HC 772 Defence CommitteeWritten evidence from the Royal United Services Institute

Remotely Piloted Air Systems (RPAS) is the term used by the British military amongst others to describe aerial platforms requiring no present human user aside from ground-based crews.

RPAS Capabilities


Nano RPAS are the smallest class of autonomous systems with a range of around 30 minutes, generally powered by a very small electric motor. The size is generally such they can fit in the palm of the users hand. Sensors used on these platforms are generally of a low quality and available only in the visible waveband, with data transmitted over unsecured and low bandwidth.

An example of a nano RPAS is the British Army-operated Proxy Dynamics Black Hornet Nano, a micro helicopter. The dimensions of this RPAS, 10cm x 2.5cm, allow for a small camera for low-resolution image capture in scenarios such as infantry local-area reconnaissance, especially in the urban environment. Able to be hand launched and using portable ground stations the whole system is transportable and suitable for use in the field.

Miniature RPAS

Miniature RPAS generally have a range for flight of less than 3 hours and are powered by small electric motors. The small size lightweight design, achieved through the use of composite and plastic materials, means that Miniature RPAS are used for the purpose of short-range surveillance using small and fairly basic sensors. The size and weight allow platforms to be carried by infantry and used in theatre without need for specific infrastructure, whilst the low-tech and simple design reduces the required training needed for use. Materials used include composites, plastics and polystyrene.

A number of this class are hand-launched, such as the Desert Hawk, with a joint system of six platforms and ground station costing around $300k. These are generally used for base surveillance, patrol and convoy monitoring, and target tracking by the 32nd Royal Artillery Regiment within the British Army.

Tactical RPAS

Tactical RPAS are a larger class, with 20m wingspans and masses of up to 2 tonnes common. The larger size allows for a greater range of payload to be carried. Roles carried out by this class include:

C4ISR—U-TacS Watchkeeper WK450.

Surveillance—Boeing Insitu ScanEagle.

Targeting and attack—General Atomics MQ-1 Predator.

Surveillance RPAS carry medium-quality imaging and transmission systems as the primary payload, feeding into military intelligence and operational units live feeds of a battlefield or other targeted area. Ranges for these units can be up to 20 hours dependent on weight, power source and propulsion system.

C4ISR RPAS undertake the tasks previously provided by manned aircraft such as the Nimrod. Watchkeeper will act as an all-round area transmission unit for the British Army, providing amongst other abilities communication, intelligence-gathering and reconnaissance.

Targeting and attack RPAS are able to acquire and strike selected targets as directed by a ground-based team. Current systems run by the UK require a man-in-the-loop for any firings, following a similar legal process to a manned air strike using a Pavia Tornado GR4. Currently forces use the Hellfire ground-to-air missile or GRU-12 Paveway II 500lb bomb for use with the Predator system, with an investigation into the use of the MBDA Brimstone missile also underway. Other options in the form of the Israeli Spike, believed to be used on the Heron platform by the Israeli Defence Force, also exist.

Ground stations for Tactical RPAS will include control points, processing units for incoming data from active RPAS and stations for use by intelligence units. This will allow live mission data to be processed by ground crews and used to update the RPAS’ own progress. This requires an active datalink between the RPAS and ground station, provided for the US by the SATCOM satellite array. As the Reaper is a US-produced RPAS all transmissions currently pass through US-controlled datalinks.

Strategic RPAS

Strategic RPAS are the largest class of current unmanned systems, having wingspans analogous with manned aircraft and able to carry large payloads. The RQ-4 Global Hawk is one example, having a wingspan of 39.9m and a gross mass of 14.6 tonnes. The design is primarily for use in battlefield reconnaissance, undertaking roles previously filled by manned aircraft such as SR-71 Blackbird. The large airframe and more powerful turbofan engines allow for a much greater payload to be carried, including high-powered surveillance systems able to work in numerous spectrums and high-quality video feeds.

A prime example of this class is the Global Hawk. The unit cost of $174 million is comparable with almost any manned aircraft, reflecting the expanded capability gained through its size and payload. However, through-life costs and those involving training and staff are much lower, leaving the economics of large-scale RPAS affordable in the long-term.


