Any new propulsion system capable of doubling an aircraft’s effective altitude, increasing its dwell time by many hours, and significantly boosting its capability to run silently in “stealth” mode must be special indeed. That’s the view of Sanford “Sandy” Mangold, as he talks about the upcoming first flight of the Wolverine 3 engine.
“The U.S. Air Force considers this engine to be ‘disruptive technology’ because it’s the first purpose-built heavy fuel engine for UAVs,” said Mangold, President and CEO of Unmanned Aerial Systems (UAS), a Las Vegas-based developer of tactical UAVs. He said the Wolverine obviously is attractive to military customers who are transitioning to JP-8 fuel exclusively.
Mangold also expects the compact two-stroke, twin-cylinder Wolverine 3, developed by Ricardo specifically for UAV applications, to find favor in the burgeoning market of civil and commercial UAV customers—pipeline and highway surveyors, border patrols, police departments, and first responders.
UAS and Ricardo are slated to begin flight testing the Wolverine 3 next month in Nevada, Mangold told AEM during a recent technical briefing.
The air-cooled, naturally aspirated engine will fly first in UAS’ Nightwind 2, a portable blended-wing aircraft with a 2-m wingspan. Nightwind 2 is a pusher-type configuration, with the direct-drive propeller facing rearward. It is designed so its prop wash disburses the trailing engine and exhaust heat. The aircraft (officially coded NW-2R to designate the Ricardo engine) is capable of 12-lb payload.
UAS has a strategic alliance with CenTauri Solutions to provide mission-specific models of the Nightwind family of UAVs to the U.S. Department of Defense and various intelligence agencies. CenTauri is serving as prime contractor and systems integrator for the aircraft’s sensor suite.
The Wolverine 3 displaces 88 cm3 and is rated at 3.1 hp at 6000 rpm. It features a proprietary combustion system and direct fuel injection specially designed and calibrated for JP-8 and JP-5 fuels. It is one of only two UAV engines currently capable of using heavy fuel, and the first in a new family of engines Ricardo is developing for lightweight unmanned aircraft.
The engines are designed for low mass, extremely low thermal and acoustic emissions, high fuel efficiency, and package efficiency. Their displacements are scalable depending on application. Designed for the UAV’s duty cycle, they include two- and four-stroke units using spark- and compression-ignition combustion systems.
With electric generators mounted on the front of their crankcases, the engines function as compact hybrid-electric propulsion units.
The Wolverine 3 features a 0.5-kW integrated motor/generator adapted by Ricardo engineers from a medical-robotics application. It provides supplemental power and also enables the aircraft to operate quietly in all-electric mode for low-altitude operations.
Compared with the small industrial and hobby-type engines that currently dominate the UAV industry, the purpose-built Ricardo engine dramatically improves the Nightwind 2’s performance.
According to Mangold, the aircraft’s operational ceiling is expected to increase from 10,000 to 20,000 ft. Silent operation using all-electric mode is capable of being achieved at 1000 ft of altitude instead of 6000 ft, and the Nightwind 2’s cruise window will increase from 30 minutes to several hours, depending on fuel load.
Ricardo’s Wolverine 4, a 300-cm3 horizontally opposed, liquid-cooled, compression-ignition four-stroke rated at 25 hp, is under development for a larger, higher performance UAV with expanded range. It will be capable of lifting a 150 lb payload.
UAS and Ricardo were brought together on the program by Rick Scudder, Director of the Center for UAV Exploitation (CUE) and University of Dayton (Ohio) Research Institute. He explained that when his team first saw the initial Wolverine 3 concept, “we were universally impressed.”
Ricardo is no stranger to aero engine developments, having previously prototyped a small V-twin for UAV applications. Also currently in the UAV space from the automotive sector are Ford and Mahle Powertrain. The companies are collaborating on a hydrogen-fueled Duratec four-cylinder program intended for a prototype of Boeing’s Phantom Eye high-altitude, long-endurance aircraft.