Indian aerospace major Hindustan Aeronautics Limited (HAL) has put forward a ‘2-Segmented Blade’ proposal to meet Indian Navy’s long-standing requirement of a compliant blade fold system on the 5.5-ton naval variant Advanced Light Helicopter (ALH) ‘Dhruv’.
The IN holds a total of eight ALH based at two locations on the western coast. These were inducted commencing 2003 and forms a miniscule part of over 250 ALH produced by HAL. Two key non-compliances for sustained embarked operations, viz. folded dimension and a simple, practical, manual blade fold system, has thus far relegated the helicopter to a largely shore-based role.
Indian Navy was unhappy with the manpower and parts-intensive blade folding procedure on ALH. Many rounds of design modifications and adaptations to improve the procedure and folded width failed to meet naval specifications. IN curtailed further orders of ALH and initiated the Naval Utility Helicopter (NUH) program in 2009.
This key requirement is now proposed to be overcome with the 2-segmented main rotor blade. As per details obtained from HAL, “in the proposed concept, the blade is segmented to Root and Aerofoil portions, interconnected by metallic fittings. The folding is achieved by the extraction of one bolt of the metallic fitting attachment and rotating about the other bolt. The blades are folded one below the other on either side due to the geometry of the metallic fittings. The blade folding process is thus simplified with reduced tools and timings.”
HAL has incorporated the ‘2-Segmented Main Rotor Blade’ concept on its 3-ton Light Utility Helicopter (LUH) which recently received initial operational clearance. The LUH prototypes are undergoing flight testing in this configuration and as per HAL “no abnormalities have been observed w.r.t. integrity and performance of the 2-segmented MRBs”.
Indian Navy has not signed into the LUH project as their future plans exclude single-engine helicopters for shipborne use.
The 2-segmented blade concept is planned to be ported on the ALH to meet navy’s folded dimensions. It is understood that a techno-commercial proposal has been forwarded to the navy for approval with a lead time of two years. This will involve modifications to the ALH integrated dynamic system (IDS), upper control system, stub shaft and main rotor head, among other sub-assemblies.
The 2-segmented blade on LUH was originally designed for stowage and air transportation of the LUH. A demonstration on the LUH was recently organised by HAL for naval officials. How this modification ported to the ALH will hold-up aboard a naval ship where folding/unfolding is a daily activity would be revealed only after naval approval, flight trials and certification.
HAL sources feel that if successfully implemented, this modification could open new orders for ALH naval variant. An order for 16-each additional ALH Mk-III for the navy and coast guard (without this modification) is currently pending with HAL.
© KP Sanjeev Kumar, 2020. All rights reserved. Cover photo courtesy Indian Navy. I can be reached at firstname.lastname@example.org.