CEN16LA218 · Aeronca 7AC
Aeronca 7AC · Accident: loss of engine power (total) en route
From Sackman Field (H49) to Sackman Field (H49)
Event
- NTSB case
- CEN16LA218
- 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
Aeronca 7AC
- Aircraft type
- Aeronca 7
- 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
- N82694
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Sackman Field (H49), Columbia, ILTo Sackman Field (H49), Columbia, IL
- Aircraft age
- About 70 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
- Loss of engine power (total)
- 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 airline transport pilot and passenger departed on a local flight from an uncontrolled airport. The pilot flew for about 15 minutes when he heard "a loud noise, a rattle," and the engine lost total power. He chose to conduct a forced landing on a section of closed highway; however, the pilot was unable to slow the airplane and impacted barricades at the end of the road closure.
Postaccident examination of the engine revealed two holes through the top of the crankcase, and cylinders No. 1 and No. 2 were separated from their mounts on the crankcase. Inside the No. 2 cylinder, the connecting rod was found fractured just below the piston head. Upon further examination of the connecting rod, the piston pin, which was manufactured from resulfurized steel, was also found fractured inside the connecting rod bore.
The No. 2 cylinder failed due to a fractured piston pin that retained the connecting rod inside the piston crown underside. The fracture of the piston pin led to misalignment of the connecting rod, which eventually failed from fatigue in reverse bending. The fatigue stresses on the connecting rod were relatively low, consistent with most of the fracture surface exhibiting fatigue propagating from multiple crack initiation sites. The piston pin likely fractured first, in part exacerbated by intergranular cracking in the outer, case-hardened layer. Resulfurized steels, designed for better machinability, exhibit reduced notch toughness and ductility. Carburizing or carbonitriding of these steels is generally not recommended, as the surface treatment can increase susceptibility to intergranular fracture in the hardened condition. In addition, the degree of the surface case hardening was deeper than typical for this alloy. It is likely that a stress high enough to fracture the outer layer would lead to through-fracture of the pin. However, the location of the pin fracture was such that immediate failure of the engine did not occur until the connecting rod subsequently fractured from fatigue. The pin had been partially embrittled by the surface case hardening, which sufficiently lowered the fracture toughness to cause the pin to fracture prematurely.
Probable cause
A total loss of engine power due to fracture of the piston pin, which led to fatigue cracking and eventual fracture of the adjacent connecting rod.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN16LA218
- Event ID
- 20160614X40501
- Case number
- CEN16LA218
- 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. 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: 5f6553ffbdd07df7b1630f57d513364204d43701771f6dbf5790b12c6b45c25d; retrieved 2026-09-16T03:30:50.409Z.