# NTSB CEN24LA061: Cessna 421C, N146TJ, McGregor, TX, December 8, 2023 - Type: NTSB accident investigation - Classification: Accident · No injuries · Class 3 · Limited · Final report - Date: December 8, 2023, 12:32 local (18:32 UTC) - Place: McGregor, TX - Coordinates: 31.4127, -97.3666 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=31.4127&lon=-97.3666&mi=10 - Phase of flight: [Enroute](https://openairdocs.org/ntsb-phases/400) (OpenAirDocs' grouping) - Defining event: [Enroute-climb to cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) - Highest injury: No injuries - Injuries: 1 uninjured - Status: Completed, report November 5, 2025 - Report: Approved by Office Director - Investigation class: Class 3 - NTSB office: Central Region - Parties: McCauley Propeller Systems, Continental Engines, FAA FSDO, Hartzell - NTSB case key (mKey): 193520 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=CEN24LA061 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193520/pdf - NTSB docket: https://data.ntsb.gov/Docket?ProjectID=193520 - Page: https://openairdocs.org/ntsb/CEN24LA061 ## Probable cause The failure of the spring pin in the right propeller governor, which precluded the pilot from controlling the propeller pitch to maintain engine rpm, resulting in a loss of engine thrust, excessive drag, and the subsequent forced landing to a field. ## Findings NTSB's coded findings; those marked are part of the probable cause. - [Propeller system: propeller governor](https://openairdocs.org/ntsb-findings/01046122): Aircraft › Aircraft propeller/rotor · Failure (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01046122/cases.md?model=2076016), [All aircraft, 16 cases](https://openairdocs.org/ntsb-findings/01046122/cases.md) - [Performance/control parameters: powerplant parameters](https://openairdocs.org/ntsb-findings/01062050): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01062050/cases.md?model=2076016), [All aircraft, 81 cases](https://openairdocs.org/ntsb-findings/01062050/cases.md) - [Performance/control parameters: altitude](https://openairdocs.org/ntsb-findings/01062012): Aircraft › Aircraft oper/perf/capability · Attain/maintain not possible (probable cause); cases with it: [Cessna 421C, 1 case](https://openairdocs.org/ntsb-findings/01062012/cases.md?model=2076016), [All aircraft, 1,310 cases](https://openairdocs.org/ntsb-findings/01062012/cases.md) ## Sequence of events The events NTSB coded, in order, by phase of flight. The defining event best describes what happened. - [Enroute-climb to cruise: Powerplant sys/comp malf/fail](https://openairdocs.org/ntsb-events/340) (defining event); cases with it: [Cessna 421C, 2 cases](https://openairdocs.org/ntsb-events/340/sequence.md?model=2076016), [All aircraft, 820 cases](https://openairdocs.org/ntsb-events/340/sequence.md) ## Analysis As the airplane climbed through about 11,500 ft, the right engine speed increased suddenly from about 2,200 rpm to about 4,500 rpm, and the pilot thought that the right propeller governor had failed. He pulled back the right propeller condition lever, which resulted in no change, so he pulled the right engine mixture control back to near cutoff, which reduced the engine speed to about 2,000 rpm. The right engine continued to run, and the pilot initiated a turn back toward the departure airport; however, the airplane could not maintain altitude as he expected. The pilot declared an emergency and, after determining that the airplane would not make it to the airport or a closer one, he performed a forced, gear-up landing into a flat, harvested corn field. The airplane came to rest upright, sustaining substantial damage to the lower fuselage. After the accident, the right engine was placed in a test cell; the engine started without issue. Examination of the right propeller blades and hub assembly revealed evidence that the blade angles were on or near the low pitch stop at ground impact; the propeller was not feathered. No mechanical anomaly was identified with the right propeller hub that would have precluded normal operation. Examination of the right propeller governor revealed that the steel spring pin that held the pilot spool in place had fractured in shear overload into multiple