Remotely Piloted Aircraft (RPA) technology has become increasingly available for non-military purposes. The number of RPA types has expanded from a few tens to hundreds. They cover a wide spectrum of size and performance, with flight endurances ranging from hours to weeks and ranges in some cases exceeding 7,000 nautical miles.

The potential benefits of RPA in civil aviation have been recognised by, amongst others, the International Civil Aviation Organisation, the US Federal Aviation Administration, the European Aviation Safety Agency and the European Commission. RPA exist that are capable of undertaking long endurance or hazardous flights. They offer cost efficiencies, for example replacing manned aircraft for aerial survey work. Eventually more fundamental improvements in operational efficiencies are foreseen; for example as a result of not having to accommodate crew on board commercial freight aircraft.

This article highlights some of the challenges facing the expansion of RPA operations in civil aviation and looks  at two particular initiatives, the US Federal Aviation Administration’s Road Map and the European Road Map.

The three pillars of safety regulation

RPA involve considerations which are novel to civil aviation. The removal of the pilot introduces the need for a remote piloting station and also a link between the pilot and the RPA (the control and communications, or C2, link). The C2 link may be a direct line of sight radio link or relayed (for example through other aircraft or satellites). The removal  of the pilot from the RPA gives rise to questions concerning situational awareness and their ability to maintain separations from other aircraft (the “detect and avoid” considerations).

To realise their potential benefit, RPA will have to be fully integrated into the civil aviation system. However RPA have not been developed or operated in accordance with the demanding safety requirements of civil aviation, which they will now have to meet. They will be required to comply under the three pillars of civil aviation safety used in the 1944 Chicago Convention and which are reflected in national regulation: airworthiness certification; pilot licensing; and operating rules (importantly including rules for navigation of the civil airspace).

The rules of navigation in certain airspace classes require pilots to use visual means to ensure separation from other aircraft and to identify and avoid cloud, adverse weather conditions and collision hazards. In the case of RPA, inevitably the pilot will depend on alternative means to comply with these “detect and avoid” requirements (or “sense and avoid” requirements, in FAA terminology).

However, currently RPA cannot demonstrate compliance with those rules. The technology and procedures for detect and avoid purposes have yet to be demonstrated; and the related performance and technical standards have yet to be defined. This illustrates the two broadly inter-related challenges: the need to define the procedural and technical standards to ensure civil safety standards are met; and the need to develop technology and procedures to realise the requisite degree of safety.

Detailed requirements will also have to be defined addressing the novel airworthiness aspects of RPA, such as the remote pilot control station and the C2 link. Loss of the C2 link renders the aircraft without piloted control, and creates a hazard to other airspace users or those on the ground. A number of military heritage RPA are able to fly autonomously in a holding pattern or to designated safe holding airspace, while piloted control is re-established; failing that the aircraft may autonomously fly to a safe  area to land or crash. However that scenario gives rise to other considerations: how will the autonomous flight of  the RPA be accommodated in congested airspace; and will “safe” volumes of airspace need to be set aside out of busy airspace?

The US

With very limited exceptions, it has not been possible to obtain a civil certificate of airworthiness for RPA.

Non-military operation of RPA, large and small, in the US is limited to use by public authorities such as law enforcement (so called “public” category use). US Customs & Border Protection have operated Predator RPA since 2005. However all such operations are “accommodated” (rather than integrated); they are authorised by the FAA subject to restrictions and mitigation measures that keep them away from populated areas and large volumes of busy airspace.

In November 2013, the FAA published the US Road Map (“Integration of Civil Unmanned Aircraft Systems (UAS) in the National Airspace System (NAS) Road Map”). This sets out the activities to be undertaken by the FAA in conjunction with industry to integrate RPA into the US civil aviation system.

The initial focus is to enable the civil use of small RPA (less than 55lbs or 25kg) and a Notice of Proposed Rule Making is due to be published in early 2014. When brought in to force (some time in 2014-2015), this is expected to enable small RPA to be used in civil (including commercial) operation by accommodating them within limited ranges and below a defined minimum altitude in certain classes of airspace.

The FAA intends to use “pathfinder” airworthiness certification programmes to publish standard airworthiness requirements for civil RPA during the period 2014-2017. Those will include remote pilot stations and C2 links.

