After one of the longest-ever groundings, Advanced Light Helicopters (ALH) of the Indian Navy (IN) are likely to resume flights in a phased manner with restrictions. Jan 5, 2026 marked one year to the fatal accident of CG 859 at Porbandar in Western India that killed two coast guard pilots and an aircrewman diver. The manufacturer Hindustan Aeronautics Limited (HAL) had recommended grounding the entire ALH fleet after preliminary analysis of the flight data recorder revealed the helicopter did not respond to pilot inputs seconds before impacting the runway shoulder.
Fatigue failure of NRSP
The Board of Inquiry (BoI) and Defect Investigation (DI) committee that were constituted to analyse CG859 accident localised the problem to a catastrophic failure at the non-rotating swash plate (NRSP). This critical component in the upper control circuit of the ALH transmits pilot control inputs to the four-bladed hingeless main rotor. Previous failures in the control circuit that caused major accidents were related to booster rods in the “collective” circuit. That was addressed by replacing the original control rods with stainless steel rods of a new design. CG859 was the first recorded case of catastrophic failure at the NRSP of ALH that caused the helicopter to lose “cyclic” control. There is no known method or flying technique to recover from such a failure in helicopters. As such, airworthiness certification requires that design, metallurgy and manufacturing process of such components ensure a fatigue life far in excess of the envisaged life of helicopter itself.
Strip examination reveals more NRSPs on the verge of failure
During the year long grounding, HAL undertook a fleetwide inspection of the Integrated Dynamic System (IDS) that houses most of the critical components in the ALH dynamic system and upper controls. Multiple cases of fatigue failure of NRSP were observed, primarily on the batch of brand-new wheel variant ALH Mark3 Maritime Role operated by the IN and ICG, while similar failure was not noticed in any other variant of the ALH, as per a former HAL official who headed the rotary design centre at Bengaluru. It is understood that the defective batch of NRSPs have since been withdrawn from all users, to be replaced by new Cat A NRSPs. While this has not been publicly acknowledged by HAL, findings of the DI committee on similar lines likely formed the basis for lifting the grounding of skid-variant ALH. Army and Indian Air Force which operate skid variant ALH resumed flying in May 2025, while IN and ICG frames continued to be grounded.
The most salient difference between IN/ICG ALH and army/IAF versions is the landing gear. Navy/CG operate the wheeled landing gear version of ALH whereas others predominantly use the skid variant. The 5.75-ton enhanced maximum all-up weight (MAUW) ALH Mk3MR that IN and CG inducted between 2021-23 have non-retractable, fixed wheel landing gear.
Could this have been avoided or predicted?
HAL is the singular repository of all developmental and usage data of wheeled variant ALH since year 2000. However, they have not revealed if the reduction in fatigue life of NRSPs by an order of magnitude could have been foreseen or predicted. This fuelled speculations around “usage pattern” of IN/CG ALH from HAL designers while independent analysts such as this writer opined it could be related to manufacturing process of a particular “batch” (extract of a previous blog post below).
“ALH have been operating with the IN and CG now for over 22 years with an accident-free record till IN 709 ditched off Mumbai. Syam’s hypothesis by itself is a damning indictment of the manner in which HAL has mapped fundamental user requirements, much less meet their operational expectations. Further, the 16+16 ALH Mk3MR supplied to IN and CG are brand new airframes with an order of magnitude lesser marine exposure compared to the Mk1s which were inducted early this millennium. Possibility of manufacturing/fabrication defects in the Mk3MR swash plates/NRSB that could have crept in while servicing an order for 32 helicopters post haste is the elephant in the room HAL seems to be unwilling to accept, much less address. Instead, specious arguments around usage pattern, maintenance and type of operation are being advanced at the topmost levels.”
