Aurora Flight Sciences is raising the stakes in airborne intelligence surveillance reconnaissance (ISR) platforms by lowering costs and increasing operational flexibility. The Manassas-based company's $4.5-million Centaur OPA, short for Optionally Piloted Aircraft, can perform most of the ISR missions of the $8.3 million Hawker Beechcraft King Air 350ER C-12W or $3 million General Atomics RQ-1 Predator, among other piloted or unpiloted ISR aircraft. The first customer is Armasuisse, the Swiss defense department's procurement agency. Based at Emmen, the aircraft will be used as a flying testbed to evaluate the integration of unmanned aircraft into the Swiss national airspace system.

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Centaur OPA can be operated as a manned or unmanned ISR aircraft. The conversion between piloted and unpiloted configurations can be finished in under 4 hr. by two technicians using standard hand tools, according to the company. Just as important, without its unmanned flight-control-system equipment connected to the controls, Centaur can be piloted as a fully certified Federal Aviation Regulation (FAR) Part 23/European Aviation Safety Agency (EASA) CS-23 airworthy aircraft that can be flown through Class B, C, D, E and G airspace.

Our pilot report from inside the aircraft is most unusual because we never touched the flight controls during the entire mission. That is a first for Aviation Week. We belted into the right rear seat of the Centaur with Jason Fine, project engineer, who strapped into the left rear seat. From this spot, Fine played the role of UAV ground controller. His laptop was tied to the aircraft's automatic flight-control-system (FCS) computer by an Ethernet cable rather than using the standard ground-to-air or optional satellite-to-air data link of a ground control station.

Tom Washington, chief engineer for the Centaur project and the company's chief pilot, occupied the left pilot seat, while the 55-lb. FCS servo package tray occupied the space where the right front seat normally is mounted.

Washington's primary function was to ferry the aircraft between Manassas Regional Airport where Aurora Flight Sciences has its headquarters and Warrenton-Fauquier Airport in Midland, Va., where the automated demonstration flight would begin and end. During the demo mission, he would cede control to the robotic FCS in the right seat.

On Runway 33 at Warrenton-Fauquier, Washington positioned the aircraft for departure. He flipped on the FCS computer switches, causing the servos to engage, and he removed his hands and feet from the controls. After that, he monitored the functionality of the automated FCS computer to assure the safety of the three occupants for the rest of the flight.

Fine clicked on the “launch” screen icon of his laptop that initiated a hands-off, autonomous takeoff and the three of us just watched the sequence that unfolded. Centaur's unmanned aircraft system (UAS) flight-control-system computer automatically held the brakes, pushed up the throttles to 100% power, checked the engine and flight instruments and then released the brakes to begin takeoff roll. Using a Novatel real-time kinematic, ground-based augmented GPS navigation system with 2-cm accuracy, the aircraft precisely tracked the runway centerline as it accelerated. The FCS also can use satellite-based augmented GPS systems, such as Omnistar, for precision runway guidance where local area augmented GPS is not available. At 80 KIAS, the aircraft rotated and commenced a 95-KIAS climb out.

All-engine takeoff distance over a 50-ft. obstacle for the 4,100-lb. aircraft was about 1,650 ft. as we departed the airport. Total fuel flow on takeoff was 125 lb./hr., quite efficient considering the two 2-liter (121.5-cu.-in.) Austro AE300 turbo-diesels were producing a total of 332 hp. The small displacement turbo-diesels also were comparatively smooth, turning 3,880 rpm at takeoff while MT-Propellors' three-blade props never exceeded 2,300 rpm because of 1.69:1 reduction gearboxes. A pair of conventional 5.9-liter four-cylinder avgas-fueled engines, in contrast, would have been consuming more than 150 lb./hr. at takeoff, and their noise and vibration at full throttle/maximum 2,700 rpm would have been considerably higher.

Once safely airborne, the FCS “right seater” raised the landing gear and pulled back the throttles to 92% maximum continuous power as we climbed to our initial cruise altitude of 3,500 ft. Total fuel flow dropped to 112 lb./hr. Fine engaged the “mission” mode of the FCS and the aircraft proceeded directly to Casanova VOR [CSN], the first waypoint programmed into its flight plan. The planned route would guide us around an FAA-authorized operating area southwest of and outside of the Washington Class B airspace.

