CEN23LA188 · Cessna 172 N
Cessna 172 N · Accident: powerplant system/component malfunction/failure en route
From Denton, TX to Roanoke, TX
Event
- NTSB case
- CEN23LA188
- 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
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
- N5550J
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Denton, TXTo Roanoke, TX
- Aircraft age
- About 43 years (built 1980)
- 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 · descent
- 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 from the NTSB case API, which marks them as estimated or does not say; no uncertainty radius is established.
NTSB narrative
The flight instructor reported the engine began to run rough and lose power as they descended from cruise flight. Unable to restore full engine power, the instructor performed a forced landing to a field. During the landing the airplane collided with a barbed wire fence and trees, resulting in substantial damage to the wings and fuselage.
A postaccident examination of the engine found that one of the rocker arms (p/n LW-15014) had failed. A metallurgical examination revealed a portion of the rocker arm adjacent to the oil squirt hole was pressed inwards in the direction the pushrod drives the rocker arm. Fatigue cracks emanated from the circumference of the oil squirt hole.
Rocker arms with similar damage have been observed previously by the engine manufacturer. Lycoming Service Bulletin No. 639 (dated January 17, 2020) details the damage anticipated to the rocker arm oil squirt hole due to contact with the mating pushrod and provides an inspection methodology. Radial cracks are highlighted as warning signs that damage is occurring and once observed, the rocker arm should be replaced. In the subject rocker arm, the missed and/or unaddressed radial cracks likely led to the circumferential fatigue cracking and subsequent failure of the rocker arm and pushrod assembly.
The airplane operator was under the impression that the service bulletin only applied to engines overhauled by Lycoming. The service bulletin states that the models affected are “O-320-H2AD, O, LO, TO, LTO-360-E1A6D new, rebuilt, or overhauled engines shipped from Lycoming since June 2017 with less than 500 hours of operation or engines with less than 500 hours of operation since rocker arm replacement.” The service bulletin should then be complied with “at next scheduled oil change, then every 50 hours until 500 hours of engine operation.”
The engine had accrued about 173 hours since the overhaul during which the rocker arms were replaced.
Probable cause
The fatigue failure of the rocker arm which resulted in a partial loss of engine power. Contributing was the airplane operator’s failure to inspect the rocker arm in accordance with the engine manufacturer’s service bulletin.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record CEN23LA188
- Event ID
- 20230517174544
- Case number
- CEN23LA188
- 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: local date, investigation status, coordinates, cause areas. Values present in the bulk record are kept.
- The date is the local date; the NTSB stores the UTC date 2023-05-17.
- API snapshot SHA-256: 47f214060ad65391dacb5ac0fafe6e1cdc5b01bc422af9b6a58426639cb555a6; retrieved 2026-09-16T17:36:54.653Z.