AUVSI 2013: Sense & Avoid: A Piece of the Puzzle

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SENSE & AVOID: A PIECE OF THE PUZZLE
Laura Samsó Pericón*
Current airspace is experiencing a continuous and substantial growth in terms of traffic and future challenges, such as the introduction of Remotely Piloted Air- craft (RPA) and the difference in the classification and use of airspace, repre- sents a ‘problem’ to the aviation community not yet solved. The initial euphoria in some markets is on the other hand offset by the public concern of having the- se platforms flying over, in non-segregated airspace and the perception of un- controlled flight by pilots and aircraft that do not have rigorous training and test- ing required to be human-rated.
Sense and Avoid (S&A) is performed using an on-board sensor suite that ob- serve the environment and calculate trajectories establishing possible solutions to de-conflict scenarios or collision risk and the near-real time transmission of this huge amount of data air-air/air-ground is critical. They shall be small, light, with low power consumption and act as a human like together with the same or similar capacity of situation analysis and decision-making.
There is a need to make S&A systems reasonably affordable and sustainable for the stakeholders, technology needs to demonstrate reliable capabilities and with an equivalent level of safety to human pilots and at the same time, regulatory bodies should work in a common agreed framework.
Can small RPA reliably detect and avoid collision with objects, both stationary and moving, that do not announce their position and within near real time? Is it possible to obtain a cost effective and power safe small payload that would per- mit RPA to fly safely in uncontrolled airspace? Why national authorities don't think in a sustainable change model when planning the introduction of S&A sys- tems? What is missing in this global framework?
It seems future is not so encouraging however this could be achieved with a co- ordinated approach between unmanned aircraft systems stakeholders.
* Lead Support Role Volunteer for Community Involvement, Leadership Council, Project Management Institute (PMI) Aerospace and Defense CoP, US.
US13-SAMSÓ

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INTRODUCTION
Unmanned Aircraft Systems (UAS) in general are facing different challenges that are delaying their introduction into the airspace and experts agree that it will be gradual and evolutionary. One reason relies in that, i.e. not all key technologies required for those systems to fly in non- segregated airspace are mature and standardized. It seems that initial access to the airspace will be restricted under some defined conditions and as soon as technology, regulation and societal ac- ceptance progress, restrictions will be alleviated (Reference 1).
On the other hand, concern about the Pilot-In-Command (PIC) training of those systems should be addressed as well as the detect & collision avoidance equipment needed either in manned and unmanned platforms. In Canada and the U.S., small planes aren’t required to have transponders or radios, as long as they aren’t flown near cities or large airports. National Airspace System (NAS) RPA introduction in US is expected to happen in 2015 and by 2020, all aircrafts must be equipped with ADS-B transponders, so after having mentioned some of the challenges that RPA will need to face, some questions arise in terms of affordability and sustainability for the stakeholders, reliability wrt technology capabilities and regulatory efforts.
With respect to that point, Article 8 of the Convention on International Civil Aviation signed in Chicago in 1944 already made provision of the ‘pilotless aircrafts’ and, in order to bust the in- tegration the unmanned aircrafts into the airspace, some Annexes of the Chicago Convention (2- Rules of Air, 7-Aircraft Nationality and Registration Marks and 13-Aircraft Accident and Inci- dent Investigation) have been amended until now. In that situation, the Member States of the In- ternational Civil Aviation Organization (ICAO) may adapt their legislation in order to permit the RPA integration. ICAO UASSG group has published Circular 328 Unmanned Aircraft Systems (UAS) and are expected to publish the UAS guidance manual in 2014.
In line with the ICAO recommendations, the recently published European RPA roadmap reaf- firms the need that the unmanned aircrafts have to comply with the aviation rules. This means i.e. that RPA should not introduce any change in current ATC operations and procedures, they must comply with the trajectory management concept though in the SESAR system (analog to the con- cept in the NextGen system in US), they should follow the Communication, Navigation and Sur- veillance (CNS) requirements belonging to the class of airspace where they are going to operate and it seems that additional equipment will be needed on board, but this is a point to discuss in- depth in the future between authority bodies.
Figure 1. Global Unmanned Aircraft Activities (Reference 2).

