NTSB Identification: WPR13FA269
14 CFR Part 91: General Aviation
Accident occurred Wednesday, June 12, 2013 in Montague, CA
Probable Cause Approval Date: 08/07/2014
Aircraft: GRAVES SH-2F, registration: N15GG
Injuries: 2 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The two pilots departed for a personal flight so that the right-seat pilot could become familiar with the airplane, which was owned by the left-seat pilot. The airplane was equipped with dual flight controls; however, it could not be determined which pilot was manipulating the controls at the time of the accident. Witnesses located adjacent to the accident site reported that they heard the sound of an airplane maneuvering with its engine operating at a high power setting followed by the sound of impact. Postaccident examination of the engine and airframe revealed that the flap handle interconnect was disconnected from the flap torque tubes with no corresponding bolt or nut located within the wreckage. Although the flaps in the disconnected configuration would have prevented the pilot from selecting a flap setting, airflow during flight would have kept the flaps in a retracted position. No evidence of any additional preexisting mechanical anomalies that would have precluded normal operation was found. Wreckage and impact signatures were consistent with an inverted flat-spin impact with terrain. Postmortem toxicology tests for the right-seat pilot, who had a valid Federal Aviation Administration (FAA) medical certificate, was positive for metoprolol (a beta-adrenergic receptor antagonist), which he was taking due to a valve replacement and aortic repair. Nothing from the autopsy suggested impairment or incapacitation from a medical condition or medication. Postmortem toxicology tests for the left-seat pilot, who did not have a current FAA medical certificate, were positive for norfluoxetine (an atypical antidepressant), fluoxetine (an antidepressant), olanzapine (commonly used for treatment of schizophrenia), and Warfarin (an anticoagulant medication). It is likely that the underlying psychiatric condition and/or medication being used to treat the conditions could have been impairing to some degree; however, the right-seat pilot should have been able to successfully fly the airplane even if some impairment was present in the left-seat pilot. No evidence suggests that pilot impairment or incapacitation contributed to the accident.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot’s failure to maintain airplane control while maneuvering for reasons that could not be determined during postaccident testing and examination, which resulted in a stall and subsequent spin.

Full narrative available

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