MilitaryHAL ALH Dhruv may finally operate on Indian Navy warships with easily...

HAL ALH Dhruv may finally operate on Indian Navy warships with easily foldable blades

The ship deck-based operations of ALH have been limited because the stowage size required for ALH exceeds the hanger sizes constructed in Navy ships

Indian aircraft major, Hindustan Aeronautics Ltd (HAL) today announced the maiden flight of the wheeled version of Advanced Light Helicopter (ALH) with “segmented Main Rotor Blades” (MRBs) and Main Rotor Head (MRH) in “pre-cone configuration”.

The 2-Segment MRBs and Pre-Cone Configuration of MRH are incorporated to cater to the stringent stowage dimension requirement specified by the Indian Navy. The two features will improve the Time Between Overhauls (TBO) life of the Main Gear Box, said Mr R. Madhavan, CMD, HAL.

As per the HAL release, after the mandated ground testing, the prototype helicopter was built with ‘Segmented Pre-Cone MRBs’ and ‘Pre-Cone MRH’. 

HAL Dhruv to fit Indian Naval ship hangers with ease

HAL Dhruv is primarily built to cater to the Indian Army and Air Force needs, and these two services form the bulk of the HAL orders. The Indian Navy has just eight ALHs as Naval Utility Helicopter (NUH) (compared to 250 + orders from sister services) as they don’t fit the ship hanger very well. 

Indian Navy has to bear with the manpower and parts-intensive blade folding procedure on the helicopter, and multiple design modifications and adaptations to improve the procedure and folded width have failed to adhere to the naval specifications.

“The ALH takes more than 10 minutes to fold its blades where as the world standards is 10 minutes. ALH at present when we fold the four blades the maximum distance is 5.5 metres whereas the requirement of NUH is 3.5mts because of there stowage condition in the ships,” says Girish Linganna, a Defence & Aerospace analyst and Consulting editor – Industry and Defense at Frontier India.

In 2020, HAL put forward a ‘2-Segmented Blade’ idea to meet the Indian Navy’s requirement of the blade fold system on the 5.5-ton ALH naval variant.

ALH with 2-segmented MRB
ALH with 2-segmented MRB

As per the image released by the HAL, the blade is segmented into Root and Aerofoil portions and is joined by metallic fittings. The folding is accomplished by the extraction of one bolt of the metallic fitting attachment and rotating about the other bolt. The blades are then folded one below the other on either side due to the geometry of the metallic fittings. The blade folding process is hence simplified with reduced tools and timings.

Diagrammatic representation of 2-segment 4-blade folding on ALH. Image: HAL

The HAL release states that the Indian Navy and Coast Guard (ICG) have operated ALH for the last 18 years. But the ship deck-based operations of ALH have been limited because the stowage size required for ALH exceeds the hanger sizes constructed in Navy ships. With the introduction of the “segmented blade feature,” the folded length and width of ALH are reduced, making it consistent with the hangar space available on most Indian Navy ships. The time required for folding or unfolding operations is also reduced.

HAL has used the ‘2-Segmented Main Rotor Blade’ on the 3-ton Light Utility Helicopter (LUH), which has already received initial operational clearance (IOC). Indian Navy has not shown interest in the LUH project as its future plans exclude single-engine helicopters for shipborne use.

“The two-segmented blade adopted for the first time on the LUH rotor system offers a compact folded dimension. It can fold the blades within 7 minutes and can be used in aircraft carriers,” says Girish Linganna, adding that “if HAL has met the Indian Navy standards then NUH must have met the 7 minute folding and 3.5 m stowing.”

The modification is now due to flight trials aboard a naval ship where folding and unfolding is a regular activity. If the naval approval and certification are obtained, HAL can look forward to new orders for ALH naval variant. 

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