LAX97LA224 · Enstrom F-28-F
Stits Aircraft Enstrom F-28-F · Accident: partial loss of engine power (mechanical failure) en route
From Riverside Municipal Airport (RAL) to L66 · Corona, CA
Event
- NTSB case
- LAX97LA224
- 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
Enstrom F-28-F
- Aircraft type
- Enstrom F-28
- Category
- Helicopter
- 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
- N99YC
- Operator
- Stits Aircraft
- Onboard fatalities
- Unknown
- Route
- From Riverside Municipal Airport (RAL), CATo L66 · Corona, CA
- 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
- En route · climb to cruise
- 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
- Partial 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
- Engine assembly, rocker arm/tappet › Loose part/bolt/nut/clamp/etc
- Engine assembly, rocker arm/tappet › Shifted
- Engine assembly, valve, intake › Inoperative
- Other maintenance personnel › Maintenance, installation, not verified
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
During takeoff, the helicopter lost power and landed hard. Postaccident examination revealed the No. 2 cylinder intake valve rocker shaft migrated out of the shaft bosses of the cylinder head. The shaft, cover, and nuts were found; the washers were not. According to owner/pilot there were internal star washer imprints on the cover plate commonly caused by torque or tightening of the nut. The helicopter had 61.5 total hours since new, and received one 50-hour inspection since delivery to the owner/pilot. The owner/pilot changed the oil and filter just prior to the inspection.
Probable cause
failure by unknown maintenance personnel to retorque the nuts on the retainer cover.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX97LA224
- Event ID
- 20001208X08181
- Case number
- LAX97LA224
- 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: 22f2eb4518445005f15e41cd56242a510fcb943866f9f8cec11b79c86c6b13e4; retrieved 2026-09-21T21:24:35.974Z.