Here are a couple of examples:
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Under the nose of modern airliners is weather radar that helps the crew to see and avoid hazardous weather conditions. This is required by FAA CFR §121.357 for transport category aircraft. The radar signal would be blocked by the aluminum that makes up the rest of the fuselage, so the radome is made of a non-metallic material, generally a fiberglass composite.
These threads discuss the topic. The last post in the first linked thread suggests that most paint needed lead to prevent fading and/or a zinc-based primer, which would interfere with the radar. Black was one color that did not require these. Modern paint has done away with these metal additives, allowing more color options without interfering with the radar.
The Museum of Flight claims that the black color is only to remind crews to not paint over the radome. Painting over it would affect the radar signals.
According to this thread, the color of the radome affects the operation of the weather radar underneath. They were painted black because it has the lowest reflectivity. Modern radars are able to deal with different colors much better.
Because the nose of the plane is where the weather radar antenna is, and paint would interfere with the signals.
This is not just the 60's and 70's, and its not only on the nose. Here's a brand new PC-12 with a radar dome (radome) on the right wing, painted black:
Inside of the radome is a radar array that can be tilted and panned using a control inside the cockpit:
This is the pilot's view inside the cockpit, which shows the knobs used to adjust the pan/tilt, range, and sensitivity:
And you can read a brochure about a particular aviation radar system here.
It is called a nose cone.
- Aircraft used to be painted with a lead-based paint, which is unsuitable for radomes. Instead, they had a rubber coating. Nowadays, the paint used (epoxy on military planes, I believe) won't affect the radar.
- It's as much a fashion statement as anything else
- It started out as an anti-glare panel. The fuselage within pilot's view is painted dark and of matte finish to reduce the chance of any glare that might obscure pilot's vision.
Even today, you can find some military aircraft with a darker nose cone.