Aircraft camouflage
Aircraft camouflage is the use of camouflage on military aircraft to make them more difficult to see, whether on the ground or in the air. Given the possible backgrounds and lighting conditions, no single scheme works in every situation. A common approach has been a form of countershading, the aircraft being painted in a disruptive pattern of ground colours such as green and brown above, sky colours below. For faster and higher-flying aircraft, sky colours have sometimes been used all over, while helicopters and fixed-wing aircraft used close to the ground are often painted entirely in ground camouflage. Aircraft flying by night have often been painted black, but this actually made them appear darker than the night sky, leading to paler night camouflage schemes. There are trade-offs between camouflage and aircraft recognition markings, and between camouflage and weight. Accordingly, visible light camouflage has been dispensed with when air superiority was not threatened or when no significant aerial opposition was anticipated.
Aircraft were first camouflaged during World War I; aircraft camouflage has been widely employed since then. In World War II, disruptive camouflage became widespread for fighters and bombers, sometimes combined with countershading. Some air forces such as the German Luftwaffe varied their paint schemes to suit differing flight conditions such as the skyglow over German cities, or the sands of the Mediterranean front.
During and after World War II, the Yehudi lights project developed counter-illumination camouflage using lamps to increase the brightness of the aircraft to match the brightness of the sky. This was abandoned with improvements in radar, which seemed to render visible light camouflage redundant. However, aircraft continue to be painted in camouflage schemes; recent experiments have again explored active camouflage systems which allow colours, patterns and brightness to be changed to match the background, and some air forces have painted their fighters in digital camouflage patterns. Stealth technology, as in the Lockheed F-117 Nighthawk, aims to minimize an aircraft's radar cross-section and infrared signature, effectively providing multi-spectral camouflage at the price of reduced flying performance. Stealth may extend to avoiding or preventing vapour contrails.
History
World War I
The French were among the first to introduce camouflage, starting with Nieuport fighters with which they tested a variety of schemes during the Battle of Verdun in early 1916. A light blue-grey Nieuport 11 was flown by Georges Guynemer which he named Oiseau Bleu while some Voisin IIIs were also painted in the same colour. At the same time, disruptive schemes using several colours were also tried out. By mid-1916 a silver-grey aluminium dope became the norm for Nieuports until the French introduced a standardized disruptive camouflage scheme for combat aircraft in 1917. This was used widely on such aircraft as the Breguet XIV and SPAD XIII that consisted of dark and light green, dark and light brown, black and an underside of grey or beige.File:Fokker D VII SE-XVO OTT 2013 01.jpg|thumb|Fokker D.VII in lozenge camouflage
In mid-1916, the Germans experimented with a transparent cellulose acetate covering on several aircraft, including a Fokker E.III, that rendered the aircraft nearly invisible from most angles, however the sun reflecting off it defeated it even before its lack of durability did.
When the Germans fielded the Albatros D.III biplane, pilots readily confused them with similarly shaped Nieuports which used the same combination of colours. The solution the Germans came up with was to replace the red-brown with purple, which from a distance still worked well as a camouflage colour, but could readily identify the aircraft as German. As in France, individual manufacturers applied a variety of camouflage finishes, dependent on their own interpretations of what was required. Light grey, patches of greens and browns and streaky olive green finish over a turquoise base were all used until April 1917, when pre-printed lozenge camouflage was introduced with up to 5 colours.
Aircraft of the British Royal Flying Corps and Royal Naval Air Service were either coloured on top and sides with a protective dope called PC.10 or PC.12 while the undersides were given a clear dope. These colours were not intended originally as camouflage but were developed to prevent the fabric from being damaged by UV radiation from the sun, and their camouflage effect was an added bonus. Both services also used black for night bombers, while a wide variety of experimental camouflages were tried out for specific roles such as trench strafing, with multiple colours. Alternatives were tested in late 1917 at Orfordness Experimental Station, resulting in the introduction of NIVO in early 1918; this was used for all external surfaces on night bombers until superseded by World War II colours. Ship-style dazzle camouflage was tested on aircraft such as Sopwith Camels, but was not used on operational aircraft.
