Stealth aircraft
Stealth aircraft are aircraft’s that use stealth aircraft technology (low observable technology) employing a combination of features to avoid stealth aircraft detection in war and reduce radar visibility in infrared spectra. Today no stealth aircraft is totally invisible to modern radars. Stealth aircraft technology prevents conventional radar from effective tracking or detecting it, decreasing the odds of attack. You can’t attack stealth fighter aircraft if you are unable to see it. The same tactics and camouflage is used and tested in ground battles and ground vehicles.
Developing of stealth aircraft technology started in United States in ninety sixties, after earlier attempts of preventing radar tracking’s of U2 planes from the period of cold war.
To achieve stealth aircraft, designers needed to develop particular design shape which needs to redirect electro magnetic waves from radars. Radar absorbent material was tested and put to use on stealth aircraft. The main feature of that material is to reduce or block radar signals reflecting back from surfaces of the stealth aircraft. The best example of that stealth aircraft technology is as currently used on the Northrop Grumman B-2 Spirit.
Principles behind stealth fighter aircraft technology
To put invisibility to work, combinations of technologies are in use today. The main aim is to reduce distance at which vehicle, stealth aircraft or person in general can be detected. The most important aspects of stealth aircraft technology are; radar crosses section reduction, thermal and acoustic. The term “aircraft stealth” becomes known to general population in late eighties when stealth fighter aircraft F117 become known and popular. The F117 stealth aircraft was put to use in the Gulf War in 1991. Stealth aircraft were put to use for the first time in US invasion of panama in December 1989.
As the stealth aircraft technology is improving there is also lot of effort put in improving radar tracking systems and developing tracking systems with means of detecting stealth aircraft such as passive radar arrays, low frequency scan radars etc.
Shape of the stealth aircraft
The most significant difference in detect ability of modern stealth aircraft is their shape. The Avro Vulcan, British bomber from the late sixties, had a very small appearance on the radar despite large aircraft size. The Aircraft had fortuitously stealthy shape.
Internal construction of stealth aircraft is another important factor. The idea of its construction is to put radar transparent material (radar absorbing) on the skin of the aircraft in order to have radar waves penetrating the skin and get in special structures behind skin which are called re-entrant triangles. Those structures are designed to capture radar beams reflecting off internal surfaces and loosing energy. The method was first proven on Blackbird series stealth aircraft (A-12 / YF-12A / SR-71).
Shape requirements have a strong negative impact of aerodynamic characteristics of the stealth aircraft. F117 has a very poor flight characteristic it’s unstable and can be flown only with fly by wire flight control. Similar stealth methods are widely used in modern warships design.
Composite airframe and radar absorbing paints
Composite derivate airframes are more transparent to radar and they may also contain ferrites optimizing magnetic and dielectric properties of construction material used. Often radar absorbents are used on the edges of surfaces; metal edges are simply paint with special radar absorbent. Further specifications of material used are classified so no detailed information is available on stealth aircraft.
IR and acoustic signature of stealth aircraft
Another important factor of stealth aircraft capability is his IR signature. Stealth aircraft can bee seen in infrared specter if giving out the infrared signature. Thermal imaging systems makes clear images of aircraft because of their high temperature exhaust systems. Compared to conventional aircraft, IR signatures of stealth aircraft are minor. The best option would be to have engines completely removed and that way completely reducing infrared and acoustic component of stealth aircraft technology. The engine design and placement is very important in reducing infrared signature of stealth aircraft.
Technology behind this is all top secret. We can analyze only what is already seen. Closer look on B-2 or F-22 stealth fighter aircraft show us that engines are almost completely incorporated into fuselage of stealth aircraft.