MIA97LA123 · Cumberland SKYBOLT
Cumberland SKYBOLT · Accident: total loss of engine power (mechanical failure) on approach
From Lowcountry Regional Airport (RBW) to Naxos Island National Airport (JNX)
Event
- NTSB case
- MIA97LA123
- 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
- 0
- 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
Cumberland SKYBOLT
- Aircraft type
- Cumberland SKYBOLT
- 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
- N4TZ
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Lowcountry Regional Airport (RBW), Walterboro, SCTo Naxos Island National Airport (JNX)
- Aircraft age
- Not recorded
- 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
- Approach
- First occurrenceThe 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
- Total loss of engine power (mechanical 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
- Other maintenance personnel › Maintenance, installation, improper
- Other maintenance personnel › Supervision, inadequate
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The engine failed and seized as the flight approached the airport for landing. During a forced landing in a field the aircraft nosed over. Post crash examination of the engine showed a counterweight retaining clip, washer, and pivot pin had separated allowing the counterweight to move around on the remaining pivot pin. The counterweight struck the No. 5 piston connecting rod causing it to fail and seize the engine. The counterweight retaining washer was found to have been ground and to not meet the manufacturers specified dimensions. Two pieces of the washer had separated. The engine had been taken by the owner to a community college aircraft maintenance school for overhaul. The engine was returned and installed on the aircraft 83 flight hours before failure. No logbook records were found to show the engine had been overhauled. Representatives of the aircraft maintenance school stated the work performed on the engine was a repair not an overhaul and that the original counterweight retaining washers and clips had been reused.
Probable cause
Installation by a student mechanic of a counterweight retaining washer that did not meet engine manufacturers specifications resulting in partial separation of the counterweight, failure of the No.5 connecting rod adjacent to the counterweight, and seizure of the engine. Contributing to the accident was improper supervision of the student mechanic by aviation school personnel.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record MIA97LA123
- Event ID
- 20001208X07779
- Case number
- MIA97LA123
- Dataset
- historical-pre2008
- Source SHA-256
- 89e2df6d848e7ab3b42e7d7c7a03ff403303057a26ca04c95b3ea67201c3ce74
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: b0d3ce5d911d58705379ef3e363110087d354f23e01eac041684ccccbe4a1024; retrieved 2026-09-22T19:59:28.529Z.