ERA21FA029

Radar data revealed that, about 20 minutes after departure, the airplane’s groundspeed decreased from 94 knots to 47 knots, and the airplane entered a descending left turn. Data from the airplane’s onboard engine analyzer revealed that this deceleration was preceded by a sudden and simultaneous drop in the airplane’s fuel flow rate and exhaust gas temperature (EGT) values, consistent with a loss of engine power. Following the accident, less than 1 gallon of fuel was recovered from the intact right wing fuel tank, and about 1 cup was recovered from the left wing (which was breached from impact). About 1 teaspoon of cloudy water was found in the airframe fuel filter bowl and the screen was partially blocked with debris. A review of the airplane’s fueling and flight records, including data from the onboard engine analyzer, revealed there would have been about 1 gallon of usable fuel onboard about the time of the loss of engine power. Examination of the engine revealed no other mechanical deficiencies that would have precluded normal operation at the time of the accident, and the total loss of engine power was likely the result of fuel exhaustion. Following the loss of engine power it is likely that the pilot exceeded the airplane’s critical angle of attack (as evidenced by the low recorded ground speed during the final moments of the flight), which resulted in an aerodynamic stall/spin and loss of control. Though Diazapam (Valium) and its metabolites were detected in the pilot’s system in post-accident toxicology testing, it could not be determined if the pilot’s use of diazepam contributed to the accident.

HISTORY OF FLIGHT On October 25, 2020, at 1052 eastern daylight time, a Cessna 172 airplane, N724BC, was substantially damaged when it was involved in an accident near Dunnellon, Florida. The pilot/registered owner was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. A review of air traffic control (ATC) communications and radar data provided by the Federal Aviation Administration (FAA) revealed that the pilot was not in communication with ATC and had not filed a flight plan. The airplane departed to the south from Back Achers Airport (8FL3), Belleview, Florida, about 1034. The airplane then turned toward the southeast and flew over Lake Weir before turning onto a westerly heading toward the Marion County Airport (X35), Dunnellon, Florida, at an altitude between 1,250 and 1,300 ft mean sea level (msl). Around 1038, the airplane began a slow descent down to about 900 ft msl before climbing back up to around 1,000 ft msl. Between 1051:39 and 1052:02, the airplane decelerated from a groundspeed of about 94 knots to 47 knots, which was below the airplane’s published stall speed of 50 knots with the flaps retracted. A second later, the airplane climbed to 1,025 ft msl, then entered a descending left turn before the data ended at 1052:12. A witness saw the airplane flying low and slow in a 45º to 60º right turn. She said that the airplane sounded “like it was howling, and the engine was just barely running.” The witness described the sound of the engine as if it was not “catching” or “normally combusting.” She did not see the airplane descend or impact the ground. PERSONNEL INFORMATION The pilot held a private pilot certificate with ratings for airplane single-engine land and instrument airplane. A review of the pilot’s logbook revealed that he had logged about 506 total hours of flight experience. AIRCRAFT INFORMATION The airplane had a total fuel capacity of 43 gallons, of which 40 gallons were usable. WRECKAGE AND IMPACT INFORMATION The airplane impacted an open grass field in a nose-low attitude about 1.2 miles north north-east of X35. The initial impact point was a ground scar that contained pieces of the left wing tip fairing. The airplane traveled about 120 ft before coming to rest. All major components of the airframe were located at the accident site and there was no postimpact fire. Both wings remained attached to the airframe but sustained extensive leading edge impact damage. The tail section was folded over the top of the airplane and sustained impact damage. The wing flaps were retracted. Flight control continuity was established for all major flight control surfaces to the cockpit. There was no obvious odor of fuel or vegetation blight on or around the wreckage site. The right fuel tank was suspended approximately 6 ft in the air and remained intact. Less than 1 gallon of 100LL fuel was drained from the tank. The left fuel tank was breached and about 1 cup of 100LL fuel wasdrained from the tank. The airframe fuel strainer bowl contained less than 1 teaspoon of cloudy liquid which tested positive for water using water-finding paste. Debris was observed in the fuel strainer screen, but only a portion of the screen was blocked. The engine partially separated from the firewall and came to rest next to the airplane. The two-blade propeller remained attached to the engine. One blade was bent aft about 20° and exhibited some leading-edge polishing; the other blade was straight. The engine was placed on flatbed truck and the top spark plugs were removed. The engine was rotated manually via the propeller. Compression was established on all but the No. 6 cylinder due to impact damage of the pushrods. As the engine was being rotated, valve train continuity was established for each cylinder and spark was produced to each magneto ignition lead. The carburetor separated from the engine during impact. The carburetor was disassembled and found void of fuel; a small amount of corrosion was observed in the fuel bowl and on the carburetor inlet screen. Examination of the engine revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. MEDICAL AND PATHOLOGICAL INFORMATION An autopsy was conducted on the pilot by the District 5/24 Medical Examiner’s Office (Citrus, Hernando, Lake, Marion, Seminole, and Sumter Counties). The cause of death was multiple injuries sustained in an aircraft crash, and the manner of death was accident. Toxicological testing identified diazepam at 34 nanograms per milliliter (ng/mL) and the diazepam metabolite nordiazepam at 45 ng/mL in cavity blood. The FAA Forensic Sciences Laboratory identified diazepam at 36 ng/mL and nordiazepam at 48ng/mL in cavity blood; both of those substances were also detected in urine. The diazepam metabolites oxazepam and temazepam were detected in urine but not in cavity blood. 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. ADDITIONAL INFORMATION On October 8, 2020, the pilot flew the accident airplane from 8FL3 to Greenville Downtown Airport (GMU), Greenville, South Carolina, and returned to 8FL3 the following day. A fuel receipt indicated that, before departing GMU on October 9th, the pilot purchased 33.2 gallons of 100LL aviation fuel. Data downloaded from the onboard engine monitor revealed that the flight began at 0959:18 and ended at 1358:18, for a total of 3 hr and 59 minutes. The average fuel burn rate was about 9 gallons per hour, for a total of about 36 gallonsused. There were no other recorded flights in the pilot’s logbook or on the engine monitor until the day of the accident. A review of the engine monitor data for the accident flight revealed the flight departed 8FL3 about 1032 and ended at 1052. The inflight portion of the recording was unremarkable until 10:51:42 when fuel flow and EGT values for all cylinders suddenly and simultaneously dropped to zero. The average fuel burn rate was about 9 gallons per hour, for a total of about 3 gallons used during the accident flight.