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.