WPR24LA261 · Aeronca 11AC
Aeronca 11AC · Accident: powerplant system/component malfunction/failure en route
From Brown Field Municipal Airport (SDM) to Hemet Ryan Airport (HMT)
Event
- NTSB case
- WPR24LA261
- 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
- Event fatalities
- Unknown
- 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
Aeronca 11AC
- Aircraft type
- Aeronca 11
- 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
- N86270
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Brown Field Municipal Airport (SDM), San Diego, CATo Hemet Ryan Airport (HMT), San Jacinto, CA
- Aircraft age
- About 78 years (built 1946)
- 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 · 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 power plant
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot of the tailwheel-equipped airplane reported that, while nearing his intended destination on a cross-country flight, the engine lost partial power followed by a vibration and grinding sound. The pilot attempted to restore engine power by troubleshooting; however, the engine subsequently lost total power and he initiated a forced landing to an open field. When the main wheels touched the soft terrain, the airplane nosed over, which resulted in substantial damage to the left wing.
Postaccident examination of the engine revealed metallic debris in the oil sump. The engine was disassembled by the previous owner, and the crankshaft was found fractured at the forward area of the No. 1 cylinder connecting rod journal. The entire fracture surface exhibited beach marks, consistent with high cycle fatigue over multiple duty cycles. The reason for the fatigue fracture was not determined.
The engine was last overhauled about 60 years before the accident and had accumulated about 1,569 hours of operation since overhaul. The supplied logbook excerpts consisted of 2 entries, and as such, it could not be determined what engine work was accomplished since the overhaul was performed. The engine manufacturer’s recommended time between overhauls is 12 years or 1,800 hours since overhaul.
Probable cause
A total loss of engine power due to a fatigue fracture of the crankshaft.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR24LA261
- Event ID
- 20240729194801
- Case number
- WPR24LA261
- 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: 15d013e44457a181602c22b362ce058b895e486c3d99861ba8ed60a577b1e70b; retrieved 2026-09-16T19:06:22.141Z.