N9M N9MB accident near Norco, California

Probable cause

The pilot's loss of control for undetermined reasons.

NTSB analysis

The pilot was conducting a local post-maintenance test flight following the completion of the airplane's annual inspection. Radar information showed the airplane flying on a roughly easterly heading before the accident; however, no altitude information was captured. Multiple witnesses located adjacent to the accident site reported observing the airplane flying at low altitude when it pitched upward and banked left before abruptly banking right and nosediving toward the ground. One witness stated that, as the right roll continued, the rpm of the engines increased quickly, and the airplane entered a "diving right corkscrew turn" until it descended out of sight. A video provided by a witness near the accident site did not capture the airplane but did capture the sound of modulating engine noise before the impact, likely a result of an in-flight loss of control.

Wreckage and impact signatures were consistent with a near-vertical, high speed impact with terrain. All major structural components of the airplane were accounted for during the examination of the accident site and recovered wreckage, and no evidence of any preexisting mechanical malfunction was observed with the airframe, engines, or propellers; however, the extent of damage sustained in the accident sequence precluded functional testing of the flight control system, its associated hydraulics, and the engine systems. The location of the canopy located within the debris path and the unlatched seat restraint suggest that the pilot, who was wearing a parachute, may have initiated egress following a loss of control, but it is likely that he did not have sufficient altitude to do so before impact occurred.

Although toxicology revealed the presence of ethanol in the pilot's muscle tissue, it is likely that some or all the detected ethanol may have been from sources other than ingestion. Additional testing from a secondary laboratory found unspecified amounts of ethanol and pseudoephedrine/ephedrine. It is unlikely that ethanol or medication use contributed to the accident.

It is likely that the pilot experienced an inflight loss of control; however, given the significant fragmentation of the wreckage, the reason for the loss of control could not be determined from the available information.

Text from the NTSB. Open the NTSB docket for WPR19FA118 for the full record.