World War II
During the Munich Crisis of 1938, the Royal Air Force implemented plans to camouflage its aircraft in its disruptively patterned Temperate Land Scheme of "Dark Earth" and "Dark Green" above and "Sky" below. This scheme was known colloquially as "Sand and Spinach" when the pattern was painted on at the factory, large rubber mats serving as guides. For many types of aircraft, particularly fighters, the rubber mats were reversed for even and odd serials, named A and B patterns. The undersides, and lower half of the fuselage, of night bombers were painted black.Variations on fighters at the start of the war included painting the underside of one wing black. Later in the war the dark earth was replaced with "ocean grey" and the underside was "Sea Grey". Naval aircraft used two tones of grey over sky. Coastal Command, which carried out patrols for enemy vessel over the open sea, used white instead of sky. In the North Africa campaign a combination of "Dark Earth" and "Middle stone" were used for the top surfaces, the underside was "Azure blue". The same azure was used on day bombers overseas. High flying RAF
Photographic Reconnaissance Unit aircraft were given an all over blue colour, but they were given "licence in the camouflaging" of their aircraft.
Some United States Army Air Forces aircraft used a variation of the British camouflage schemes but most USAAF aircraft did not use multiple shades on the top side of the aircraft. Instead, most were camouflaged in olive drab above and neutral gray below, though some had the edges of flying surfaces painted in medium green. In the later stages of the war, camouflage was often dispensed with, both to save time in manufacturing and to reduce weight, leaving aircraft with a natural metal finish.
Soviet Air Forces aircraft were painted with shades of green, either plain or in disruptive patterns above, and blue-grey on the undersurfaces.
File:ME-110G-2 at RAF Hendon.jpg|thumb|right|Countershaded Messerschmitt Bf 110G night fighter, with pale underside to match skyglow
The basic German camouflage during most of the war was based on a light blue undersurface and a two tone splinter pattern of various greens for the upper surfaces. In the first year of the war, the top colours were dark green and black-green; later, lighter and more greyish colours were used for fighters, though bombers mostly maintained the dark green/black green camouflage. The side of the fuselage on fighters and some light bombers often had irregular patches sprayed on, softening the transition from the upper to the lower surface. The undersides of night bombers and night fighters were painted black early in the war, but by 1943 switched to lighter base colours of their usual light blue undersurfaces for aircraft flown by day, and a light gray base coat over the upper surfaces to match the skyglow over the German cities they were tasked with defending. A special pattern was devised for the Mediterranean front, consisting of a sand yellow that often faded to tan, with or without olive green patches. As Germany lost air supremacy, ground camouflage became increasingly important, and late war fighters received a two tone scheme like the British Sand and Spinach, in dark brown and light green.
Cold War and after
During the Cold War, camouflage was partially abandoned; for example, glossy anti-flash white was used on aircraft as protection from nuclear flash, including high-flying Royal Air Force nuclear weapon-carrying V-bombers. When SAMs made high level attack too dangerous, the plans for RAF bombers changed to low level attack and camouflaged top surfaces returned.Apart from American and Soviet strategic forces, however, camouflage continued to be applied tactically. For example, in the Korean War, American B-29 bombers were switched to night flying with black undersides when Chinese fighters became a significant threat. In the Vietnam War, North Vietnamese MiG-21 fighters were painted by hand in green ground camouflage patterns, while the USAAF and US Navy both restarted experiments with painted camouflage. In the Soviet–Afghan War, Soviet Mil Mi-24 helicopters were camouflaged in a sand and spinach pattern.
In the 1970s, heat-seeking missiles were developed that had a range greater than the visual acuity of pilots. Aircraft camouflage now had two major threats that it was not able to fully defeat—radar and infrared detection. Camouflage accordingly became less important. However, by the 1980s, the human eye was again seen as sufficiently important a threat that aircraft like the ground attack A-10 Thunderbolt were painted in camouflage schemes that included both disruptive ground coloration and automimicry, in the form of a false canopy on the underside.