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For long time US, Israel and Australia have been paving the way in UAS technology devel- opments and now other countries are following their steps. Figure 1 presents the different un- manned aircraft activities that are being developed around the world. I.e. in US some of the activ- ities are among FAA, the UAS Executive Committee composed by the FAA, Department of De- fense (DoD), National Aeronautics and Space Administration (NASA) and DHS, the RTCA/ASTM/SAE standards, etc. Other countries with initiatives are Israel, Africa, India, China and Japan.
Table 1. EU UAS Organization Work (Reference 2).
Focal Point in
Organization
Policy
Support to EC
Guidelines, Integration, Training
ATM
EUROCONTROL
Regulation
EASA, JARUS
R&D
SJU, EDA, ESA etc (until SESAR2)
Standardization
ICAO UASSG (EUROCONTROL)
EUROCAE WG-73/93
NATO FINAS
RTCA SC228
Table 1 presents the organization of work in EU in terms of policy, guidelines, integration, training, regulation, R&D and standardization.
Figure 2. EUROCONTROL UAS Integration Path (Reference 2).

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Figure 2 presents the UAS integration path and the different support and work carried out in order to achieve the UAS integration goal in EU. Organizations such NATO, the European De- fense Agency (EDA), the European Space Agency (ESA), the industry itself, the universities will act as integration supporters, a second step will be a consultation forum in order to fill the gaps, obtain best practices, etc; after that, a key point will be to consolidate regulations and a last step would be to work EU and US bodies together.
The objectives of the European RPAs roadmap (Reference 1) mentioned above include the safe integration of civil and military RPA operations into the European aviation and ATM system from 2016 in non-segregated airspace and complying with SESAR master plan (Reference 4). This roadmap presents three annexes covering a regulatory work plan, a strategic R&D plan and an analysis of societal impact aspects of RPA (insurance, privacy, security). Regulatory efforts should be placed in three main domains: airworthiness, flight crew licensing and air operations.
Figure 3. Current Status Civil (left) and Military (right) UAS regulation in EU states: Green- has regulation, Light green - underway, Blue - accommodation case by case but no regulation, Orange- no regulation (Reference 2).
Regulations are constantly evolving as it could be observed in the figure above (Figure 3): cur- rent civil and military UAS regulation in EU states. On the other hand it is necessary to highlight that the greatest amount of the emerging applications, both civil and military, are related to light RPAs (< 150 Kg).
At the moment of writing this paper, Czech Republic, France, Ireland, Italy, Sweden, Switzer- land and UK, have national regulations in place and in Belgium, Denmark, The Netherlands, Aus- tria, Turkey, Norway and Spain are finalizing National regulation. The problem rely in the appre- ciable differences between these regulations, there is a need of consolidation and better agreement between them and this is impacting cross-border operations (airspace). On the other hand, it is clear that RPAs introduction will boost the economy of the different countries.
JARUS has been tasked by the EC to develop harmonized regulation for RPAS below 150kg which will be adopted by EASA. EUROCONTROL will support the States to implement or de- velop harmonized regulation in order to create an open European market.

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Tests Sites: A Tool to Boost Local Economies
Unmanned systems and associated applications and niches are expected to grow in the near fu- ture, mainly due to the fact that 2015/2016 (US and Spain, respectively) seems to be the departing point for allowing their integration into the national airspace.
US Congress mandated (FAA Modernization and Reform Act) that by December 2012, the FAA must select six unmanned aerial systems test sites across the country and on February 2013 the process to select six UAS Test Sites began. Different proposals came from governments, uni- versities and other public organizations around the country. This would imply an important boost, mainly to local economies and, in general, to the national balance, creating jobs and developing new technologies.
Figure 4. UAS Test Sites as of May 2013 (Source: FAA).
More than 20 states expressed, through a fierce competition, their interest (Figure 4 in green) in becoming an FAA test site as of May 2013. At the same time, it is really important to take into account issues such privacy as they could jeopardize the whole process of integra- tion/accommodation.
Another recent regulatory example in EU (there are more than 40 test sites including civil ones), is Spain which is involved in a process to develop a regulation involving small RPAs, on the other hand, some test sites already exist, mainly military, i.e. el El Arenosillo Test Center (CEDEA) located in Mazagón (Huelva, Spain) is the test essay center of the Spanish National Institute of Aerospace Technology (INTA), another test center is located in Rozas (Province of Lugo, Spain) both property of the Spanish Minister of Defense.
Figure 5. Optronic Station MPS-2000 with telemetry antennae (left)
and Mirach 100/4 drone system (right) (Source: INTA).

