# NTSB ANC25LA028: Piper PA-28-140, N261FC, Royal Kunia, HI, March 27, 2025 - Type: NTSB accident investigation - Classification: Accident · Minor injuries · Class 3 · Limited · Final report - Date: March 27, 2025, 12:00 local (22:00 UTC) - Place: Royal Kunia, HI - Coordinates: 21.412104, -158.03393 - Nearby events: https://openairdocs.org/map.md?lat=21.4121&lon=-158.0339&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: Minor injuries - Injuries: 2 minor - Status: Completed, report January 21, 2026 - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Alaska Regional Office - Parties: FAA, Lycoming - NTSB case key (mKey): 199932 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=ANC25LA028 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/199932/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=199932 - Page: https://openairdocs.org/ntsb/ANC25LA028 ## Probable cause Improper alteration of the crankshaft propeller flange at an unknown time, which resulted in an in-flight separation of the propeller assembly. ## 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 · Failure (probable cause); cases with it: [Piper PA-28-140, 1 case](https://openairdocs.org/ntsb-findings/01046110/cases.md?model=7102802), [All aircraft, 29 cases](https://openairdocs.org/ntsb-findings/01046110/cases.md) - [Maintenance: scheduled/routine maintenance](https://openairdocs.org/ntsb-findings/02062010): Personnel issues › Task performance · Maintenance personnel (probable cause); cases with it: [Piper PA-28-140, 9 cases](https://openairdocs.org/ntsb-findings/02062010/cases.md?model=7102802), [All aircraft, 320 cases](https://openairdocs.org/ntsb-findings/02062010/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: [Piper PA-28-140, 6 cases](https://openairdocs.org/ntsb-events/338/sequence.md?model=7102802), [All aircraft, 563 cases](https://openairdocs.org/ntsb-events/338/sequence.md) ## Analysis During an instructional flight, the flight instructor detected a vibration; shortly thereafter he heard a loud bang, the engine lost total power, and the nose dropped. He performed a forced landing to a heavily vegetated field. After landing, the flight instructor noticed that the propeller was missing. It was later found in a nearby residence; no one was injured. The airplane sustained substantial damage to both wings, the fuselage, and the empennage. Examination of the separated propeller revealed that the engine crankshaft had fractured and separated just aft of the crankshaft propeller flange (CPF). This flange is an integral part of the crankshaft and is where the propeller attaches to the engine; however, the CPF was found attached to the separated propeller and not the crankshaft where it belonged. The CPF was removed from the propeller and examined by an NTSB metallurgist to determine why the crankshaft had fractured and separated. The examination revealed that the CPF had been improperly modified by the drilling and installation of additional bolts. Investigators were unable to determine the purpose for the modification, when it was made, or by whom. Available maintenance records did not include any entries noting that the propeller assembly had been removed or altered since initial installation. Additionally, there are no Lycoming maintenance instructions, repair instructions, or service bulletins that permit hole drilling and filling of the CPF. ## Factual narrative On March 27, 2025, about 1200 Hawaii-Aleutian standard time, a Piper PA-28-140, N261FC, was substantially damaged when it was involved in an accident near Royal Kunia, Hawaii. The flight instructor and student pilot reported minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor and student departed Honolulu Airport (HNL), Honolulu, Hawaii, for the student’s first instructional flight. As the airplane climbed to about 1,500 ft mean sea level the instructor reported feeling a slight vibration, which he had not felt on a previous flight in the accident airplane earlier that day. The flight instructor initiated a climb and turned back to HNL. He then heard a loud bang, the engine lost total power, and the nose of the airplane dropped. The flight instructor subsequently initiated an off-airport emergency landing to a field. The airplane impacted several small trees and vegetation during landing, resulting in substantial damage to the fuselage, wings, and empennage. Upon landing, the flight instructor noticed that the propeller was missing. It was later found in a nearby residence; no one was injured. Examination of the separated propeller revealed that the engine crankshaft had fractured and separated just aft of the CPF. The separated CPF, mating flywheel starter ring gear, and six attaching bolts with washers were sent to the NTSB Materials Laboratory for examination. The examination revealed that the CPF had separated from the crankshaft through the webs between the