On March 6, 2018, about 2226 Pacific standard time, a Piper PA-28R-200 airplane, N33807, was substantially damaged when it was involved in an accident near Paso Robles, California. The flight instructor and private pilot receiving instruction were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The instructor reported that, before the flight, he watched as the airplane was fueled to capacity and he checked the engine oil level, which was 6 quarts. He then asked the pilot receiving instruction to conduct a preflight inspection while he went inside. Upon returning to the airplane, he verbally confirmed the fuel and engine oil levels with the pilot and they subsequently departed. The flight was uneventful, and they performed a touch-and-go landing at the destination airport. During takeoff following the touch-and-go, the pilots heard a "loud tick" noise, followed by the illumination of the low vacuum annunciator light. The instructor took control of the airplane, retracted the landing gear, and instructed the pilot to retract the wing flaps; about 350 to 400 ft above ground level, the airplane stopped climbing, the engine lost all power, and the propeller came to a complete stop. The instructor performed a forced landing to a nearby field. During the landing roll, the wings and aft fuselage were substantially damaged. The following day, a Federal Aviation Administration inspector examined the wreckage and noted that the oil filler cap was not secured, and that the engine contained about 1 quart of oil. In addition, oil was splattered inside the engine compartment. (see Figure 1.) Figure 1. Loose oil cap visible through the access panel on the engine cowling