Indian eye in the sky

Print edition : March 09, 2012

In the System Test and Integration Rig at the Centre for Airborne Systems (CABS) in Bangalore.-K. MURALI KUMAR In the System Test and Integration Rig at the Centre for Airborne Systems (CABS) in Bangalore.

The CABS is the DRDO's nodal agency for developing an indigenous airborne early warning system for the IAF.

A MODEL on a table of a Brazilian Embraer aircraft with an antenna mounted on its fuselage caught the eye as we entered a hall in the System Test and Integration Rig (STIR) unit at the Centre for Airborne Systems (CABS) in Bangalore. Inside, women software specialists were busy in front of computer screens. A few feet away, a life-size model of the fuselage of the Embraer EMB-145 aircraft had been modified into five operator work stations (OWS) where Indian Air Force (IAF) officers were simulating combat situations on computer screens.

In an air battle, it is the pilot-controller coordination and trust that will win the battle. This software is one of its kind and has been developed by the CABS, said S. Christopher, Director, CABS, which is a unit of the Defence Research and Development Organisation (DRDO). He has been at the helm of affairs since January 1, 2007.

Elsewhere inside the aircraft was an Airborne Early Warning and Control (AEW&C) system simulator. You can simulate any kind of aircraft, radars, and emitters in the form of radars, which can be airborne or ground-based, said Reena Sharma, scientist, CABS. In OWS-3 is the electronics support measures (ESM) system, which provides the bearing and location of hostile emitters and analyses their characteristics. The communication support measures (CSM) intercepts communication signals and analyses them. The Mission Systems Controller (MSC), the heart of the AEW&C system, integrates the data from all the sensors and facilitates the airborne surveillance operations. All the five OWSs were developed in-house by CABS scientist Rekha Sinha and her team. On December 6, 2011, an Embraer EMB-145 fitted with the Indian AEW&C system made its maiden flight at Sao Jose dos Campos at Sao Paulo in Brazil. It had about 1,000 mission system components developed by the CABS, including the critical Active Electronic Scanning Array (AESA) developed by the Electronics and Radar Development Establishment (LRDE), Bangalore, a DRDO laboratory. While the antenna called Active Antenna Array Unit (AAAU) is made by CABS, the AESA radar, which is the processor part of the AAAU, is made by the LRDE.

The flight is a major milestone towards realising the dream of developing an AEW&C system indigenously, which will put India in a select club of countries, said V.K. Saraswat, DRDO Director General and Scientific Adviser to the Defence Minister.

While this aircraft will now undergo a full certification process over the next two years, India will receive two more Embraer aircraft by the middle of next year to be integrated with the AEW&C System.

The Indian AESA radar is the primary sensor for the indigenous AEW & C. The radar can look 240 degrees within a short time and has a range of 350 km; it can track more than 500 targets simultaneously.

The DRDO is spearheading the indigenous AEW&C programme with the CABS as the nodal agency. The latter is executing it in association with DRDO laboratories such as the LRDE; the Defence Avionics Research Establishment (DARE), Bangalore; the Defence Electronics Research Laboratory (DLRL), Hyderabad; and the Defence Electronics Application Laboratory (DEAL), Dehradun. Each of these laboratories is developing subsystems for the AEW&C programme.

The IAF has stationed an Air Force Project Team at the CABS to interact with the in-house team and convey the IAF's requirements. Air Commodore A.I. Mehta is the Project Director of the team.

The Brazilian Embraer aircraft EMB-145 was chosen because Brazil, Mexico and Greece had based their AEW&C systems on this aircraft. The DRDO was tasked with the mission.

The primary radar mounted on the Embraer aircraft is the AESA radar. The secondary surveillance sensor is the Identification of Friend or Foe (IFF) system. Two radiating planar arrays assembled back-to-back and mounted on the fuselage in an AAAU will provide 120 degrees coverage on either side of the AAAU. The important modes of operation of the system are surface surveillance and air surveillance, Christopher said.

SOURCE: CABS, Bangalore

The IFF system has been developed entirely by the CABS. Christopher said, The IFF determines whether the target determined the primary radar is a friend or foe. The interrogator emits a message querying the target in a particular sector. Replies from the target are automatically associated with the primary radar detections. This information is then used by the AEW&C system to identify friendly and unfriendly aircraft in the area and deal with them appropriately.

The Defence Acquisition Council has given approval for the indigenous development of 2,700 IFF systems and the Services want a single-box solution in the IFF system. The government has the option of buying the remaining 500 IFF systems in the global market.

It was a challenge for the CABS to integrate the AEW&C system components in the Embraer transport aircraft. While the aircraft's payload capacity was four tonnes, the AAAU alone weighed 1.5 tonnes. Besides, there were five OWSs with electronic systems inside, crew seats, special protection suites, and so on.

The AAAU had to be mounted on the fuselage without affecting the aircraft's structure and stability. If the aircraft were to crash, the AAAU should not get detached. The attachment had to be capable of bearing nine times the weight of the AAAU, that is, 13.5 tonnes, said Christopher. The attachment is done with only four bolts, which should be able to carry all the weight. Each bolt, made of titanium, has a diameter of one inch.

DR S. CHRISTOPHER, Director, CABS.-K. MURALI KUMAR

There are two levels of operation here. In the first, the aircraft is modified in Brazil and the DRDO sent all the components, including the antenna, the AAAU with dummy electronics, and so on for integration with the aircraft. M/s Embraer Engineers mounted them on the aircraft and configured it for the flight. Embraer's engineers also received the air-worthy certification for the aircraft from the Agencia Nacional de Aviacao Civil, the Brazilian agency responsible for overseeing the safety of civil aviation in that country.

In the second level, when the three aircraft with the Indian AEW&C systems are delivered in India after flight trials in Brazil, the remaining mission systems will be integrated inside the cabin and the IAF will do the flight trials again. The CABS will be responsible for having the AEW & C system certified for mission functions and flight safety in association with the IAF and the Centre for Military Airworthiness and Certification (CEMILAC), Bangalore.

Massive facilities that the CABS has built on its premises include an anechoic chamber, a lightning test facility, and highly accelerated life testing (HALT) and highly accelerated stress screening (HASS) facilities. The anechoic chamber is a huge shielded facility, 35x15x18 metres. The AESA radar is tested here.

In the lightning test facility, artificial lightning of four million volts is created to test the effect of lightning on aircraft and ensure that the electronics inside are not affected. The AAAU underwent qualification here. S.K. Venkatesh, scientist, CABS, is the architect of the facility. In the HALT and HASS facilities, different components are hammered or subjected to freezing or scorching temperatures to ensure they are robust.

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