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Figure 5 shows on the left an optronic station, model MPS-2000, carrying different sensors and telemetry antennae, and on the right, a launch of a Mirach 100/4 target drone (max speed 979 kpm – 608 mph/service ceiling 9.150 m – 30.000 feet, endurance > 1h) from the CEDEA test site commented above. Huelva (Andalucía) will accommodate a new center named CEUS that will operate together with the CEDEA center. CEUS is co-founded with FEDER funds and the An- dalousian Government. Finally, the test center ATLAS (province of Jaen) is being prepared as an experimental center which is a joint venture between the Andalusian Advanced Aerospace Tech- nology Center (CATEC) and the Andalousian Government again. Other planned centers are un- derway i.e. the Spanish Air Force aims at developing a dedicated UAS center in the Bárdenas Reales (Navarra, Spain). As it could be seen from the above, Spain is pushing hard in terms of the RPAs developments and, the need to create new jobs in the middle of the deep crisis, is doing the rest.
In June 2013 a group of companies and individuals founded in Madrid (Spain) the Spanish RPAs Association (AERPAS) with the objective of promoting the different applications and to represent the Spanish industry. Following the path, during the 2013 Paris Air Show, France also launched in July their RPAs association named Fédération Professionelle du Drone Civil (FPDC) composed by manufacturers, operators and players in the civilian UAS industry in France.
Paving the way to the integration it is so near and so far (in terms of challenging develop- ments) at the same time.
AIR TRAFFIC MANAGEMENT: RPA INTEGRATION CHALLENGE
Due to the air traffic volume increase, the need to reduce costs, to be environment friendly and the need to increase safety, Air Traffic Management (ATM) is preparing itself for a change in the near future: SESAR program in Europe and NextGen program in US, a unique sky between other features. Both programs while similar will introduce the use of some new concepts such 4D tra- jectory management, the System-Wide Information Management (SWIM), collaborative envi- ronment, Detect & Avoid technologies (ADS-B, T-CAS – ACAS X, etc), enhanced communica- tions, etc. NextGen included UAS from the very beginning, while SESAR is considering these systems as future potential users of the airspace.
Airspace Classes
One of the targets of the above commented ATM programs is to ensure the harmonization of airspace in the near future in order to be able to integrate RPAs safely and reliably.
Figure 6. Air Traffic Airspace (Reference 3).

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Figure 6 presents the worldwide air traffic division, as it could be observed it is highly frag- mented because each continent, country, airport has a different classification.
The International Civil Aviation Organization (ICAO) is the body of the United Nations (UN) that provides a worldwide airspace classification mainly defined in terms of flight rules and inter- dependencies between the aircraft and the Air Traffic Control (ATC). ICAO airspace classifica- tion is defined as standards that each country/nation can use flexibly to design their airspace (Reference 5).
ICAO airspace classifications are the following (Reference 5): A, B, C, D, E, F and G. The two categories of airspace are regulatory and non-regulatory. Within these two categories there are four types: controlled, uncontrolled, special use and other airspace. From A to E are defined as controlled airspace and from F to G are uncontrolled.
Figure 7. NAS Airspace Classification (Reference 6).
Every country has the right to design their own airspace, i.e. US adopted a similar ICAO air- space classification, it is divided as follows (Figure 7): A, B, C, D, E and G, where A to E is de- fined as controlled and the G as uncontrolled (note that they don’t use Class F).
Table 2. US Airspace Classification (Reference 7).
Airspace Class
Communications
Entry
Requirements
Separation
Special VFR in
Surface Area
A
Required
ATC clearance
All
N/A
B
Required
ATC clearance
All
Yes
C
Required
Two way communi- cations prior to en- try
VFR/IFR
Yes
D
Required
Two way communi- cations prior to en- try
Runway operations
Yes

