WPR12LA439

A total loss of engine power due to fuel exhaustion during cruise flight for reasons that could not be determined because postaccident examination did not reveal any anomalies that would have resulted in the loss of engine power.

The flight instructor and the student pilot were part of a community college flight technology department, and the airplane was owned and maintained by the department. The flight instructor reported that, when he conducted the airplane's first flight of the day, he took off with the fuel tanks completely full. The airplane was then used for another flight; the airplane was operated for a total of 2.5 hours after the most recent refueling. Based on both that time and his visual inspection of the fuel tanks, the instructor determined that there was sufficient fuel for 2 more hours of flight, and he and the student pilot then departed in the airplane for some basic airwork. About 42 minutes into the flight, while returning to the airport for landing, the engine experienced a power loss, and the instructor conducted a forced landing in a field about 8 miles from the airport. Examination of the airplane revealed that the total quantity of fuel remaining onboard was about 1.5 gallons, which was the same as the manufacturer's designated amount of unusable fuel. A small quantity of fuel was observed in the lower cowl, but this appeared to be consistent with spillage from the carburetor as a result of the accident. No other evidence of any in-flight or postimpact fuel leaks was observed. Postaccident engine examination did not reveal any anomalies that would have contributed to the power loss. Review of the airplane's calculated average fuel consumption rates for several recent flights revealed that the rates were consistent with the manufacturer's published data. However, the calculated fuel consumption rate during the flights since the last refueling was significantly higher than other recent flights and the manufacturer's data.   Despite the industry-accepted unreliability of fuel quantity indication observations, the instructor's observation of slightly less than half full tanks before the accident flight confirmed his calculations and would have resulted in 2 hours of flying time. These calculations and the instructor's observation support the validity of his preflight planning, decisions, and actions.   Although uncertainties regarding initial fuel quantity, on-site spillage, and postaccident recovered fuel quantity reduced the fidelity of that calculated value, slightly more than half of the usable fuel would have to be unaccounted for, which seems unlikely. The available evidence was insufficient to enable a determination for the reason(s) for the fuel exhaustion and subsequent engine power loss.

