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Meeting	ACGS Committee Meeting 102 - Niagara Falls - October 2008
Agenda Location	4 GENERAL COMMITTEE TECHNICAL SESSION 4.2 Government Agencies Summary Reports 4.2.4 US Navy 4.2.4.2 NAVAIR
Title	NAVAIR
Presenter	Shawn Donley
Available Downloads*	presentation
	Downloads are available to members who are logged in and either Active* or attended this meeting.
Abstract	The NAVAIR update elected to focus on one activity, the SAE initiative to develop an Aerospace Recommended Practice for Military UAV flight control systems, ARP94910. This effort is sponsored by the SAE A-6A3 Flight and Utility Control Systems Panel. In 2007, the A-6 Systems Panel completed a new Aerospace Standard, AS94900, for Manned Military Aircraft Flight Control Systems. AS94900 is based on the old MIL-F-9490D specification and includes significant updates and new material. In July, 2007, the US Department of Defense accepted AS94900 as a replacement for MIL-F-9490D for new acquisitions. A spin-off version of AS94900 was suggested for UAV¡¯s, but recognizing the relatively immature state of UAV flight control technology, particularly for smaller UAV¡¯s, the SAE steering council recommend we proceed with development of an Aerospace Recommended Practice document rather than an Aerospace Standard. Work on ARP94910 commenced in early Sep 2008 with the goal of having a first draft completed by late 2009. As we began this work, it became obvious that simply tailoring paragraphs from AS94900 for the UAV arena would not be enough. One fundamental difference is that, for manned aircraft flight control systems, failures leading to a total loss-of-control should be an exceedingly rare event rather than an occasionally acceptable event, as is the case today for at least some classes of UAV¡¯s. Historical evidence shows a five order of magnitude difference in vehicle loss rates per 100,000 hours when one includes commercial Part 121 carriers at one extreme and some UAV¡¯s at the other extreme! Even with increasing efforts to improve UAV reliability, it became clear that a ¡°one size fits all¡± approach to FCS requirements would not work. One possible approach to this dilemma may be to specify a range of acceptable behaviors for the UAV flight control systems (FCS) after first and second failures, thus creating a set of FCS ¡°Types¡± based on post-failure behavior. In this context, ¡°flight controls¡± is expanded to include not only the core flight control sensing, computational and actuation resources, but guidance and navigation systems as well. The clear direction from SAE was not to include the UAV ground station functions, however. Expanding this concept, the ARP would attempt to link the recommended ¡°Type¡± of FCS to the UAV operating area/mission, and to characteristics of the UAV such as weight, cost or kinetic energy. An initial attempt at defining UAV FCS Types is shown below: Type Acceptable Behavior After First FCS Failure Comments Acceptable Behavior After Second Failure 0 Immediate loss of attitude, altitude or speed control, resulting in immediate loss of flight path control and eventual or immediate uncontrollable impact with terrain/obstructions. Characterized by a single thread system with no analytical redundancy or control reconfiguration features. N/A 1 Degraded control of attitude, altitude or speed. Vehicle unable to complete the original mission. Vehicle able to maintain safe altitude and airspeed in some cases. Sufficient flight path control to maintain a pre-defined fail-safe heading that minimizes risks to third parties. Type 0 system where special efforts are made to keep the processors and their power sources alive. If data link is available, ground control could provide vector to alternate recovery area. Controllable landing may not be possible. Type 0 2 Degraded control of attitude, altitude or speed. Vehicle unable to complete the original mission or a modified mission without risk of loss. Vehicle attempts to estimate if it can reach the recovery point of original intent or an alternate for a controllable but possibly degraded recovery. If not, vehicle attempts to reach a pre-defined geographical coordinate and terminate flight. Characterized by very high integrity simplex digital processors and processor power supplies/sources, or at least duplex redundancy in these components . Servos may be simplex but designed to minimize probability of hardover failures. Analytical redundancy and control reconfiguration used to provide sufficient control and navigation to safely reach a recovery point for degraded landing, or a pre-defined flight termination coordinate. Type 