UAS in the National Airspace System

As aviation has grown throughout history the issue of separating aircraft from each other has been a long standing mission of the Federal Aviation Administration (FAA).  The National Airspace System (NAS) has seen tremendous growth as the evolution of aircraft and passenger demand has driven the amount of aircraft co-existing in the skies.  Most model aircraft and hobbyist have remained in specially designated areas as part of the regulations set forth by the FAA.  However, the rapid development of various types of Unmanned Aerial Systems (UAS) has seen in unprecedented amount of incursions into the airspace specifically reserved and managed by the FAA.  These incursions represent a severe hazard to air traffic currently operating within the rules and regulations specified by the FAA.  The FAA is now attempting to regulate and integrate these new types of aircraft into the NAS.  Expanding UAS research and training objectives and the resulting increase in demand for NAS access is driving the need for additional FAA policies and procedures to authorize and manage UAS operations in a safe and effective manner (Federal Aviation Administration, 2012).  The FAA has currently developed a Certificate of Waiver or Authorization (COA) for UAS use within the NAS as an interim solution.  UAS that are granted NAS access today are limited by the restrictions of each COA or special airworthiness certificate, which often impose constraints on timeframe (daylight only), weather (visual meteorological conditions only), flying over populated areas, and other operational factors (Federal Aviation Association, 2012).  While imposing this COA allows flights of UAS within the NAS it does not allow for aircraft, manned and unmanned, to co-exist and operate in the same environment.  The FAA must block off and prevent other aircraft from flying into areas where UAS are operating in order to manage them effectively.  This creates a tremendous amount of workload and inconvenience for the FAA.

Numerous manufacturers are developing and experimenting various ways for aircraft to communicate to each other for the purposes of deconfliction, both manually (pilot initiated) or automated.  Most aircraft today use Identification Friend or Foe (IFF) combined with a Traffic Collision Avoidance System (TCAS) as a means of both communicating to ground control and providing location awareness to other aircraft.  However, not all aircraft are equipped with this equipment.  That being said, there is strict guidance and enforcement on the areas in which these aircraft can operate.  Because each pilot carries a certificate that is subject to revocation many pilots operate in a professional manner that respects the rules and regulations set forth by the FAA.  In relation to UAS, specifically Groups 1 -3, the IFF required equipment is too large, cumbersome, and requires a power source that is beyond their ability to operate.  Most Group 4 – 5, and some Group 3 UAS are equipped with IFF but it is not required in most cases due to the lack of current guidance and regulation.  With the advent of Automated Dependent Surveillance-Broadcast (ADS-B) and its adoption by the FAA and other civil aviation authorities around the world, aircraft will begin broadcasting their state vector to Air Traffic Control (ATC) and other ADS-B equipped aircraft independent of transponder interrogators (Strain, R., DeGarmo, M., and Moody, C., 2007).  However, the limited payload and power generation capabilities of small UAS make it impractical for them to equip with existing ADS-B units, not to mention the transponder-based system available today (Strain, R., DeGarmo, M., and Moody, C., 2007).  However, most manufacturers have realized that ADS-B doesn’t necessarily need to be installed directly on the aircraft and can instead be placed mostly inside the Ground Control Station (GCS).  This allows the aircraft to only transmit position and status to the GCS which will in turn communicate via ADS-B to the other players.  While this is one of many potential solutions it negates the operations of aircraft that have no means of communication (i.e. dirigibles, crop dusters, experimental, and some simple VFR aircraft).  Additionally, the various types, capabilities, sizes, and flight profiles of different types or groups of UAS make it incredibly difficult to define a standard profile requirement for their operations.   

              This is an ongoing issue among the integration of UAS in the NAS and the FAA has yet to fully grasp an effective means of managing this issue.  As technology continues to evolve at a rapid pace, solutions to these issues will become easier to navigate as bright young minds tackle these problems with fresh perspective and new technology. 

