HAL Dhruv - Design

Design

The HAL Dhruv is of conventional design; about 29 percent of its empty weight (constituting 60 percent of the airframe's surface area) is composite materials. It has been reported that the unique carbon fibre composite developed by HAL reduced the helicopter's weight by 50%. The high tail boom allows easy access to the rear doors. The twin 1000 shp Turbomeca TM333-2B turboshafts are mounted above the cabin and drive a four-blade composite main rotor. The main rotor can be manually folded; the blades are mounted between carbon-fibre-reinforced plates, the rotor head is constructed from fibre elastomers. In February 2004, US helicopter company Lord Corporation were awarded a contract to develop an active vibration control system (AVCS), which monitors onboard conditions and cancels out fuselage vibrations.

The cockpit section of the fuselage is of Kevlar and carbon-fibre construction; it is also fitted with crumple zones and crashworthy seats. The aircraft is equipped with a SFIM Inc four-axis automatic flight control system. Avionics systems include a HF/UHF communications radio, IFF recognition, Doppler navigation, and a radio altimeter; a weather radar and the Omega navigation system were options for the naval variant. IAI has also developed targeting systems and an electronic warfare suite for the Dhruv, as well as avionics for day-and-night flight observation. HAL's claim that the Dhruv is indigenous has been challenged by Comptroller and Auditor General of India, who reported that as of August 2010 the helicopter was: "...against the envisaged indigenisation level of 50% (by 2008), 90% of the value of material used in each ALH is still imported from foreign suppliers".

In September 2010, it was reported that the Dhruv's Integrated Dynamic System (IDS), which combines several key rotor control functions into a single module carrying the engine's power to the rotors, was suffering from excessive wearing and was necessitating frequent replacement; as a consequence the cruising speed had been restricted to 250 km/h and high-altitude performance was lessened as well. HAL contracted Italian aerospace firm Avio for consultancy purposes, Avio replicated production of the IDS in Italy in order to isolate the problem; the early testing of the Dhruv has been criticised as "rushed". In June 2011 HAL has reported that the issue was now resolved and not present in the Dhruv Mk III, a number of alterations both to the design and production had been made to improve the IDS; a programme of retrofitting the Mk I and Mk II was also completed by June 2011.