Avionics News February 2012 - 57

…the three passengers just sat there and watched the Rockwell Collins fly-by-wire system make a landing that would have scored better than most of the other Bonanza touchdowns the runway has seen.

can control the aircraft all the way from takeoff to touchdown. We do that thousands of times per month. There is no such thing as a pilot or operator landing this aircraft.”

Pre-autonomous Flight
Of course, if you’re going to demonstrate autonomous flight in a general aviation aircraft, why not make it one of the industry’s true icons, the venerable Beechcraft Bonanza. “Hawker Beechcraft got excited about demonstrating automatic landing capabilities on its test bed Bonanza,” Voss said. “It was quite easy to take our little 1-kilogram box, drop it in there and let it do its job.” The “little 1-kilogram box” he referred to is Rockwell Collins’ Athena 411 flight control system. Developed to provide full autonomous operations for UASs, the Athena 411 houses all the inertial sensors, global positioning system, magnetometers, air speed, altitude, angle-of-attack, angle-of-sideslip, pressure transducers and accelerometers in one compact unit. More important to autonomous operations, it also carried the advanced software to control it all. “It had all of the autopilot control laws, all the guidance

laws and all the autoland trajectories,” he said. “It is truly a complete flight control system and sensor suite.” As for installing the 411 in the Bonanza, Voss said it was literally a crank turning exercise. “It was a drop-in from what we do as standard business with our fly-by-wire applications in the UAV market,” he said. “We literally took our existing stuff and put in the characteristics of the Bonanza. We have a standard suite of autopilot or flight control laws that control rates, attitudes, angle-of-attack, airspeed, groundspeed, heading, 3-D nav, glideslopes and latitudinal and longitudinal tracking in our flight controls toolbox. “Once the hardware was installed, we went through the validation exercises and simulations to make sure the interfaces are properly worked out. They all worked as expected.” You are probably wondering why Voss referred to the system as “fly-bywire” when the Bonanza has mechanical control linkage. Well, like in much of aviation today, it’s a matter of definition. Voss explained it this way: “Depending on whom you speak with, people get a little bit purest about what is meant by fly-by-wire. We literally

think of it as if your input into the control system is purely some kind of digital flight plan or FMS profile – as long as you download that mission and software controls the entire airplane – in a flight control way and not a cruise control way – we consider it to be fly-by-wire. “In some cases, wires run out of the servo actuators that literally live out at the control surfaces. In others, there may be pullies and cables between those servo actuators and the actual control surfaces. It doesn’t matter. In the end there is a computer basically flying the airplane. It is sending out commands to some actuator, and that actuator is turning those digital commands into physical control. “The reason we call it fly-by-wire is the pilots don’t have to do anything in a control sense. They’re not taking off or landing the aircraft. If you take this same Bonanza and fly it as an unmanned aircraft, it is literally being flown by wires – electrical signals connected to pullies, cables and servos.” And, because it all comes down to servos pulling cables, it was easy to rig all of the Bonanza’s flight controls,
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Avionics News February 2012

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