LAX99LA111 · Cooper VANS RV-6
Cooper VANS RV-6 · Accident: total loss of engine power (mechanical failure) en route
From Hooker Municipal Airport (O45) to an unrecorded destination
Event
- NTSB case
- LAX99LA111
- 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
Cooper VANS RV-6
- Aircraft type
- Cooper VANS RV-6
- 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
- N36VR
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Hooker Municipal Airport (O45)To not recorded
- 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 · 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
- 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
- Engine assembly, connecting rod bolt › Fatigue
- Engine assembly, connecting rod bolt › Fractured
- Engine assembly, connecting rod bolt › Undertorqued
- Other maintenance personnel › Maintenance, overhaul, improper
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The pilot made a forced landing into rough terrain following a bang and sudden loss of engine power. The engine had accumulated about 70 hours since overhaul. The sump contained a connecting rod, a wrist pin, bearings, many pieces of metal debris, and several rod cap bolts and nuts. None of the rod cap bolts in the sump were intact. They were all bent, fractured, and separated approximately at their midpoint. The pieces were covered with oil. The connecting rods for cylinders number two and four were leaning on the camshaft. The camshaft was not discolored. The crankshaft did not show evidence of discoloration or mechanical damage. A report of metallurgical testing of various engine pieces and their fracture surfaces strongly suggested that the nuts were not tightened on the connecting rod bolts according to specifications. A bolt that corresponded to the head of the bolt from cylinder number two exhibited failure characteristics of low cycle-high stress reverse bending fatigue. Reverse bending fatigue is indicative of an under-torqued bolt. The inspection revealed additional evidence that some of the nuts were not tightened to specification. Some bolts had flattened and polished bolt threads, as well as wear marks on the bolt's outer diameters. Some nut threads had only one end flattened. No fractured bolt had a nut on it except the fatigued bolt.
Probable cause
The failure of the engine assembler to apply the proper torque on the connecting rods bolts, which led to fatigue cracking and ultimately fracture of the rod bolts.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX99LA111
- Event ID
- 20001205X00196
- Case number
- LAX99LA111
- 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: 266422169a62f617d0cb325eb6fc06e102621e62dc0a24bd093a53b150a8ae08; retrieved 2026-09-21T20:36:00.176Z.