Fine's laptop showed our position on a moving map display window during the entire flight. It also indicated when turns over flight-plan waypoints would occur and when pre-programmed speed and altitude changes would be initiated. Centaur's FCS computer automatically made several such pre-programmed changes, illustrating the aircraft's dash, loiter and surveillance capabilities during a mission. Centaur can loiter at 100 KIAS while burning fuel at about 50 lb./hr. Most Centaur aircraft will be configured with a top-mounted noise and IR (infrared) suppression exhaust system that will make the aircraft virtually impossible to hear at 3,000 ft. altitude or higher. Equally important, the IR heat suppression makes it difficult for man-portable air-defense surface-to-air missiles to track the aircraft.

While the FCS computer inputs to the flight controls generally were crisp and precise, they were anything but smooth. At speeds of 100 KIAS or greater, it snapped into 45-deg.-bank turns for course changes over waypoints and sawed the throttles to maintain airspeed in rough air. During acceleration maneuvers, the FCS dumped the nose to gain speed and then later followed with a substantial power increase, resulting in a 100-200-ft. altitude change. It reversed the procedure for automatic decelerations.

Clearly, this was no glass-smooth Garmin GFC-700 autopilot, but one adequate for tactical ISR missions with no humans onboard. Such crude control inputs would have gone unnoticed by a ground controller.

Next, Fine disengaged the pre-programmed “mission” mode and he demonstrated the “knobs” mode that enables a ground controller to command impromptu speed, heading and altitude changes to fly to a sensor point of interest on the ground.

When I made laptop inputs in the knobs mode, the Centaur's robotic pilot responded with crisp, but rough additude, heading and speed shifts. When I entered a heading change on the laptop, for example, the aircraft snapped into a sharply banked turn as it altered direction. Similarly, when I typed in a speed increase the robot dove the aircraft and then added throttle to accelerate to the commanded speed as rapidly as possible. Its responses to altitude changes were a bit smoother but if the robot pilot had been my student, we would have spent considerable time during the debrief discussing the need to have a lighter hand on the controls.

A “points nav” mode also is being developed that will enable the aircraft automatically to orbit a sensor point of interest so as to keep a designated target in continuous view of onboard sensors.

Fine then reselected “mission” mode and the FCS flew the aircraft to “Haney” intersection, another waypoint in the pre-programmed flight plan. The FCS automatically resumed flying the remainder of the original route.

As we approached Warrenton-Fauquier, the aircraft automatically began to descend to enter the VFR traffic pattern for Runway 33 and slowed to 100 KIAS. Following Aeronautical Information Manual procedures, Centaur aimed for the airport on a 104-deg. course to enter the downwind pattern on a 45-deg. angle and then paralleled the runway on a 149-deg. course.

The Centaur OPA's FCS computer and data link do not yet have a traffic awareness system capability. Centaur also lacks a videocamera that could spot proximate traffic and obstacles or wildlife on the runway. Thus, the ground controller cannot see and avoid traffic as effectively as a pilot aboard the aircraft.

But, the data link will be capable of communicating with onboard VHF/UHF transceivers, so in theory, an unmanned Centaur will be able to exchange radio transmissions in real time with ATC and with other aircraft operating in the vicinity of uncontrolled airports. And the ground controller also will be able to use the data link to control the functions of a Mode A/C/S or Identification Friend or Foe (IFF) transponder, including “squawk ident.”

For now, though, unmanned ops must be conducted in restricted, controlled airspace and at restricted, government-controlled airports in home or host countries. Such restrictions will not apply if the aircraft is being operating over hostile areas.

Nearing the airport, we devoted a large portion of our time to watching for other aircraft in the pattern, including a Robinson R-22 and Bell JetRanger being flown on training missions.

Flying a wide VFR pattern, when the aircraft was abeam the threshold, the FCS automatically lowered the landing gear, extended the flaps to approach, slowed to 85 KIAS and continued on the downwind course for several seconds. It then commenced a base leg turn about 3 mi. south of the airport and began a long final approach.

About 1.5 mi. from the threshold, Fine selected the “wave off” icon on his laptop to demo Centaur's ability to abort a landing approach and execute a go-around maneuver. In response, the FCS advanced the throttles to 100%, began a climb, retracted landing gear and flaps and then resumed flying the VFR traffic pattern.

