UAS Crew Member Selection

In this paper we will examine a scenario where we work at a company that has just purchased the Insitu ScanEagle and a variant of the General Atomics Ikhana to conduct oceanic environmental studies.  We are now responsible for identifying the required crew positions to be filled and determine the qualifications, certifications, and training requirements.  Additionally a minimum and ideal set of criteria for those potential operators.

In order to identify the crew positions available we will look at each platform’s published figures starting with the Insitu ScanEagle.  The ScanEagle uses a pneumatically actuated launcher and a recovery system called the SkyHook, so it does not require a runway like a conventional aircraft.  Additionally its wing span is only 10.2ft and its maximum takeoff weight is 48.5lbs, making it fairly light and relatively portable.  It has a maximum speed of 80knots and a 24+ hour endurance. Its ground control station (GCS) is portable and allows for point-and-click control, (ScanEagle, 2015). 

With the above information, we can use the ScanEagle in a somewhat mobile operations such as having the launcher on a ship or on the ground.  We would also require, two positions to launch fly and recover a ScanEagle, a launch crewman and operator.  Depending on the length of operations required we may need more than one operator, additionally the launch crewman can be trained in maintenance so that a traveling crew can be kept to a minimum of two if operations allowed.

Next, we will look at the variant of the General Atomics Ikhana.  The Ikhana is an MQ-9 Predator B that has been adapted and instrumented for use by NASA, (NASA Armstrong Fact Sheet: Ikhana Predator B Unmanned Science and Research Aircraft System, 2015).  The Predator B has a wingspan of 66ft and maximum gross takeoff weight of 10,500lbs, thus the system is not as portable as the ScanEagle, (Guardian Multi-Mission Maritime Patrol, 2015).  The Ikhana GCS is portable in the fact that it fits inside of a large trailer.  The trailer houses “the pilot control station, engineering monitoring workstations, science monitoring stations, and range safety oversight,” (NASA - Large UAS Aircraft, 2008). “Predators and Reapers currently require two crew to function: a pilot and a sensor operator,” (Whittle, 2015).  In this scenario, one pilot will be required for Ikhana operations and a ground handling crew will be required.  However depending on the length of a particular mission more than one pilot may be required.

In examining current Certificates of Waiver or Authorization (COA) issued by the Federal Aviation Administration, we will require pilots for either platform to hold a minimum of a private pilot license and pass a third class medical examination, (Freedom of Information Act Responses, 2016).  While it is assumed that most flights will be conducted due regard, where the pilot is responsible for safe separation, it can also be inferred that the possibility exists for taking off while in the National Airspace System (NAS) before switching operations over to due regard.  Additionally, we will not let a pilot act as Pilot in Command (PIC) unless three proficiency flights have been conducted in the past 90 days.  We will ensure we work with General Atomics and Insitu to get the required proficiency before we take delivery of the vehicles and we will maintain this proficiency.

Finally, minimum and ideal set of criteria for these potential operators will be established.  Minimum criteria for selection for pilots on either platform without UAS experience, will be a private pilot certificate and a third class medical examination with at least 18 months remaining.  These are just minimums and ideal set of criteria for no experience in a UAS platform.  Ideally, operators from the military with experience in these platforms would be ideal, but military operators may not have a private pilot certificate or third class medical.  In a case such as this as long as the potential operator was medically cleared for UAS flights upon military discharge, we can supplement obtaining a private pilots certificate.  In either case training will have to be conducted before the operator is able to be a PIC on either platform.

While, both platforms will assumably be operating in the maritime environment in due regard, it is conceivable that the UAS could operate in the UAS.  In order for our company to ensure that we operator safely in the NAS as well as protecting our investment in these UAS systems we have set forth the above minimums for operator minimums.

References

Freedom of Information Act Responses. (2016 May 9). Federal Aviation Administration. Retrieved from https://www.faa.gov/uas/public_operations/foia_responses/

Guardian Multi-Mission Maritime Patrol. (2015). General Atomics Aeronautical Systems. Retrieved from http://www.ga-asi.com/Websites/gaasi/images/products/aircraft_systems/pdf/Guardian_032515.pdf

NASA - Large UAS Aircraft. (2008 Oct 3). NASA.gov. Retrieved from https://www.nasa.gov/centers/dryden/research/ESCD/ikhana.html#.VzEAO_krK00

sUAS Operational Risk Management

Enclosed is an Operational Risk Management worksheet created for the DJI Phantom 2 Vision.  I chose this platform because this is a small unmanned aerial system (sUAS) that I fly.  Additionally, I am awaiting a section 333 exemption, which will allow me charge for services I can provide DJI Phantom 2 Vision.

