Background
A check airman was conducting the first company training flight for a newly hired second-in-command (SIC). Automatic Dependent Surveillance-Broadcast (ADS-B) data showed that after departure, the airplane began a series of training maneuvers consistent with normal operations.
Accident Sequence
About 21 minutes into the flight, when the airplane was at approximately 3,400 ft mean sea level, it began a steep descent and subsequently impacted terrain. An airplane performance study revealed that the airplane reached a nose-down pitch of about -40 degrees and a descent rate of about 16,000 ft per minute. Review of archived ADS-B data and interviews with other pilots indicated that the initial upset occurred during a point in the training when the check airman typically simulated an in-flight emergency and descent.
Postaccident Examination
Postaccident examination of the airframe and control surfaces showed the airplane was configured for cruise flight at the time of the initial upset. Examination of the primary and secondary flight control cables indicated they were intact at impact. Trim actuator measurements showed an abnormal trailing-edge-up, nose-down configuration on both trim tabs. The two elevator trim actuator measurements were inconsistent, suggesting that one actuator was likely moved during wreckage recovery. Based on supporting data, it is likely that one actuator indicated the correct trim tab position at impact.
Simulated airplane performance calculations indicated that during a pitch trim excursion, the control forces required to counter an anomaly increase to unmanageable levels unless appropriate remedial procedures are quickly applied. Given the simulated calculations, trim actuator measurements, and the check airman's known training routine, it is likely that the check airman simulated a pitch trim excursion and the SIC, lacking experience in the airplane type, did not appropriately respond. The check airman did not take remedial action and initiate the recovery procedure in time to prevent the control forces from becoming unmanageable and to ensure recovery from the associated dive was possible.
Probable Cause
The probable cause was the check airman's delayed remedial action and initiation of a recovery procedure after a simulated pitch trim excursion, which resulted in a loss of airplane control.