It looks like a cross between an airplane and an artillery shell, but a 12-pound unmanned aircraft named Coyote may prove to be a potent tool for maritime surveillance.
Coyote, five feet long and with a wingspan of 30 inches, is designed to be dropped from sonobuoy launchers on the Navy's P-3C Orion antisubmarine aircraft. Using a single rear-mounted propeller powered by an electric motor, the aircraft has an endurance of about 90 minutes at a cruise speed of about 52 knots and a range of about a hundred miles.
With the folding wings extended, the craft is roughly H-shaped. Coyote carries an electro-optical or infrared camera in its nose. Maximum payload is 5 pounds, though a typical load would be 2.5 pounds. A P-3 can carry 48 external and 36 internal sonobuoys. Modified Coyotes can be launched from external racks, but the Navy hasn't yet asked the manufacturer to add the capability.
Coyote is designed to provide a standoff surveillance capability for aircraft, according to Lars Studley, lead design engineer for the vehicle's manufacturer, Advanced Ceramics Research of Tucson, Ariz. The GPS guidance allows the operator to just "load up a mission, choose the area they want to look at, and then hit the fire button," said Studley. "It flies itself to that location, and they're able to use the camera to decide what they want to look at."
Like standoff weapons on strike aircraft, a standoff surveillance unmanned air vehicle, or UAV, protects valuable manned aircraft and crews. Instead of having to descend to visually check out a target, the launch aircraft can remain at a distance. "If P-3 receives radar or sonar data of vessel, rather than have P-3 fly potentially into harm's way, they can launch the UAV, which collects and sends imagery back to the P-3, and allows it to remain at high altitude" Studley said.
But therein lies the design challenge. For this concept to work, the UAV has to be small enough to fit in a narrow sonobuoy tube that's less than 3 feet long and 4.5 inches wide. Yet the vehicle must be strong enough to withstand the stresses of high-speed, high-altitude launch. UAVs have previously been launched from transport aircraft, but they were larger vehicles operating under less severe launch conditions, Studley said
Coyote solves the size problem by fitting the vehicle inside a canister. The launch procedure begins with the flight crew inserting the canister inside a sonobuoy tube. When it is fired out of the tube, a parachute deploys, the canister's outer sleeve is discarded, the UAV's control surfaces pop out, and the autopilot begins a pull-up maneuver. All of these steps are completed in less than 20 seconds. Coyote can be launched from up to 30,000 feet, though Studley expects 20,000 feet to be a more typical launch altitude.
While Coyote can do freefall drops, it is "designed for ejection at high speeds and high altitude," Studley said. "It has a 100-G launch tolerance. We took the parameters of a standard sonobuoy launch and designed the plane to meet those requirements."
Despite the canister, the small size of the vehicle did impose restrictions. "We were limited by the size of the tube to electric power. The endurance of the UAV is pretty much limited to the batteries you can pack in there, and battery technology," said Larry Branthoover, Coyote project lead for Naval Air Systems Command.
Coyote is not equipped with landing gear - though it can belly land - so the UAV is expendable. That puts a premium on price. The Navy wants the vehicle to cost less than the fuel that would be expended by a P-3 that would otherwise have to descend to low altitude to observe a target and then climb back up. Branthoover estimated the cost of the Coyote prototype at $15,000 per unit. Advanced Ceramics Research would only estimate the cost of a single Coyote at less than $10,000.
Coyote is not designed to carry weapons, but Studley said that the vehicle can be constructed out of explosive materials similar to reactive armor, which in effect would transform it into a flying bomb.
Branthoover said the idea of an offboard sensor for the P-3 has been around for years. "Initially, they were looking at putting wings on sonobuoys and calling them glide buoys. The way we drop them now, they're just dropped and you fly back over to mark the exact location." However, an unpowered sonobuoy would lack standoff range.
Branthoover foresees an antisubmarine version of Coyote as a possibility, but this would require miniaturized detection gear such as magnetic sensors. The Navy currently has no plans to arm the vehicle.
Branthoover said Coyote is scheduled for a test launch from a Navy C-12 aircraft next spring, followed by a launch from a P-3 in the summer. However, one advantage of using a canister-launch system is that Coyote can be launched from any platform equipped with a sonobuoy tube, including helicopters. "Anything that can launch a sonobuoy can launch this vehicle," said Studley.