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E
Not required for VFR
None for VFR
None for VFR
Yes
G
Required
None
None
N/A
Depending on the country, airspace classification and parameters could be different i.e. the levels, in US, airspace above 18.000 feet (5.500 m) is considered Class A, while in EU it is most- ly Class C. See Table 2 for more details on US airspace classification. Special use areas or also named as special area of operation (SAO) refers to prohibited areas, restricted areas, warning are- as, Military Operations Areas (MOAs), Alert areas and Controlled Firing Areas (CFAs).
Classes B, C and D (Reference 8) relate to surroundings airports (terminal airspace) where Mid-Air Collision (MAC) potential is higher; Classes A, E and G mainly relate to altitude and nature of flight operations (en route airspace). ATC provides separations services and/or adviso- ries to all flights in Class A, B and C, also to some flights in Class E and not in Class G. Regard- less of the class of airspace, or whether ATC provides separation services, pilots are required to D&A other aircraft during all conditions. Currently, in some EU countries (Reference 1), light RPA (< 150 Kg) operations in Visual Line Of Sight (VLOS) and Extended VLOS (EVLOS) are already taking place under national rules, in all airspace classes (additional safety requirements apply when flying over populated areas) but in visual contact (PIC or observer). IFR operations are taking place but mostly in segregated airspace (mandatory for operations at airports) as D&A technology it is still not mature enough.
Table 3. Military UAS categories and relevant UAS regulations (Reference 9).
Category
FAA Regulation
Airspace Usage
Airspeed Limits, KIAS
Cat I – R/C Model Aircraft
None (AC 91-57)
Class G
100 (proposed)
Cat II – Non standard Aircraft
FAR Parts 91, 101 and 103
Class E,G and non-joint-use D
NTE 250 (proposed)
Cat III - Certified Aircraft
FAR Part 91
All
None
Table 3 presents the relation between airspace usages, UAS regulations applying and military UAS categories. These are reduced to three categories: I, II and III depending on airworthiness and operator qualifications.
It is clear that there is a need to harmonize the airspace in order to overcome the present prob- lems with aviation. RPA integration will pose a challenge to the present airspace system and, in that sense, SESAR and NextGen programs (Figure 8) are proposing different UAS operational environment solutions.

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Figure 8. UAS Elements in the NextGen NAS (Reference 10).
A CHALLENGE FOR SAFE “INTEGRATION”: SENSE & AVOID
An RPA will have to operate in the NAS following the rules of a manned aircraft, in that sense, the 14 CFR Part 91.113 right-of-way rules, explains that any aircraft must detect traffic that might be a conflict and act in consequence, yielding if required. However, due to the size and signalization of the RPA, the PIC should be prepared for any contingence in order to terminate the flight (Reference 6).
A related important factor when discussing about integration/accommodation in the airspace is the ability of RPA to, not only detect other aircrafts (either civil or military), but obstacles, mete- orological conditions, visual signs, distance from clouds and other possible hazards (Reference 11), providing enough information to the PIC so he/she can have “situational awareness” ensuring the RPA will avoid the hazards in a timely manner and, at the same time, the RPA itself won’t become a hazard to others. Another definition from the military point of view (Reference 12): “A UAV must achieve an “equivalent level of safety” (ELOS), comparable to See & Avoid of a manned aircraft”.
In the case of the military (Reference 6), small UAS operations are conducted only in author- ized airspace and are subject to demonstrating reliable D&A capability. In case this is not accom- plished, separation will be conducted through mitigation measures: segregated airspace, external observers or altitude blocks. If operations in the NAS take place outside Warning and Restricted areas there will be needed a FAA authorization (i.e. FAA Certification of Waiver or Authoriza- tion – COA- or others agreed).
Operations under Instrumental Flight Rules (IFR) are not possible (Reference 6) at the mo- ment due to the lack of technology development wrt small RPA certifications, training and equipment. On the contrary, RPA VFR operations could be possible, and i.e., are classified under USAF VFR Cloud Clearance and Visibility Minimums, differentiating FAA airspace class and ICAO airspace class.
S&A capability (ICAO uses the word ‘Detect’ instead of ‘Sense’) is divided in two compo- nents or services: Self-separation and Collision Avoidance (CA). The Self-separation service is defined as a maneuver to maintain “well clear” (Reference 10) and the CA service is defined as a last-minute aggressive maneuver.

