to side lighting (see figure). Figure: View of the fracture area of the propeller blade. The leading edge exhibited an area of post-fracture impact damage when examined using the scanning electron microscope (SEM), however, further examination with the SEM revealed fracture features consistent with progressive crack growth on the fracture surface in the area described as having a darker and smoother appearance, consistent with a fatigue fracture originating at the leading edge of the propeller. Review of the propeller logbooks revealed that the propeller was overhauled on December 4, 2014. The last 100-hour inspection was completed on December 4, 2019. It could not be determined how much total time since new or time since overhaul the propeller had accrued at the time of the accident. ## Aircraft - Registration: [N1658F](https://openairdocs.org/aircraft/N1658F), registered now, S/N 17255053, built 1966 (OpenAirDocs) - Reported make and model: Cessna 172H - Registry model: [Cessna 172H](https://openairdocs.org/model/cessna-172h) (registry code 2072424) (OpenAirDocs) - Registry engine: [Continental 0-300 series](https://openairdocs.org/engine/continental-0-300-series) (registry code 17022, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 17255053 - Year built: 1966 - Airframe hours: 9794 - Engines: Continental O-360-A4M 145 horsepower reciprocating - Damage: Substantial damage - Flight: Personal, Part 91 - Operator: Mondo Beyondo Thrill Squadron - Registered owner: Mondo Beyondo Thrill Squadron - Airworthiness certificate: Standard, Normal - Last inspection: 100 hour, December 4, 2019, 33 hours before - Airport: EMT, San Gabriel Valley - Equipment: ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 57; injuries: none; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, with waivers/limitations; last flight review January 30, 2018; seat: left; restraint: 4-point; flight hours: 5,208.7 total, 1,258.4 in this make and model, 5,064.4 as pilot in command, 159.5 in the last 90 days, 44.2 in the last 30 days, 3.2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: calm - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 77 °F, dew point 25 °F - Altimeter: 30.23 inHg - Observed at: KEMT ## 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 20200106003269A](https://openairdocs.org/incident/20200106003269A), Jan 6, 2020: Cessna 172H, El Monte, CA, Substantial damage. On January 6, 2020, at approx. 12:09 pm, a Cessna 172H, N1658F, reregistered to mondo beyond thrill squadron, experienced a propeller blade separation at… ## Docket (4 files) The files NTSB released with the investigation on March 21, 2022, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=100785. 3.4 MB in all. - NTSB materials laboratory report (item 1, PDF, 5 pages, 6 photos, 623 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12428051&FileExtension=pdf&FileName=Materials%20Laboratory%20Report%2020-052-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 10 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12427693&FileExtension=pdf&FileName=6120_Redacted-Rel.pdf - Evidence control form (item 3, PDF, 1 page, 28 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12427898&FileExtension=pdf&FileName=Evidence%20Control%20Form%20(003)-Rel.pdf - Photo array (item 4, PDF, 3 pages, 3 photos, 422 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=12426788&FileExtension=pdf&FileName=photo%20array-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.