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India's flying Testbeds
By B Harry
Sep 12, 2005, 10:07

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India's Centre for Airborne Studies (CABS), a division of the Defence R&D Organization (DRDO), at Bangalore, was home to two, now one, specially modified HAL/Hs-748 transport aircraft, used as R&D testbeds. The two aircraft, H-2175 and H-2176, were transferred from the IAF in the late 80s and modified to Airborne Surveillance Posts (ASP) in the 90s in response to IAF requirements of an indigenous AWACS similar to the E-2 Hawkeye. Called "Project Guardian" and later "Airawat", the Rs.60.80 Crore programme carried on until Jan 11, 1999 when H-2175 crashed in the jungles of Arakonnam in the state of Tamil Nadu, killing all 8 personnel onboard, including four scientists who were critical to the project. The programme was restarted in 2004-05, with Rs.1800 Crore expected to be allocated for the same. The new system will be based on the Embraer EMB-145 as the parent aircraft and an active phased array radar similar to the Ericcson Erieye. These aircraft will supplement the IAF's Phalcon AWACS by acting as their subnodes of the network.

The HAL/Hs-748 frieghter H-2176 was the second to join the ASP programme, after H-2175. This aircraft had a very large 24x5 ft black rotodome (with white bands painted across the diameter) mounted on two dorsal pylons, accomodating LRDE's planar AEW radar. H-2176 appeared for the first time in public during Aero India 1996, allowing for a glimpse into this higly obscure project. Although the project was under wraps for most of its life, it shot to fame towards 1996. (All artwork by B.Harry)

H-2175 seen here few months before its tragic loss on Jan 11, 1999. With H-2176 modified as the 'Hack', H-2175 was the only aircraft in ASP configuration. As can be seen, this aircraft's rotodome was painted white overall, with black bands across the diameter. The aircraft flew very nicely at the Aero India airshows but some have questioned the use of the HAL/Hs-748 airframe as old and unreliable. While H-2176 appeared at Aero India 1996, H-2175 appeared instead at Aero India 1998. (B.Harry)

H-2175 was the first and also the last ASP after H-2176's conversion. An interesting fact is that this aircraft originally wore Blue-Green Jungle camo overall, even after conversion. It is said to have first flown in May 24, 1989 after installation of the pylons, without the dome, at HAL Transport Division, Kanpur. First flight with the rotodome is said to have taken place on November 5, 1990. This airframe was lost on Jan 11, 1999 after what some eyewitnesses describe as a rotodome collapse. The project was at a stage where the radar and rotodome assembly were ready to transfer to an IL-76MD airframe. LRDE's radar had acheived a detection range of 300 km against fighter sized targets and the capability to track more than 50 targets.

CABS revealed this AEW&C concept at Aero India 2007. The medium-range AESA radar will be mounted on an Embraer EMB-145 platform and will feature SIGINT and COMINT capabilties as well. The aircraft is being designed as a sub-node for the IAF's longer range Phalcon AWACS and should be able to datalink to more than 40 other aircraft and will have multiple redundant air-to-air and air-to-ground datalinks. The bulge/blister seen above the cockpit, is for the SATCOM antenna. The aircraft has integrated IFF with mode-4 capability and V/UHF antennae are also seen on the front fuselage section. The aircraft is will also have an IFR probe for extended endurance as per IAF requirements. The platform aircraft is already ready for purchase but the contract is facing bureaucratic delays.(Artwork by B Harry) (Image expansible)

The wind tunnel model of the new AEW&C. (CABS via B Harry)

Brochure of the T/R modules developed in India, by LRDE (DRDO).(Image expansible)

Between 1996 and 1997, the ASP H-2176 was reconverted into a testbed for the avionics and radar of the Light Combat Aircraft (LCA). Now known as the 'Hack', the only major structural modification besides the removal of the rotodome assembly, was the addition of the LCA's nose cone in order to accomodate the Multi-Mode-Radar (MMR). Special provisions include a GPS based target tracking system, the Sigma-95 INS, a high density data recorder, a mission crew intercom system, ARINC-429 plus MIL-STD-1553B databuses, a dedicated thermal management system and an 120 KVA APU with 115V-400 hz AC, 230V-50 hz AC and 28 DC supplies. The aircraft also hosts 15 consoles with an equal number of operators. The post-processed data from radar testing is analyzed on the ground using the appropriate software tools. Even as the Hack was being configured, some elements of the ASP H-2175, now the only remaining ASP, were still undergoing integration, the fully integrated ASP system ready for demonstration only by August 1998.

H-2176 did not spend too much of its life in ASP configuration. Between 1996 and 1997, the need to use this aircraft as the testbed for the LCA's radar and avionics saw rotodome assembly dismantled and further modification take place, the latter being the installation of the LCA's dielectric nose cone in order to accomodate the Multi-Mode-Radar (MMR). This required considerable structural modification to the nose of the aircraft. For a while, H-2176 continued to fly with the rotodome's dorsal pylon attached for reasons unknown. The newly configured aircraft was rechristened as the 'HACK' or 'Radar-Hack'. The dorsal pylons were eventually removed. The black rotodome itself was permanently placed outside the CABS Hangar at Bangalore's HAL Airport.

Currently flying in this configuration, the Hack's primary mission is to flight-trial the LCA's radar - the MMR and other avionics including the Sigma-95 INS/GPS, MFD hardware, HUD, Datalink, RAM-1701 radar altimeter and other avionics. The Hack appeared for the first time in public view at Aero India 2001 and again 2003, performing some stunning manuevers and flight at very low level. This aircraft is currently based at CABS, HAL Airport, in Bangalore. The onboard avionics and modifications come at the price of some performance. H-2176 has a service ceiling of about 20,000 feet, an endurance of 5+ hrs and a payload capacity of 3 tons.The aircraft can sometimes be spotted at its hangar, right next to DRDO's Lightning test facility.

The MMR radar is seen installed on the 'Hack' aircraft. This radar is being developed under the LCA 'Tejas' programme and has an intended detection range of 120 km vs a 2 sq.m target. The Hack is offered for other testing purposes as well. (CABS via B Harry)

Recommended Further Reading:

Photo 1
Photo 2
CABS T/R modules for AEW&C radar
ACIG Exclusives Tejas page (Aero India) 2005
ACIG Exclusives Tejas page 2007

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