On April 10, 2004, at 1145 Pacific daylight time, a Yakovlev Yak-54, N14026, sustained substantial damage during landing at a private airstrip near Friday Harbor, Washington. The airplane is owned by the pilot, and was being operated as a visual flight rules (VFR) personal flight under the provisions of 14 CFR Part 91, when the accident occurred. The commercial pilot was not injured in the accident. Visual meteorological conditions prevailed and no flight plan had been filed for the local aerobatic flight. In a written statement dated April 16, 2004, the pilot reported that the purpose of the flight was to practice aerobatics in the local area. He reported that shortly after rolling the airplane inverted, to accomplish a "belt check", oil appeared on the airplane's windscreen and canopy. The oil on the windscreen impaired the pilot's vision and he elected to return to the departure airport and land. He stated that the airplane touched down on the left edge of the runway, encountered rough/uneven terrain and the nose gear collapsed. The pilot stated that he did not secure the engine oil cap prior to departure. The oil cap was later found laying on the ground in the run-up area of the airstrip.