India’s Dhruv chopper needs critical safety upgrade: Panel

A government regulatory body has called for a design review of a "safety-critical system" on the Dhruv advanced light helicopter

A design review of a “safety-critical system” of the Dhruv advanced light helicopter, involved in a string of accidents including one last week, may be in order, according to a top government regulatory body responsible for the certification of the airworthiness of military aircraft.

An Indian Army Dhruv ALH

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 a “safety-critical system” on board the India-made helicopter by an expert panel to improve its airworthiness even though the helicopter has a stable and mature design, officials familiar with the matter said on Tuesday, asking not to be identified.

The call for the design review comes on the back of the ALH’s troubling safety record. In the past five years, it has been involved in 12 accidents. The army grounded its ALH fleet for a comprehensive safety check after a helicopter crash-landed in Jammu & Kashmir’s Kishtwar on May 4, killing a soldier and injuring the two pilots. The helicopter is operated by the army, air force, navy, and coast guard.

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, the officials said.

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.

Most of the military’s ALHs are currently grounded for comprehensive checks after the string of accidents. The Indian Air Force’s latest light combat helicopters (LCH), which inherit several features of the ALH, were also grounded, the officials said.

The regulatory body has red-flagged the drastic reduction in the fatigue life of the rods, the officials said.

The design review is critical as the Indian armed forces operate more than 300 multi-role ALHs, designed and developed by state-run aircraft maker Hindustan Aeronautics Limited. HAL began delivering these helicopters in the early 2000s.

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, said one of the officials cited above.

It has recommended short and long-term measures to enhance the safety of the twin-engine ALH, Hindustan Times has learnt.

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 a letter dated April 23 to 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 April 23 letter accessed exclusively by HT. It was written by CEMILAC director (helicopters and missiles) DM Isack.

The CEMILAC-constituted committee’s finding related to the malfunctioning of the booster control rods on the navy ALH is in line with the failure analyses done by Council of Scientific and Industrial Research-National Aerospace Laboratories (CSIR-NAL), Bengaluru, and HAL’s Rotary Wing Research & Design Centre (RWR&DC), said a second official, who also asked not to be named.

“The drastic reduction in the fatigue life of the control rod with wrongly assembled serrated washers has been verified experimentally at RWR&DC, HAL as part of the committee’s investigation,” the letter said.

A coast guard and an army ALH were involved in accidents after the March 8 navy incident. The coast guard helicopter made a forced landing in Kochi on March 26, followed by the precautionary landing by the army ALH on May 4 in Kishtwar.

On May 4, the pilots reported a technical fault to the air traffic control before the incident, which led to the army suspending ALH operations for the second time in less than two months.

The three services grounded their ALH fleets for safety checks after the navy ALH ditched into the sea following unexplained loss of power. The navy choppers are still grounded, while IAF is clearing its ALHs for flying in batches after the mandatory checks. The army had resumed ALH operations a few weeks before the May 4 crash landing after which it grounded the helicopter again.

The LCH, inducted last October, was also grounded. It is capable of targeting enemy air defences, slow moving aircraft, high-altitude bunkers as well as carrying out counter-insurgency operations.

CEMILAC has 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, the officials 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, they said.

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, the officials said.

The top regulatory body has also called for evolving an accelerated life testing (ALT) methodology to pinpoint any other potential failure modes and to assess the life of the ALH’s integrated dynamic system (IDS), the officials said. The main gearbox, upper controls and rotor head as a single unit is called IDS.

“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,” said Air Marshal Anil Chopra (retd), director general, Centre for Air Power Studies.

A defence ministry spokesperson declined to comment on the design review.

The armed forces grounded their ALH fleets last year too after an army Rudra helicopter (armed version of Dhruv ALH) crashed in Arunachal Pradesh in October 2022, killing all five personnel on board.

To be sure, it is not uncommon for an aircraft fleet to be grounded for inspection after an unexplained crash or incident.

The Dhruv ALH is a multi-mission helicopter in the 5.5-tonne class.

ALH operations have been hit in the past too -- the helicopters were grounded in 2006 following tail rotor problems, and later again in 2014 after a fatal crash.

The July 2014 crash, which left the chopper’s seven-man crew dead near Sitapur in Uttar Pradesh, was one of the worst crashes involving the helicopter. The aircraft involved had logged only two hours of flying after being serviced at Bareilly.

In another incident, former Northern Army commander Lieutenant General Ranbir Singh and eight others were injured in a crash in the Poonch sector in October 2019.

The grounding of the ALH comes at a time when HAL is looking at tapping the export potential of the chopper. It is currently in talks with the Philippines for a possible order. In 2015, Ecuador unilaterally terminated a contract with HAL after four of the seven ALHs it bought from the Indian firm were involved in crashes.