Radomes: Why Their Colors Often Didn’t Match The Aircraft

Often coated in black in earlier years, aircraft radomes frequently differed in color from the rest of the aircraft, creating visible contrasts between panels and sections.

The concepts of RADAR (Radio Detection and Ranging) were developed in the late 19th and early 20th centuries, but it was during the World War II years that it emerged as a practical tool, with the ground-based version proving its value during the Battle of Britain. The technology also found its way into aircraft for detecting ships and other aircraft, leading to the need for aerodynamic protective coverings for the antennas.

Early Antenna Mounting

The first aircraft to carry radar was a British Handley Page Heyford in the fall of 1936. The well-shielded engines didn’t generate much interference with the radar, which utilized a long cable stretched between the bomber’s fixed landing gear acting as the antenna, detecting other Heyfords at a distance of 12 miles at times. Further testing by mounting units in Fairey Battle bombers and Avro Anson multi-role aircraft indicated the needed improvements.

A Royal Air Force Handley Page Heyford Mark III heavy bomber of No 102 Squadron at Honington in 1938. A rather unusual design, the aging bomber was the first aircraft to carry radar in 1936. | Source: Imperial War Museum Attempting to create a night fighter to combat an anticipated night bombing campaign by the Germans, similar to the one they waged during World War I, Hugh Dowding of RAF (Royal Air Force) Fighter Command chose the Bristol Blenheim twin-engine light bomber for the covnersion. Two of the aircraft were provided for radar fitting.

The Mk. I radar utilized on the Blenheims used two horizontal antennas and two vertical antennas mounted externally on the wings of the aircraft for receiving. The horizontal antennas saw targets on the left and right, with the vertical antennas detecting targets above and below the aircraft. A single arrowhead antenna mounted on the nose was used by the transmitter. Most early Airborne Interception (AI) radars used by the Allies had similar antenna arrays including the improved and successful Mk. IV.

An RAF Mosquito Night Fighter fitted with AI Mk. IV radar. Details of the AI Mk. IV antenna system can be seen in this image. The transmitter antenna is mounted on the nose, and the vertical dipoles of the horizontal receiver antennas can be seen near both wing tips. The lower vertical receiver antenna can be seen near the landing light (the circular object on the bottom of the near wing); the upper antenna is directly above it, obscured behind the wing in this image. | Source: Wikimedia Commons Antennas created drag, resulting in engineers working on protective aerodynamic covers to reduce drag at high speeds, as well as protect the antennas from the elements and to prevent the build up of ice on the antennas. These early covers had to be constructed of materials that would allow electromagnetic waves to pass through them, resulting in the use of laminated wood or fiberglass composites. Merriam-Webster’s Dictionary records the first use of the term ‘radome’ in 1944 as a combination of the words ‘radar’ and ‘dome’ to describe the coverings.

A De Havilland Mosquito Night Fighter Mark XIII prepares to taxi for a night sortie. Note the radome covering the radar antenna on the nose. | Source: Wikimedia Commons Radomes Stand Out

Aircraft radomes are constructed in many shapes, depending upon application. Many fixed-wing aircraft with forward-looking radar in the nose area will have some variation of a nose cone covering the radar, protecting it from the elements, providing aerodynamic benefits, and preventing personnel from being struck by rotating antennas. Other aircraft will carry a discus-shaped rotating radome such as the E-3 Sentry or have radomes appearing as bulges or large streamlined appendages mounted on fuselages or wings.

The thimble-like black radome protrudes obviously from the nose of this U.S. Air Force Convair XC-99 prototype heavy cargo aircraft. In 1953, an AN/APS-42 weather radar with this distinctive radome was installed. | Source: National Museum of the United States Air Force Often, the radomes will be of a different color than the aircraft itself, sometimes only slightly, sometimes very distinctly, and sometimes only parts of the radome will be painted a non-matching color such as black.

For example, early F-16As sporting the well-known grey camouflage scheme had a distinctive black radome, breaking up the camo pattern. Soviet aircraft, some in natural metal finishes, displayed radomes in various shades of green and grey. Civilian airliners had their all-white or colorful liveries interrupted by a black nose. Even if the radome appeared to be painted in a color similar to the rest of the aircraft, it could still sometimes be easily distinguished.

An early F-16A displaying the familiar grey camouflage scheme along with a black nose cone radome. Pilots complained the black nose made the aircraft easier to spot against the sky. | Source: Wikimedia Commons Material World

There are two main reasons radomes or sections of a radome will be distinguishable from the rest of the aircraft. One is that the materials radomes are constructed from must allow electromagnetic signals to pass through. This eliminates anything metallic, limiting materials to things such as wood, fiberglass, coated fabrics, resins, ceramics, glass-ceramics, and plastics.

The other reason is the paint or coating applied to the outside of the radome. Once again, the radome has to allow radio signals to pass through without interference. This limits what can be applied to protect the radome from the elements.

An F-4E Phantom and an F-16C in flight, with the Phantom sporting the black nose cone radome and the F-16 with a grey one. The grey nose cone radome of the F-16 is a slightly different shade from the FS 36270 Medium Grey applied to the rest of the upper side of the front of the aircraft. | Source: United States Air Force/SSgt. David S. Nolan Fiberglass radomes had a tendency to degrade while taking a constant pounding from the elements during flight such as rain, hail, dust, even birds. Over time, this damage could cause issues with the radar’s performance. Wood, plastics, and resins could also be damaged or degrade.

Early Coatings in any Color as long as its Black

Early radomes were often coated with a black rubber or neoprene coating, which offered a weather-resistant shield. The coating did not interfere with radar signals and provided a tough layer of protection against the constant beating from rain, sleet, hail, dust, birds, and debris.

A lot of black noses. The 45th Reconnaissance Squadron’s RC-135 Cobra Ball together on the flight line at Offutt Air Force Base, Nebraska. | Source: United States Air Force/SRA Jeremy Smith A durable black paint eventually replaced the rubber coatings. Most paints of the day were lead-based, meaning it contained metallic compounds that interfered with radar signals. Black paint however, for the most part, did not contain metallic components.

Black paint had other benefits as well, it was often applied to the nose area of aircraft anyway for glare reduction, and carbon-based paint formulas were developed to drain away static electricity that tended to build up on an aircraft’s exterior during flight. The graphite additive in the paint gave it a natural black color. The black paint also alerted ground crews applying paint to the rest of the aircraft to not apply it on radomes.

The collapsed radome of a Fokker 100 in Poland in 2010. The incident occurred during climb out. Investigation revealed that there was no actual impact on the radome that day; the radome’s honeycomb structure had been weakened by earlier water damage that was allowed in by damage from possibly undetected bird strikes. This led to the collapse of the radome under the pressures of flight. | Source: Poland State Commission on Accident Investigation Technology Advances

Black radomes are not as common now because radome materials have improved, as well as paint technology. Radomes are now constructed from composite materials that are more resistant to the elements.

Modern paints are formulated in a broader range of colors that do not interfere with radar signals. Some radomes, even painted the same color or similar to the rest of aircraft, will still be distinguishable because the radome materials differ from those used on the aircraft, as well as limitations to primers that can be applied under the paints.

An American Airlines McDonnell Douglas MD-80 with a black radome. Some of American’s fleet had black tips on their radomes and some were gray. | Source: Wikimedia Commons Black radomes or non-matching colored radomes can still be seen on older aircraft and some military aircraft. Many historical aircraft still carry the legacy colors and some airlines display retro liveries to the delight of aviation enthusiasts.