N8580T – CESSNA 182C – 2024-05-22 NTSB Accident Report

On May 22, 2024, about 1030 mountain daylight time, a Cessna 182C airplane, N8580T, was substantially damaged when it was involved in an accident near Vernal, Utah. The pilot and two passengers were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that he conducted a comprehensive preflight the day before the accident flight and organized the luggage in the airplane following an oil change. The pilot determined that the total weight was 265 pounds less than the airplane's maximum gross weight. He then witnessed the fueler fill both the left and right main tanks to their capacity, which totaled 55 gallons of 100 low lead aviation grade gasoline, 27.5 gallons for each tank. The pilot verified that the fuel gauges were indicating the correct level and that the tanks were full by dipping them. Prior to their departure, the pilot set the fuel flow computer to 54 gallons of usable fuel.

ADS-B data from a commercially available third-party source revealed that the airplane departed to the east and climbed for about 30 minutes to a cruise altitude of about 9,600 ft msl. The airplane then maneuvered to the south and continued its cruise for another 1 hour and 15 minutes. About 70 nm from its destination airport, the airplane began a climb to about 11,500 ft msl and continued its cruise flight for about 1 hour and 30 minutes. The pilot reported that the left and right fuel tank gauges showed fuel levels to be about one half and one third, respectively, at the start of the climb. About 20 nm from the airport, the airplane entered a steep descent. The pilot reported that he gradually reduced power to lose altitude while keeping the airspeed indicator in the green arc. He further stated that to prevent the engine from shock cooling, he maintained a low engine power setting and added carburetor heat when the engine was below 10 inches of manifold pressure. The pilot reported that the engine was not running rough, the mixture was still leaned out, and the carburetor heat was on.

About 5 nm from his destination airport, the pilot initiated a forward slip during his descent and, about 3 nm out, he reduced the engine power to idle to lower airspeed into the flap operation range. At this time, he also deployed full flaps (40°) and continued slowing the airplane and sinking into the glide path. He received an audible message from ForeFlight over his headset when the airplane was about 500 ft above ground level (agl). While on the glidepath for final approach, the pilot reported that the engine stumbled and stopped producing power as he was about to increase the throttle setting. Immediately after, the pilot advanced the mixture lever to full rich, the propeller lever to full forward, and the throttle lever to full while attempting to restart the engine but was unsuccessful in restoring engine power. He attempted another engine restart by cycling the mixture lever positions and turning the carburetor heat to OFF, but he did not switch the fuel selector lever to BOTH or the right tank. The pilot then decided to initiate an off-airport landing to a field short of the runway. The pilot reported that the airplane stalled about 10 to 20 ft agl, descended, and impacted terrain. The local law enforcement officers who responded to the accident site did not report any fuel leaks from either tank nor did they observe any fuel in the left tank during a visual inspection. Law enforcement was unable to access the right fuel tank due to its orientation.

Postaccident examination of the airplane revealed that the engine truss was substantially damaged. The engine remained attached to its engine mounts, which were connected to the engine firewall. Both propeller blades remained attached to the propeller hub and flange, which was connected to the crankshaft. No anomalies were observed within the combustion chamber of each cylinder. The accessories and accessory case were unremarkable. The spark plugs were all massive electrode plugs and displayed coloration consistent with normal wear. The electrodes had symmetrical coloration and were free of mechanical damage. No obstructions of the air induction or exhaust systems were noted. No evidence of a breach in the fuel system and tanks was observed.

The pilot reported that throughout the flight, he would switch between the left and right tank about every 30 minutes to maintain fuel load balance and added that while he was in cruise flight, he set the manifold pressure to 19 inches and the propeller lever to 2,300 rpm. The pilot further remarked that the flight computer showed a burn rate of 11 gallons per hour. NTSB fuel performance calculations showed that this was consistent with the manufacturer’s cruise performance chart. According to the pilot’s recount, the fuel selector lever was set to the left tank, the mixture setting was leaned out, and the carburetor heat was on prior to the loss of power. He added that he did not set the fuel selector valve lever to BOTH, as prescribed by the manufacturer’s pre-landing checklist because he had not stabilized the airplane and was not yet on short final.

