There are some significant legal and ethical implications of the employment of UAVs (incidentally, in modern military parlance the abbreviation is for Uninhabited Aerial Vehicles, not Unmanned Air Vehicles), especially in a combat role. Uninhabited combat aerial vehicles (UCAVs) are perceived as a future replacement for combat aircraft. During my training at the Royal Air Force College one thing that was repeatedly emphasized to us was that the main problem with a combat aircraft is the 160-pound lump of flesh controlling it. The problems with piloted aircraft can be broken down as follows:

1.    Endurance. Human beings are delicate creatures. We need water, food and warmth to survive. We also need to get enough sleep in order for our higher mental functions to work properly. We are extremely dependant upon a certain level of air pressure to provide us with enough oxygen for respiration to occur. Lack of oxygen, known as hypoxia, is an extremely dangerous condition that can lead to confusion, blackout and asphyxia.

Breaking these elements down, human endurance leads to three problems in the use of combat aircraft - the need for sustenance (food and water), crew fatigue and environmental conditions. These all place significant limitations on the range, altitude and combat environment to which a combat aircraft can be deployed. Go too high, and the crew could suffer from hypoxia. Go too far (assuming air-to-air refuelling (AAR) is in use), and fatigue becomes a major factor. And deploying the crew into an area of intense aerial activity (AIAA) leads to problems with mental endurance, as fatigue sets in quicker and is exacerbated when the crew relaxes.

By replacing a pilot with a computer, you remove these problems. A computer will continue to operate within a vast range of operational conditions. You can dispense with expensive heating and canopy seals, and fill the big gap where the aircrew would sit with some more useful military hardware.

2.    Control problems. The Eurofighter is the most advanced combat aircraft in the world. Its onboard avionics enable the aircraft to autonomously make 200 minute adjustments to the control surfaces (rudder, ailerons and foreplane (the Eurofighter does not have fins for elevators)) every second. Yet there is one crucial control element without which the aircraft cannot function at all - the pilot. Kill the pilot, and you kill the aircraft, incapacitate him and the aircraft is neutralised. Basically, the pilot's brain is the highest control system in the aircraft, and the aircraft's performance can be limited or neutralised by causing pain or death to the pilot. Aircraft can usually function relatively well with the loss of an engine; the loss or damage of some of the fuselage is a serious problem but aircraft have been known to continue operating under such conditions. If the pilot is neutralised, however, the aircraft stops flying and starts plummeting.

With a computer you can build in redundancy, by having one or two spare CPUs to take over control of the UAV in the event of one failing. In addition, the pilot is located in a vulnerable position, in a transparent glass bubble at the front of the aircraft. A computer does not need to be in such a position, and hence can be located in a highly defended part of the UCAV.

3.    Ethical implications. Pilots are human beings. In the military we are petrified of the CNN Factor - those constraints placed upon operations by the consideration of ethical and humanist factors and consequences of military actions. Basically, if a pilot is shot down the military is obliged by the public to try and recover him. Witness the events in Mogadishu in 1992 - the US military had to recover its lost Black Hawk pilots, and did so at a great cost of military and civilian lives. Combat Search and Rescue (CSAR) is a costly and highly risky enterprise, and is necessitated by the loss of any aircrew due to modern considerations of human rights - during the Second World War, for example, a lost pilot was lost full stop. The onus was on him to get back to friendly forces, not for the forces to recover him.

UAVs do not have significant ethical implications in this respect - no-one really cares whether it is lost. The public don't care at all unless the cost is borne heavily by the taxpayer, and the military doesn't care as long as operations are not significantly degraded.

So, UCAVs seem to be the way forward. They do not need to be comfortable. With AAR they are capable of loitering for weeks. CSAR is not a factor. There are, however, some important ethical implications when you take the human control element away from air combat/bombing.

Firstly, all pilots are bound by the Nuremburg Principle - basically, if a pilot is called to Court-Martial to explain his decisions, he cannot say "I was only following orders" in defence. He is ultimately responsible for any unlawful actions, and can therefore refuse to carry out orders he feels to be illegal; UCAVs do not have a conscience, they cannot make reasoned judgement - they cannot refuse orders. Since a commander is not in the theatre of battle, he cannot predict with absolute accuracy the consequences, in terms of collateral and additional damage, of an on-the-spot combat decision, and he has to rely upon the pilot, on the scene, making the absolute final decision. The removal of the pilot is the removal of front-end decision making. Even if the UCAV is under positive control - ie, an operator is directing its actions - it lacks the situational awareness of a pilot, and many believe that the public will not support the use of fully-autonomous UCAVs due to the removal of the human element of control.

Secondly, the Principle of Humanity or Unnecessary Suffering places strict limitations on the types of weapons systems employed by military forces in that they should not cause undue human suffering, or exceed internationally agreed limits on range, explosive power, etc. The legal status of UCAVs is brought into question by the 1988 Intermediate-range Nuclear Force Treaty (INF), agreed by the United States and the Soviet Union. INF prohibits the US and USSR (and, by proxy, Russia and former Soviet Republics) from using ground-launched cruise missiles with ranges of between 500 and 5,500km. Since the UCAV is essentially a cruise missile - an airborne vehicle under procedural or positive control intended for the delivery of an explosive payload - some critics feel the INF should outlaw its use. The Israelis developed and employed a UCAV called the Harpy during Operation ALLIED FORCE. It was essentially a cruise missile with a 32 kg warhead and range of up to 600 km. Due to its international obligations under INF and the Strategic Arms Limitation Talks (START) the US could not have used this UCAV.

Military commanders, however, point out that UCAVs are actually aircraft and not missiles, due to their design, flight profiles and recoverability. This is contentious in itself, however, because International Law prohibits the deployment of recoverable missiles, and, again, some critics believe that this is exactly what UCAVs are. In addition, the INF and START protocols only apply to the US and USSR. Other leading UAV-capable nations, in particular the United Kingdom and Israel are not bound by them (UK policy is to limit ranges to meet INF in principle).

UCAVs have been the dream of Generals for centuries, and now that they are a reality the facts of the issue are as contentious as older military techniques - the attritional approach to the First World War, strategic bombing during the second world war, right up to Shock and Awe in Operation TELIC/IRAQI FREEDOM. For as long as the issue is burning, the military will continue to find ways to reduce the adverse effects of UCAVs in favour of the percieved future "clean" battlefield.