I started this ORM assessment tool by making a Primary Hazard List (PHL).  The PHL consists of likelihood category and severity category. Each category has 4 possible outcomes; not likely, possible, probable, and certain for likelihood; and negligible, moderate, high, and catastrophic for severity.  All range in value from 1-4 where one has a low value and 4 has a high value.  A matrix could then be built giving a risk assessment value by multiplying the value of the severity and likelihood, see FIGURE 1.

FIGURE 1. PHL for the DJI Phantom 2 Vision.

Once the PHL was completed I moved on to the Preliminary Hazard Assessment (PHA).  A list of hazards were compiled and the likelihood and severity were assessed giving a risk level (RL) value by multiplying the values.  Mitigating actions are also listed for each hazard to decrease the risk level resulting in the residual risk level (RRL).  An attempt was made to ensure all RL could be mitigated to some point but not all resulted in a lower RRL.

An Operational Hazard Review and Analysis (OHR&A) was created but has not been filled out because no flights have taken place.

FIGURE 2. ORM Worksheet for the DJI Phantom 2 Vision.

Lastly, an ORM Worksheet was created.  The worksheet can be completed digitally or manually, the digital method automatically sums entered line values.  The total value can then give the operator or myself an ORM level.  One caveat with the line listed as “AIRFIELD TOWER NOTIFIED” created with the assumption that operations will be taking place within the required 5nm of an airfield where the airfield would need to be notified.  If the flight is outside of this radius then the line can be skipped.

I will incorporate this ORM tool into flying of my DJI Phantom 2 Vision in addition with the checklist that I already operate with.  This tool can also let me assess the operational risk of flying when operating with my section 333 exemption.

Automatic Takeoff and Landing

There’s a saying in aviation, “Flying is the 2^nd greatest thrill known to man. Landing is the 1^st.”  This is because landing along with takeoff is a very dynamic part of a flight, and often the most dynamic part of a flight.  Pilots are often talking to approach or tower controllers, running checklists, scanning gauges, and physically controlling the aircraft during this part of flight.  Even in the early years of aviation, inventors and engineers have sought to ease the demands of an aviator, and this was seen as early only about 10 years after the Wright Brothers first flight, with Elmer Sperry’s gyrostabilizer, (Elmer Sperry, Sr., 2016).  The world of aviation has seen many changes from the early days of flight, but engineers still face many challenges including automation.

            For pilots, talks of automation in takeoff and landing can be a touchy subject for those who pride themselves on being able to land an airplane with hand-eye skills.  The Airbus A320 is capable of taking off and landing through automation.  Once the pilot has aligned the aircraft for the approach, speed is adjusted through an auto-throttle system, in where the pilot turns a dial to select an indicated speed and the aircraft adjusts the throttle levers accordingly, (Airbus A320: Auto Landing Tutorial, 2012).  Once the appropriate speed is set and the navigation aid (NAVAID) is selected, the approach button can be depressed, (Airbus A320: Auto Landing Tutorial, 2012).  During all of these processes the pilot is still receiving information from the aircraft and NAVAID and should be backing up the automation by checking the speed, ensuring NAVAID guidance is being received.  Once the glideslope is intercepted the pilot will further input the final approach speed, lower the landing gear, set the flaps, and set the spoilers and autobrakes, (Airbus A320: Auto Landing Tutorial, 2012).  The pilot will leave their hands on the power lever in the event of a go around, (Airbus A320: Auto Landing Tutorial, 2012).

            This system helps to alleviate the additional demands put on a pilot in the terminal by automating parts of the evolution, allowing the pilots to focus on things such as navigation (visual), and communication.  The system in the A320 is capable of flying in a zero vertical visibility and 50 meter horizontal visibility situation, (Airbus A320: Auto Landing Tutorial, 2012).  With the automated system taking care of the aviation portion of the evolution, the pilot must never forget the basics of, “aviate, navigate, communicate.”  This is the priority of skills often taught to aviators early in flight training.  This being said the pilot is always there in the cockpit ready to take control if required or making the judgement call for a go around.