Two such pathfinder programmes have already produced restricted airworthiness certificates for two types of RPA that have flown in Alaskan airspace.

The stated aim in the US is to accommodate “initial” routine civil RPA operation in the National Airspace System by 2020. However that target is for accommodation using mitigation measures (for example to compensate for the lack of proven “sense and avoid” measures) and the airspace available will inevitably be limited as a result. The Road Map envisages enabling use of ground based “sense and avoid” methods for military and public operation by the end of 2018. The Road Map does not specify a “target date” for enabling airborne measures and the implication is that this may not be achieved within ten years. The achievement of those (particularly the airborne) measures is likely to be a key factor determining the timeline for full civil integration of RPA.


The picture within the European Union, is slightly different to (and more fragmented than) that in the USA.

Small RPA are allowed by various European states to fly for civil (including commercial) use, subject to being duly licensed by the national aviation authority in question. Again this is by way of “accommodation”; they cannot demonstrate compliance with airworthiness and operating requirements and their access to airspace is limited. Typical restrictions in non-segregated airspace require the RPA to be within (unaided) visual line of sight of the pilot, and generally below 400 ft altitude.

Large RPA operation for civil purposes is non-existent. As yet no RPA have obtained EASA certificates of airworthiness and there are no established means of compliance with operating requirements, such as “detect and avoid”, beyond the (unaided) visual line of sight of the pilot.

The European Road Map was published in June 2013 by the European RPAS Steering Group (consisting of safety oversight and industry bodies, including EASA). It is expected that it will be used to direct regulatory and joint EU/industry initiatives over the next 15 years.

The Road Map focuses initially on enabling the expansion of light (less than 150kg mass) RPA operation within European states during the period 2014-2015. By 2018 it envisages harmonised pan-EU rules that allow the opening up of the European market to commercial light RPA use. Those commercial operations are likely to be limited in range due to restricting the pilot to maintain visual control of the RPA, either directly (line of sight) or through other visual observers.

The Road Map envisages gradual expansion of “accommodation” of civil RPA followed by partial integration into certain classes of airspace and initial limited mixed (ie, manned and unmanned aircraft) operation at aerodromes by 2023. The stated objectives, by 2028, include full integration into all classes of airspace, with regulations enabling “file and fly” operations and remotely piloted commercial freight transport.

Other challenges

Inevitably there are other challenges posed by RPA.

The scale of intentional damage that can result from terrorist activity has regrettably been demonstrated. The RPA introduces at least one new element, namely the C2 link, which might be viewed as a new potential vulnerability to terrorist attack. C2 links will need to be protected against jamming or “hacking” and related standards and technology will need to be developed.

Privacy issues have been aired extensively in the US and are the subject of study activities set out under the European Road Map.

A number of questions arise concerning insurance and liability. Liability regimes vary from state to state. Within Europe the tendency is to impose strict liability (ie, without proof of fault on the part of the pilot/operator/owner) for damage suffered on the ground as a result of an aircraft in flight. However the detailed provisions vary; for example certain European states impose limits on the liability, whereas others (such as the UK) do not.

For international flights, the question arises as to whether the Rome Convention 1952 applies and whether it is appropriate when addressing RPA operations. The Convention imposes strict liability for damage on the ground caused by aircraft in flight, subject to limits which are prescribed according to aircraft weight. The Rome Convention makes no mention of RPA; numerous commentators argue (convincingly, in our view) that the Rome Convention should apply to RPA, but this may be challenged before national courts.

If applicable, it has been questioned whether the Rome Convention is fit for purpose with regard to RPA. The Convention is poorly supported and within Europe, the UK, France, Germany and the Netherlands do not apply it. There is also some scope for confusion in the application of its provisions to RPA; liability for ground damage is imposed on the “operator”, but who is the “operator”? The pilot and who controls the pilot may change in the course of a single flight.


Full integration of RPA into civil aviation faces significant challenges. However in the US, Europe and elsewhere  the efforts to overcome those challenges are gaining momentum. Whether the timelines envisaged in the US and European Road Maps prove to be realistic remains to be seen, but there appears to be a good chance that there will be an expansion in RPA use over the next decade; and quite possibly remotely piloted commercial freight operations within the next couple of decades.