Aircraft Survivability Equipment [ASE]

The role of Aircraft Survivability Equipment [ASE] is to reduce the vulnerability of aircraft, thus allowing aircrews to accomplish their immediate mission and to survive. The methodology for achieving survivability is supported by the ASE philosophy. The ASE philosophy is a five-step approach ensuring that Army aircrews are able to accomplish their mission again and again. These five steps include the following, in order of least cost and most effective to the most cost and least effective:

Step 1. Tactics (electronic protection). Proper tactics reduce exposure times to enemy weapons. Low-level flight limits LOS (Line of Sight) exposure times and places the aircraft's radar, infrared, and optical signature in a cluttered environment. Low-level tactics, combined with ASE protection, allow Army airplanes to survive and perform their mission. ASE protection is severely degraded when the aircraft is not flown in a tactically sound manner (i.e., against a sky blue background).

Step 2. Signature reduction (electronic protection). These measures are implemented through engineering or design changes, such as flat canopies, exhaust suppressers, and coating the aircraft with low-infrared reflective paint. Signature reduction alone greatly increases survivability. Without signature reduction, ASE effectiveness is degraded and, in some cases, erased. Signature reduction is also influenced by the aviator controlling how much signature to expose to the threat.

Step 3. Warning (electronic support). The next step, in the ASE philosophy, is to provide warning to aircrews when they are about to be engaged, allowing time to react. Examples include radar detecting sets, laser detecting sets, and infrared missile warning systems. At present, none of the Army's OSA airplanes are equipped with any ASE. Such equipment is needed to reduce the threat to the airplanes conducting many of the missions assigned to the TAB. Commanders must use valid risk management to balance risk with mission success.

Step 4. Jamming and decoying (electronic attack). When aircrews must stay on station despite warnings, there is a requirement for countermeasures capable of jamming, and/or decoying the fire control or guidance systems of threat weapons. Chaff, flares, and radar and IR jammers provide this type of protection. Future modifications to the Army airplane fleet must include consideration of methods to counter threat weapons.

Step 5. Aircraft hardening (vulnerability reduction). This step provides for ballistic tolerance, redundant critical flight systems, and crashworthy features, to assist in minimizing the damage to an aircraft after it has been hit.

All weapon systems must complete a series of events, called an engagement sequence, to actually have an effect on the target (aircraft). Missing any step in the engagement sequence forces the threat engagement sequence to be started over again.

The threat must detect, acquire, track (establish fire control solution), and fire at the aircraft. The time of flight of the projectile must be determined. The threat must predict where the aircraft target will be (within a few meters) as the ordinance travels to a point in space and time. The difference between detection and acquisition, versus tracking is very important. In detection and acquisition, the threat weapon system does not have enough refined data to facilitate firing at the aircraft. The threat weapon system must track the aircraft long enough to acquire range, azimuth, elevation, and velocity, to determine the time and position of firing. Indications of search or acquisition activity may provide the aircrew time to initiate a response. Tracking indications alert the aircrew to an immediate action requirement, such as masking, employing ASE decoys, or executing evasive maneuvers.

All threat systems are confined by physics. Each threat system has a minimum and maximum effective altitude and range. These numbers are computed against a cooperative engagement (nonmaneuvering aircraft, blue sky background, flat terrain, steady velocity, etc.). The effective envelope for a threat system is based on a "50 percentile". That is, at the maximum (or minimum) effective range (or altitude), the weapon system is able to hit the target one out of two times. As the target progresses further into the threat envelope, the probability of a first shot kill increases. As the target progresses further outside the threat envelope, the probability of being hit decreases, until the target has reached a point where it is impossible to be hit.

Tactics, signature reduction, warning, jamming and decoys are the tools available to preclude a successful threat engagement. If hit, the pilot may have to rely on aircraft hardening.

The aircrew has the ability to make an accurate engagement more difficult for the threat. A stationary target allows the threat to adjust each shot from the previous shot, until it hits the aircraft. A moving, constant velocity target provides a more difficult engagement procedure. A prediction can be made from the previous shot and adjustments imposed to enhance accuracy. The most difficult engagement is the moving target that varies range, altitude, azimuth, and velocity. Utilizing this technique makes prediction nearly impossible since four factors are changing at differing rates.

There are generally four major types of threat weapon sensors. These may be man-portable or transported by land, sea, or aerial platforms. It is important to determine the actual sensor type, and guidance package, for each threat and understand their inherent capabilities and limitations. (For in-depth information concerning particular threat systems, contact your unit electronic warfare officer or tactical operations officer.) The four major types of threat weapon sensors are radar, IR, laser and DEW (Directed Energy Weapons), and Optical/EO.