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Figure 9. Collision Volume
Figure above presents a general accepted collision volume definition to be avoided as a cylin- der ± 100 ft in height and 500 ft approximately in radius (military operations (Reference 6) take into consideration different exceptions such authorized formation flights, emergency situations requiring assistance from other aircraft (if not increasing overall hazard) and MAJCOM-approved maneuvers (Reference 6).
Some errors must be taken into account in the avoidance maneuver: lack in positioning preci- sion and uncertainty in predicting a target’s trajectory.
Figure 10. Sense & Avoid Concept (References 13 and 14).
The S&A functional execution time-line is categorized by the FAA into the following sub functions (Figure 10): Detect, Track, Evaluate, Prioritize, Declare, Determine, Command and Ex- ecute (Reference 14). Some of these steps could increase the communications latency, i.e. PIC decision about what action to take, aerodynamic response of the aircraft, acquisition of enough data through sensors, etc compromising the on time maneuver.
Figure 11. RPA ATC separation, self-separation and CA (Reference 10).
1000 ft (304,8 m)
200 ft (60,96 m)
RPA

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These two components, Self-separation and CA, are generally represented by a four-layer model presenting the separation layers from the RPA perspective (Reference 15): CA (coopera- tive and non-cooperative), self-separation, ATM and procedural (Figure 11).
To detect and resolve a conflict it is necessary to compare the trajectory of the RPA and the trajectory of the sensed object. On the other hand, if other aircraft know in advance our flight plan they could predict the RPA behavior at some extent. Trajectory Based Operations (TBO) will be then the main mechanism for managing traffic in NextGen and in SESAR (Reference 16), allow- ing the creation, exchange and execution of four-dimensional (Reference 17) trajectories (4DTs). There has been some past research projects dealing with this concept and D&A, i.e. REACT pro- ject (Reference 18) that was based in the Aircraft Intent Data Language (AIDL) developed by Boeing.
The Aircraft Intent Data Language (AIDL) is an emerging technology that represents a prom- ising approach to enhance trajectory predictability in support to trajectory management automa- tion.
Figure 9. Trajectory concept, in blue the enhanced trajectory
(Source: BR&T-E).
The AIDL has been designed to formally capture the necessary and sufficient information that completely determines the 4D motion of the RPA and to support the trajectory management au- tomation (References 19, 20 and 21).
Sensing the Airspace Environment
The first question was if small RPAs could reliably detect and avoid collision with objects, both stationary and moving, that do not announce their position and within near real time. This would ensure a great part of the safety chain and would permit the integration/accommodation of these systems in the airspace. How could a RPA ‘detect and avoid’ like a human? This is highly unrealistic at that moment but different developments are under way.

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Figure 10 GBSAA (left) and ABSAA (right) – Reference 13.
D&A technology is divided between ground and air segments and the tendency is to merge both architectures in order to get advantages either from Ground Based S&A (GBSAA) or from Airborne Based S&A (ABSAA). Using different sensors and combinations on-board (i.e. EO/IR, LIDAR, acoustic sensors, radar - i.e. W-band radar – References 22 and 23) , off-board (radar from ground) with different characteristics together with algorithm processing in near-real time (Reference 24), final system capabilities become really diverse.
Airborne sensors could be divided in cooperative and non-cooperative. Cooperative refers to ATC transponders and Automatic Dependent Surveillance – Broadcast (ADS-B) equipment mainly. Depending on the airspace class where the RPA will be flying, it will be required to carry an ATC transponder. Nowadays the problem is located with aircrafts flying VFR without tran- sponder, especially for small RPAs due to size limitation when carrying different sensors.
The Traffic Alert and Collision Avoidance system (Reference 25 and 27) – (TCAS in US and ACAS in other countries like Europe), but it has not been yet validated (References 26 and 28) as an acceptable system for D&A, however some developments are underway. This system will be required in aircraft by 2020 in US as commented above. TCAS/ACAS can receive messages from ADS-B system and use them to enhance its overall performance. ACAS-X is the new system un- der development though to replace the existing TCAS II, introducing new logic and capabilities.
ADS-B is the satellite-based substitute of the radar that will make use of the Global Position- ing System (GPS) to determine and broadcast precise aircraft location plus other additional flight information (indication of the accuracy and integrity – Reference 14). This system is composed by two services, ADS-B Out and ADS-B In, and it will act as primary system to control aircraft.
Table 4 IR Subdivision Scheme (Reference 29).
Division Name
Abbreviation
Wavelength
Characteristics
Near IR
NIR
IR-A DIN
0.75-1.4 um
Close to visible light. Night vision de- vice/LLLTV/Image Intensifier Systems (IIS).
Short- wavelength IR
SWIR
IR-B DIN
1.4 – 3 um
Night vision devices.
Good resolution but needs illumination.
Can penetrate fog, smoke, dust, haze at long range and remains unaffected by thermal cross-

