On December 10, 2014, about 1313 mountain standard time, an experimental McHolland Glastar amateur-built airplane, N16XP, was substantially damaged following impact with terrain after experiencing a loss of engine power during approach to landing to a private airstrip about 3 nautical miles south of the Sheridan County Airport (SHR), Sheridan, Wyoming. The private pilot, who was the registered owner and sole occupant of the airplane, was not injured. Visual meteorological conditions prevailed for the local flight, which was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The flight had departed the private airstrip about 10 minutes prior to the accident.In a written statement provided to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot stated that he had not flown the airplane in some time, and that about two weeks before the accident, and after checking the battery, fuel and general condition of the airplane, he performed a fast taxi down the pasture [airstrip], "…and it just didn't feel like it had normal power." The pilot reported that he then removed the sediment bowl and found a little dust in the bottom; no report of water contamination was reported. The pilot related that about 2 weeks later he performed a full power run up, followed by another fast taxi, and that this time "…it [the engine] felt normal." The pilot opined that on the day of the accident he performed a full power run up and another fast taxi, and again "…it [the engine] felt good; proper rpm, etc." The pilot stated that after taking off the climbout was great, and that the rpm was smooth; however, while at 1,200 feet above ground level and staying close to the airstrip, the engine began to lose power. The pilot reported that he flew directly to the airstrip, but was too high and fast to land on the [departure runway], and subsequently got too slow while trying to make it to the alternate airstrip on his property. During the attempted landing the airplane impacted an irrigation pipe with its main landing gear, then impacted a post with its left wing tip before sliding 50 to 60 feet and coming rest upright. The pilot opined that a postaccident examination of the airplane revealed a broken wire on the cowl flap cable, which he stated would have allowed the cowl flap to close completely, thereby heating the fuel lines, gascolator, fuel pump and engine driven fuel pump, fuel injection lines, and spider unit, along with the engine oil cooler. The pilot reported that the engine's most recent conditional inspection was performed on November 10, 2014, at a total time in service of 427.6 hours. The pilot also reported that all previous maintenance records for the engine had been consumed by fire about 2 years prior to the time of the accident. At the request of the NTSB IIC, a local Federal Aviation Administration certified airframe and powerplant mechanic examined the engine in an attempt to identify what could have precipitated the reported loss of engine power. As a result of the examination, the mechanic confirmed engine continuity through the drive train, which rotated freely. Additionally, the magneto impulse couplings were observed to function normally. Fuel was noted to possess the smell of old car gas, and the gas filter bowl revealed signs of rust and a light amount of sediment when drained; no water contamination was reported. The mechanic stated that the fuel system had an old fuel varnish look and staining. When the spark plugs were removed, the top plug electrodes had a black carbon look, while the lower plug electrodes were observed to have had heavy lead deposits, but not to the top of the porcelain. Cylinder compression tests revealed the following values: #1 = 69, #2 = 62, #3 = 60, and #4 =60. The mechanic concluded, that based on his examination of the engine and component parts, he was not able to identify the cause of the reported loss of engine power.