**This report was modified on 10/5/2018. Please see the public docket for this accident to view the original report.** On July 08, 2015, about 1515 central daylight time, a Piper PA-28-140 airplane, N3949K, sustained substantial damage following a collision with an embankment and trees during takeoff from a private airstrip in Oakdale, Louisiana. The private pilot, who was the registered owner, and passenger were seriously injured. Visual meteorological conditions prevailed at the time of the accident. The flight was being operated in accordance with 14 Code of Federal Regulations Part 91 as a personal flight and an instrument flight plan had not been filed. The intended destination for the flight was the Livingston Municipal Airport (00R), Livingston, Texas. The pilot departed on runway 05. The dirt runway was about 1,130 ft in length with trees approximately 525 ft from the departure end of runway 05. According to the Piper Cherokee 140 Owner's Manual, at a density altitude of about 2,500 ft, the takeoff distance needed would be about 1,000 ft ground roll, and 2,050 ft to clear a 50-ft obstacle. Clearing a 40-ft obstacle would require a takeoff distance of about 1,640 ft. Takeoff distances without calculating for density altitude would have been about 700 ft for ground roll, and 1,500 ft to clear a 50-ft obstacle. The weather conditions reported at Allen Parish Airport, located about 10 miles south-southwest of the accident site, were winds from 200 degrees at 7 kts. With a departure on runway 5, the pilot would have experienced a left quartering tailwind. The pilot reported a loss of engine power at 40 feet above ground level (agl) and the airplane settled back to the ground about 2,000 ft from the beginning of the takeoff roll. He reported that his grandson, who was watching, stated "the takeoff was normal and then it sounded like the engine quit running." The pilot also reported his neighbor was sitting outside and saw the airplane "lift off the ground for several feet as normal and it sounded as if [the pilot] let off the gas." A Federal Aviation Administration (FAA) inspector interviewed the pilot the day after the accident. The pilot reported he looked at the wind sock prior to take off and noticed it was hanging down and not moving. He proceeded to takeoff to the north as he typically liked to do because of the height of the trees on the south end of the airstrip. As the airplane became airborne, about 40 ft agl, he realized he had a 10 to 15 knot tail wind and the aircraft began to lose altitude. He advanced the throttle to full power. The FAA inspector asked the pilot if the engine was producing power and the pilot confirmed it was. The inspector reported the pilot stated, "it was at that moment he realized he had messed up." The airplane hit trees, became inverted and hit the ground. The pilot added that his grandson told him he looked at the windsock during takeoff and noticed "a gust of wind had filled the windsock in the direction of departure." The pilot remarked the next time he flew he was going to get wind direction in his local area from the weather service.