On July 19, 2007, approximately 0900 mountain daylight time, a Beech C-45H, N9562Z, piloted by an airline transport-certificated pilot, was destroyed when it struck trees and impacted terrain following a dual engine loss of power while maneuvering near Longmont, Colorado. Visual meteorological conditions prevailed at the time of the accident. The local instructional flight was being conducted under the provisions of Title 14 CFR Part 91 without a flight plan. The airline transport (ATP) certificated instructor pilot was seriously injured, and the ATP pilot receiving instruction received minor injuries. The flight originated at Platte Valley Airpark (18V), Hudson, Colorado, approximately 0845, and was en route to Boulder Airport (1V5) Boulder, Colorado. A witness pbserved the airplane flying at low level about 200 feet and descending. It made a turn to the west, leveled off, then descended sharply. The engines appeared to be "stopped." The airplane flew between two large trees, clipping the left tree. The airplane then impacted an open field. Upon impact with the ground, both engines separated from the airframe. The airplane slid across the field, struck a power pole, slid across a road, and came to rest. There was a post-impact fire According to accident reports submitted by the two pilots, they had planned to fly to Boulder, Colorado, and while en route, they would practice abnormal and emergency procedures. They spent about 1-1/2 hours preflighting the airplane, then departed Platte Valley Airport. During the flight, the right engine was shut down and the propeller feathered. It was subsequently restarted, but the left engine started "running very rough suddenly, and vibrated excessively." The left engine was shut down and the propeller feathered. Level flight was maintained from power produced by the right engine. "Thinking the left engine might still be able to produce thrust, we restarted the left engine," the instructor wrote. Instead of producing thrust, the engine produced more drag so it was secured again. Then the right engine began losing power. Full power was applied but the airplane continued to descend. The instructor's intention was to land on Niwot Road or in the adjacent field. He lowered the landing gear and while the gear was in-transit, the airplane clipped the tops of trees. The instructor was able to guide the airplane between two houses. It impacted an open field, slid 310 feet before bouncing across County Line Road, struck and downed a power pole, and slid another 40 feet before coming to a stop. There was a post-impact fire. The two pilots evacuated the airplane via the main cabin door. The airplane came to rest in the southwest corner of the intersection of County Line Road and Niwot Road (County Road 16). Upon hearing of the accident, the mechanic who maintained the airplane went out to where the airplane had been parked. There were two pools of oil in the run-up area, and trails of oil led out onto the runway. The airplane was recovered and transported to Beegles Aircraft Services, Greeley, Colorado, where, on July 24, 2007, both engines were partially disassembled and examined. There was evidence indicating both engines had failed catastrophically due to oil starvation. The left engine crankshaft was broken and all the piston heads were at the tops of their cylinders. Pieces of metal, including pieces of piston rings, were recovered from the right engine oil sump. According to the airplane operator, Commemorative Air Force, the drain valve in the Engine Rocker Box Recovery System (Saf-Air oil drain valve p/n 00880), used to prevent hydraulic lock and minimize oil clean-up, is opened when the collection vessel is attached after flight. During preflight, the recovery vessel is removed and the valve closed. The internal barrel of the Saf-Air lock open oil drain valve on the left engine was found in the nearly closed position, and the internal barrel on the right engine was in the open position. The open/close lock control on the valves is on the external part of the valves and these external parts were sheared off both engines at impact. According to FAA's airworthiness inspector, the drains are not approved for installation in the Pratt & Whitney R-985 engines (as installed on the Beech C-45). The pilot was later interviewed by telephone. He stated that when they preflighted the airplane, the drain valves were open (the drained oil is captured and recycled). He thought they had closed both valves. According to the Commemorative Air Force, either the pilot failed to close the drain valves or they were jammed in the open position, but the latter would be unlikely "because you can feel the valve move when you close it."