History of Flight
On September 8, 2012, at approximately 1235 Pacific daylight time, an experimental Edward R. Moore MXS, registration N21MX, departed controlled flight and struck terrain near Borrego Valley Airport (L08) in Borrego Springs, California. The pilot, operating under 14 CFR Part 91, was on a local personal aerobatic flight that had departed L08 around 1225. Visual meteorological conditions prevailed; no flight plan was filed.
The airplane's owner/builder had loaned it to the pilot to evaluate. The pilot owned a different make and model of aerobatic aircraft.
Witnesses reported seeing the airplane depart controlled flight during aerobatics, the pilot leave the airplane, and a parachute deploy that did not fully inflate before the pilot reached the ground.
Personnel Information
The 58-year-old pilot held a commercial pilot certificate with ratings for airplane single-engine land and instrument airplane. A third-class medical certificate issued on April 17, 2012, required corrective lenses for near and distant vision. The pilot reported 4,500 total flight hours with 50 hours in the previous 6 months on his medical application.
Aircraft Information
The airplane was an experimental amateur-built Edward R. Moore MXS, serial number 008. It had a total airframe time of 311.8 hours at the last annual condition inspection on March 30, 2012. The engine was a Lycoming-Ly-Con AE10-540EXP. The builder/owner reported 351 total hours at the time of the accident. The aircraft received its experimental airworthiness certificate on March 11, 2009.
Wreckage and Impact
The wreckage was located about 200 yards north of runway 08/26 at Borrego Springs Airport, on level sandy desert terrain with sparse vegetation. The aircraft was recovered for further examination.
Medical and Pathological Information
An autopsy was performed by the San Diego County Coroner on September 10, 2012. Toxicological testing by the FAA Civil Aerospace Medical Institute detected Minoxidil in urine but not in blood; the medication does not cause impairment.
Tests and Research
Examination of the engine and airframe revealed no mechanical anomalies or structural failures. Control systems were intact with no pre-impact abnormalities.
Examination of the flight control torque tube assembly found that the forward bearing was not engaged prior to impact. The structure supporting the forward bearing was constructed using 0.040-inch aluminum sheet attached with AN hardware, differing from other MXS airplanes. Two aluminum extruded channels were placed on either side of the bearing. The forward and aft bearing housings were installed in reverse orientation, and aluminum alloy flanges attaching the support panel allowed flexing. An exemplar airplane showed composite flanges on the aft side of the forward bearing support panel.
Thirteen MXS aircraft built by MX Aircraft had the front bulkhead made of glass-reinforced epoxy laminate with carbon fiber brackets bonded to the structure.
The forward face of the torque tube had sliding contact marks consistent with contact on the aileron control stop assembly; the stop assembly showed missing paint and contact damage.
Video Recorder
A GoPro camera mounted on the left side recorded the flight. The 16-minute video showed aerobatic maneuvers starting at 1228:10. At 1235:26, the airplane pitched up and rolled rapidly left, with full left aileron deflection before 90° of bank. After a rapid right roll starting at 1235:30.9, the aileron displacement reduced. At 1235:44, the canopy began to open and separated; pieces of Plexiglas and insulation were observed. The pilot's head was visible moving forward until the recording ended at 1235:49.
GPS and Engine Monitor Data
A Garmin GPSMAP 496 recorded the flight from 19:16:03 to 19:36:39 UTC. At 19:35:32, the aircraft was at 4,216 feet msl heading west. It then performed a 360° left turn descending to 2,743 feet by 19:35:44. The last reliable altitude point was 709 feet msl at 19:36:05.
An Electronics International MVP-50P engine monitor showed a presumed takeoff at 19:26:12. Manifold pressure and RPM decreased at 19:35:35, then RPM increased slightly as recording ended.
Additional Information
FAA Advisory Circular AC 20-27F allows amateur builders freedom in design; no design standards are approved.
A review of FAA records showed 14 MXS model airplanes produced. The accident aircraft was the only one built as an experimental amateur-built by an individual.
On January 28, 2009, MX Aircraft emailed the owner/builder and Angel Fire Aero expressing concerns about the torque tube assembly construction. Angel Fire Aero replied on January 29, 2009, stating it was unlikely the part would come loose or cause life-threatening results. The email exchange occurred three months before the aircraft was certified airworthy on March 11, 2009.
Post-accident, MX Aircraft LLC notified MXS operators to inspect torque tube assemblies for proper installation and security. An article on inspection procedures was published in September 2013.