1 3 Partial degradation of attitude, altitude or speed control. Vehicle may be unable to complete the mission without risk of loss unless mission parameters are modified. Vehicle still capable of reaching recovery point of original intent or an alternate for a controllable but possibly degraded recovery. Characterized by at least duplex or higher levels of redundancy in control & guidance processing and power sources. Analytical redundancy, control reconfiguration or sensor/actuator physical redundancy used to mitigate failure effects. Type 2 4 No degradation of attitude, altitude or speed control, or degradation not severe enough to warrant termination of the mission. Vehicle capable of returning to recovery point of original intent or a pre-defined alternate for safe recovery. Characterized by at least triplex or higher levels of redundancy in control & guidance processing, sensors and actuator control paths. Flight control actuators physically redundant or use redundant surfaces. Analytical redundancy and control reconfiguration may be used to further mitigate failure effects. Type 3 Implicit in this initial set of definitions is the assumption that UAVs can and should adopt state-of-the-art analytical approaches for suppressing the effects of failures without resorting to brute-force hardware redundancy. A quick study of UAV physical characteristics shows that there is no universally accepted categorization scheme. For the moment, we have elected to adopt one taxonomy outlined in the 2007 DoD UAV roadmap document, as shown below: Current System Attributes JUAS Categories Operational Altitude (ft) Typical Payload Launch Method Weight (lbs) Airspeed (kts) Endurance (hrs) Radius (nm) Current Systems (Projected by 2014) 1 T1 - Tactical 1 Special Operations Forces (SOF) Team Small Unit Company & below ¡Ü 1,000 Primarily EO/IR or Comm Relay Hand launched ¡Ü 20 ¡Ü 60 < 4 < 10 Hornet, BATCAM, Raven, Dragon Eye, FPASS, Pointer, Wasp, BUSTER (rail-launched), MAV 2 T2 - Tactical 2 Battalion/Brigade Regiment SOF Group/Flight ¡Ü 5,000 Mobile launched 20 - 450 ¡Ü 100 < 24 < 100 Neptune, Tern, Mako, OAV-II, Shadow, Silver Fox, ScanEagle, Aerosonde 3 T3 - Tactical 3 Division/Corps MEF/Squadron/ Strike Group ¡Ü 10,000 Above, plus SAR, SIGINT, Moving Target Indicator (MTI), or WPNS Conventional or Vertical Take-off and Landing (VTOL) 450 ¨C 5,000 ¡Ü 250 < 36 < 2,000 Maverick, Pioneer, Hunter, Snow Goose, I-Gnat-ER, ER/MP, Dragonfly, Eagle Eye, Firescout, BAMS, Hummingbird, Onyx ¡Ü 40,000 Conventional ¡Ü 15,000 > 250 Predator, N-UCAS, Reaper 4 O ¨C Operational JTF 5 S ¨C Strategic National > 40,000 Above, plus RADAR > 15,000 Theater wide Global Hawk An initial attempt to define a possible range of operating areas/missions is as follows: Op Area 1 UAS intended to operate only in Restricted and Warning Areas under controlled and supervised conditions, or in combat areas with few no-combatants present. 2 UAS intend to regularly operate over areas of low population density, and/or in Restricted and Warning Areas, and/or in a maritime environment, and/or in combat zones. 3 UAS that are intended to regularly operate a majority of the time in densely populated urban areas where uncontrolled loss of the UA may cause injury/fatalities to civilian population or damage to property. 4 UAS that intend to regularly operate in all classes of airspace including those outside of Restricted/Warning Areas and combat zones. Combining these ideas leads to a notional mapping of UAV FCS ¡°Type¡± to UAV Airframe Category and Operating area as follows: FCS Type UA Category Level 1 Level 2 Level 3 Level 4 Level 5 Op Area 1 0 1 2 3 4 2 0 1 2 3 4 3 1 3 4 4 4 4 2 3 4 4 4 Op Area 1 UAS intended to operate only in Restricted and Warning Areas under controlled and supervised conditions, or in combat areas with few no-combatants present. 2 UAS intend to regularly operate over areas of low population density, and/or in Restricted and Warning Areas, and/or in a maritime environment, and/or in combat zones. 3 UAS that are intended to regularly operate a majority of the time in densely populated urban areas where uncontrolled loss of the UA may cause injury/fatalities to civilian population or damage to property. 4 UAS that intend to regularly operate in all classes of airspace including those outside of Restricted/Warning Areas and combat zones. At this early stage, it is hard to say if this proposed approach will hold up to more detailed scrutiny or turn out to be a false start. In many ways, it looks like development of ARP94910 is going to be more challenging than the AS94900 project. We are looking for volunteers to assist with the project!