For decades, homebuilders all over the country have been enamored with the little air-cooled, two-stroke, four (and six)-cylinder, horizontally opposed, compact target drone engines built by McCulloch, most known for producing chainsaws. But not many have actually seen the drone in its full glory. At this year’s AirVenture, we got the chance to look one over closely.
This little gem of an engine was built to power target drones for use during WWII. The four-cylinder version’s displacement is 100 cubic inches (O-100), and the six-cylinder is 150 (O-150). Since the compact size of the drones allows for the use of a small diameter propeller, these little engines are allowed to spin up to 4100 rpm, with the O-100 producing 72 hp and the O-150 making 110, or 120 hp with a turbocharger.
Since the little single ignition engine is a two-stroke and it contains no oil system other than what’s mixed with the fuel, it can be installed vertically or horizontally.
Beechcraft is the manufacturer of the drone we found in the Warbirds area. Its design postdates WWII by a decade or so and is generally more sophisticated than its predecessors, having the ability to tow banners and carry targets that carried scoring devices. This little Model 1001-A Cardinal is designated MQM-39A by the U.S. Navy and MQM-61A by the U.S. Army. With its incredible power-to-weight ratio, it was capable of a top speed of nearly 350 mph and had an endurance of more than one hour of flying time.
A total of 2,200 of these petite Cardinals (of different variations) were built, the majority of which were for the U.S. Army, with the balance being operated by the U.S. Navy, the U.S. Marine Corps, and the country of Spain.