New Delhi The military has started clearing the advanced light helicopter Dhruv (ALH) for urgent flying missions in batches after comprehensive safety checks to keep itself operationally ready, but routine sorties are still no-go after the indigenous multi-mission chopper was grounded following three incidents in less than two months earlier this year, officials aware of the matter said on Tuesday.

Most ALHs operated by the armed forces were grounded for checks after the recent incidents -- including the crash-landing of an army helicopter in Jammu & Kashmir’s Kishtwar on May 4 in which a soldier was killed, and two pilots were injured -- raised serious safety concerns. The pilots reported a technical fault to the air traffic control before the incident.

New Delhi The military has started clearing the advanced light helicopter Dhruv (ALH) for urgent flying missions in batches after comprehensive safety checks to keep itself operationally ready, but routine sorties are still no-go after the indigenous multi-mission chopper was grounded following three incidents in less than two months earlier this year, officials aware of the matter said on Tuesday.

Most ALHs operated by the armed forces were grounded for checks after the recent incidents -- including the crash-landing of an army helicopter in Jammu & Kashmir’s Kishtwar on May 4 in which a soldier was killed, and two pilots were injured -- raised serious safety concerns. The pilots reported a technical fault to the air traffic control before the incident.

The directorate general of military operations on May 22 wrote to different command headquarters about the restoration of flying of the ALH Dhruv, Rudra (the armed version of ALH) and the light combat helicopter (LCH). The Indian Air Force’s latest LCHs were also grounded earlier as they inherit several features of the ALH.

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“ALH and LCH hepters are op endorsed to be cleared for op emer flg (operational emergency flying),” the letter stated. “Op endorsed” here refers to helicopters that have been cleared in servicing and certified fit to fly, one of the officials cited above explained, asking not to be named. To be sure, it is not uncommon for an aircraft fleet to be grounded for inspection after an unexplained crash or incident.

The DGMO letter accessed by Hindustan Times lays down two pre-conditions for restoring emergency flying.

It says such resumption of flights will follow the prescribed “satisfactory conduct of independent maintenance flight safety audit” of critical items and systems, and compliance with safety-related “special technical instructions and alert notices” issued by the technical authorities. The two directives were issued after the May 4 crash, said a second official, who also asked not to be named.

The DGMO instructions only talk about the resumption of critical operational missions. “This operational flying includes air maintenance (cargo transport to forward areas), casualty evacuation and other missions to support forward deployments. Training sorties are, currently, not on,” one official said, asking not to be named.

HT reported on May 10 that a design review of a “safety-critical system” on the ALH may be in order, according to a top government regulatory body responsible for the certification of the airworthiness of military aircraft. The Bengaluru-based Centre for Military Airworthiness and Certification (CEMILAC) wrote to the three services and the coast guard about this on April 23. It has ordered the design review of the booster control rods to improve the ALH’s airworthiness.

The call for the design review follows the ALH’s troubling safety record. In the past five years, it has been involved in 12 accidents.

The design review is critical as the Indian armed forces operate more than 330 twin-engine ALHs, designed and developed by state-run aircraft maker Hindustan Aeronautics Limited. HAL began delivering these helicopters in the early 2000s.

CEMILAC, which functions under the Defence Research and Development Organisation (DRDO), reached the conclusion that the design review of the booster control rods is mandatory after an expert committee, formed in the backdrop of a navy ALH ditching (emergency landing in water) into the Arabian Sea on March 8, explored the possible failures that led to the incident. These rods allow pilots to control the helicopter’s motion, and any failure can severely affect power input to the rotor blades and cause accidents.

The committee, constituted by the CEMILAC chief executive (airworthiness), found that the most probable cause of the navy ALH incident on March 8 was a technical failure -- an error in the assembly of serrated washers in the booster control rods. It recommended short and long-term measures to enhance the safety of the ALH.

The design, development and qualification of the steel booster control rods that are tolerant to assembly errors shall be expedited, and the compliance of the new design shall be aimed for implementation in six months to one year, CEMILAC wrote in the letter dated April 23 to Hindustan Aeronautics Limited (HAL), the three services, and the coast guard.

“Though the helicopters are matured from the design point of view, having been exploited for more than 3 lakh hours, still there is scope to review the design/lifting aspects of the safety-critical system by an expert committee as a long-term measure,” said the letter, written by CEMILAC director (helicopters and missiles) DM Isack.

CEMILAC prescribed measures for the resumption of ALH and LCH operations.

Clearance for both platforms, limited to 100 flight hours each, will be given after mandatory inspections, it said. Further clearance for up to 500 flight hours or one year, whichever is earlier, will be based on the successful completion of two critical tests by HAL, it added. These tests involve the flight testing of two helicopters with instrumented control rod assembly for verifying the multi-axis loads on the control rods, and the fatigue testing of the rods with correctly assembled serrated washers to confirm their original capability.

“It is critical to fix the flaws on the ALH as there are flight safety implications. It plays an important operational role and India operates a large number of ALHs. Also, there are many potential foreign customers who are watching the helicopter closely,” Air Marshal Anil Chopra (retd), director general, Centre for Air Power Studies, said while commenting on the CEMILAC findings.