pieces. Although mechanical interference between the pilot spool and one (or more) of the parts that rotate about it could impart shear loads on the spring pin, the investigation identified no evidence of metal fatigue, binding, or interference from foreign material. Thus, the reason for the failure of the spring pin was not determined. During the accident flight, when the spring pin failed, it precluded the pilot from controlling the propeller pitch to maintain engine rpm. It also allowed the propeller to move to low pitch, which resulted in excessive drag that further degraded the performance characteristics of the airplane. ## Factual narrative On December 8, 2023, about 1232 central standard time, a Cessna 421C airplane, N146TJ, sustained substantial damage when it was involved in an accident near McGregor, Texas. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight. The purpose of the flight was to reposition the airplane from Waco, Texas (ACT), to Boerne, Texas (5C1). The airplane had just undergone an inspection and the new owners were taking possession of the airplane. The pilot reviewed the logbooks, conducted a preflight inspection, and then filed an instrument flight rules flight plan to 5C1. The pilot, who had previous experience flying the accident airplane, reported that the takeoff and initial climb were normal. As the airplane climbed through about 11,500 ft, the right engine speed increased suddenly from about 2,200 rpm to about 4,500 rpm. The pilot reported that he thought that the right propeller governor had failed. He pulled back the right propeller condition lever, which resulted in no change, so he pulled the right engine mixture control back to near cutoff, which reduced the engine speed to about 2,000 rpm. The right engine continued to run, and the pilot turned the airplane back toward ACT, expecting that the airplane would be capable of holding altitude or climbing about 200 to 300 feet per minute (fpm). As the pilot continued to assess the situation, he identified that the airplane’s airspeed started to decay and that he had to maintain a descent rate of about 1,000 to 2,000 fpm just to hold sufficient airspeed. The pilot pushed the left engine controls to full throttle, full propeller, and full mixture. About 25 miles from ACT, the pilot declared an emergency with air traffic control and chose to divert toward the McGregor Executive Airport (PWG) airport, which was closer. The pilot stated that the right engine continued to run, but, when he tried various propeller, mixture, and throttle settings, it responded with “massive vibrations.” When the airplane was about 1,500 ft and about 4 miles from PWG, the pilot assessed that the airplane would not make it to the airport. He elected to perform a forced landing into a flat, harvested corn field instead. He landed the airplane with the landing gear retracted, and it traveled about 100 ft before coming to rest upright. The airplane sustained substantial damage to the lower fuselage; the propeller blades from both engines struck the ground. Postaccident testing of the right engine in a test cell revealed that the engine started without issue. Examination of the right propeller blades and hub assembly revealed evidence that the blade angles were on or near the low pitch stop when they struck the ground; the propeller was not feathered. No mechanical anomaly was identified with the right propeller hub that would have precluded normal operation. Examination of the right propeller governor revealed that the steel spring pin that held the pilot spool inplace was broken into multiple pieces. (During normal operation, the pilot spool is a nonrotating component that is housed inside the rotating drive gear.) Metallurgical examination revealed that the spring pin was fractured in shear overload. No evidence of metal fatigue, binding, or interference from foreign material was identified to explain the source of the shear loads on the spring pin. According to the manufacturer, if the pilot spool is not held in place, it can move down the drive gear shaft (as would happen if the spring pin were sheared), which would allow high pressure oil to be directed to the propeller dome, driving the propeller to low pitch and allowing