Flight trials & unanswered questions
The DI committee and HAL designers in consultation with certification (CEMILAC), quality assurance (DGAQA) and IN decided to further investigate if unmapped loads on the dynamic system arising out of usage pattern and operating environment peculiar to the IN & ICG could hold the keys to the mysterious failure of NRSPs at extremely low cycle counts. For this purpose, fully instrumented flight trials were undertaken on a navy ALH Mk3MR jointly by HAL and IN test crew. This included ashore and afloat trials, including multiple deck landings in heavy seas (Jul-Aug 2025).
Informed sources indicate flight test results did not unearth any significant unmapped loads, raising questions why NRSPs which typically have a life running into tens of thousands of hours failed at a few hundred hours. It also remains unanswered why such failures were not detected in the older ALH Mk1 that have been flying for over 20 years, both afloat and ashore. With the available information in open domain, the needle of suspicion swings towards manufacturing process, testing or quality control of a particular batch of NRSPs that were fabricated in the 2018-19 timeframe. Unfortunately, three coast guard personnel had to pay with their lives for the system to correct itself.
Thankfully, the grounding and strip examination that followed CG859 accident detected similar failures across the ALH fleet before it could claim more lives. One hopes necessary course corrections have been instituted to ensure a more proactive approach and no more nasty surprises are in store. In a fairer world, compensation to families of victims, entire cost of grounding, instrumented trials, repair/retrofitment/replacement of defective components–all would be billed to the manufacturer. But in the system that obtains here, the user pays for the manufacturer’s oversight and negligence.
Cautious, stepladder approach advised
The resumption in flying is likely to follow a stepladder approach using brand new NRSPs with significant reduction in life while alternative pathways to improve fatigue life of the NRSP are explored. This may involve redesign, improved metallurgy & fabrication process (shot peening), etc. details of which are yet to be made public. Till such time lasting solutions are found, the ALH will continue to remain a maintenance nightmare with extremely conservative fatigue life on key components in the flight control chain. But a helicopter with restrictions is still better than no helicopter at all, as beleaguered military users would have realised by now.
A long journey to regain currency, proficiency and confidence in the machine now follows. Let us wish them the best.
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© KP Sanjeev Kumar, 2026. All rights reserved. An edited version of this story was first published by VERTICAL Magazine. You can access it here.
Views expressed are personal except where quoted, written with a view to raise awareness and contribute to flight safety. Feel free to debate and contribute to the discourse. Please keep the comments respectful and civil. I can be reached at realkaypius@gmail.com or on my X handle @realkaypius.
Sincerely hope that the right lessons have been learnt and the remedial actions are foolproof and long-lasting.
An excellent and informative article about the ALH. All I can say is that ‘elephant in the room’, apart, we need better management, honest acceptance publically by HAL and yes CEMILAC that when disaster strikes then a fairer open mind must take priority. Too often “blame” the operators, the aircrew and the maintenance system is not fair. Hope better sense prevails all around
CEMILAC AND DGAQA are two external agencies who does the certification during design and production phase . These agencies should have sufficient competence to carry out ,analyze and conclude detailed inspectrions and investigations, unfortunately that is not the case. These organizations should have ex- pilots,metallurgists as scientists and scientific officers. Mostly they are academic and incompetent ,barring a few.
Thanks for doing the job our compromised media refuses to do that is to bring out the harsh truth of system failure without any bias. Given the massive corruption prevalent in India, it is quite possible that this swashplate failure can be attributed to poor quality stuff being accepted from vendors for a few pieces of silver. That it wasn’t traced indicates failure to carry out mandatory inspections by quality control agency at HAL & certifying agencies like CEMILAC. To avoid recurrence of such catastrophes, the Navy should set up its own naval aviation design bureau & design it’s own aircraft. HAL can build them with the Bureau’s oversight. The idea may seem hare brained but the best designs are made by those who use them for a living.
Dear KP. Wonderful analysis. But in all this what is or was CEMILAC doing. Are they not responsible too. Apparently HAL has the elephant in the room, which only an independent CEMILAC can help remove.