Document created: 31 December 03
Air University Review, May-June 1972

AWACS to Bridge the
Technological Gap

Captain Harry A. Pearce 

Military radar technology was dramatically introduced to the world in 1941 when the British effectively used it to win control of the English sky in the Battle of Britain. After World War II, radar saw a variety of military uses in nearly every part of the world, and in the fifties we developed elaborate ground-based radar systems to provide early warning and command and control for both strategic defensive and tactical employment.

These ground-based systems have inherent limitations. Because of their fixed locations they are range limited and are vulnerable targets. Probably a more important limitation of ground-based systems is their inability to detect low-flying aircraft beyond a short distance because of radar’s horizon limitation resulting from the curvature of the earth.

The Air Force developed an Airborne Early Warning and Control (AEW&C) system to extend the range of the ground-based systems and to improve their low-altitude coverage capability. The AEW&C system operates relatively well over water, but it is ineffective over land because of its inability to distinguish actual radar target returns from the clutter generated by the radar beam striking the ground and causing multiple returns. Thus, the inherent limitations of the ground systems, plus the inability of the AEW&C to reject clutter, have created a technological gap that could be exploited by an enemy either in attacking a strategic defensive system or in trying to gain air superiority in a tactical theater.

The Air Force is currently building a system designed to close this technological gap and provide new capability for Air Force use in the total spectrum of operation from peacetime to war. This system, called the Airborne Warning and Control System (AWACS), will provide a flexible, highly mobile command, control, and surveillance system for both the Aerospace Defense Command (ADC) and Tactical Air Command (TAC). AWACS is being built by the Boeing Company under the direction of the Electronic Systems Division, Air Force Systems Command, Hanscom Field, Massachusetts.

Proponents of the AWACS system have realized the value of this type of technology since ADC first stated a requirement for AWACS in 1963. In 1966, TAC, realizing the possible tactical applications of the system, along with ADC stated a joint requirement for AWACS. Efforts to define the system continued until contract definition ended on 8 July 1970, when Secretary of the Air Force Robert C. Seamans, Jr., announced that Boeing would be the prime contractor for a production option of 42 AWACS. The cost of the program was set at approximately $2.5 billion, and the contract represented a “fly-before-buy” contracting procedure. This procedure is tied firmly to technical milestones.

The AWACS contract is divided into three consecutive phases: Brassboard, which is currently under way; design, development, test, and evaluation (DDT&E); and production. Brassboard is a program planned to demonstrate the capability of detecting targets over land through full-scale flight testing. Another Brassboard objective is to select, based on test results, the most successful radar of the two prime radar contractors (Hughes and Westinghouse) to continue in the AWACS program. DDT&E, which is structured to prove the total AWACS system in the operational environment, will not begin until after the Brassboard phase proves that long-distance overland radar detection is feasible. Full AWACS production will not begin until the system has demonstrated this operational capability in DDT&E.

the need for AWACS

AWACS is being developed primarily to fulfill two vital military requirements, those of strategic air defense and tactical command and control. It can also be useful in nonmilitary peacetime uses. There has been no great technological advance in radar since the 1950s, when the basic threat was high-altitude subsonic bombers. While the preponderant threat to the North American continent presently is the missile, the bomber threat has not diminished; rather, current bomber systems have even greater capability to make low-level penetrations and launch standoff air-to-surface missiles. Our present air defenses, with their limited overland radar coverage, have minimal capability against these tactics. These limitations add up to a military deficiency that could be exploited by an enemy planner in any level of war from small bomber “harassment” or “blackmail” raids, designed to embarrass or force decisions by our national authority, to all-out attack designed to insure a favorable balance of power in case of nuclear war.

