Multiengine Airplane Enters Flat Spin During Instructional Flight (N8164R)

Accident Overview and Witness Accounts During a local instructional flight, a multiengine airplane entered a flat spin and collided with the terrain. A witness holding a private pilot certificate observed the aircraft approximately 1,500 feet above ground level in a flat spin. The airplane impacted the ground flat on its bottom in a pasture, roughly 400 yards north of the witness. Another witness reported that the aircraft was in a flat spin and could not recover. The private pilot with a multiengine rating occupied the left seat, while the multiengine flight instructor occupied the right seat. ## Physical Evidence and Mechanical Findings At the accident site, the landing gear actuator was found in the extended position, and the flap actuators were in the 10-degree flap position. Examination of the right propeller revealed that the blade counterweight signature markings on the blade sockets indicated the propeller was in the feathered position at impact. The right propeller unfeathering accumulator showed three separate cracks at the transition between the circumferential stiffener and the thin-walled hemisphere of the diaphragm. ## Toxicological Findings Toxicological tests of the private pilot indicated the presence of several substances in blood and urine. Citalopram, a prescription antidepressant, was detected at 0.462 ug/ml, along with its metabolites N-desmethylcitalopram at 0.114 ug/ml and di-N-desmethylcitalopram at 0.024 ug/ml. Diphenhydramine, an over-the-counter antihistamine with sedative effects, was detected at 0.194 ug/ml. Acetaminophen was detected in the urine at 17.406 ug/ml. The diphenhydramine levels were consistent with recent ingestion of several times a normal dose, and the pilot was likely impaired by its effects.