ALH to be grounded for 3 more months

The military’s Dhruv advanced light helicopter (ALH) fleet, which was grounded nearly three months ago following a fatal crash in Gujarat, will stay out of action for at least three more months with investigators struggling to determine the root cause of the accident in which two Indian Coast Guard pilots and an aircrew diver were killed, officials aware of the matter said on Tuesday.

Hindustan Aeronautics Limited (HAL), which has designed and developed the ALH, has broadened the scope of the ongoing investigation by involving Bengaluru-based Indian Institute of Science (IISc) to perform fatigue testing of a critical part in the twin-engine helicopter’s transmission system to get to the bottom of the matter, the officials said, asking not to be named.

The prolonged grounding of the workhorse fleet is a setback for the three services and the coast guard who together operate around 330 ALHs. Military helicopters such as Mi-17s, Chetaks and Cheetahs are overworked because of the ALH’s grounding, HT has learnt.

A high-powered panel found that a swashplate fracture caused the coast guard ALH crash at Porbandar in Gujarat on January 5, but a question mark hangs over the reason for the breakdown of the critical component that compromised the ability of the pilots to control the helicopter’s motion.

A fleet-wide inspection conducted after the crash has revealed that some navy and coast guard ALHs are facing the same problem — cracks in the swashplate assembly — and this could be linked to sustained operations in a saline environment, said one of the officials cited above. In recent discussions among stakeholders, some people proposed that the army and Indian Air Force (IAF) helicopters could resume flying but the suggestion was shot down factoring in safety concerns.

“HAL has provided IISc with the raw material — essentially an aluminum alloy — that the swashplate is made of. It is carrying out tests to determine the material’s ability to withstand loads in different operating conditions. Once that report is in, we will know whether it was a material failure or something else,” the official added.

HT was the first to report on February 4 that a detailed analysis by the Council of Scientific and Industrial Research-National Aerospace Laboratories (CSIR-NAL), Bengaluru, pointed to a swashplate assembly failure.

IISc is expected to submit by April-end its report to the defect investigation committee (DIC) formed after the crash, said a second official. The committee was set up to find out what caused the material failure and how to address it to achieve safe flight operations. It consists of officials from the Bengaluru-based Centre for Military Airworthiness and Certification (CEMILAC), the Directorate General of Aeronautical Quality Assurance and HAL.

“The DIC will incorporate the IISc’s findings into its report, which is likely to be submitted in May. It will take at least another month to carry out fleet-wide checks and fix the problem. How fast the ALH fleet can return to service will also depend on whether the checks can be carried out on the field or the integrated dynamic system, including the transmission system, gearbox and rotor hub, of each helicopter will have to be brought to HAL,” a second official said.

The fleet could stay grounded way beyond three months if the problem turns out to be more than a material failure — a design issue, said a third official.

The ALH underwent a design review followed by a replacement of a defective control system only in 2023-24. The ALH’s armed version Rudra was also grounded after the January 5 crash. The army and the IAF account for more than 90 Rudra helicopters. The ALH has been involved in around 15 accidents during the last five years, putting the spotlight on its troubling safety record.

The coast guard suspended ALH operations following an accident last September when a helicopter crashed into the Arabian Sea near Porbandar. Then too, two pilots and an aircrew diver were killed. The grounding was for a one-time check. The three services did not ground their fleets then.

The coast guard cleared the helicopters for flying a few weeks later, after a safety inspection involving HAL, CEMILAC and all coast guard units. Last September’s accident, too, came after the design review that culminated in a critical safety upgrade on the ALH fleet, initiated by HAL. It involved installing upgraded control systems on the helicopters to improve their airworthiness. The comprehensive design review came after the ALH fleet was grounded several times in 2023 too after a raft of accidents called into question its flight safety record.