            These systems have also found their way in to unmanned aerial systems (UAS).  The MQ-9 Reaper, remotely piloted aircraft (RPA), boasted in September 2012 that it had, “successfully completed 106 full-stop Automatic Takeoff and Landing Capability (ATLC) landings, a first for the multi-mission aircraft. The milestone was first achieved with four ATLC landings on June 27 at the company’s Gray Butte Flight Operations Facility in Palmdale, Calif,” (Predator B Demonstrates Automatic Takeoff and Landing Capability, 2012).  Other systems have been created to assist in this process since in its simplest for the computer is simply following a predefined flight path.  “The Visually Assisted Landing System (VALS), lets the drones use their cameras to identify landmarks, adjust speed and direction accordingly, and navigate to a smooth landing. And since runways are clearly defined, flat, obvious pieces of topography, identifying them should be easier… By utilizing the drones existing cameras, the system can be used for both the larger UAVs like the Predator, and smaller drones like the Scan Eagle,” (Fox, 2009).

                                     

FIGURE 1. Vision based landing technology called The Visually Assisted Landing System (VALS).  Courtesy of Popular Science.

            Both manned and RPA can be equipped with systems that can follow a preset published approach to get back on the ground.  But, an RPA is missing one key thing that manned aircraft has, a pilot in the aircraft making judgment calls based on what they are seeing and feeling.  While a RPA operator can see and make decisions, these are typically in a limited field of view and are subject to communications links.  If a communication link is broken, the RPA operator is now, for all intents and purposes, blind.  “Vision-based landing has been found attractive since it is passive and does not require any special equipment other than a camera and a vision processing unit onboard,” (Huh, 2010).  A visual based system would let the RPA make a split second decision such as a go around due to reduced visibility or a fouled runway.

            While aviation has made major changes from its beginnings in 1903, we still face the some of the same basic issues, of trying to find ways to assist the pilot to make aviation safer and easier.  We have even gone so far to pull the pilot out of the aircraft, but still face some of the same issues.

References

Airbus A320: Auto Landing Tutorial. (2012 Apr 6). BAA Training. Retrieved from https://www.youtube.com/watch?v=LIaMALJjOEc

Elmer Sperry, Sr.. (2016 Apr 27). The National Aviation Hall of Fame. Retrieved from http://www.nationalaviation.org/sperry-sr-elmer/

Fox, S. (2009 Aug 4). Popular Science. Retrieved from http://www.popsci.com/military-aviation-amp-space/article/2009-08/new-system-allow-automated-predator-drone-landings

Huh, S., & Shim, D. H. (2010). A vision-based automatic landing method for fixed-wing UAVs. Journal of Intelligent and Robotic Systems, 57(1), 217-231. doi:10.1007/s10846-009-9382-2. Retrieved from http://search.proquest.com.ezproxy.libproxy.db.erau.edu/docview/873356418?pq-origsite=summon

Predator B Demonstrates Automatic Takeoff and Landing Capability. (2012 Sep 17). General Atomics Aeronautical. Retrieved from http://www.ga-asi.com/predator-b-demonstrates-automatic-takeoff-and-landing-capability

UAS Shift Work Schedule

              As a human factors consultant for the MQ-1B squadron for the United States Air Force (USAF) this paper will attempt to address concerns of fatigue brought to the attention of the squadron’s Commanding Officer (CO).  Figure [1], has been submitted on behalf of the MQ-1B squadron outlining current operations.

“Fatigue is a condition characterized by increased discomfort with lessened capacity for work, reduced efficiency of accomplishment, loss of power or capacity to respond to stimulation, and is usually accompanied by a feeling of weariness and tiredness,” (Salazar).  Military life can lead to, “Late nights, deadlines, night-shift work, early briefs, time-zone travel, deployments, combat stress, and anxiety all compete for limited sleep time,” (Davenport, 2009).  These factors along with dealing with stresses of home life and collateral jobs create what is known as operational tempo (OPTEMPO).  “[C]ombat-aviation missions are presumably significantly more stressful than commercial air-transportation operations. For instance, although airline-transport pilots no doubt experience stress from their responsibility for the safety of up to 400 passengers, they are rarely targets of enemy aggression. Combat pilots, however, routinely perform their duties under imminent and palpable threats to their own safety and, in fact, their very lives,” (Caldwell, 2008).