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over.
Can penetrate glass.
Mid- wavelength IR
MWIR
IR-C DIN
3-8 um
Can penetrate fog, smoke, dust.
Sensitive to rain. Image appears hazy and with low resolution. No vision through glass.
Long- wavelength IR
LWIR
IR-C DIN
8-15 um
‘Thermal’ imaging region, no external illumi- nator needed.
Can penetrate fog, smoke, dust but resolution is low. Sensitive to rain.
No vision through glass.
Far IR
FIR
15-1000 um
Terahertz laser
Concerning non-cooperative traffic, some technologies (References 14, 26 and 30) to detect them are EO/IR cameras, LIDAR, acoustic sensors, etc that have their own characteristics (i.e. see Table 4 for IR subdivision scheme). One of the current developments in this area is the minia- turization of the components in order to obtain a reliable solution for small RPA, on the other hand, a complete system will be obtained combining the strengths of each, cooperative and non- cooperative elements. Some research efforts have been made in this line of reduction i.e. the MITRE Corporation began (in 2006) the use of lightweight and low-power versions of ADS-B for small RPA among other developments (Reference 31).
Some interesting S&A projects aimed to obtain the ‘Holy Grail’
Some remarkable examples are the Smart Skies project (Reference 32) that took place from 2008 to 2011. It had de objective of testing four enabling aviation technologies: an electro-optical Mid-Air Collision (MAC) avoidance system, a static obstacle avoidance system, a mobile ground-based air traffic surveillance system, and a global automated airspace separation man- agement system. The project was jointly undertaken by Boeing Research & Technology (BR&T), Boeing Research & Technology – Australia (BR&T-A) and the Australian Research Centre for Aerospace Automation (ARCAA), which is a joint-research venture between Queensland Univer- sity of Technology (QUT) and the Commonwealth Scientific and Industrial Research Organisa- tion (CSIRO) ICT Centre. The project was supported, in part, by the Queensland Government Smart State Fund and Insitu Pacific Ltd.
The Autonomous Systems Technology Related Airborne Evaluation & Assessment (ASTRAEA) programme was created in 2006 with the support of the UK government to research and demonstrate how RPA could safely be integrated into airspace shared with other aircraft. It is composed by two projects: Separation Assurance and Control and Autonomy & Decision Making (Reference 33). The consortium was composed by different companies such AOS, BAE Systems, Cassidian, Cobham, QinetiQ, Rolls-Royce and Thales. The Innovative Operational UAS Integra- tion (INNOUI) project (Reference 34) was conducted between October 2007 and March 2010 by a consortium formed by BR&TE, Ingeniería de Sistemas para la Defensa de España (Isdefe), INNAXIS, Office National d’ Etudes et Recherche Aérospatiales (Onera) and Deutsche Flugsicherung GmbH (DFS). It was funded by the 6th Framework of the EU Commission and it was focused on the integration of UAS into non-segregated airspace within the new unique sky concept, SESAR.