UCAV RPAS represent a future ground strike capability using increased stealth technologies. Whilst the strike role is currently carried out by Tactical RPAS such as the Predator the future UCAV units, such as the BAE Systems Taranis and the Northrop Grumman X-47B will include the ability to strike at long distance without the need for refuelling. At the current time plans for engagements using this class would require a large part of the mission to be carried out autonomously, a break from the current practice of man-in-the-loop missions undertaken by users such as the RAF. Outside of take-off and landing mission computers would use pre-inputted co-ordinates, mission data and artificial intelligence to fulfil the main mission objectives.

Expected unit costs for the Taranis currently stand at £143 million for the prototype, similar to an F-35, though once technological issues are solved and manufacturing techniques are developed this would be expected to drop significantly.

Swarm RPAS

A future capability in development is the unmanned swarm. This technique requires a high level of autonomy and advanced processing power to allow for the hive artificial intelligence required for the swarm to function correctly. Early efforts in this field have required the use of a man-in-the-loop for safety reasons. The benefits of RPAS swarms include the ability for a large number of smaller units being able to scan larger areas, a lower cost than single larger RPAS models, and extra system redundancy. Current challenges to swarms include multiple access attempts to ground station datalinks and bandwidth availability for communication.

Recent examples of tests in this area include Boeing’s use of two ScanEagles as part of a group with a Procerus Technologies Unicorn. The three RPAS were able to scan a defined area and communicate data to each other with minimal input from the manned ground station.

Producers and Operators


The majority of military RPAS are produced by either the US or Israel. Companies such as Northrop Grumman (US) and IAI (Israel) dominate the international market. The primary producers of RPAS are with examples are:

Northrop Grumman, US (Global Hawk).

General Atomics, US.

Israeli Aircraft Industries, Israel.

Insitu, US.

Elbit, Israel.

EADS, Europe.

BAE Systems, UK.

Countries such as Turkey (ANKA) and the UAE have also developed a number of RPAS.


The US is currently the world’s largest operator of RPAS. The units currently in active service with the US Air Force include:

General Atomics MQ-1 Predator (Armed or unarmed).

Northrop Grumman RQ-4 Global Hawk (Unarmed).

General Atomics MQ-9 Reaper (Armed or unarmed).

AeroVironment RQ-11 Raven (Unarmed).

Lockheed Martin RQ-170 Sentinel (Unarmed).

Aside from the USAF, large numbers of RPAS are operated by other US services. The US Navy, Army, Border Agency, Coast Guard and CIA also operate fleets, totalling a larger number than in USAF service.

The UK is also amongst the lead users of RPAS in active duty. At the current time control of UK assets is shared between the RAF and Army. The British fleet consists of:

10 Reaper, RAF No. 13 Squadron, used in armed strikes (four in service, five to be delivered next year and one in maintenance).

54 Thales Watchkeeper, expected to enter service in 2014, 32nd Royal Artillery Regiment, British Army.

9 Elbit Hermes 450, 32nd Royal Artillery Regiment, British Army.

Desert Hawk, various British Army infantry units.

Black Hornet Nano, various British Army infantry units.

ScanEagle, confirmed to enter service with the Royal Navy later this decade.

Israel is another nation with an armed RPAS capability. Like the US Israel derives most of its military RPAS from an indigenous industrial base. In addition to the following the Elbit Hermes 900 is currently in development as a reconnaissance unit:

IAI Eitan, MALE Tactical RPAS, Israel Air Force.

IAI Heron, MALE Tactical RPAS, Israel Air Force.

Elbit Hermes 450, Tactical RPAS, Israel Air Force.

BlueBird SpyLite, Miniature RPAS, Israel Air Force.

France is currently expanding its own unmanned capabilities, driven by the experiences of Mali and Libya. The fleet consists of:

EADS Harfangs, developed from the IAI Heron.

The DGA also plans to place an order for 16 Predator RPAS for unarmed surveillance and reconnaissance use and has conducted joint trials of Watchkeeper with the British Army.

Italy is one of the other few countries in the world with a confirmed armed unmanned capability. The Italian RPAS fleet includes:

MQ-1 Predator.

MQ-9 Reaper.