Current OPTEMPO requires 3 shifts, Day, Swing, and Night.  Each team takes one particular shift for a 6 day week and then shifts the following week.  While this helps to create a circadian rhythm for the week, this is desynchronized the following week. By the end of the week as synchronization is happening, it is then changed again.

Figure 1

Figure 2

Proposal of the schedule in Figure [2], still has a 6 day work week stating with 2 Nights, 2 Swings, 2 Days shifts.  This schedule allows for a clockwise flowing shift change, allowing the body to adapt quicker and easier.  Additionally, since the week start on a Night shift and ends on a Day shift it allows for 78.5 hours off or 3.2 days of continuous time off.

Additionally, since this appears to be a high OPTEMPO environment, it is suggested that the CO seek advice from the flight surgeon on the USAF “Go, No Go” Program or the prescription use of stimulants and sedatives.  In this author’s opinion, having flown ISR missions for the United States Navy (USN), the prescription use of the sedatives can help in a high OPTEMPO environment.

References

Caldwell, J. A. (2008). Go Pills in Combat: Prejudice, Propriety, and Practicality. Air & Space Power Journal (Fall 2008). Retrieved from http://www.airpower.maxwell.af.mil/airchronicles/apj/apj08/fal08/caldwell.html

Davenport, N. (2009). MORE FATIGUE! (yawn). Approach, 54(3), 3. Retrieved from http://search.proquest.com.ezproxy.libproxy.db.erau.edu/docview/274584729?pq-origsite=summon

Salazar, G. Fatigue in Aviation. Federal Aviation Administration (Publication # OK-07-193) Retrieved from https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/Fatigue_Aviation.pdf

UAS Beyond Line of Sight Operations

       Beyond line of sight (BLOS) operations can present a number of problems to an unmanned aerial system (UAS) operator that is not encountered when operating line of sight (LOS).  However, despite these problems, they can also present a number advantages.  From a technical aspect a number of command and communications problems arise when a UAS system is operated BLOS due to environmental conditions.  It is up the control system on board to take over in the event of a lost link situation, however, when not in a lost link situation, it is up the operator to provide full control or supervisory control.  While in control, a number of human factor issues can come in to play.

In 2013, a study was conducted by S. Giese, using 15 years of U.S. Air Force (USAF) data consisting primarily of “Predator” series statistics (Including MQ-1A and MQ-9). The study noted, “high in-service mishap rates for the RQ-1 Predator, RQ-5 Hunter and RQ-2 Pioneer of 32, 55 and 334 mishaps per 100,000 flight hours respectively,” (Giese, 2013).  This is high when compared the equivalent safety level of civil aviation of 1 in 100,000 hours, (Giese, 2013).  Aside, from these statistics, mishaps were broke down by times of error, “The highest percentage of human-related mishaps was connected to skill-based errors. As [15] had also found, most common in the present study were procedural errors, followed by checklist errors, inadvertent operation, overcontrol/undercontrol, and finally breakdown in visual scan… Skills have to be learned and practiced, thus the results suggest deficiencies in initial and recurring crew training. They could also imply that pilots recruited to control UASs are not ideal for the task, implicating issues with recruitment and selection processes,” (Giese, 2013).

            UAS are generally operated by aviators who at some point have flown a manned aircraft of some sort.  However, not all UAS developers are not traditional aircraft manufactures, “UASs are mainly developed by entities other than the traditional aircraft manufacturers and are not flown conventionally and thus do not necessarily follow the same design rules as manned aircraft. Therefore, GCSs can be quite dissimilar to manned aircraft cockpits, and in fact, the only comparable interface is that of Predator [15]. However, the Predator GCS has not changed fundamentally for 20 years,” (Geise, 2013).

“The results of this study support previous findings where the presence of perceptual and cognitive failures combined with perceptual and skill-based errors suggested pilot Situation Awareness (SA) had been compromised. Cognitive failures were mainly due to inattention, channelized attention and confusion. Misperception of operational conditions (such as altitude and speed) and expectancy were the most common perceptual failures. Hence primarily, the crew’s ability to make observations about the environment in time and space is affected,” (Giese, 2013).

With all of this in mind, it can be interpolated that ground control station (GCS) layouts when flying BLOS does not provide an aviator with data in a familiar format.  Additionally, a pilot can longer rely on tactile senses, which are sometimes referred to as the “seat of the pants” feeling that further reduces situational awareness (SA).  This is not to say that BLOS flights are dangerous due to a loss of SA, but that due to a reduction of SA other cues must be given to the operator in the GCS.  BLOS flights can in the private sector could provide a large market for delivery, transportation, surveying, traffic control/reports.

