On September 17, 2017, about 1600 eastern daylight time, a Cessna 177B airplane, N35170, sustained substantial damage during a forced landing following a complete loss of engine power near London, Ohio. The flight instructor and student pilot were not injured. The airplane's right-wing spar was bent, and the fuselage was wrinkled aft of the cabin. The airplane was registered to an individual and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as an instructional flight. Visual meteorological conditions prevailed for the flight, which was not on a flight plan. The local flight originated from the Madison County Airport (UYF), London, Ohio, about 1415, performed a landing at the Lima Allen County Airport (AOH), Lima, Ohio, and was returning to UYF when the accident occurred. The instructor pilot reported that after making a full stop landing at AOH, they started to fly back to UYF and had just began a descent about 6 to 7 miles from UYF when the engine "sputtered" several times and then stopped producing power. He established a proper glide speed and checked the fuel selector to ensure that both fuel tanks were selected. He noted that the fuel pressure was low and fluctuating, and the engine restarted for several seconds after the electric fuel boost pump was turned on and then it stopped producing power again. After making several turns to find a more suitable landing area to no avail, he landed the airplane in a corn field. The pilot noted that the airplane's engine was recently overhauled and was being operated at high power settings and a full rich mixture for engine break-in. He noted that during previous flights the fuel consumption was about 11 gallons per hour (gph). He stated that before the accident flight he checked the fuel quantity and was confident that there was 25 gallons of fuel on-board the airplane, and the engine recording tachometer read 2069.3 hours prior to the flight. The tachometer indicated 2,070.6 hours at the time of the accident. Based on the fuel consumption on previous flights and the tachometer readings the pilot calculated that the airplane should have consumed about 14.3 gallons of fuel. Examination of the airplane at the accident site revealed no usable fuel in either wing tank and no breaches of the fuel system. Since the airplane was not being operated at normal cruise power settings, fuel burn calculations based on information in the Pilot's Operating Handbook could not be made. A subsequent examination and testing of the airplane was performed by a third party after its removal from the accident site and after wing removal. The airplane was placed in a hangar and after one day minor fuel stains were observed under the airplane. To further investigate if there was significant fuel leakage, the airplane was outfitted with a temporary fuel container secured to the cabin roof and plumbed into the left and right wing tank fuel line assembly inlets. The airplane's engine was run on two separate occasion using left, right, and both fuel selector positions, and with and without the electric fuel boost pump running. The engine speed that was attained during the test was 1,400 to 1,500 rpm, and the engine ran smoothly in all fuel configurations. Thorough examination of the airplane after each run did not reveal any fuel leakage and fuel consumption was not excessive.