To correct this deficiency and at the same time reduce the total expenditures for air defense, the decision to develop and procure the AWACS was formally made by the Secretary of Defense in November 1967, when he approved modernization of our air defense forces to include AWACS, over-the-horizon backscatter radar, and an improved interceptor. The decision to modernize air defense was confirmed by Deputy Secretary of Defense David C. Packard in April 1971. The importance of this modernized air defense force was emphasized by Secretary Seamans when he spoke of the need for these complementary (but not interdependent) systems in testimony before the Senate Armed Services Committee:

For an effective air defense, we must be able to detect and destroy a major portion of the approaching bombers. But our present detection radars are ground-based and vulnerable to enemy missile attack. They might be eliminated before the bombers arrived, and our interceptors would be left blind. Also, our present ground-based system has a very poor low altitude capability.

Both the vulnerability and lack of adequate low altitude detection can be solved by Over-the-Horizon (OTH) radar and an Airborne Warning and Control System (AWACS). CONUS OTH radar will provide long-range bomber detection which will allow AWACS to reach combat positions from ground alert. AWACS will provide precise intercept direction which will not be interrupted, as OTH would be, by nuclear explosions. While airborne, AWACS will not be vulnerable to ballistic missile attack. In addition, its radar will be above the surface looking down, able to spot intruders at any altitude. AWACS is our first priority need for air defense.

The net result of modernization will be a flexible and highly survivable air defense command and control system with long-range radar coverage at all altitudes over all terrain.

The second requirement is for the AWACS command and control in a tactical environment. Experience in Southeast Asia has shown that the effective employment of tactical forces is seriously reduced by the lack of an integrated airborne command and control capability which can react to enemy forces operating at low altitude over any terrain and identify and control our own aircraft.

The AWACS is to provide tactical air forces with quick-reaction surveillance, command and control, for gaining and maintaining air superiority in a tactical theater. The AWACS aircraft will provide an extension of the ground surveillance and control system during sustained air operations such as counter-air, interdiction, close air support, reconnaissance, and airlift.

The flexibility of the AWACS system will permit its employment at any level of military action, ranging from show of force through general war, with a capability to serve as an Airborne Command Post, Tactical Air Control Center, Airborne Direct Air Support Center, and Airborne Control and Reporting Center. AWACS not only will afford a wartime capability but can react to peacetime emergencies needing relief or mercy missions.

In peacetime, AWACS can quickly respond to emergency or civil disasters on a worldwide deployment basis and provide vital surveillance and communications over an entire area. It has the ability to manage air traffic and direct relief and rescue operations. A graphic example of where AWACS could have been used in this role was the recent earthquake in Peru, where a number of relief aircraft, in weather and without navigational assistance, were lost in the mountains. An AWACS aircraft could be used to provide the surveillance necessary to avoid this type of disaster in the future. Thus, AWACS is being developed to provide the increased flexibility and responsiveness required to react throughout the spectrum of operations from peacetime through total war.

characteristics and features of AWACS

Development of AWACS is unique in the Air Force since it combines a proven commercial air vehicle (AF designation E3A) with a complete mission avionics package (AF designation 411L System). The airframe will be a Boeing 707-320B, modified to accommodate eight General Electric TF-34 engines and an elliptically shaped rotodome, 30 feet in diameter by six feet thick, mounted on the fuselage to house a three-dimensional radar antenna.

The TF-34 engines are being developed under the Navy S3A program. The higher performance of the high-bypass ratio engine for takeoff, cruise, and loiter enables optimization of the radome shape for better radar performance. These engines also require less fuel to accomplish a given mission; thus a lighter-gross-weight airplane is possible which could be based at shorter-length fields if the mission dictates.

AWACS is being developed with the capability to operate from a bare base (with only POL support required) for extended periods of time. It will be capable of sustained flight at high speed and extended station loiter time at considerable distance from home base. The interior of the airplane will be modified to accommodate mission avionics and crew of 17.

In addition to a pulse Doppler search radar, the mission avionics package will include the data processing, software system, displays, and communications to enable detection of targets, automatic tracking, identification, and weapons control. The radar technology development can also be traced back to the 1963 ADC requirement. Hughes and Westinghouse were invited by the Air Force to compete for the AWACS contract because of their performance in the Overland Radar Technology (ORT) flight program which the Air Force conducted in 1968. During ORT the Air Force evaluated data from five radar companies that were asked to demonstrate overland detection capability in airborne tests conducted on modified EC-121s.