an engine rpm runaway. ## Aircraft - Registration: [N146TJ](https://openairdocs.org/aircraft/N146TJ), registered now, S/N 421C0500, built 1978 (OpenAirDocs) - Reported make and model: CESSNA 421C - Registry model: [Cessna 421C](https://openairdocs.org/model/cessna-421c) (registry code 2076016) (OpenAirDocs) - Registry engine: [Continental GTSIO-520 series](https://openairdocs.org/engine/continental-gtsio-520-series) (registry code 17039, turbo-prop) (OpenAirDocs) - Category: Airplane - Serial number: 421C0500 - Year built: 1978 - Airframe hours: 5020 - Engines: Continental GTSIO-520-L 375 horsepower reciprocating; Continental GTSIO-520-L 375 horsepower reciprocating - Damage: Substantial damage - Flight: Positioning, Part 91 - Operator: Birdboys2 Aviation LLC - Registered owner: Birdboys2 Aviation LLC - Airworthiness certificate: Standard, Normal - Last inspection: Annual, May 15, 2023 - Departed: ACT, Waco, TX - Destination: 5C1, Boerne, TX - Flight plan: IFR - Equipment: Auto-pilot, Angle of attack indicator, ADS-B, Electronic flight bag or handheld device, Electronic multifunction display, Electronic primary flight display, Onboard weather, Stall warning system ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; age 56; injuries: none; airline transport, commercial, military; airplane ratings: single-engine land, multi-engine land; instrument ratings: airplane; medical: class 2, without waivers/limitations; last flight review June 20, 2023; seat: left; restraint: 3-point; flight hours: 11,000 total, 79 in this make and model, 10,450 as pilot in command, 88 in the last 90 days, 35 in the last 30 days, 2 in the last 24 hours ## Weather - Conditions: Visual (VMC), Day - Wind: 190° at 15 knots - Visibility: 10 statute miles - Lowest ceiling: none - Temperature: 73 °F, dew point 61 °F - Altimeter: 29.80 inHg - Observed at: ACT, 23 nm away - METAR: KACT 081755Z 19015KT 10SM SCT026 23/16 A2980 RMK AO2 T02280161 ## 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 20231208021649A](https://openairdocs.org/incident/20231208021649A), Dec 8, 2023: Cessna 421C, Mcgregor, TX, Minor damage. Pilot departed act to 5C1 on IFR flight plan. During level off pilot experienced prop governor failure and RPM in excess of 4500. Attempted to return to… ## Docket (8 files) The files NTSB released with the investigation on November 5, 2025, on NTSB's docket system: https://data.ntsb.gov/Docket?ProjectID=193520. 33.8 MB in all. - Pilot/operator aircraft accident report, NTSB form 6120.1 (item 1, PDF, 9 pages, 4.4 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19188539&FileExtension=pdf&FileName=6120_1%20N146TJ%20Snow%20-%20Final_Redacted-Rel.pdf - Right engine maintenance logs excerpt (item 2, PDF, 4 pages, 4.3 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19290903&FileExtension=pdf&FileName=Right%20Engine%20Log%20Book%202%20Excerpts%20CEN24LA061_Redacted-Rel.pdf - Right propeller maintenance log excerpts (item 3, PDF, 9 pages, 18.0 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19291599&FileExtension=pdf&FileName=Right%20Propeller%20Log%20Book%20Excerpts%20CEN24LA061_Redacted-Rel.pdf - Examination summary statement (item 4, PDF, 3 pages, 74 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19373678&FileExtension=pdf&FileName=CEN24LA061%20-%20Examination%20Summary%20Statement-Rel.pdf - Textron aviation mccauley governor and spring pin exam report (item 5, PDF, 20 pages, 3.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19189434&FileExtension=pdf&FileName=24-359-183.Rev.---.N146TJ%20governor%20examination.publicly%20releasable-Rel.pdf - Photos (item 6, PDF, 4 pages, 1.8 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19373468&FileExtension=pdf&FileName=Accident%20Report%20Photographs-Rel.pdf - Release of aircraft wreckage, NTSB form 6120.15 (item 7, PDF, 1 page, 96 KB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19189018&FileExtension=pdf&FileName=Wreckage%20Release%20-%20Signed%20Final_Redacted-Rel.pdf - Statement of party representatives to NTSB investigation (item 8, PDF, 2 pages, 2.1 MB): https://data.ntsb.gov/Docket/Document/docBLOB?ID=19372122&FileExtension=pdf&FileName=Signed%20Party%20Forms_Redacted-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.