References

Giese, S., Carr, D., & Chahl, J. (2013). Implications for unmanned systems research of military UAV mishap statistics. Paper presented at the 1191-1196. doi:10.1109/IVS.2013.6629628. Retrieved from http://ieeexplore.ieee.org.ezproxy.libproxy.db.erau.edu/stamp/stamp.jsp?tp=&arnumber=6629628

UAS Integration in the NAS

       “FAA, collaborating with other federal agencies and the aviation industry, is implementing NextGen, an advanced technology air-traffic management system that FAA anticipates will replace the current ground-radar-based system,” (United States. Federal Aviation Administration, & United States. Government Accountability Office, 2013).  FAA’s Next Generation Air Transportation System (NextGen) consists of multiple programs including, Automatic Dependent Surveillance-Broadcast (ADS-B), Collaborative Air Traffic Management Technologies (CATMT), Data Communications (Data Comm), National Airspace System Voice System (NVS), NextGen Weather, and System Wide Information Management (SWIM), (NextGen Programs, 2016).  Through 2018, the NextGen program is expected to cost $18 billion, (United States. Federal Aviation Administration, & United States. Government Accountability Office, 2013).  Through the implementation of multiple programs the NextGen program will, “enhance safety, increase capacity, and reduce congestion in the national airspace system,” (United States. Federal Aviation Administration, & United States. Government Accountability Office, 2013).  While the NextGen program is made to make the National Airspace (NAS) more efficient, it could benefit remotely piloted vehicles (RPV) which are better known as unmanned aerial vehicles (UAVs).  “By determining how UAS flight operations and protocols may be different than those of traditional manned aircraft, informed decisions can be made concerning the data and interfaces required to accommodate routine UAS operations by NextGen automation systems, ultimately leading to safer and more efficient integration of UAS into non-segregated civil airspace,” (Paczan, 2012).

“ADS-B makes use of GPS technology to determine and share precise aircraft location information, and streams additional flight information to the cockpits of properly equipped aircraft,” (NextGen Programs, 2016).  Unmanned aircraft equipped with ADS-B will be able to share its location with aircraft and flight following services.  This will be helpful in the event of a lost link where the unmanned aircraft operator is unable to communicate commands to the unmanned vehicle.  When there is a lost link the operator is unable to continue to see and avoid, the unmanned systems typically have a failsafe in the event of a lost link, but with ADS-B the precise location of the unmanned system will be reported, enabling air traffic control to route aircraft around the lost link aircraft.

Data Comm, “will enable controllers to send digital instructions and clearances to pilots. Precise visual messages that appear on a cockpit display can interact with an aircraft's flight computer. Offering reduced opportunities for error, Data Comm will supplant voice communications as the primary means of communication between controllers and flight crews,” (NextGen Programs, 2016).  Data Comm could raise issues with unmanned systems, especially with plans to have it replace voice communications.  The Data Comm would have to be sent to the unmanned vehicle and then the instructions would be relayed to the ground control station (GCS).  In the event of a lost link where the unmanned vehicle and GCS are no longer able to communicate, this would mean that the Data Comm would no longer be able to be received by the operator.  This is no different than how voice communications with current unmanned systems currently work.  Currently Data Link plans to use digital radio frequencies, however, in theory, it could be connected to the internet, and could allow the operator to inform flight following services of a lost link.

“Once all planned programs are in place, FAA expects NextGen to deliver $134 billion in direct airline, industry, and passenger benefits (passenger value of time and carbon dioxide emissions) through 2030,” (NextGen Programs, 2016).  While, there is no deliberately stated goal of helping to integrate RPVs or UAVs through the implementation of the NextGen program, the unmanned industry can benefit from the integration of the NextGen systems and programs.