REFERENCES

Federal Aviation Administration (2012, September).  Integration of Unmanned Aircraft Systems into the National Airspace System; Concept of Operations v. 2.0.  Retrieved from http://www.suasnews.com/wp-content/uploads/2012/10/FAA-UAS-Conops-Version-2-0-1.pdf

Strain, R., DeGarmo, M., and Moody, C. (2007).  A Lightweight, Low-Cost ADS-B System for UAS

Applications.  Retrieved from https://www.mitre.org/sites/default/files/pdf/07_0634.pdf

Weeding Out a Solution

A UAS is to be designed for precision crop-dusting. In the middle of the design process, the system is found to be overweight.

Two subsystems – 1) Guidance, Navigation & Control [flying correctly] and 2) Payload delivery [spraying correctly] have attempted to save costs by purchasing off-the-shelf hardware, rather than a custom design, resulting in both going over their originally allotted weight budgets. Each team has suggested that the OTHER team reduce weight to compensate.

The UAS will not be able to carry sufficient weight to spread the specified (Marketing has already talked this up to customers) amount of fertilizer over the specified area without cutting into the fuel margin. The safety engineers are uncomfortable with the idea of changing the fuel margin at all.

Write a response describing how you, as the Systems Engineer, would go about resolving this issue. Use your imagination, and try to capture what you would really do. Take into account and express in your writing the things you’ve learned so far in this module: What are your considerations? What are your priorities? What do you think about the future prospects for the “next generation, enhanced” version of the system as a result of your approach?

While it is important that the vehicle both fly correctly and spray correctly there needs to be a solution to the overweight dilemma.  Reducing the weight of unmanned aerial vehicles (UAVs) pays large dividends in their ability to carry more fuel, support more advanced payloads (radar, imaging, sensors, navigation and guidance, uplinks and downlinks), achieve longer flight times, and operate from shorter runways (Oliver, 2012).  Both teams have decided on using off-the-shelf (OTS) hardware which has resulted in an overweight situation.  The fixed factors are the fuel and the amount of fertilizer.  Therefore, the only manageable means of navigating this situation is to design custom lighter options for guidance, navigation & control, payload control, increase propeller lift capability, increase motor size, or utilize a lighter design structure for the entire craft.

In most design projects it comes down to two very important factors; time and money.  Therefore, I will begin this project by mandating that each team compile a report that specifies the time and money required to design a custom solution instead of the OTS version.  By forcing the teams to figure out a solution within the design parameters, it will encourage creativity and possibly flush out new ideas or theories that can lead to breakthrough solutions.  The best case scenario is that one or both teams find an easy solution to the weight problem by either slightly modifying the OTS version or designing a new version that is within cost, time, and weight parameters.   Reducing the weight of the electronics, and especially the power-supply subsystem, is a major area for potential improvement (Oliver, 2012).     

Meanwhile, I will consult the propulsion department and have that department begin an evaluation to determine if a different type of propeller is capable of carrying the weight with no negative fallout in regards to the fuel or time aloft considerations.  If the propulsion department cannot produce a better lifting mechanism I will suggest investigating a larger power source.  However, I will stress that the power source must not use any more fuel than what is currently allotted per the original design specifications.  

Lastly, consulting with the structure design engineers may result in some ideas that will result in a lower overall weight to the vehicle.  I will encourage they investigate other materials that may be more durable and lower weight.  However, the cost consideration along with ability to procure material will need to be considered as part of the overall project goals and objectives. 

Ultimately, both teams have failed to fully analyze the problem and create a solution within their parameters which is unacceptable for the success of the project.  They need to go back to the drawing board and come up with custom intelligent designs that meet the demands of the project, thus keeping the project on track.  However, if neither team is able to accomplish a better solution than the OTS, I have consulted with other departments that might be able to offer a solution to the overweight problem. 

REFERENCES

Oliver, S. (2012, August). Take A Multifaceted Power Approach To Reduce Your UAV’s Weight:  Electronic Design.  Retrieved from http://electronicdesign.com/power/take-multifaceted-power-approach-reduce-your-uav-s-weight