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.