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.