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Homebuilt Discovery S-12 Airaile Involved in Taxi Incident (N999)

Salinas, CA, US

On June 18, 1994, a Mascari DISCOVERY S-12 (registration N999) operated by Mascari, David M. was involved in an aviation accident near Salinas, CA. No fatalities were reported. Investigators recorded the probable cause as: 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. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 2026-07-04Data APIEditorial standards

An experimental homebuilt Discovery S-12 Airaile inadvertently became airborne during high-speed taxi tests. The non-pilot mechanic conducting tests contacted the tower before engine failure led to a forced landing and collision with a standpipe.

Background

The aircraft involved was an experimental homebuilt Discovery S-12 Airaile. The individual conducting the high-speed taxi tests was a mechanic who did not hold a pilot certificate.

Events

During the high-speed taxi tests, the aircraft inadvertently became airborne. The mechanic contacted the tower to inform them of the unexpected flight. Shortly thereafter, the engine failed, necessitating a forced landing in a nearby field. The airplane subsequently collided with a standpipe.

Witnesses reported that the propeller, muffler, and reduction gearbox had separated from the aircraft before it struck the standpipe.

Examination Findings

Post-incident examination revealed that the muffler had fractured at a factory weld. The fracture surface showed evidence of oxidation. This fracture led to the muffler separating as a result of normal vibration during engine operation. Following the separation, the muffler struck the propeller, causing propeller damage. The damaged propeller became out of balance, which resulted in the reduction gearbox separating from the engine.

Frequently asked questions

What happened in the 18 Jun 1994 Mascari DISCOVERY S-12 accident near Salinas, CA?

An experimental homebuilt Discovery S-12 Airaile inadvertently became airborne during high-speed taxi tests. The non-pilot mechanic conducting tests contacted the tower before engine failure led to a forced landing and collision with a standpipe.

Were there any fatalities in the 18 Jun 1994 Mascari DISCOVERY S-12 accident?

No fatalities were recorded in this accident.

What aircraft was involved and where did it happen?

The accident on 18 Jun 1994 involved a Mascari DISCOVERY S-12, registration N999, operated by Mascari, David M., at Salinas, CA.

What was the probable cause of the accident?

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.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001206X01575. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.