References

NextGen Programs. (2016 Apr 6). NextGen, Federal Aviation Administration. Retrieved from https://www.faa.gov/nextgen/programs/

Paczan, N. M., Cooper, J., & Zakrzewski, E. (2012). Integrating unmanned aircraft into NextGen automation systems. Paper presented at the 8C3-1-8C3-9. doi:10.1109/DASC.2012.6382440

United States. Federal Aviation Administration, & United States. Government Accountability Office. (2013). NextGen air transportation system: FAA has made some progress in midterm implementation, but ongoing challenges limit expected benefits : Report to congressional requesters. Washington, D.C.: U.S. Govt. Accountability Office. Retrieved from http://www.gao.gov/assets/660/653628.txt

UAS Integration in the NAS

            “FAA, collaborating with other federal agencies and the aviation industry, is implementing NextGen, an advanced technology air-traffic management system that FAA anticipates will replace the current ground-radar-based system,” (United States. Federal Aviation Administration, & United States. Government Accountability Office, 2013).  FAA’s Next Generation Air Transportation System (NextGen) consists of multiple programs including, Automatic Dependent Surveillance-Broadcast (ADS-B), Collaborative Air Traffic Management Technologies (CATMT), Data Communications (Data Comm), National Airspace System Voice System (NVS), NextGen Weather, and System Wide Information Management (SWIM), (NextGen Programs, 2016).  Through 2018, the NextGen program is expected to cost $18 billion, (United States. Federal Aviation Administration, & United States. Government Accountability Office, 2013).  Through the implementation of multiple programs the NextGen program will, “enhance safety, increase capacity, and reduce congestion in the national airspace system,” (United States. Federal Aviation Administration, & United States. Government Accountability Office, 2013).  While the NextGen program is made to make the National Airspace (NAS) more efficient, it could benefit remotely piloted vehicles (RPV) which are better known as unmanned aerial vehicles (UAVs).  “By determining how UAS flight operations and protocols may be different than those of traditional manned aircraft, informed decisions can be made concerning the data and interfaces required to accommodate routine UAS operations by NextGen automation systems, ultimately leading to safer and more efficient integration of UAS into non-segregated civil airspace,” (Paczan, 2012).

“ADS-B makes use of GPS technology to determine and share precise aircraft location information, and streams additional flight information to the cockpits of properly equipped aircraft,” (NextGen Programs, 2016).  Unmanned aircraft equipped with ADS-B will be able to share its location with aircraft and flight following services.  This will be helpful in the event of a lost link where the unmanned aircraft operator is unable to communicate commands to the unmanned vehicle.  When there is a lost link the operator is unable to continue to see and avoid, the unmanned systems typically have a failsafe in the event of a lost link, but with ADS-B the precise location of the unmanned system will be reported, enabling air traffic control to route aircraft around the lost link aircraft.

Data Comm, “will enable controllers to send digital instructions and clearances to pilots. Precise visual messages that appear on a cockpit display can interact with an aircraft's flight computer. Offering reduced opportunities for error, Data Comm will supplant voice communications as the primary means of communication between controllers and flight crews,” (NextGen Programs, 2016).  Data Comm could raise issues with unmanned systems, especially with plans to have it replace voice communications.  The Data Comm would have to be sent to the unmanned vehicle and then the instructions would be relayed to the ground control station (GCS).  In the event of a lost link where the unmanned vehicle and GCS are no longer able to communicate, this would mean that the Data Comm would no longer be able to be received by the operator.  This is no different than how voice communications with current unmanned systems currently work.  Currently Data Link plans to use digital radio frequencies, however, in theory, it could be connected to the internet, and could allow the operator to inform flight following services of a lost link.

“Once all planned programs are in place, FAA expects NextGen to deliver $134 billion in direct airline, industry, and passenger benefits (passenger value of time and carbon dioxide emissions) through 2030,” (NextGen Programs, 2016).  While, there is no deliberately stated goal of helping to integrate RPVs or UAVs through the implementation of the NextGen program, the unmanned industry can benefit from the integration of the NextGen systems and programs.

References

NextGen Programs. (2016 Apr 6). NextGen, Federal Aviation Administration. Retrieved from https://www.faa.gov/nextgen/programs/

Paczan, N. M., Cooper, J., & Zakrzewski, E. (2012). Integrating unmanned aircraft into NextGen automation systems. Paper presented at the 8C3-1-8C3-9. doi:10.1109/DASC.2012.6382440

United States. Federal Aviation Administration, & United States. Government Accountability Office. (2013). NextGen air transportation system: FAA has made some progress in midterm implementation, but ongoing challenges limit expected benefits : Report to congressional requesters. Washington, D.C.: U.S. Govt. Accountability Office. Retrieved from http://www.gao.gov/assets/660/653628.txt