lightening holes at roughly the same radial location. The separation was due to multiple fatigue fractures through the flange webs. The fracture surfaces on two diametrically opposite webs were perpendicular to embedded cylindrical-shaped items, consistent with bolt shanks. The fatigue fractures initiated at these bolt pieces in two of the crankshaft propeller flange webs and propagated over a long period of time. Maintenance records indicated that the Lycoming O-320-62A engine and the Sensenich propeller were installed on the airplane on September 15, 2019. Available maintenance records did not include any entries noting that the propeller assembly had been removed or altered since its initial installation. The most recent annual inspection was completed on February 5, 2025, and indicated 1,805.1 hours on the engine since overhaul. The most recent 100-hour inspection of the propeller was completed on March 7, 2025, and records indicate that it had about 3,975.6 hours since new. There is no record of a crankshaft modification, and no part markings were observed on the outer diameter of the propeller flange as specified on the manufacturer’s drawing; therefore, the exact age and model of the crankshaft could not be determined. Historical engine records indicating the date and details of the last engine overhaul could not be located. ## Aircraft - Registration: [N261FC](https://openairdocs.org/aircraft/N261FC), registered now, S/N 28-24697, built 1968 (OpenAirDocs) - Reported make and model: PIPER PA-28-140 - Registry model: [Piper PA-28-140](https://openairdocs.org/model/piper-pa-28-140) (registry code 7102802) (OpenAirDocs) - Registry engine: [Lycoming 0-320 series](https://openairdocs.org/engine/lycoming-0-320-series) (registry code 41508, reciprocating) (OpenAirDocs) - Category: Airplane - Serial number: 28-24697 - Year built: 1968 - Airframe hours: 12238.6 - Engines: Lycoming O-320-62A 150 horsepower reciprocating - Damage: Substantial damage - Flight: Instructional, Part 91 - Airworthiness certificate: Standard, Normal - Last inspection: Annual, February 5, 2025, 42 hours before - Departed: HNL, Honolulu, HI - Airport: NONE - Equipment: Handheld GPS, ADS-B ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 38; injuries: none; commercial, flight instructor; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 1, without waivers/limitations; last flight review October 9, 2024; seat: right; restraint: lap only; flight hours: 1,707.1 total, 33 in this make and model, 1,569.8 as pilot in command, 140.3 in the last 90 days, 33.4 in the last 30 days, 1.1 in the last 24 hours - Student pilot; age 22; injuries: minor; seat: left; restraint: lap only; flight hours: 0 total, 0 in this make and model ## Weather - Conditions: Visual (VMC), Day - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 82 °F, dew point 68 °F - Altimeter: 30.07 inHg - Observed at: PHNL, 7 nm away - METAR: PHNL 272153Z 16010KT 10SM FEW025 FEW035 28/20 A3007 RMK AO2 SLP181 T02780200 VISNO RWY04R $ ## 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 20250327007819A](https://openairdocs.org/incident/20250327007819A), Mar 27, 2025: Piper PA-28-140, Waipahu, HI, Substantial damage. Flight was part 91 intrductory flight instruction departed hnl and precedded to practice area. During flight to practice area, pilot noticed significant… ## Docket (7 files) The files NTSB released with the investigation on January 21, 2026, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=199932. 80.7 MB in all. - Materials laboratory factual report (item 1, PDF, 22 pages, 17.9 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19263360&FileExtension=pdf&FileName=25-058%20Materials%20Laboratory%20Factual%20Report%20(ANC25LA028)-Rel.pdf - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 2, PDF, 11 pages, 8.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18604910&FileExtension=pdf&FileName=Pilot%20Accident%20Report%206120_Redacted-Rel.pdf - Memorandum for record a�� telephone interview, pilot (item 3, PDF, 1 page, 64 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19552537&FileExtension=pdf&FileName=MOR%20pilot-Rel.pdf - Lycoming crank drawing (item 4, PDF, 1 page, 369 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19563968&FileExtension=pdf&FileName=Lycoming%20crank%20drawing-Rel.pdf - Maintenance records (item 5, PDF, 42 pages, 50.7 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19161077&FileExtension=pdf&FileName=Maintenance%20Records%20redcated-Rel.pdf - Party member form (item 6, PDF, 10 pages, 977 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18604771&FileExtension=pdf&FileName=ANC25LA028%20Party%20Certification%20Lycoming_Redacted-Rel.pdf - Photos (item 7, PDF, 5 pages, 2.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=18604920&FileExtension=pdf&FileName=Investigative%20Photographs-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.