Automatic takeoff and landing systems (ATLS) have been under development for decades as a natural progression of the instrument approach. An auto-land capability is typically found in commercial aviation as a means of satisfying the requirements for Approach Category IIIb minimums under Advisory Circular 120-28D, which allow approaches with a decision height of zero and runway visual range of 150 feet (FAA, 1999). These include a suite of sensors and systems that demonstrate the “fail operational” concept, which can be satisfied by a single system with dual-redundant components, or two independent systems with redundant components. Pilots must also satisfy lengthy requirements for initial qualification and currency, featuring academics and simulator events. While several enabling technologies have enhanced the accuracy of ground movement, the manned aircraft community has not shown significant interest in automatic takeoff systems. In the Unmanned aerial system (UAS) market, ATLS has been fielded as a means to reduce mishaps stemming from pilot error in close proximity to the ground. Takeoff systems are typically a simple stabilization after a catapult or vertical launch (Marshall, Barnhart, Shappee, & Most, 2016). Landings systems range from simple guidance to an arresting apparatus, to a complex replication of a conventional runway recovery. In contrast to CAT III requirements, UAS ATLS does not currently require any additional aircraft certification or airman rating. The following paper will review the state of the art for manned and unmanned aircraft ATLS integration.
Manned Aircraft: DA 50/52
The Diamond Aircraft Consortium is developing an automatic landing system for light general aviation aircraft, advertising that its DA50 and 52 will be first to enter the market with this capability at the $100,000 price point (Marsh, 2012). Garmin has also been working towards a similar capability with its G3X autopilot for the sport and kit plane markets (Garmin, 2017). While details of both systems are scarce, they are highly likely to rely on Differential Global Positioning System (DGPS), as light aircraft do not typically have radar/laser altimeters, auto-throttles, auto-braking/anti-skid, and are unable to demonstrate the reliability required in AC 120-28D. Diamond and Garmin understand this, and are instead marketing their auto-land systems as a safety-enhancing contingency feature should the pilot become incapable of landing, but without the destructive effects of an airframe recovery parachute. While not certified for approaches below Category I, general aviation pilots are also expecting this new technology to assist with single pilot operations under Instrument Flight Rules (IFR), reducing workload and increasing safety (SportPilotTalk, 2015).
Figure 1. Diamond DA-52 auto-landing test platform. Reprinted from Airplane Owners and Pilots Association (2016).
Unmanned Aircraft: Kingfisher II
The Intelligent Landing System (ILS) is a novel creation of BAE Systems-Australia that is installed on the medium altitude/long endurance Kingfisher II for test purposes (Williams & Crump, 2012). Many UAS rely on teleoperation for takeoff and landing phases, which requires crews and control stations, and limits operations to/from locations that were planned for well in advance. ATLS for fixed-wing UAS has been fielded on a few aircraft like the MQ-1C or RQ-5, although these tend to rely on Differential Global Positioning System (DGPS) or other unique active systems that reduce, but not eliminate the logistics footprint. Another typical requirement is that the runway, taxiways, and parking areas be surveyed to generate a digital model from which the aircraft can estimate its position. The goal of ILS is to enable ad hoc takeoff and landing, without pre-staged equipment or surveys. The key is closed-loop image processing onboard the vehicle and makes two assumptions: the vehicle carries a gimbaled optical sensor, and the runway has standard Precision Instrument Runway Markings. ILS is given direct control over sensor orientation and zoom to automatically search for and characterize the designated runway. Image frames are adjusted for camera lens distortion and each pixel is transformed from the image reference frame to the aircraft reference frame. During flight tests, a pilot was positioned at the field with a standard Kingfisher II control station and “kill switch” to decouple ILS from the controls, although they were never required to intervene. At this early developmental stage, ILS does not have any fail-safe or redundant backup, and would be completely inoperative should the gimbaled sensor fail. This would have to be addressed if the system was ever to see wide-spread use as the primary landing method as opposed to a contingency method (in response to an engine failure for example). As with any new system, pilots would need to be trained on normal and emergency operations. In the case of long-range UAS that have typically divided pilots between terminal and mission phases, all pilots would need to demonstrate acceptable skills for near-aerodrome operations. Additionally, ILS was demonstrated on the relatively benign, 275lb Kingfisher II. Should it be installed on a larger UAS, it will likely need to be fused with precision altitude data such as that provided by a radar altimeter to appropriately manage vertical velocity and the flare.
Figure 2. Example of ILS automatic runway detection using the Precision Instrument Runway Markings as a reference. Reprinted from Intelligent Landing System for Landing UAVs at Unsurveyed Fields, 2012.
Conclusion
This short essay has researched and summarized the current state of ATLS systems as they apply to manned and unmanned aircraft. New developments in the general aviation field were identified as a way to reduce pilot workload and increase safety. ATLS for UAS is continuing to progress towards less onboard equipment so that lighter vehicles can have this capability.
References
Euronews. (2012, November 29). Small aircraft, smart safety. Retrieved from http://www.euronews.com/2012/11/28/small-aircraft-smart-safety
Federal Aviation Administration. (1999). AC-120-28D: Criteria for Approval of Category III Weather Minima for Takeoff, Landing, and Rollout. Retrieved from https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC120-28D.pdf
Garmin. (2017). G3X™. Retrieved from http://www.garmin.com/us/products/intheair/sport-aviation/g3x/
General Atomics. (2017). Gray Eagle UAS. Retrieved from http://www.ga-asi.com/gray-eagle
Marsh, A. (2012, December 19). Diamond to offer auto landing in 2016. Retrieved from https://www.aopa.org/news-and-media/all-news/2012/december/19/diamond-to-offer-auto-landing-in-2016
Marshall, D. M., Barnhart, R. K., Shappee, E., & Most, M. (2016). Introduction to unmanned aircraft systems. Boca Raton: Taylor & Francis, CRC Press.
Sport Pilot Talk. (2015). Tl 3000 & Garmin G3X = Fully Automated Landing Approach. Retrieved from http://sportpilottalk.com/viewtopic.php?f=1&t=3790
Williams, P., & Crump, M. (2012). Intelligent Landing System for Landing UAVs at Unsurveyed Fields. 18th International Congress of the Aeronautical Sciences. Retrieved from http://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/131.PDF
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