Message posted by Magoo on May 10, 2000 at 10:51:46 EST:
Hey all Just wanted to clarify what is meant by the word 'stealth'! Stealth design when applied to an aircraft can take many forms. The F-117 is perhaps the most obvious example of an airframe optimised for low observability (LO), but it is at the expense of controllability, manoeuverability, weapons load and range. It really is just a short range small load carrier designed to evade radar. The masked engine intakes and exhausts are inefficient, but effective at shielding the fan blades and hot exhaust plume. The B-2 is not just a pure stealth shape, but also combines LO design with many active (radar) and passive sensors to avoid enemy radar sites, either by flying around them or by destroying them before it can be seen by them. It also has masked intakes and exhausts, but these are more efficient than those on the F-117 due to the additional shielding from below provided by the larger airframe. It is also fast and very manoeuverable for an aircraft of its size. The F-22 and YF-23 took the B-2 design concept one step further, by combining LO design, multiple sensors, and powerful engines able to give these aircraft a supercruise capability (supersonic speed without afterburner), and a Mach 2.5+ top speed with burners. The F-117, B-2 and F-22 all have internal weapons carriage and rapid weapon ejection sequences, so that the stealthy shape may be maintained. External hardpoints are usually covered, and would only be used to carry additional weapons or fuel once air supremecy had been achieved, or for ferry flights. Stealth, however, is so much more than just airframe design and shaping. The tactical and strategic doctrinal use of these platforms contributes as much to their surviveability as their airframe design does. The deployment of longer ranging BVR (Beyond Visual Range) missiles and stand off weapons, combined with more powerful but 'quieter' radars play a big part in the 'first see, first shoot' scenario. It is the intention that the F-22 will see its foe from 100+ miles away, and have an AMRAAM (or successor) in the air long before the enemy pilot even knows the F-22 is there! The Eurofighter will operate in a similar way. If however, the enemy somehow manages to get close enough, these aircraft will still have the ability to mix it in a close in dogfight. Whether the governments have the political 'balls' to allow these aircraft to fight at BVR ranges is another matter!!! Stealth doctrine also means using the lowest possible engine power rating so as to reduce an aircraft's IR signature. Modern Infra Red Search and Track (IRST) systems can see a hot exhaust from dozens of miles away, and even see the heat coming off a hot speeding airframe. This is probably not an issue once the fight is on, but it can be if you're trying to sneak up on an opponent. New IRST systems will most likely see the light of day on the Eurofighter and possibly the SAAB Gripen in the coming decade, and are already in use on the MiG-29 and Su-27, albeit in cruder and less capable forms. Obviously, being able to fly at night or in bad weather is of huge benefit too. The last thing you want is to lose your $80 million fighter to a lucky AAA or portable SAM shot as happened to the F-117 in Kosovo, or worse still to small arms fire. If you can fly at night and in bad weather, then the chances of being seen from the ground are almost nil. Other doctinal factors include flying in single-ship formations, and never in trail, and keeping a radar site head-on to you so as to present the smallest possible signature (e.g SR-71s would almost always directly overfly SAM sites where possible because they had a tiny head-on cross section, and it was too late to shoot once the SAM had acquired it from below. They could be acquired from side on much earlier). Hope this helps in explaining some of the mysteries of stealth. Stay tuned for an upcoming article on the subject, and hopefully Joerg will allow it to be posted on this site. Magoo
Replies: