ANC22LA080

On September 25, 2022, about 1300 Alaska daylight time, a float-equipped Cessna 180A airplane, N9728B, was substantially damaged when it was involved in an accident near Skwentna, Alaska. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to a family member, the pilot sent a text message at 1240 indicating that she was ready to taxi for departure from Whiskey Lake so the family member would know when to expect her arrival. The intended route of flight was from Whiskey Lake to Lake Hood (PALH), Anchorage, Alaska. The family member estimated that it would take about 45 minutes to get from the departure point to the destination, and when the airplane was about 15 minutes overdue, he started calling around. A friend of the family flew over Whiskey Lake and found an airplane submerged in the water. Members from the Alaska State Troopers (AST) Search and Rescue team located the airplane and pilot about 1630. Initial on scene photographs taken by AST indicated that the left float separated from the airplane, and it was subsequently located about 175 yards away from the main wreckage. The right float remained partially attached to the submerged airplane wreckage. On October 4, 2022, members from the Alaska Dive Search Rescue and Recovery Team traveled to Whiskey Lake and recovered the submerged airplane, then moved it to the shoreline. PERSONNEL INFORMATION The pilot’s logbooks were not located. AIRCRAFT INFORMATION According to airworthiness records the floats were installed in June 1960. There were no maintenance records available for review. WRECKAGE AND IMPACT INFORMATION On October 6, 2022, the National Transportation Safety Board investigator-in-charge, along with representatives from Cessna Aircraft and the Federal Aviation Administration, traveled to the accident site. During the on-scene wreckage examination, flight control cable continuity was established from the control inputs to the control surfaces. The right wing was damaged from the tip of the wing inward; the wing tip was not located. The left wing remained submerged. The water rudder handle was in the UP position; the flaps were retracted. The propeller remained attached to the engine crankshaft flange. One blade was curled aft at the tip; the second blade was bent aft at midspan. Damage consistent with propeller strikes was noted on the inboard portion of the right float. The bottoms of both floats were heavily corroded and discolored. The right float remained attached to the airframe by the fly wire. There were six patches of varying size noted on the hull of the right float. A portion of the float hull, about midspan from the tip of the float to the step, was partially separated and bent aft. No evidence of impact with a foreign object was noted. (See Figure 1.) Figure 1 View of partially separated section on hull of the right float. The left float separated and was also recovered to the shore. Impactdamage was noted on the front tip of the float. There was one patch on the hull of the left float, with another patch on top of it. The aircraft was equipped with EDO 249-2870 floats. According to airworthiness records the floats were installed in June 1960. There were no maintenance records available for review. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy of the pilot was performed by the Alaska State Medical Examiner’s Office, Anchorage, Alaska. The cause of death was blunt force injuries and subsequent drowning. Toxicology testing performed by the Federal Aviation Administration’s (FAA) Bioaeronautical Sciences Laboratory detected diazepam in the pilot’s femoral blood at 12 ng/mL and the diazepam metabolite nordiazepam at 9 ng/mL in femoral blood. Venlafaxine and its metabolites were detected in femoral blood at 18ng/mL and 112 ng/mL, respectively. The high blood pressure medications metoprolol and timolol were detected in the pilot’s liver tissue; metoprolol was also detected in her femoral blood, while the result for timolol in her femoral blood was inconclusive. Diazepam, sometimes marketed as Valium, is a prescription benzodiazepine medication that can be used to treat a variety of conditions, including anxiety, muscle spasms, alcohol withdrawal, and seizures. Diazepam has sedative effects and can impair cognitive and psychomotor performance. The FAA considers an open prescription for diazepam disqualifying for medical certification and states that pilots using diazepam should not fly. Nordiazepam, oxazepam, and temazepam are active metabolites of diazepam.