LAX94LA259 · Mascari DISCOVERY S-12 DISCOVERY
Mascari DISCOVERY S-12 DISCOVERY · Accident: propeller failure/malfunction during initial climb
From Salinas Municipal Airport (SNS) to an unrecorded destination
Event
- NTSB case
- LAX94LA259
- 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
Mascari DISCOVERY S-12 DISCOVERY
- Aircraft type
- Mascari DISCOVERY S-12
- 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
- N999
- Operator
- Mascari, David M. · private individual
- Onboard fatalities
- Unknown
- Route
- From Salinas Municipal Airport (SNS)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
- Initial climb
- 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
- Propeller failure/malfunction
- Also codedOther events the NTSB coded in the sequence, such as a wire strike after a loss of power. Flight Findings uses them for its kinds of event. Glossary
- Pole
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Destroyed
Cause areas
- Exhaust system, muffler › Corroded
- Propeller system/accessories, blade › Foreign object damage
- Propeller system/accessories, blade › Out of balance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
THE EXPERIMENTAL HOMEBUILT DISCOVERY S-12 AIRAILE INADVERTENTLY BECAME AIRBORNE DURING HIGH-SPEED TAXI TESTS. THE MECHANIC CONDUCTING THE TAXI TESTS WAS NOT A CERTIFICATED PILOT. HE CONTACTED THE TOWER AND INFORMED THEM OF HIS SUPRISE FLIGHT. WITHIN MOMENTS THE ENGINE FAILED, AND A FORCED LANDING WAS MADE IN A NEARBY FIELD. THE AIRPLANE COLLIDED WITH A STANDPIPE. WITNESSES REPORTED THAT THE PROPELLER, MUFFLER, AND REDUCTION GEARBOX HAD SEPARATED BEFORE THE AIRPLANE STRUCK THE STANDPIPE. EXAMINATION REVEALED THAT THE MUFFLER FRACTURED AT A FACTORY WELD; THE FRACTURE EXHIBITED EVIDENCE OF OXIDATION. THE MUFFLER THEN SEPARATED AS A RESULT OF NORMAL VIBRATION DURING OPERATION OF THE ENGINE. THE PROPELLER WAS DAMAGED AFTER THE MUFFLER STRUCK IT. THE DAMAGED PROPELLER WAS THEN OUT OF BALANCE, RESULTING IN THE REDUCTION GEARBOX SEPARATING FROM THE ENGINE.
Probable cause
THE FAILURE OF THE MUFFLER ASSEMBLY DUE TO PREEXISTING CRACKING IN THE OXIDIZED AREA OF THE WELD, WITH SUBSEQUENT DAMAGE AND SEPARATION OF THE PROPELLER AND REDUCTION GEAR BOX. A RELATED FACTOR WAS THE EXCESSIVE TAXISPEED WHICH RESULTED IN THE AIRPLANE BECOMING INADVERTENTLY AIRBORNE.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record LAX94LA259
- Event ID
- 20001206X01575
- Case number
- LAX94LA259
- 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: 9c282971ebefb7206b1d556be795eaddcc9c05d9318342e459b50ebe6fbe84f9; retrieved 2026-09-21T13:50:58.169Z.