# NTSB LAX94LA259: Mascari Discovery S-12, N999, Salinas, CA, June 18, 1994 - Type: NTSB accident investigation - Classification: Accident · Serious injuries · Limited investigation · Final report - Date: June 18, 1994, 16:04 local (23:04 UTC) - Place: Salinas, CA - Coordinates: 36.670185, -121.610137 (estimated) - Nearby events: https://openairdocs.org/map.md?lat=36.6702&lon=-121.6101&mi=10 - Phase of flight: [Initial climb](https://openairdocs.org/ntsb-phases/350) (OpenAirDocs' grouping) - Highest injury: Serious injuries - Injuries: 1 serious - Status: Completed, report May 10, 1995 - Report: Approved by Office Director - NTSB case key (mKey): 28777 - NTSB case page: https://web.ntsb.gov/investigations/?ntsbnumber=LAX94LA259 - NTSB report (PDF, downloads): https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/28777/pdf - Page: https://openairdocs.org/ntsb/LAX94LA259 ## 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. ## Sequence of events In NTSB's coding before 2008 (https://www.ntsb.gov/GILS/Documents/codman.pdf). - Propeller failure/malfunction, takeoff - initial climb - taxispeed - excessive, unqualified person (contributing factor) - exhaust system,muffler - corroded (cause) - exhaust system,muffler - separation - propeller system/accessories,blade - foreign object damage (cause) - propeller system/accessories,blade - out of balance (cause) - propeller system/accessories,blade - separation - reduction gear assy,propeller shaft - separation - Forced landing, emergency landing after takeoff - In flight collision with object, emergency landing after takeoff - object - pole ## Analysis 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. ## Factual narrative On June 18, 1994, at 1604 hours Pacific daylight time, a homebuilt experimental Discovery S-12 Airaile, N999, collided with a standpipe during an off-airport forced landing near Salinas, California. The airplane was being operated by the noncertificated owner/pilot when it inadvertently became airborne during high-speed taxi tests at the Salinas Municipal Airport, Salinas, California. The airplane was destroyed. The pilot received serious injuries. Visual meteorological conditions prevailed. Witnesses reported the propeller, muffler, and reduction gearbox separated before the airplane struck the standpipe. Examination of the three-bladed propeller by the Federal Aviation Administration (FAA) revealed one of the propeller blades had separated several inches outboard of the hub. The airplane then glided into a lettuce field. During the force landing flare, the right wing struck a 6-inch-diameter standpipe separating the right wing tip. The muffler and dampener plate from the reduction gearbox was sent to the Safety Board's Material Laboratory for examination. The muffler was fractured in the area of a factory weld. The weld area was oxidized. Numerous fractures were found in the dampener. Microscopic examination of the fractures disclosed no evidence of progressive separation. A copy of the Safety Board's Materials Laboratory Report is attached. ## Aircraft - Registration: [N999](https://openairdocs.org/deregistered/N999-2012-09-25), registration cancelled 2012-09-25, S/N PAD0003 (OpenAirDocs) - Reported make and model: MASCARI DISCOVERY S-12 (DISCOVERY) - Registry model: [Mascari David M DISCOVERY](https://openairdocs.org/model/mascari-david-m-discovery) (registry code 05625BK) (OpenAirDocs) - Registry engine: [NONE](https://openairdocs.org/engine/none) (registry code 00000, none) (OpenAirDocs) - Category: Airplane, amateur-built - Serial number: PAD0003 - Airframe hours: 40 - Engines: MAZDA RX7 ROTARY 200 horsepower reciprocating - Damage: Destroyed - Fire: On-Ground - Flight: Part 91 - Operator: Mascari, David M. - Registered owner: Mascari, David M. - Airworthiness certificate: Special, Experimental (Special) - Departed: SNS - Airport: SNS, Salinas Municipal, runway 31, 4,825 × 150 ft, asphalt ## Flight crew As NTSB recorded them. NTSB leaves out names. - Pilot; seat: left ## Weather - Conditions: Visual (VMC), Day - Wind: 300° at 9 knots - Visibility: 25 statute miles - Lowest ceiling: none - Temperature: 64 °F, dew point 48 °F - Altimeter: 29.00 inHg - Observed at: SNS, 2 nm away ## FAA reports on this event (1) The FAA's own accident and incident reports, matched to the aircraft by N-number and date (OpenAirDocs). - [Accident 19940618047859A](https://openairdocs.org/incident/19940618047859A), Jun 18, 1994: Amtr DISCOVERY, Salinas, CA, Destroyed. During high speed taxi prop assembly separated. Glided into field. Struck standpipe. Muffler fractured at a weld. From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. --- OpenAirDocs.org is an independent research project of [Contrail Labs](https://contraillabs.com/). It is not affiliated with the FAA or the NTSB. Source documents are U.S. government works in the public domain.