Most NATO nations operating under ISAF have invested in RPAS—Germany and Canada for example—as they proved an effective means to provide over the wall/horizon surveillance and force protection against IEDs. Other countries such as Russia, Iran and China also have unmanned capabilities, covering many of the categories listed previously. However, a lack of concrete information means it is difficult to provide a detailed analysis at the current time.

Current Usage and Ethical Issues

Military Issues

The primary ethical argument surrounding military RPAS has centred on the dislocation of the pilot from the platform, particularly when the platform is operated via SATCOM from a location well away from the theatre of operation. Many people struggle to reconcile the fact that the operator can deliver lethal effect without any risk of coming under attack. There is also deep concern about UCAV systems under development that could potentially autonomously select and strike targets, although there is no appetite within the military at present for humans to be completely removed from the targeting chain.

Public concern over the use of remotely piloted air systems has been aggravated by the deployment of RPAS in non-combat areas as a means of targeting and striking suspected and known terrorists as designated by authorities in the US and others. The primary user of RPAS in this way has been the CIA, with the countries most targeted being Pakistan, Yemen, Somalia and other non-frontline states. Much of the controversy here is raised from the lack of a state of war between the US and the states targeted and public disagreement in some cases as to whether the host nation had given permission for the US to operate in sovereign airspace. Furthermore, the issue of a non-military body having control of an armed capability, as seen by the CIA use of RPAS, also calls into question the role of intelligence agencies and the level of scrutiny and control government can exert over them.

Concern over the control of armed RPAS and the targeting sequences employed, in some cases by air crew with no prior flying experience, has increased. While air forces recruit their RPAS operators from pilots who already have flying experience on manned aircraft, this is not the case with land forces and some border agencies employ contractors to operate the RPAS for them. This has led to concerns that RPAS pilots are not sufficiently “air minded” ie qualified to operate within the air space and this has brought training under scrutiny. Forces such as the RAF have instituted command chains for firings to a level in excess of those used for manned missions. The required presence of legal representatives means the decision for firings is never solely based on the recommendations of the present commanding officer, but on the advice of the forces own legal position.

Safety and reliability in RPAS are a cause for concern. The case of the US Army-developed Gray Eagle showed a large difference between design requirements and operational standards: a system failure was occurring every 25 hours of flight rather than every 100 hours, whilst ground control stations were failing every 37 hours rather than 150. The extent to which human error causes failures has also been shown, with 60.2% of US armed force mishaps caused by the man-in-the-loop. The training of operators and command structures were also the cause of a British Hermes crash in Afghanistan in 2010. The report that followed pointed to a lack of airmanship and understanding of flying within the Army command structure, even in RPAS-equipped units. A lack of intermediate training between tours for type rating maintenance was also highlighted.

Civil Issues

The use of RPAS in the civilian and corporate environment has to this point been for surveillance purposes (forest fires, oil spills, farm land) and exploration, specifically for potential oil and gas reserves in remote areas. Recent examples include the US and Canada of governments granting licences for use of unmanned vehicles within the Arctic Circle and currently uninhabited airspace.

Within the UK civilian deployment of RPAS has been severely limited by the regulations enforced by the Civil Aviation Authority (CAA) owing to heavy use of UK airspace by civilian operators (principally commercial airliners). Existing legislation, which is being used as a stop-gap until a better system is constructed, allows for only line-of-sight flight within a pre-arranged segregated airspace and away from any built-up areas. The UK has a programme, ASTRAEA, which is working to help develop some of the enabling technologies and at the same time provide a suitable regulatory framework. The issues of co-operation between nations, especially in the future joint airspace environment of Europe, has led to the proliferation of national rule sets. Efforts are still ongoing to design RPAS requirements into the future Single European Sky system to be implemented by EUROCONTROL.

Further Details

In addition to the evidence provided above, the following papers are also submitted:

Quintana, Elizabeth, The Ethics and Legal Implications of Military Unmanned Vehicles, Occasional Paper, RUSI, 2008–09

Quintana, Elizabeth, Manning the Unmanned, RUSI Newsbrief, RUSI, 2013

Elizabeth Quintana and Sean Nolan

13 September 2013

Prepared 24th March 2014