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Stealth Aircraft Vulnerabilities

There are short failings with existing Stealth technologies such as the use of toxic chemicals in the construction, susceptibility to the effects of weather and abrasive materials such as sand, as well as continued high levels of maintenance. But most importantly, there are two major flaws with current Stealth technology. First of all, the techniques outlined above are a permanent fixture of the airframe and cannot be altered or removed without adversely affecting the either the Stealthy or the aerodynamic characteristics of the Stealth aircraft. As such, non-Stealthy aircraft and other vehicles can not be made to take on Stealthy characteristics once they are constructed, commissioned and deployed. Secondly, Stealth technologies currently in use cannot alter, adjust, adapt or modulate the RCS of a particular Stealthy design in response to new, different or varying radar frequencies employed by an adversary. As such, current Stealth techniques are static, not dynamic, once deployed.

Stealth technology minimizes aircraft signature in several ways but most notably by greatly reducing its radar signature. Low-Observable (LO) aircraft such as the first operational stealth aircraft, the F-117 and the B-2, demonstrated the feasibility of LO aircraft and their importance to more effective air operations. Like all combat aircraft, they have limitations that must be recognized to ensure proper employment. Naturally, there is an effort among missile and radar designers to develop systems that can detect stealth aircraft. Low-frequency radar will spot virtually any stealthy aircraft but is bad at determining its exact location. Communications networks enabling a defensive system to combine information and locate a target also connect these and other radars. Other systems attempt to pick up radio and television signals that may bounce off a stealthy airplane.

Improvements have been made in all areas with the exception of Infra-Red (IR) suppression devices which are limited in efficiency. Infra-Red weapons systems are prolific worldwide both air-to-air and surface to air. As a measure of their impact, approximately 90 percent of all combat losses over the 15 years 1985-2000 are attributable to infra-red missiles.

A very low frequency radar has very little ability to track a conventional, first- generation or a third-generation stealth airplane with precision. They know the general area that the airplane may be in, but they can't track it with the precision needed to guide either another airplane to it or a SAM to it. The higher frequency target-tracking radars are much more accurate, and that's where the stealth airplanes that are designed from the bottom up have their significant advantages.

The term "bistatic" is commonly used in the RCS community to describe an orientation of the radar system in which the transmitting and receiving antennas are physically separated. Operationally, this condition arises in a semi-active missile engagement scenario in which the intercepting missile carries the radar receiver while the transmitter is separately located on an air-, land-, or sea-based platform. The angle subtended at the target by the line-of-sight directions to the transmitter and receiver constitutes the bistatic angle. The bistatic RCS can be dramatically different from the monostatic RCS depending on the target scattering characteristics.

An aircraft on a mission may become proximate to anti-aircraft fire or fragments which can strike the aircraft. Conventionally, such a fragment typically doesn't do a great deal of damage however, the fragment is capable of disfiguring the aircraft to actually compromise the aircraft by increasing the radar signature. In order to maintain the stealthyness, the aircraft must be repaired between missions. Unfortunately, the repairs may appear sound upon visual inspection however, the repair work may still be apparent on radar.

Currently one method for testing the RCS of an aircraft involves the building of a model of an aircraft and hoisting it up on a big radar pole. The aircraft is then shot with radar and the radar signature or the radar cross section (RCS) is measured. The aircraft signature can also include, for example, infra-red signatures, visual signatures, or acoustic signatures. RCS measurements are customarily made on radar cross section ranges or labs. Such ranges basically consist of a test radar that sends radar signals to a remotely positioned test target and receives and measures any returned radar echo, as may be reflected from the object. Typically the test target is supported upon or suspended from an RCS test mount.

When operating LO aircraft, one doesn't always know if the RCS is as low as that which it was designed. Many actions and events in the aircraft's life can affect is RCS, e.g., maintenance, battle damage, erosion. Scattering centers may be produced on the LO aircraft by patches of dirt, production defects, exterior damage, or incompletely closed access doors. Such conditions may go unnoticed by maintenance personnel and pilots in the field. Furthermore, repairs and production defects may leave imperfections that may not be detected by visual inspections. As a result, the aircraft may be vulnerable to radar detection. Unless the aircraft is brought to an ISAR test range, these conditions will often remain undetected.

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