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Another interesting feasibility study developed through the European Space Agency (ESA) together with other companies in EU (Indra as leader, AT-One, GMV, Astra and Ineco) is the Satellites enabling the Integration in Non-segregated airspace of UAS in Europe (SINUE). It is aimed to investigate the feasibility and economic impact of merging space based systems with UAS in order to enable their integration in non-segregated airspace and to act as relay nodes in near real time for different possible commercial applications.
Harmonization of military and civil D&A requirements is essential since the risk, problems and challenges will be the same. Advantage of advanced projects, such as the EDA project Mid- air Collision Avoidance System (MIDCAS) or the Multiple Intruder Autonomous Avoidance (MIAA) programme (Reference 35) developed from the US Air Force Research Laboratory (AFRL) together with other companies (with Northrop Grumman, Calspan Flight Research, ICx™ Technologies, Defense Research Associates, Bihrle Applied Research, FAA William J. Hughes Technical Center and the C2Projex), could help to mature the S&A technology in the near future. MIAA programme consists in a set of EO sensors, a TCAS and an ADS-B as main systems used to detect cooperative and non-cooperative traffic and maneuver to avoid conflict.
In conclusion, S&A capability should be seen as a complex function rather than a technology or a group of them in order to fulfill all the needed functional requirements.
PILOT IN THE LOOP
The International Council of Aircraft Owner and Pilot Association (IAOPA) is a non-profit in- ternational (i.e. the Aircraft Owners and Pilots Association –AOPA- in US) federation represent- ing more than 470.000 pilots that own general aviation aircraft for business and recreation. A recent publication (Reference 36) from Mr. Frank Hofmann, IAOPA Representative to ICAO, presents the organization position and concerns with respect to the introduction of the RPA in the airspace. They have been contributing with the development of operational standards participating in various national groups and through its participation on the ICAO UAS Study Group expecting to have a regulation document in 2014. Regulations are expected to change over time as RPA industry will continue to evolve, on the other hand, IAOPA is focused in reducing General Aviation (GA) two main concerns: the possi- ble risk increase in operations and the reduction of airspace usage (restrictions to existing class E and G airspace in favour of RPA), not only using theory but different reliable technology demon- strations to the community. There are other concerns such the need of new equipment require- ments (S&A) for GA operators which seems not being accepted by the community because they are said to be impracticable. It is clear that meanwhile all these development processes take place (advances in command and control links, S&A technology, etc) RPA operations will continue to be viewed with incertitude. So it seems, after all, that some pieces in the puzzle are missing here too … Why national au- thorities don't think in a sustainable change model when planning the introduction of S&A sys- tems? Maybe it is a tough question but something seems lacking in this global framework sur- rounded by regulations and rules. RPA operations are here and, like it or not, they will continue between us in the coming years. Although the near future is not so encouraging this could be achieved with a coordinated approach between unmanned aircraft systems stakeholders and GA operators.

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CONCLUSIONS
RPA introduction into the airspace will be not easy, although present efforts from the different bodies are constant and the industry is pushing hard through technology developments: there is no doubt; something is out there waiting like it or not. Technology will evolve gradually directly affecting the integration/accommodation of RPA in the airspace.
On the other hand, air airspace is highly fragmented and needs to be homogenized (SESAR and NextGen programs) in order to ease, not only manned aviation management but RPA opera- tions. At the same time, traffic has been increasing during the last years accelerating our experi- ence of chaos: when a loss of separation between aircraft takes place, Mid Air Collision (MAC) situations arise. Here is when the S&A concept become relevant.
Harmonization of military and civil S&A requirements is essential since the risk, problems and challenges will be the same.
Sensors (on-board, on-ground and/or mixed) performance, miniaturization and near-real algo- rithm performance are areas to spur in the near future. Not to mention collaboration between all the official actors, bodies and the industry in order to solve issues such human factors, privacy, etc.
The experience in international projects dealing with S&A represents an advance when look- ing for new solutions and concepts.
Last but not least important the GA community, it is crucial to put them into the loop and iter- ate with them in order to arrive as much as possible to a favorable scenario for both.
ACKNOWLEDGMENTS
I would like to thank you all the people/organizations that re- vised/authorized/contributed/provided information to complete this paper: the International Council of Aircraft Owner and Pilot Association (IAOPA), FAA, Mr. Manuel Mulero, Depart- ment Director at INTA, Ms. Leslie Cary, Technical Officer at ICAO, Mr. Eduardo Carrillo, Strat- egy & BD Deputy Director at Boeing Spain, Mr. Mike Lissone, UAS ATM Integration Manager at EUROCONTROL, Mr. Manuel Oñate, Spanish UAS Association/EUROCAE WG-93 secre- tary and Mr. John Walker, Executive Consultant at The Padina Group.
REFERENCES
1European RPAS Steering Group, "The European Roadmap for the integration of civil Remotely-Piloted Aircraft Sys- tems into the European Aviation System". 2013.
2Lissone, M., "RPA Activities in EU: Toward Civil Applications", EUROCONTROL, June 2013.
3Walker, J., "UAS Global Airspace Integration: RTCA Special Committee 203", ICAO & LACAC USA Seminar, The Padina Group, 2012.
4EUROCONTROL & EU, "SESAR: European ATM Master Plan", October 2012.
5ICAO SARPS Annex 11, "Air Traffic Services".
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