On May 13, 2017, about 1500 central daylight time, a Piper PA-28-140 single-engine airplane, N3976K, sustained substantial damage during a forced landing following a partial loss of engine power during cruise flight near Muskogee, Oklahoma. The private pilot was not injured and his passenger sustained minor injuries. The airplane was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 without a flight plan. Day visual meteorological conditions prevailed for the local flight that departed Davis Field Airport (MKO), Muskogee, Oklahoma, about 1440.The pilot reported that he had flown from Robert S. Kerr Airport (RKR), Poteau, Oklahoma, to MKO earlier in the day. The pilot stated that before departing RKR he observed the fuel level was below the filler tab in each wing tank, and estimated that each wing fuel tank contained 10 to 12 gallons of fuel. He recalled that the cross-country flight from RKR to MKO was uneventful and that he switched fuel tanks (from right to left) about halfway through the 45 minute flight. After landing at MKO, the pilot met a friend and two of her children, to whom he provided two short flights. The first flight was about 10 minutes and remained in the airport traffic pattern. The second flight was over the city of Muskogee, Oklahoma. The pilot reported that about 20 minutes into the second flight, the airplane experienced a partial loss of engine power at 3,000 ft mean sea level over downtown Muskogee. The pilot stated that he applied carburetor heat, switched fuel tanks (from left to right), activated the electric fuel pump, and verified magneto operation; however, despite his corrective actions, the engine continued to operate at 500 rpm. He chose to make a forced landing on the southbound lanes of US Highway 64. The pilot reported that shortly before the landing flare, the left wing struck a road sign, and the airplane swerved left into the grass median. The nose landing gear fork then separated from the strut and the airplane came to rest in a nose-down attitude.

A Federal Aviation Administration airworthiness inspector examined the airplane after it had been recovered from the accident site to MKO. The inspector observed substantial damage to the main wing spar, immediately outboard of the left wing tank. The inspector stated that the he found the fuel selector positioned to draw fuel from the right fuel tank, which contained about 10 gallons of fuel. The inspector observed the fuel level was about 1.5 inch below the right tank filler tab. The left wing tank did not contain any usable fuel; less than 1 quart of fuel was drained from the tank. The fuel recovered from the left wing tank was blue in color and did not contain any water or particulate. A visual inspection of the left wing tank revealed it was intact with no apparent damage. Additionally, there was no evidence of a fuel leak from either wing tank. The fuel supply line located between the engine driven fuel pump and the carburetor did not contain any fuel. The carburetor bowl contained residual fuel. The inspector stated that when he turned-on the electric fuel pump, with the fuel selector on the left fuel tank, the pump cavitated and discharged minimal fuel. The inspector then switched to the right fuel tank and the pump cavitated for a few seconds before it established a typical fuel flow. The fuel discharged from the electric fuel pump was blue in color and did not contain any water or particulate.