The Hughes and Westinghouse radars currently being tested have one thing in common: both designs are characterized by the ability to reject severe radar ground clutter or interference caused by weather. The technique used to achieve this is common to both companies. Ground return from immediately below the target is eliminated by airborne moving target indication (MTI); ground returns from elsewhere are suppressed by use of a very low side-lobe antenna. The target signal is further enhanced by narrow-band Doppler filtering to achieve high detection probability. Even in severe clutter conditions, such as mountainous terrain, this technique will allow low-flying targets to be detected.

test program

The AWACS test program is designed to prove the technical capability of the system under operational conditions. Testing will begin in March 1972 with the Brassboard flight test program, which has been called a “physics experiment” since it is designed to demonstrate the radar capability to detect targets over land and in the presence of ground clutter. (The results will also be used to select one of the radar companies for continuation in the program.) To accomplish the experiment, Boeing and the AWACS Systems Program Office (SPO) made a gigantic “laboratory” of a portion of the Pacific Northwest extending from Vancouver, British Columbia, to southern Oregon. During the Brassboard flights the two radar companies will be required to demonstrate radar detection capability over five specific clutter areas, all of which are in this Northwest “laboratory”: desert; sea; vegetated farmland; rolling, wooded hills; and bare mountain peaks. To accomplish this, two 707 Brassboard testbed aircraft (one for each radar) will be modified to carry the rotodome, which houses one radar antenna; the testbed aircraft has minimum test gear on board. (Since demonstration of endurance is not a test objective, these aircraft will be configured with four standard 707 engines.) The Brassboard flights will stage from Boeing Field, Seattle.

To support the tests, the Air Force will provide F-4, F-106, and B-57 aircraft, staged from McChord AFB, Washington, as targets for the tests. In addition, ADC’S 25th Air Division, which has ground-based radar coverage over this Northwest area, will provide SAGE radar tracking (from the 25th Hq at McChord) to determine Brassboard air vehicle and target position. ADC radar controllers from the 25th will also aid in vectoring targets on prescribed headings and altitudes to insure proper positioning during the tests.

If success is achieved in Brassboard, the second phase of the test program, called “Single Thread” demonstration, will be entered. “Single Thread” is designed to demonstrate system integration. One or more of the components of each of the AWACS avionics package subsystems will be added to the winning Brassboard testbed, enabling it to demonstrate an integrated system for detection, tracking, and control of interceptors against airborne targets. To meet the “fly-before-buy” concept, this “Single Thread” demonstration must be successful to gain release of funds for production. Following this demonstration the Air Force plans to use five prototypes, fully configured AWACS, for final operations and qualification testing. The five test aircraft will be incorporated into the AWACS operational inventory after testing is completed.

Brassboard flight testing is scheduled from 23 March 1972 to 23 July 1972. This will mark a major AWACS milestone, since it will be the first “hardware” to have flown since the system was conceived in 1963. The data collected from Brassboard should provide the Air Force insight as to whether the candidate radars are capable of bridging the technological gap that currently exists in radar systems. Should AWACS be able to close the gap, the potential uses that the system can offer are unlimited throughout the spectrum of military operations.

Hq Aerospace Defense Command


Contributor

Captain Harry A. Pearce (B.S., University of Florida) is assigned to the AWACS Project Office, DCS/Plans, Hq Aerospace Defense Command. Previously he served as an instructor in the Interceptor Weapons School at Tyndall AFB, Florida, and as Weapons Director, Instructor/Intercept Director and Weapons Training/Standardization Officer in both SAGE and manual aircraft control and warning operations. Captain Pearce is a graduate of Squadron Officer School.

Disclaimer

The conclusions and opinions expressed in this document are those of the author cultivated in the freedom of expression, academic environment of Air University. They do not reflect the official position of the U.S. Government, Department of Defense, the United States Air Force or the Air University.


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