Surveillance aircraft are military aircraft used for monitoring enemy activity, usually carrying no armament. This article concentrates on military aircraft used in this role, though a major civilian aviation activity is reconnaissance and ground surveillance for mapping, traffic monitoring, science, and geological survey. In addition, civilian aircraft are used in many countries for border surveillance, fishery patrols or the prevention of smuggling and illegal migration.
A surveillance aircraft does not necessarily require high-performance capability or stealth characteristics. It may in fact be a modified civilian aircraft which has been disguised in order to look harmless. Technically, anything which can fly and make observations (dynamically or via recording equipment/sensors) of visual information or electronic emissions qualifies as a surveillance aircraft.
Such efforts long predate the invention of heavier-than-air flight, with experiments using balloons to provide targeting information for artillery beginning in France in 1794. Continued attempts throughout the 19th Century proved militarily useless, but aerostat-based radar platforms are now in use.
Airborne reconnaissance goes back to the early era of ballooning. After the French Revolution, the new rulers became interested in using the balloon to observe enemy manoeuvres and appointed scientist Charles Coutelle to conduct studies using l'Entreprenant -- its name literally meaning "The Undertaking," which was the first reconnaissance aircraft. The balloon found its first use in the 1794 conflict with Austria, where in the Battle of Fleurus the gathered information and the demoralizing effect on the Austrian troops ensured victory for the French troops.
One of the first aircraft used for surveillance was the Rumpler Taube during World War I, when aviators like Fred Zinn evolved entirely new methods of reconnaissance and photography. The translucent wings of the plane made it very difficult for ground based observers to detect a Taube at an altitude above 400 m. The French also called this plane "the Invisible Aircraft", and it is sometimes also referred to as the "world's very first stealth plane". German Taube aircraft were able to detect the advancing Russian army during the Battle of Tannenberg (1914).
Before World War II the conventional wisdom was to use converted bomber types for airborne photo reconnaissance, since these were the only aircraft with the long range needed for the reconnaissance missions. These bombers retained their defensive armament, which was vital since they were unable to avoid interception.
The Japanese designed a twin-engine purpose-built reconnaissance aircraft in 1939, the highly effective Mitsubishi Ki-46, armed with only one light gun facing rearward. It entered service in 1941. Allied airmen designated it the "Dinah".
In 1939 Flying Officer Maurice Longbottom was among the first to suggest that airborne reconnaissance may be a task better suited to fast, small aircraft which would use their speed and high service ceiling to avoid detection and interception. Although this seems obvious now, with modern reconnaissance tasks performed by fast, high flying aircraft, at the time it was radical thinking.
As a result, fighters such as the British Spitfire and Mosquito and the American P-38 Lightning and P-51 Mustang were adapted for photo-reconnaissance during World War II. Such craft were stripped of weaponry, painted in sky camouflage colours to make them difficult to spot in the air, and often had engines modified for higher performance at very high altitudes (well over 40,000 feet). Early in the war the British developed a warming system to allow photographs to be taken at very high altitudes. The collection and interpretation of such photographs became a considerable enterprise. One site claims that the British, at their peak, flew over 100 reconnaissance flights a day, yielding 50,000 images per day to interpret. Similar efforts were taken by other countries.
Immediately after World War II, long range aerial reconnaissance was once again taken up by adapted bombers, albeit with jet engines, enabling them to fly faster and higher than before. Examples of such aircraft include the English Electric Canberra, and its American development, the Martin B-57.
In the 1950s, the first purpose-built jet covert surveillance aircraft, the Lockheed U-2 was constructed secretly for the United States. Designed for flights over Soviet territory, the plane remained an obscurity until one piloted by Gary Powers was shot down over the Soviet Union in 1960, leading to the U-2 Crisis. Modified versions of the U-2 remain in service in 2007, though its capabilities and operations remain secret. In the 1960s the SR-71 Blackbird, the fastest manned jet-propelled aircraft ever built, was constructed. However, as both the United States and Soviet Union possessed surveillance satellites, overt interest in new types of photo-reconnaissance aircraft declined.
There are claims that the US constructed a new, secret, hypersonic surveillance aircraft - dubbed the Aurora - in the late 1980s to replace the Blackbird, but no confirmation of this has ever emerged.
Another category of surveillance aircraft that has been in vogue since World War II is the maritime patrol aircraft. These are typically large, slow machines capable of flying continuously for many hours, with a wide range of sensors and electronic equipments on board. Such aircraft include the Avro Shackleton, the Hawker-Siddeley Nimrod, the Breguet Atlantique, the Tupolev Tu-95, and from Lockheed, the Neptune and later the Orion. The latter type became famous when a Chinese interceptor collided with the wing of a US Navy example patrolling. The crew of the larger US aircraft made an emergency landing. The Orion was impounded by the Chinese authorities then dismantled and returned to the USA. The crew were questioned but released prior to the aircraft's return. See Hainan Island incident.
Several unmanned remotely-controlled reconnaissance aircraft (UAVs) have been recently deployed or are under development in many countries, including Israel, the UK, the United States, China, Pakistan and India. Currently under development are, amongst others, the RQ-4 Global Hawk, a high-altitude jet-propelled craft that resembles the U-2, and the smaller, medium-altitude MQ-1 Predator. Schweizer Aircraft Corporation are developing remotely-piloted versions of a light helicopter.
Most Air Forces around the world lack dedicated surveillance planes, but have the capability of adding reconnaissance cameras to combat and transport aircraft.
Another type of surveillance aircraft is the electronic surveillance aircraft. Whilst other military aircraft, including photo-reconnaissance aircraft, have been used for that purpose, several countries adapt aircraft for electronic intelligence (ELINT) gathering. The Beech RC-12 Super King Air and Boeing RC-135 Rivet Joint are examples of this military activity, which helps to reduce opportunities for surprise attack or the risks of training exercises being misunderstood by potential enemies.
As well as the development of UAVs, another recent trend in surveillance aircraft design has been the realization that, with the addition of lightweight sensors and communications gear, every fighter plane and ground attack plane can simultaneously be used to perform surveillance. Hence, the in-development F-35 Joint Strike Fighter multirole fighter plane will have extensive surveillance and communications capabilities built in.
Published in July 2009.
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