**This report was modified on April 16, 2015. Please see the public docket for this accident to view a record of the changes made.*** HISTORY OF FLIGHT On September 28, 2012, about 1715 Pacific daylight time, a Cessna 152, N95840, was substantially damaged during a forced off-airport landing in Eugene, Oregon, following a complete loss of engine power during cruise flight. Both the certificated flight instructor (CFI) and the student pilot received minor injuries. The instructional flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no Federal Aviation Administration (FAA) flight plan was filed for the flight. The airplane was based at Mahlon Sweet Field Airport (EUG) Eugene, and was owned and operated by Lane Community College (LCC) in Eugene. According to the CFI, he was providing primary instruction to the student pilot, who had a total flight experience of about 2 hours. They had filed a flight plan with LCC, with a planned duration of about 1 hour. They departed EUG, and conducted basic airwork several miles south of EUG. When the hour meter indicated that they had been operating for about 0.6 to 0.7 hours, they began their return to EUG, and advised approach control of their intentions. When the airplane was about 10 miles south of EUG, the engine "sputtered," and the engine speed decreased to about 1,900 rpm. The CFI took control of the airplane, verified the fuel selector and throttle positions, and applied carburetor heat. The rpm decreased further, and about 2 to 3 minutes later, the engine ceased developing power. They declared an emergency to air traffic control, and the CFI identified a field suitable for an off-airport landing. Just as the airplane reached the field, they spotted powerlines, and the CFI turned the airplane to the right to avoid the powerlines. According to the CFI, the airplane "partially stalled" and landed "hard." It bounced back into the air, touched down again, and shortly thereafter, struck a ditch. The airplane came to rest about 100 feet beyond the ditch. The CFI shut down the airplane, and both occupants were able to exit the airplane on their own. PERSONNEL INFORMATION The CFI held multiple certificates and ratings, including flight instructor, airplane single engine. He indicated that he had a total flight experience of about 314 hours, including about 85 hours in the accident airplane make and model. His most recent flight review was completed about 3 weeks prior to the accident, and his most recent FAA first-class medical certificate was issued in January 2011. The student pilot had a total of about 2 hours of flight experience, all of which was in the accident airplane make and model. AIRCRAFT INFORMATION Federal Aviation Administration (FAA) information indicated that the airplane was manufactured in 1985, and was equipped with a Lycoming O-235 series engine. The airplane was maintained under a progressive inspection program by personnel from the owner/operator, LCC. The airplane was equipped with two fuel tanks, one in each wing. Total fuel capacity was 26 gallons, with a usable fuel capacity of 24.5 gallons. An electric fuel quantity gauge for each fuel tank was installed in the instrument panel. The fuel tanks were not equipped with "tabs" or other means to assist in visually gauging fuel quantity in the tank. The fuel selector valve had two positions, ON and OFF. The electrically-driven flaps were controlled by a switch/handle in the cockpit. At the time of the accident, the airframe had accumulated a total time (TT) in service of 10,098 hours. The engine had a TT of 6,454 hours, which was 1,025 hours since its most recent overhaul. The most recent inspection was completed on July 18, 2012; the airplane had accumulated about 35 hours since that inspection. About 6 weeks prior to the accident, a new #2 cylinder exhaust riser and an overhauled carburetor were installed. The airplane had accumulated about 32 hours since those maintenance actions. METEOROLOGICAL INFORMATION The EUG 1654 automated weather observation included winds from 020 degrees at 8 knots, visibility 10 miles, broken cloud layer at 25,000 feet, temperature 28 degrees C, dew point 9 degrees C, and an altimeter setting of 29.93 inches of mercury. Temperature and dew point values for the approximate time and location of the power loss indicated that the relative humidity was approximately 32 percent. When the intersection of the two temperature values was located on a chart that depicted carburetor ice envelopes, the point was in the region of the chart denoted as "Icing (glide and cruise power)," near the boundary of the region denoted as "Serious Icing (glide power)." WRECKAGE AND IMPACT INFORMATION The airplane came to rest essentially upright in a grassy field, approximately 8 miles southwest of EUG. The right main landing gear wheel and tire had separated from the gear leg, and the nose gear had collapsed. The engine cowling was crushed, and the engine mount was deformed. The propeller damage was consistent with the engine not developing power at the time of impact. The right wingtip and right horizontal stabilizer incurred minor crush damage, but the right wing was partially separated from the fuselage at the wing root. Neither wing tank was breached, and no fuel lines were disrupted. The aft fuselage sustained significant fracture and buckling damage. There was no fire. An individual who falsely identified herself to law enforcement officers as a mechanic for LCC arrived on scene very soon after the accident, and despite explicit instructions and admonitions from those officers, who were attempting to preserve the evidence, the individual accessed the airplane multiple times. The individual was neither an employee nor a representative of LCC, and did not respond to the scene at the request of, or on behalf of, LCC. The officers observed the individual reaching into the engine compartment and the cockpit. The investigation was unable to determine what changes, if any, the individual made to the cockpit configuration. Both fuel caps were observed to be in place and secured. The FAA inspector confirmed continuity between the cockpit engine controls and their respective components in the engine compartment. The engine was able to be rotated by hand. No evidence of any pre-impact deficiencies or failures that would have precluded continued operation was observed, and no additional examination or testing of the engine was conducted. Post-impact examinations by LCC, law enforcement, and FAA personnel all indicated the presence of very little fuel, and no evidence of any significant fuel spills or leaks. The fuel line between the gascolator and the carburetor was undisturbed by the accident, and there was no fuel found in that line. The gascolator was equipped with a metal bowl, and was damaged but not leaking. The FAA inspector removed the bowl. There was no fuel or any contamination inside the bowl. The recovery personnel determined that the left tank was empty, and that they recovered about 1.5 gallons total from the right tank and the fuel lines. The wing flaps were found in the fully retracted position, but the cockpit handle was near the full-down position. According to the CFI, he had placed the flap handle to the full-down position, but observed that the flaps did not extend, and he was uncertain as to why. The flap position indicator mechanism, which mechanically interacts with the cockpit flap handle to control flap position, was significantly disrupted at the rear spar. The disruption was attributed to impact damage. The investigation was unable to determine when the airplane master electrical switch was turned off, which would have prevented operation of the flaps. The investigation was unable to determine the reason for the discrepancy between the flap and flap handle positio