Direct threat radar weapons require LOS to hit the target. Direct threat radar weapons are either fire controlled AAA, semi-active radar homing, active radar homing, track via missile (for missile systems command), or ground aided seeker. Radar weapons must detect, acquire, track, launch and guide (or fire a ballistic solution), and then assess damage. Radar systems have trouble with ground clutter. To pick out targets from ground clutter, radar systems can detect movement though the use of moving target indicators, Doppler (continuous wave radar), or Pulse Doppler. Modern radar systems can track the movement of the aircraft, while some systems also detect the movement of rotor blades. A few older radar systems had blind speeds (called a Doppler notch), where they can not detect an aircraft flying at a specific velocity toward or away from the radar. Modern radar systems cancel blind speeds. Radar systems can be detected, avoided, decoyed, jammed, and destroyed by direct and indirect fires (self, artillery, and anti-radiation missiles).

Laser and directed energy weapons [DEW] weapons really fit into two distinct categories--laser guided (or aided) weapons and pure laser/DEW weapons. Laser guided (or aided) weapons are those which use the laser to perform ranging, tracking, or guiding functions for conventional explosive missiles or projectiles. Pure laser/DEW weapons use lasers and other forms of DEW to inflict damage to the aircraft or its sensors, including the eyes of the aircrews. Pure laser/DEW weapons are not required to burn a hole in the target to destroy it (although these weapons are reaching that capability). Simply igniting fuel vapor near vents or burning through fuel lines are effective, as well as glazing the cockpit glass so the aircrew cannot see out. Inherently, laser/DEW weapons are short duration, hard to detect, extremely hard to decoy or jam, and difficult to destroy. Fortunately they must rely upon LOS, certain atmospheric conditions and are presently somewhat short range.

Optical / Electro-Optical [EO] sensors are used as either the primary or secondary sensor for all these weapon systems. Although they rely upon LOS, they are, with very few exceptions, completely passive. They are limited by human eyes, atmospheric conditions, distance, operator movement, and in many cases, by darkness. The Optical/EO sensors are most difficult to detect and seldom can be decoyed. However, they can be jammed by obscurants and, when located, be destroyed.

Electronic Warfare, like most defense-related technologies, felt the pinch of declining budgets in the early 1990s, but significant progress in the modernization of EW capabilities was still made, especially in the infrared area. Reductions included the retirement of the ASPJ, EF-111, and F-4G "Wild Weasel," and the termination of the EA-6B ADVCAP, F-15 PDF, and B-1B defensive systems.

The Navy, as the lead service for the joint Integrated Defensive Electronic Countermeasure (IDECM) system, awarded an IDECM engineering and manufacturing development contract in 1996. The IDECM is the ASPJ replacement for the Navy's F-18E/F aircraft. The IDECM contains an RF subsystem consisting of an onboard techniques generator and a towed transmitter decoy. The techniques generator is actually a jammer receiver and processor. It is planned that this RF subsystem will have potential application on the B-1B as well as other platforms, such as the U-2 and TIER II+. The IDECM towed decoy also has application on the F-15.

The ASPJ, though terminated, has found use as a contingency asset. It is presently installed in F-18s and being used in the Bosnia operations area. Once it successfully completed the operational evaluation, by the end of 1996 it was installed in the F-14D using existing assets.

The ALQ-131 and ALQ-184 are the Air Force's two primary external electronic warfare pod systems. In Air Force service, they are carried externally by the A-10 and Lockheed Martin F-16. Acquisition of the ALQ-131, manufactured by Northrop Grumman, ended in 1989, while acquisition of the ALQ-184, manufactured by Raytheon, concluded in 1998. The most pressing need for the ALQ-131 and ALQ-184 pods is for test equipment. Both test sets are facing serious obsolescence issues and lack of spare parts and/or repair support from the original equipment manufacturers.

The Army has taken a significant step in modernizing helicopter survivability equipment with the introduction of the Advanced Threat Radar Jammer (ATRJ) and the award of the Advanced Threat Infrared Countermeasure (ATIRCM) system. The ATRJ is an integrated system with the jammer's receiver and processor also functioning as a radar warning device. This dual function negates the need for a separate radar warning receiver, which reduces future acquisition and support costs. The ATRJ has the capability to generate the more exotic countermeasure techniques needed to defeat the most sophisticated surface-to-air weapon systems.

The Partnership Process for EW Acquisition was commissioned in June 1995 by Darleen Druyun, the Acting Assistant Secretary of the Air Force (Acquisition), and Lt Gen Howard W. Leaf (USAF, Ret), the Director of Air Force Test and Evaluation. Lt Gen Ralph E. Eberhart, then the Air Force Deputy Chief of Staff for Plans and Operations, agreed to co-sponsor the effort in January 1996 and coined the term "Partnership Process." The Partnership members from the military Air Force, Navy, and industry EW community represented organizations with functional responsibilities across the gamut of EW acquisition (for example, acquisition, operations, logistics, requirements, test and evaluation, modeling and simulation).

The Partnership Process looks beyond technical specifications, to place the focus on system suitability/performance based on the concept of military worth to tactics and campaigns, then best solutions based on cost and schedule constraints. The Partnership Process has drawn on lessons learned from world-class companies to redesign the process of EW acquisition. The changes instituted by the Partnership provide great benefits to the EW community and the warfighter and should serve as the model for reforming other areas of acquisition.