CEN24LA061 · Cessna 421C
BIRDBOYS2 Aviation Cessna 421C · Accident: powerplant system/component malfunction/failure en route
From Waco Regional Airport (ACT) to Boerne Stage Field (5C1)
Event
- NTSB case
- CEN24LA061
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 0 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Cessna 421C
- Aircraft type
- Cessna 421
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N146TJ
- Operator
- BIRDBOYS2 Aviation
- Onboard fatalities
- Unknown
- Route
- From Waco Regional Airport (ACT), Waco, TXTo Boerne Stage Field (5C1), Boerne, TX
- Aircraft age
- About 45 years (built 1978)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- En route · climb to cruise
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Powerplant system/component malfunction/failure
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft oper/perf/capability
- Aircraft › Aircraft propeller/rotor
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
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.
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.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN24LA061
- Event ID
- 20231213193520
- Case number
- CEN24LA061
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status, cause areas. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 5b94186b30a33ffbf32309386ec10c62c78255e18e32645f0de95d4ff8a3e830; retrieved 2026-09-16T18:22:10.128Z.