ANC18LA011 · Cessna 172 N
Cessna 172 N · Accident: powerplant system/component malfunction/failure en route
From McComb-Pike County Airport / John E Lewis Field (MCB) to Hattiesburg Bobby L Chain Municipal Airport (HBG)
Event
- NTSB case
- ANC18LA011
- 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 172 N
- Aircraft type
- Cessna 172
- 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
- N739KW
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From McComb-Pike County Airport / John E Lewis Field (MCB), MC COMB, MSTo Hattiesburg Bobby L Chain Municipal Airport (HBG), Hattiesburg, MS
- Aircraft age
- About 39 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 · 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 reported that, while the airplane was about 3,500 ft above mean sea level, the engine produced a "very rapid metallic banging/clanging noise," along with an instant loss of engine rpm. The engine was creating a "violent shaking" of the entire airframe. After about 20 seconds of applying carburetor heat, the pilot applied full mixture and started adjusting the throttle to obtain more power. He reported that, with more power applied, the shaking became more violent, along with a loss of engine rpm. The pilot realized that the engine power at this point was not sufficient to hold altitude. During a forced landing to a field, both wings and the fuselage sustained substantial damage.
Examination of the airframe and propeller found no preimpact mechanical malfunctions or failures that would have precluded normal operation. Examination of the engine revealed the No. 3 piston area displayed internal impact marks from the piston impacting the exhaust valve. The No. 3 exhaust valve was open and displayed impact marks from contact with the piston. The No. 3 valve spring seat (upper exhaust) was impact damaged with fractured pieces of the valve key (exhaust) and the valve stem cap (exhaust) laying on the bottom of the rocker area of the cylinder head. The No. 3 exhaust valve assembly moved freely inside the valve seats and was contacting the top of the piston.
Based on the available evidence, the partial loss of engine power was likely due to the No. 3 valve key (exhaust) failing, which resulted in a substantial reduction in engine power output. The reason for the failure was undetermined, as the service history of the valve key was unknown.
Probable cause
A partial loss of engine power due to the failure of the No. 3 valve key (exhaust).
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record ANC18LA011
- Event ID
- 20171127X32648
- Case number
- ANC18LA011
- 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: ad6eaa344111fa340ddf50fc76b49cfda8998589186885f9755f559e808cf323; retrieved 2026-09-16T06:02:18.302Z.