jul-aug2012

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12 FEATURE Unmanned aircraft UAS enablers Although UAS are not new, having precedents from before the Wright Brothers, such as the pilotless balloons used in the Austrian bombardment of Venice in 1849, a number of factors have enabled their increasing take-up in aviation. These include: The widespread civilian use of GPS, following the U.S. decision to end selective availability of the system in 2000 Powerful lithium ion batteries have made practical small RPAs possible, particularly in conjunction with brushless electric motors Development of microelectronics made sophisticated flight control systems and lightweight sensors possible Advances in robotics, which brought artificial intelligence and self-learning computer software. Some RPAs can now analyse their previous flight paths and fly more accurately on their next pass Development and commercialisation of strong lightweight materials, including carbon-fibre composites. At the same time, the weight of the system has halved every 18 months. Now on a 35kg aeroplane you can have daylight video, nighttime video and probably low-light TV as an intermediate. All of that in a six-degree-of-freedom gimbal mount. Prices have remained quite high, but bang for buck has gone asymptotic (exponential).’ ARCAA is working on the next level of UAS ‘detect and avoid’ technology—dynamic detect and avoid, which encompasses a seamless automated process of threat detection, evaluation and avoidance. In recent trials with a vision-based system fitted to a Cessna 172, the sensor was able to ‘see’ a small RPA at 10km, far beyond human visual range. Peter Smith says when it comes to the avoid part of ‘detect and avoid’ even experienced engineers, himself included, have fallen into the trap of thinking that a UAV must behave like a manned aircraft. He realised his error in what he describes as an Isaac Newton moment. ‘What you need to create is a system on the aircraft that can detect something unusual, and in a very few seconds, calculate the likelihood of a collision and take action to avoid. ‘I was driving and drove towards some piping shrikes. One of them wasn’t looking and I almost got him, but he just threw himself sideways. This bird was thinking, “forget the laws of aerodynamics—I’ll recover later”. I suddenly thought, “That’s it”. The Aerosonde is designed to take 25 G because it is recovered in a net. You could never subject human beings to that sort of force, but with a UAV you don’t have to. You can do the tightest turn that the good Lord ever saw, and get out of the way. As soon as I mentioned it to one of our researchers he said, “of course”. ‘We have the potential to give the aircraft a considerable ability to protect not just itself, but other aircraft’, Smith says.
Flight Safety Australia Issue 87 July–August 2012 13 ‘You have to think of communication on several levels when you operate a UAV: how you control your vehicle, how you talk to the world and how you talk to your ground crew’ But technology is only one aspect of safe operations. The importance of communications emerges as a common theme among UAS developers. ‘You have to think of communication on several levels when you operate a UAV: how you control your vehicle, how you talk to the world and how you talk to your ground crew’, says BAE Systems’ technology and development program engineering manager, Nelson Evans. ‘We decided to speak openly about what we were doing so there were no surprises for any parties’, he says. BAE Systems operates the Kingfisher unmanned aircraft system at its flight test and development centre in West Sale in Victoria, within RAAF East Sale’s airspace. ‘We operate under a CASA agreement, during daylight hours in a pre-defined flight zone, NOTAMed when we operate. We’ve operated with mixed traffic without issue; that is among RAAF training, general aviation, trike operators and the like,’ Evans says. ‘One of the early lessons was that communication with the broader community was highly valuable. We talked to all the operators, the council and the farmers about what we were doing. Eight years ago, UAVs were rare and not always discussed in positive terms.’ Future challenges What particularly worries the UAS sector of aviation is what happens when the reality of RPA operation and its public image literally collide. UAS operators emphasise the operational discipline and technological redundancy they must have in order to fly, but several say this is not always reciprocated by manned aviation. One researcher said that ‘although UAS operations must advise their presence with a NOTAM, in practice many general aviation and recreational pilots either do not read the NOTAM, or having read it, on several occasions decided to fly into UAS operating areas “to have a look”.’ Another explains what he described as the ‘Florida problem’ put to them by the U.S. Federal Aviation Administration. An Australian UAS operator had to walk away from a lucrative contract for highway surveillance in the southern state. ‘The problem is the state is full of rich retirees and a significant number of airport condominium developments. You have 80-year-olds with their 40-year-old Piper Cherokees parked outside their houses. Your danger with a UAV in Florida is somebody like that is going to whack into our aircraft one day.’ A third UAS insider was brutally succinct: ‘We have triple redundancy in our systems—they have the mark one eyeball.’ There are also some specific, and immediate, technological challenges for UAS. Peter Smith says: ‘The reliability level of UAVs is not yet as high as CASA would want for completely autonomous operations in densely populated areas.’ Malcolm (Mac) Robertson, technical airworthiness manager with BAE Systems, sees two distinct challenges. ‘GPS or any satellite-based system is not reliable enough for use in UAS. The response in military research is to look at navigation through feature-recognition systems, revisiting the technology of inertial navigation and using magnetic field detection.’
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2012 Have trouble finding aviation
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