Why IAF Retained AL-31FP Engines for Su-30MKI Fleet Despite Superior Thrust AL-41F Offer from Russia? Logistics and Training Main Factors

In a decision with significant implications for the Indian Air Force (IAF), India has opted to retain the existing AL-31FP engines for its fleet of 84 Su-30MKI fighter aircraft, declining an offer from Russia to upgrade them with the more advanced AL-41F engines.

While the AL-41F offers superior thrust and improved Mean Time Between Overhauls (MTBO), the IAF's choice reflects a prioritization of logistical efficiency and training continuity.

An official from Hindustan Aeronautics Limited (HAL) confirmed that the decision to stay with the AL-31FP engines was primarily driven by the IAF.

Despite the AL-41F's proven compatibility with the Su-30MKI platform, as demonstrated by the Russian Air Force's transition to these engines on their Su-30SM aircraft, several factors influenced this decision.

Over the years, HAL, in collaboration with the Gas Turbine Research Establishment (GTRE), has successfully addressed early technical issues with the AL-31FP engines.

Furthermore, HAL has achieved the capability to manufacture these engines domestically from raw materials, enhancing India's self-reliance in engine production.

Logistical considerations also played a key role in the IAF's decision. While the AL-41F shares some commonalities with the AL-31FP in terms of service ground tools, transitioning to the new engine would necessitate significant reskilling of ground crew for maintenance and repairs.

Additionally, the higher thrust of the AL-41F could alter the flight dynamics of the Su-30MKI, requiring pilot reorientation and potentially new training modules.

Ultimately, the IAF chose to avoid the additional costs and time associated with transitioning to a new engine type, especially when the existing engines have been effectively localized and improved.

By sticking with the AL-31FP, the IAF can leverage its established supply chain and maintenance ecosystem without significant disruption.

However, this choice means forgoing the potential performance enhancements offered by the AL-41F, including increased thrust and engine longevity. The Su-30MKI, a cornerstone of the IAF's fighter fleet, will still undergo upgrades to become the "Super Sukhoi," but these will focus on avionics, radar systems, and weapon integration rather than a change in propulsion.

This decision reflects a strategic balancing act between technological advancement and operational continuity. The IAF has prioritized minimizing disruption to its existing infrastructure and expertise, even if it means forgoing potential performance gains.

 

[Rajesh]

Thrust might be a bit more than AL-31, but the reliability of AL-41 over AL-31 must have promoted the IAF to stick with AL-31, and they might be waiting for the new AL-51, which is still under development. A lot of talks on these things will be going on which will not come out in the media, and we will have to wait a bit more, especially when talks with the West are still going on as usual.

 

[Anant]

There are additional important reasons for this preference. India already purchased ToT of AL-31FP engines, but AL-41FP requires repurchase at an additional cost. Also, the improvement in the new engine is just about 10%. Paying 100% additional cost for such low improvement is detrimental to indigenization.

Additional enhancement should have been by increasing or reducing size significantly to alter performance or heat signature in a significant way. Also, India attained new technologies for stealth which can be added, thereby reducing the dependency on weight-to-thrust ratio for stealth and instead can comfortably take up higher weight/size engines.

So, putting additional cost on AL-31FP related engines with a higher size by simply scaling up with an additional size increase in critical components with super alloy metals. Importing these kinds of things, either from Russia or others, and developing a new engine similar to the AL-31FP engine could make Indian rights on the product more than how much Russia can have.

When HAL already acquired almost 100% to create AL-31FP engines and is capable of scaling up, design skills can easily create new engines with three times the thrust if size is ignored a little. This can lead ahead in looking at hypersonic variants of aircraft, either with or without a pilot.

Um, you can't just scale up or scale down an engine in size and get a commensurate increase or decrease in thrust, heat signature, etc. Doesn't work that way, and there is far, far more nuance involved in it.

Regardless, as it stands today, we cannot build a new AL-31FP solely by ourselves even if we had the raw materials handy. Russia still provides some subcomponents we can service (which technically indigenises them as per the government's definitions) but cannot manufacture. Therefore, the question of having a larger share of (or complete) IP rights over an engine developed from the AL-31 is difficult to answer, since developing such an engine to begin with is not exactly straightforward.

 

[Anant]

Any aeronautical engineer here on this blog to let me know if the AL-31FP themselves can't be improved, obviating the need for on-paper technically superior engines?

I am not an aeronautical engineer by training, but I do know for a fact that there is only so much you can do to any engine to improve various aspects of performance before you fundamentally need to change it.

For instance, the Kaveri, in its present form, can, atleast in theory, manage between 75-80 kN of thrust depending on the kind of afterburner you integrate. Said integration would impact a number of performance parameters too. However, in order to get something like 90 kN of wet thrust, you essentially need a new core in the engine, which is a fundamental change.

Similarly, to bring massive changes in engine life would necessitate changes in the materials used, which will again affect the engine enough for major modifications to be required.

 

[Varaaah]

Good decision. Russians want to make useless the expertise India gained with the AL31. Russians will make less money so they push for the AL41.

 

[Sentoki]

The most important upgrade needed for the Super 30 program, which is not being considered, is the use of composite panels and engine radar blockers. Composite panels combined with RAM coatings and engine radar blockers or S-ducts can go a great way in significantly reducing the RCS of the Su-30 and bringing it in line with the Rafale, which will really make it a potent aircraft for years to come.

This is exactly what China has done with their recent J-16 upgrade.

As usual, IAF, DRDO & HAL are going for the lowest of low-hanging fruits like avionics, radar, etc., and will be chest-thumping about a "significant 5th-gen" upgrade when it will be far from the truth.

 

[RG]

Smart decision, hopefully, DRDO can improve the efficiency of this engine using the talent pool in the country and help expand the talent pool in the country.

 

[Avada kedavra]

They haven't provided even 50% of ToT for AL31, and you think they will provide 80% ToT for AL51? 🤣🤣🤣Only West can provide real ToT to India.

You are joking right?
It was the wests reluctance for ToT that lead india towards the soviet union in the first place.
Apart from russia the main military suppliers to india is france israel and UK.
None of these 3 ever gave any ToT. Majority of their systems were purchased off the shelf just coz of their sheer superior quality over the russian junk.

 

[Avada kedavra]

Increased thrust requiring new training modules sounds like BS to me. They are not telling the real reason. Western sanctions. Their arrogance and sense of grandeur won't allow them to accept this.