The airplane was equipped with a Shadin Microflo-L Fuel Flow Computer without a GPS connection/installation. According to the manufacturer, without GPS data the computer acts only as a fuel flow indicator and totalizer and loses all navigation-dependent calculations, including nm per gallon, predicted fuel-to-destination, and predicted fuel reserve at destination. However, the unit can track real-time fuel flow, fuel used, fuel remaining, and endurance (assuming a constant fuel burn rate) using direct data from the fuel flow transducer and manual pilot-entered fuel data on the airplane’s fuel state. The POH states that, “The [cruise] charts make no allowance for wind, navigational error, pilot technique, warmup, take-off, climb, etc. All of these factors must be considered when estimating reserve fuel” and adds that each tank has about 1.5 gallons of unusable fuel.

The fuel performance during the accident flight was computed by the NTSB. According to the manufacturer’s maximum range chart, cruise performance is based on standard condition, zero wind, lean mixture, 55 gallons of fuel, no reserve and 2,650 lbs gross weight. The chart showed that at a cruise level altitude of 10,000 ft msl, an rpm setting of 2,300, and manifold pressure of 19 inches, the airplane would have had a fuel burn of 11.1 gallons per hour. The pilot estimated that he had 90 minutes of fuel remaining or about 16.5 gallons total left in the tanks when he was about 30 minutes from his destination airport. He added that the fuel gauge needles for either tank never went below the one quarter mark.

As the pilot did not report which fuel tank was selected during departure, the NTSB completed two separate fuel calculations using the BOTH, LEFT, and RIGHT fuel tank positions at takeoff. The calculations included the pilot’s recount that he positioned the fuel selector lever from RIGHT to LEFT about 45 minutes (or 70 nm per ADSB data) before the power loss event, his practice of switching fuel tanks every 30 minutes at cruise flight, and a fuel consumption of 11.1 gallons per hour.

The fuel performance involved two sets of fuel calculations, which are both provided below. The first set of fuel calculations was based on the fuel consumption provided by the fuel flow computer, or totalizer, which does not account for wind. The second set of calculations accounted for wind through groundspeed retrieved from available ADS-B data.

The first calculation assumed the pilot departed with the fuel tank selector positioned to BOTH, had selected the RIGHT tank when cruise flight was reached, and then switched fuel tanks every 30 minutes until the LEFT tank was selected 45 minutes before a total loss of power. In this scenario the airplane would have had about a total of 15 gallons of fuel, with 7 gallons of fuel in the LEFT tank and 8 gallons in the RIGHT tank, at the time of the power loss.

The next calculation was based on a departure with the fuel tank selector positioned to RIGHT into cruise flight, and then switched fuel tanks every 30 minutes until the LEFT tank was selected 45 minutes before a total loss of power. In this scenario the airplane would have had about a total of 15 gallons of fuel, 10 gallons of fuel in the LEFT tank and 5 gallons in the RIGHT tank, at the time of the power loss.

Another calculation was based on the pilot’s selection of the LEFT fuel tank during departure, then selecting the RIGHT tank when cruise flight was reached, and subsequently switching fuel tanks every 30 minutes until the LEFT tank was selected 45 minutes before the total loss of power. The airplane would have had about a total of 15 gallons of fuel, 4 gallons fuel in the LEFT tank and 11 gallons in the RIGHT tank, at the time of the power loss.

The first calculation incorporating wind through groundspeed from available ADS-B data was based on the pilot’s departure with the fuel selector positioned to BOTH, then selecting the RIGHT tank when cruise flight was reached, and subsequently switching fuel tanks every 30 minutes until the LEFT tank was selected 45 minutes before a total loss of power. In this case the airplane would have had about a total of 9 gallons of fuel, 3.5 gallons in the LEFT fuel tank and 5.5 gallons in the RIGHT tank, at the time of the power loss.

Another calculation made with the fuel tank selector positioned to RIGHT during departure and when cruise flight was reached before switching fuel tanks every 30 minutes until the LEFT tank was selected 45 minutes before a total loss of power. The airplane would have had about a total of 9 gallons of fuel, 7.5 gallons in the LEFT fuel tank and 1.5 gallons in the RIGHT tank, at the time of the power loss.

The final calculation was based on the pilot departing with the fuel tank selector positioned to LEFT, then selec...