by Richard Sheffield
Infrared and Visual Detection Avoidance
The infrared, or heat, signature of the aircraft has been reduced in several ways. First, several bypass systems are used to mix exhaust gases with cool air so these gases are cooler when they leave the aircraft. They're also vented above the wings to reduce the signature from the ground. Most IR-seeking missiles seek the hot exhaust nozzles, not the hot gases themselves, so special materials were used to keep these nozzles from heating up. Even so, there are new generation IR-seeking missiles that can detect even the hot leading wing edges from head-on. To counter this, reinforced carbon fibers that resist heating are used on most leading edges.
Visual avoidance is the subject of much speculation. There has been talk of "active background masking" techniques where the aircraft would have the ability to change colors to effectively blend in with its background, much like the alien in the movie "Predator." While such a system would be very valuable, it's also highly unlikely. More likely is the standard flat black for nighttime and dull gray for daytime flights.