- AWG-9 and APG-71 radars
The AN/AWG-9 and AN/APG-71 radars are all-weather, multi-mode radar systems designed by
Hughes Aircraft(now Raytheon) for the F-14 Tomcatfighter/interceptor aircraft used by the United States Navy and the Imperial Iranian Air Force (later the Islamic Republic of Iran Air Force).
X-Band, pulse-dopplerradar systems are designed to detect and display an unlimited number of targets in Pulse Doppler Search and Range While Searchmodes, and detect and track up to 24 airborne targets in background, while displaying up to 18 and prosecuting a maximum of 6 of those targets simultaneously when in Track While Scanmode. This function could only work with missiles that had active seeker heads (which excludes the AIM-7 Sparrow; thus the radars are optimized to work in tandem with the AIM-54 Phoenixlong-range, air-to-air missile; which was carried exclusively on the F-14 (see below for details). This function was designed originally to allow the Tomcat to shoot down formations of bombers. This kind of threat has not materialized, so, operationally, the Tomcat, in US Navy service, rarely carried more than one or two Phoenix missiles (if, indeed, it carried them at all).
Both the AWG-9 and APG-71 were designed and manufactured by
Hughes Aircraft; contractor support is now being provided by Raytheon.
The AWG-9 was originally developed in the late 1960s for use on the
F-111B, but transitioned to the F-14A when the F-111B program was canceled. The system incorporated the highest-power transmitterever installed in a production "fighter" aircraft (the MiG-25's Smerch-A radar would take the title for all combat aircraft period), and as a result was capable of detecting bomber-sized targets at ranges exceeding 100 miles (160 km). The AWG-9's advanced analog signal processor analyzes the doppler effect of returned pulses to determine the velocity of the object. This allows it to pick out moving objects from stationary ground or sea clutter, aiding in detecting and tracking small, low-flying targets. [Modern Marvels: F-14 History Channel DVD]
How Track While Scan Works
The AWG-9's track-while-scan capability, is provided by a mil-spec version of the Intel 8080 8-bit
microprocessor; programming it is accomplished using an 8- bitAssembler code.
Normally, a fighter detects targets in "pulse mode," painting a target aircraft to determine location and heading. The fighter pilot would then switch to
fire-control radarmode, which is based on continuous-wave radarprinciples; this provides the illumination needed for a semi-active homing missile such as the AIM-7 to track and destroy it. The disadvantages of this method are that the launching aircraft can attack only one target aircraft at a time, and that the target aircraft's pilot can be aware, via a radar warning receiver, that he is under attack.
Track-while-scan uses the microprocessor to calculate a target track based on pulse mode information. The AIM-54 missile can use that information, and when the target is within the AIM-54's active homing range, the missile tracks it using its own active radar. The AWG-9 continues to track other targets as this is happening. The target aircraft would know that there is an F-14 in search mode, but would not immediately be informed that there is a missile inbound until the Phoenix's own radar activates.
Hughes delivered enough AWG-9 systems and spares to equip approximately 600 F-14A/B aircraft for the U.S. Navy, and an additional 78 aircraft for the
Imperial Iranian Air Force(since 1979 the Islamic Republic of Iran Air Force). All of the U.S. Navy systems have been retired; the status of the Iranian systems is unknown, but it is believed that they are still in service.
The APG-71 was a 1980s upgrade of the AWG-9 for use on the F-14D. It incorporates technology and common modules developed for the APG-70 radar used in the
F-15E Strike Eagle, providing significant improvements in (digital) processing speed, mode flexibility, clutter rejection, and detection range. The system features a low-sidelobe antenna, a sidelobe-blanking guard channel, and monopulse angle tracking; all of which are intended to make the radar less vulnerable to jamming.
The system itself is capable of a 460 mile (740 km) range, but the antenna design limits this to only 230 miles (370 km). Use of datalinked data allows two or more F-14D's to operate the system at its maximum range.
Hughes delivered enough APG-71 radars and spares to equip 55 F-14Ds before the program was scaled back as a cost-cutting measure and eventually canceled. The F-14 was officially retired from United States Navy service on September 22, 2006, with the last flight occurring October 4, 2006. The last navy squadron utilizing the F-14 was (
Joint Electronics Type Designation System (JETDS)
* [http://home.att.net/~jbaugher1/f14.html F-14 Tomcat on Joe Baugher's military aircraft website; includes detailed radar information]
* [http://www.fas.org/man/dod-101/navy/docs/fun/part06.htm Track-While-Scan Concepts]
* [http://www.owlnet.rice.edu/~nava201/presentations/Lecture05.ppt Rice University TWS Presentation]
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