LAX99LA081 · Hiller UH-12E
Hiller UH-12E · Accident: total loss of engine power (mechanical failure) while maneuvering
Event
- NTSB case
- LAX99LA081
- 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
Hiller UH-12E
- Aircraft type
- Hiller UH-12
- 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
- N67064
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From not recordedTo 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 137: Agricultural
- 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
- Maneuvering · aerial application
- 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
- Company maintenance personnel › Maintenance, inadequate
- Engine assembly, connecting rod › Failure, total
- Fuel system, primer system › Leak
- Ignition system, magneto › Arcing
- Miscellaneous, engine pre-ignition and/or detonation
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
While maneuvering during an aerial application flight at 15 feet above an alfalfa field, the pilot heard a noise emanating from the engine, and it seized. The pilot made a forced landing in the underlying soft field, and the helicopter rolled over after touching down on the uneven terrain. Maintenance records review disclosed that the helicopter's engine had operated about 482 hours since being overhauled. The engine examination revealed that the number two connecting rod was broken at its crankshaft end. Additionally, an inspection of the associated cylinder and piston revealed evidence of detonation. Similar excessive heat exposure signatures were observed with the other five piston heads. A small hole was found chaffed into the fuel primer line. Carbon deposits and burned rotor fingers were found in both magnetos.
Probable cause
The inadequate nature of the operator's maintenance, which failed to detect the primer and magneto discrepancies. An overly lean fuel mixture and/or magneto cross firing resulted in detonation, an ensuing connecting rod failure, and a total loss of engine power. Contributing factors were the helicopter's low altitude and the uneven, soft nature of the terrain.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX99LA081
- Event ID
- 20001204X00083
- Case number
- LAX99LA081
- 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: 166961fe5ff74f0a71953b1e3b4782be16f81024700e84c95a5133056976e727; retrieved 2026-09-22T15:57:42.010Z.