On June 17, 1999, approximately 1534 Pacific daylight time, a Ryan Navion B, N870DR, was substantially damaged in an off-runway landing at Klamath Falls International Airport, Klamath Falls, Oregon, after the pilot noted oil coming from the engine area after takeoff and turned back to the airport. The private pilot-in-command of the aircraft, who was its sole occupant, was not injured in the accident. Visual meteorological conditions were reported at Klamath Falls at 1553, and no flight plan had been filed for the 14 CFR 91 personal flight to Vacaville, California. The pilot reported that he put 1 quart of oil into the engine during his preflight, but that he forgot to replace the oil filler cap. He stated he then accomplished a normal engine start, taxi to runway 14, and preflight engine runup, then took off from runway 14. He reported that at about 600 feet above ground level, he observed oil on top of the engine cowling and on the windshield. He stated he requested an immediate return and lowered the landing gear, and was cleared by the tower to land on any runway. He stated he immediately made a "60 [degree] left turn to runway 25", and that the engine was running roughly at that point. He reported that "due to altitude", he was unable to make it back to the runway, and that the aircraft landed hard at about a 45-degree angle to the runway, just to the north side of the runway in the dirt area. During the landing, the aircraft's right main gear punched through the top of the right wing, and the bottom of the left wing was also wrinkled. The pilot reported that no mechanical failure or malfunction was involved in the accident, stating on his NTSB accident report: "Cause of accident was pilot's incomplete preflight, leaving oil filler cap off. This action precipitated the hard emergency landing [and] damage to [the aircraft]."