By Sayan Majumdar


New Delhi, 06 November 2005

With the Air Exercise COPE INDIA 2005 slated to start from Monday, Sayan Majumdar has sent in this piece about the E-3C ‘Sentry’ AWACS aircraft, which is to take part in the Exercise. He suggests that the IAF will gain invaluable experience about the effectiveness of airborne early warning and control by operating with this type of aircraft.

The E-3 Sentry is an airborne warning and control system (AWACS) aircraft. It is a modified Boeing 707 commercial airframe with a rotating radar dome. The dome is 30 feet in diameter and six feet thick, mounted 11 feet above the fuselage. It contains a radar subsystem that permits surveillance from the Earth's surface, over land or water. The radar has a range of more than 200 miles for low-flying targets and farther for aerospace vehicles flying at medium to high altitudes.

It can look down to detect, identify and track enemy and friendly low flying aircraft by eliminating ground clutter returns that confuse other radar systems. Position and tracking information on enemy aircraft and ships, and location and status of friendly aircraft, naval vessels and ground troops can be sent to major command and control centres in rear areas or aboard ships instantly, and, in time of crisis, forwarded to the national command authorities. In support of air-to-ground operations, the E-3 Sentry can provide direct information needed for interdiction, reconnaissance, airlift and close air support for friendly ground forces. It can also provide information for commanders of air operations to gain and maintain control of the air battle.

As an air defence system, the E-3 can detect, identify and track airborne enemy forces far from own boundaries, and can direct fighter-interceptor aircraft to these enemy targets. Experience has proven that the E-3 Sentry can respond quickly and effectively to a crisis and support worldwide military deployment operations. It is a jam-resistant system that has performed missions while experiencing heavy electronic countermeasures.

The E-3 Sentry has an endurance of 11 hours without refuelling. Its range and on-station time can be increased through use of in flight refuelling and an on-board crew rest area.

Sentry Watch

By Sayan Majumdar

Indo-United States Air Exercise Cope India 2005 appears to be rather well planned event. Preparations were initiated months before as six Indian Air Force (IAF) staff visited Misawa from August 21 to 27, 2005 as part of a bilateral exchange program. The 13th Fighter Squadron and 610th Air Control Flight at Misawa each hosted two pilots, two controllers and two safety officers from various units in India. They toured base facilities and worksites, and learned about day-to-day military operations at the Base, including flight operations, maintenance, air traffic control and crash recovery. In the same week in August Misawa and Kadena each sent one airman who will participate in the exercise to familiarise with the Russian-made IAF operated Sukhoi-30 air dominance fighter.

Misawa and Kadena Air Base stationed on Japanese island of Okinawa are well geared up to send about 256 military personnel from the 35th Operations Group and 961st Airborne Warning and Control Systems, respectively, to Cope India 2005, to be held from November 7 to 19 to be held at Kalaikunda Air Force Base (AFB) near Kolkata (Calcutta). In preparation for the exercise, the AFB has been brought up to international standards. An initial planning conference, between IAF and United States Air Force (USAF), was held in May 2005 and a final planning conference was held in September 2005 at Kalaikunda. From United States Air Force (USAF) side twelve F-16CJ ‘Fighting Falcons’ from Misawa AFB are to take part, as is an E-3 ‘Sentry’ Airborne Warning & Control System (AWACS) aircraft from Kadena AFB. The ‘Sentry’ platform appears to be the star attraction of the show as this particular USAF type was indeed evaluated by the IAF and found to be well at par, if not better than the Israeli PHALCON AWACS platform that the IAF ultimately chose.

AWACS platforms have emerged as the central pillar of modern air defence systems and the most effective means by which a nation can avert the catastrophe of a surprise air attack. Surface-based radars, which rely on short wavelengths for detection, are limited to line-of-sight observations and oblivious to aircraft Beyond The Horizon (BTH). Even with careful positioning of the surface radar on mountaintops, the time between a fast enemy aircraft/missile being sighted and weapons being released is too little for effective countermeasures, assuming that correct identification of the enemy was instantaneous. On the other hand owing to its elevation the AWACS has the advantage of a greater radar horizon compared to ground-based radar, which translates to surveillance of a larger chunk of airspace.

A single AWACS of the E-3C class, on patrol at an altitude of say nine-km, could have the capability to provide surveillance up to a range of 400-km at low level and detect up to 600 targets. It incorporates technology sophisticated enough to direct up to 30 interceptions simultaneously. In addition the AWACS has a data link facility to pass target information to ground-based radar and the air defence network. An AWACS would also possess inherent Electronic Counter Measures (ECM) capability making it a difficult proposition for a hostile air force to electronically interfere with its operations. As far as its endurance is concerned, the E-3C has a patrol time of 11-hours on station and may be increased through in-flight refuelling. The radar on E-3 has a low-level coverage of 400-km. With this AWACS flying 150-km inside one's own territory, the lateral coverage along the border would be 750-km for each aircraft. Therefore, it could fly a racecourse pattern and still cover a 600-km long segment inside enemy territory for at least 8-hours. To cite a parallel During the Gulf War I, the Russian A-50 “Mainstay” operating over the Southern Black Sea and Caucasus area, were observed flying sorties to monitor 'Coalition Forces' air operations in Turkey and Northern Iraq. Air patrol operations were reported as normally conducted at 10-km and flying “figure of eight” [8] flight patterns, with up to 100-km between orbit centres.