During the second and final approach, however, the aircraft began a pronounced, unprogrammed dive as it turned from downwind to base leg. Without hesitation, Washington took over. He switched off the FCS computer and servos, and he flew the aircraft back to pattern altitude. He explained that the system is not designed to be temporarily overpowered by the crew, unlike the GFC 700 certified autopilot. Instead, it must be switched off to disconnect it. It also has frangible links between the servos and controls that can be broken with strong arm or foot inputs if the system does not disconnect the servos. But, once those links are severed, they must be replaced on the ground before the aircraft is capable of unmanned operations.

Washington discussed the apparent hiccup in the FCS program. He conceded that the current aircraft only has a single-channel computer and no backup to cross-check computer calculations. Production aircraft, though, will have a triple-channel FCS that will provide redundancy and cross-checking between channels.

Once Washington stabilized the aircraft, he again switched on the FCS equipment and it flew the remainder of the approach to Runway 33. On final, Centaur's FCS detected a slight right crosswind and compensated with a gentle crab into the wind. The Centaur is designed for 12-kt. demonstrated crosswind handling by the FCS. We estimated the actual crosswind to be 5-7 kt. during the approach.

As the FCS extended the flaps for landing and slowed the aircraft to final approach speed, it made crisper control inputs to maintain a stable approach. Just prior to landing flare, Centaur automatically transitioned from a crab into the wind to a wing-down/top-rudder slip to align the nose with the runway centerline. The FCS eased the throttles to idle, flared the aircraft slightly, it touched down firmly and smoothly braked the aircraft to a stop. Impressively, the FCS held the aileron into the wind during landing rollout while it used rudder and differential braking to track runway centerline during deceleration.

When the aircraft stopped, Washington switched off the FCS and taxied the aircraft clear of Runway 33. Future FCS software will be capable of controlling the aircraft from chock to chock rather than just takeoff to landing stop.

Conclusions? Centaur OPA clearly demonstrated that having a pilot at the controls literally will be optional in the future. Indeed, having a pilot aboard for ISR missions is a shortcoming because the aircraft is limited to a maximum altitude of 18,000 ft. in accordance with FAR and EASA regs. Without crew, the aircraft is not constrained by type certificate airworthiness limitations, so it can soar to 27,500 ft. as an unpiloted aerial vehicle.

Aurora Flight Systems builds on the robust capabilities of the manned DA42 Guardian multi-purpose platform furnished by Austria-based Diamond Airborne Sensing to create Centaur OPA. The U.S. company adds an autonomous UAV flight control system and other upgrades that transform it into a capable, economical, low-profile unmanned ISR aircraft that can remain airborne for up to 24 hr. when fitted with a supplemental fuel bladder (see p. 46). It also can be flown by a pilot who uses the UAV FCS to fly special mission ISR routes. Free of basic flying tasks, the pilot can operate ISR equipment, act as safety observer and communicate on the radios.

Centaur OPA makes full use of commercial off-the-shelf components, helping to hold down operating costs, increase reliability and simplify replacement parts procurement. It can accommodate a wide variety of special mission payloads, including electro-optical/IR sensor balls, high-definition reconnaissance videocameras and synthetic aperture radars, along with laser scanners, atmospheric samplers and electronic-intelligence sensors.

In light of its low acquisition and operating costs, its piloted/unpiloted flight modes, mission duration, flexibility and capabilities, Centaur OPA has the potential to change radically cost/benefit expectations in the ISR community.

DA42 M-NG Centaur OPA Specifications
Wing Loading 23.9
Power Loading 12.65
Noise (EPNdB) 78.0
Seating 0 or 1+3
Dimensions (ft./meters)
Length 28.1/8.6
Height 8.2/2.5
Width (maximum) 44.0/13.4
Engine 2 Austro Engine E4
Output/Flat Rating OAT˚C 166 hp
TBO (Time Between Overhauls) 2,000 hr.
Weights (lb./kg)
Max Ramp 4,207/1,908
Max Takeoff 4,189/1,900
Max Landing 3,979/1,805
Zero Fuel 3,891/1,765
BOW 3,291/1,493
Max Payload 600/272
Useful Load 916/415
Max Fuel 512/232
Payload with Max Fuel 404/183
Fuel with Max Payload 316/143
Vno 151 KIAS
Time to 10,000 ft. 10 min
Initial Gradient 706 fpm.
Ceilings (ft./meters)
Certificated 18,000/8,165
Service 27,500/12,474
Sea Level Cabin --/--
Certification FAR 23, 2010