UAVs take flight

Without the need for pilot space or the weight of life support equipment, UAVs are smaller and have aerodynamically superior airframes compared to manned aircraft. Add in the savings on pilot training and salary, and, in theory, UAVs should be two thirds cheaper than conventional aircraft. But recent events have shown they are vulnerable to adverse weather. Winter in the Balkans and over Central Asia has taken a high toll, with about one third of air force UAVs being lost.

Flight planning for large UAVs must be as careful as for manned aircraft. Although no pilots' lives are at risk, losing a UAV is not like losing a model aircraft; General Atomics RQ-1 Predators, for example, cost $20 million each.

UAVs would never have become such military objects of desire without great advances in electronics miniaturization. Very effective reconnaissance can now be provided with a remarkable range of low-weight, small-size sensors. Long range, high-altitude UAVs carry electro-optical/infrared (EO/IR) stabilized color video cameras, forward looking infrared (FLIR) cameras, and synthetic aperture radar (SAR) to provide near real-time video imagery day or night in all weather conditions.

UAVs can also carry sensors to detect enemy radio and radar transmissions (SIGINT), and chemical emissions, as well as air pollution and meteorological conditions. They can perform wide area searches, with sensors scanning 10-km-wide-bands, or do spot surveillance at high definition of small areas.

Remote control. Data reaches the ground via satellite links. With regard to flights over Afghanistan, for example, the air operations center is 3,000 km away in Saudi Arabia. From there it can be relayed to anywhere in the world.

As data is downloaded from the UAV, command signals are sent to the aircraft. Mission control is lengthy as large UAVs can remain airborne for more than 40 hours. A full technical team must monitor data from the aircraft and direct its course.

Controls are relatively simple. Although air force UAVs are "flown" by qualified pilots (officers), the navy and army employ enlisted men as air vehicle operators (AVOs).

A UAV will be programmed with a series of GPS waypoints to follow on its mission. The AVO will monitor position of the aircraft and the command center will analyze image data sent back. If required, waypoints, headings, and altitude can be changed with radio signals from flight control.

Other UAVs, such as those used as target drones, may fly entirely pre-loaded flight plans. For example, the OAV (see sidebar) has been designed from the outset to be fully autonomous and require little or no operator intervention.

Miniature TV cameras are the usual payloads for small UAVs. A combination of three cameras-vertical, 30 degrees and 60 degrees -whose images are electronically merged-give a broad field of view. Video signal data are transmitted to ground by line of sight using a UHF channel.

More than reconnaissance. UAVs are now being lined up for a more active role in war instead of just acting as lookouts. The first test firing of missiles from a UAV was in February 2001 when a Hellfire was launched from a Predator to disable a target tank. From testing ground to battleground took 8 months, with missiles being fired in combat from UAVs several times in Afghanistan. They appear to have had limited effect on the campaign due to scarce targets in unforgiving terrain.

Others are working on similar projects. In Germany, the STN Atlas Elektronik Taifun is being designed for attacks on tanks and strong points. Boeing is testing the technological feasibility of several UAVs carrying out extremely dangerous, high-priority combat missions alongside manned fighters to suppress enemy air defenses.

Electronic warfare is also planned, with UAVs orbiting radar sites with jamming devices aboard. Finally, there is the possible use of mini- and micro-UAVs by Special Forces. They would provide interesting capabilities for over-the-hill, look-in-the-cave, or around-the-corner surveillance.

UAVs such as these will be for very local use, but for larger aircraft there is the final design challenge of seeing that the mass of data is properly integrated into other systems, particularly army command and control (C2). Video data acquired by a UAV could be shown on a unit commander's screen in a tent as well as the Commander-in-Chief's in the White House.

That level of integration is concerned with a combat zone, but in the meantime, integration with ordinary air traffic is already difficult. The Federal Aviation Agency in the U.S. requires 60 days notice to fly a UAV in controlled airspace. For greater distances, such as transatlantic or transpacific flights, even longer notice may be needed. The long-term aim is that UAV controllers will be able to file flight plans in exactly the same way as captains of aircraft.

For more information, contact:
DARPA: Sam Wilson +1 703 696-2310.
DERA: Chris Day, Technology Area Leader, Probert Building, Farnborough, Hants, UK - GU14 0LX. +44 125 239 3300.
EADS: Bernd Sturzl +49 731 392 5487.
General Atomics: Marv Goodring, Manager Program Development, PO Box 85608, San Diego, CA 92186-9784. +1 619 455 2240.
Meggitt PLC: Nicola Bartlett +44 1202 847701.
Northrop-Grumman: Cynthia Curiel, Communications Manager, PO Box 509006, San Diego, CA 92150-9066. +1 858 618 4355.
SAGEM: Herve PHILIPPE, +33 1 40 70 62 57.
STN Atlas Elektronik: Heidelore Buhler +49 211 473 4748.