The AWACS radar of the USAF E-3C is of pulse-Doppler type like the Westinghouse AN/APY-1/2 mounted on the rear fuselage and performs multi-mode operations to maximise detection possibilities. Mounted on the back of the aerial within the same saucer-shaped envelope is the complementary antenna of TADIL-C IFF (Identification Friend or Foe) and data-link fighter-control, plus secondary surveillance radar. The pulse-Doppler radar permits AWACS platforms to locate targets flying close to the ground, filtering out “clutter” by Doppler shift induced in reflected signal pulses. By using a sharp beam and narrow Doppler filter, very low-level intruders can be tracked with accuracy in the Pulse-Doppler Non-Elevation Scan (PDNES) mode. If target elevation is required, the returning signal is electronically scanned in the vertical plane to elicit the data, this being known as Pulse-Doppler Elevation Scan (PDES) mode.

For targets beyond the horizon, there is Beyond The Horizon (BTH) scan available using the pulse radar without the Doppler option because ground clutter is in the shadow of the horizon. The AN/APY-1 or upgraded AN/APY-2 of Boeing E-3 Sentry radar operated within the rotodome rotates at a rate of 6-rpm, giving a scan every 10-seconds. Operation frequency is in the 10-cm wavelength, with seven operating modes, including a PDES, PDNES, BTH, a short-pulsed maritime mode, passive, and a test/maintenance and standby modes. However AWACS is mainly designed for detection of low level targets and its ability to pick up targets above its own level is limited.

For maritime operations, a very short pulse is employed to reduce the sea clutter and so reveal the moving and stationary vessels. Maps of coastal areas stored in the aircraft's computer automatically remove shoreline returns from the screen. Not only can the AWACS provide air battle management at sea, but also guide own aircraft to carry out anti-ship strikes. In addition it can make available data for Over-The-Horizon (OTH) targeting of ships by own missiles. Finally there is the passive mode in which the radar is silent and only the Electronic Support Measures (ESM) equipment is listening for signs of radar and radio transmissions from other airborne platforms and ships. Again it is possible to “go passive” only in selected segments of the compass and interleave radar modes in each scan. ESM equipment and IFF provides important complements to the radar.

Data received by all sensors is processed by an on-board computer like the IBM 4PiCC-1 onboard the E-3 Sentry, filtered for extraneous signals and presented to the tactical crew inside. The avionics automatically opens a file on each new plot, tracks its progress and correlates radar ESM and IFF returns. In the fourteen command & control display screens, clear computer-generated pictures appear in which each target is annotated with its vital characteristics. Under leadership of a tactical-controller the tactical crew manage target tracks and handle communications with airborne and ground units. In this context the E-3 employs the Link16 JTIDS (Joint Tactical Information Distribution System) Class II and posses “Have Quick” secure voice communications. Boeing, with the Electronic Sensors and Systems Division of Northrop Grumman as subcontractor, have carried out an E-3 AWACS Radar System Improvement Programme (RSIP) which upgrades the capability of the AN/APY-1/2 against threats from small radar cross section targets, cruise missiles and electronic countermeasures.

During Exercise Garuda II held during June 2005, both the IAF and French Armee de L’Air (AdlA) performed highly complex operations under the control of an AdlA operated E-3F/SDA ‘Sentry’ platform. In these exercises the IAF displayed a remarkable knowledge of North Atlantic Treaty Organisation/Organisation du traite de l’Atlantique Nord (NATO/OTAN) tactics and procedures, indicative of potentially smoother absorption of USAF AWACS tactics in Cope India 2005. As reported the practice missions of Cope India 2005 will include dissimilar Air Combat Manoeuvring (ACM) and Large Force Engagement (LFE) in the Beyond Visual Range (BVR) regime.

Yet the prominent “J” suffix of guest USAF F-16CJ platforms are well indicative of their primary Suppression of Enemy Air Defence (SEAD) role, having inherited the responsibility from retiring F-4J “Wild Weasel Phantoms”. The USAF F-16CJs tend to operate closely with United States Navy (USN) EA-6B ‘Prowler’ electronic warfare platforms but as it appears the IAF is reluctant to allow such a potent foreign electronic warfare platform within its airspace. IAF Mirage 2000s may well be tasked to fulfil this particular role.

The IAF has a lot to learn from USAF in these spheres of operations as the USAF by now has gained considerable experience in these roles over Iraq and in Kosovo in particular where as much 80 radar/surface-to-air missile installations were decimated within first 24-hours in combination of SEAD and Tomahawk cruise missile strikes. In one of the rare instances the USAF appears to be contributing the “lo-component” in hi-lo-mix during joint operations, with the IAF being honoured to provide the “hi-component” the Su-30. The “secure and jam resistant” digital JTIDS is sure to play a vital part in the exercise and it is high time for the Indian Armed Forces to initiate negotiations to secure the JTIDS (Link-16) technology from United States. The potential success of Cope India 2005 may well provide IAF the “prestigious ticket” to United States Red Flag Exercises held at high-profile Nellis AFB at Nevada from 2006.

Back to Top

Disclaimer   Copyright