Two potential high-thrust turbofan engines, the PD-24 and PD-26, are the subject of a significant debate within Russia’s aviation industry. Although neither engine has yet been officially launched as a serial production program, both concepts are becoming more common in the context of next-generation Russian aircraft initiatives. The display of models of the new Tupolev Tu-454 widebody with PD-26 engines compounded the discussion by associating the stretched Yakovlev MC-21-500 concept with the PD-24 class.
A basic industrial question is at the heart of the debate: should Russia consolidate all components into a single derivative of the larger PD-35 core, or should it establish separate engine families in the 24–26 ton propulsion class?
The fate of Russian civil and military aviation is greatly impacted by the response.
The Context: PD-14 and PD-35 Established the Foundation
The PD-14, which was mainly developed for the MC-21 program, marked the beginning of Russia’s modern engine roadmap. Russia’s first significant post-Soviet civil turbofan, the PD-14, served as the technological foundation for an entire engine family.
Following that, Russia escalated its efforts toward the substantial PD-35 program. As a 35-ton-class engine, the PD-35 was intended for the future widebody aircraft and potential replacements for aging heavy transport aircraft.
The PD-35 program is often referred to as a “gas generator platform” in Russian industry discussions, rather than a specific engine. Lower-thrust variants can be achieved by scaling down the gas generator, which is the engine’s heated core.
This is the exact origin of the PD-24 and PD-26 concepts.
What is the specific nature of the PD-26?
Russian aviation discussions are increasingly characterizing the PD-26 as a reduced-thrust derivative of the PD-35, which uses the same gas generator core. This relationship was explicitly mentioned in the most recent reporting regarding the Il-100 “Slon” large transport.
The PD-26 is guided by a simple logic. A complete 35-ton engine is excessive for many aircraft categories, and the PD-35 core is both extremely large and expensive. Russia could significantly reduce development costs and streamline logistics and production by decreasing the thrust output to approximately 26 tons while maintaining the same fundamental gas generator. This method would enable manufacturers to share turbine technologies, manufacturing tooling, maintenance infrastructure, and certification knowledge across multiple engine variants. Additionally, it would enhance economies of scale, as the cost of each engine is typically reduced as production volumes increase.
Consequently, it appears that the PD-26 is intended to serve as a strategic middle-ground engine, located between the PD-14 family and the massive PD-35. Russian designers may already regard the PD-26 as the preferable powerplant for future twin-engine widebody aircraft, as evidenced by the recent Tupolev Tu-454 widebody mockup, which features PD-26 engines, rather than the significantly larger and heavier PD-35.
This is a significant strategic indicator of the potential trajectory of Russia’s aviation industry.
The Importance of the Il-100 “Slon”
The entire debate is centered around the proposed Il-100 Slon.
The aircraft is currently under study as a potential long-term replacement for the Antonov An-124 Ruslan. Russian concept studies suggest that the payload targets are approximately 180 tons, and the intercontinental range capability is also indicated.
The Slon concept was initially linked to four full-scale PD-35 engines. Nevertheless, analysts promptly recognized that the use of four substantial 35-ton motors could result in severe economic and operational consequences. It is probable that the aircraft would become exceedingly costly to operate, maintain, and manufacture.
This realization paved the way for reduced-thrust derivatives, such as the PD-26 and potentially the PD-24.
There were some Russian experts who suggested that engines with a thrust of approximately 24 tons might be sufficient for a four-engine configuration. Nevertheless, this conclusion is the point at which the debate becomes more heated. The Slon program’s original strategic objectives would no longer be met by a four-engine aircraft with an estimated 24 tons of thrust per engine, according to critics. The intended 180-ton payload might not make it over a 7000-kilometer range by this aircraft, as indicated by various calculations that have been discussed in Russian aviation circles. In that scenario, the aircraft would be more akin to an enhanced An-124 than a genuine next-generation strategic airlifter.
This disagreement has resulted in the division of analysts into two opposing schools of thought.
One perspective is that Russia should prioritize the retention of higher-thrust engines in the PD-26 class and prioritize maximal military capability, as strategic airlift performance is more significant than operating economics. From this standpoint, the objective of creating a next-generation heavy transport aircraft would be compromised if payload or range were sacrificed to reduce fuel consumption.
The opposing viewpoint contends that Russia is unable to effectively fund an aircraft program that is both fuel-intensive and overpowered in light of the current industrial and economic circumstances. Advocates of this stance contend that lower-thrust engines have the potential to significantly reduce lifecycle costs while still delivering satisfactory performance in the majority of operational scenarios.
The debate bears a striking resemblance to the historical aviation disputes of the Soviet era, in which military ambitions frequently clashed with industrial realities and economic constraints.
So, what is the PD-24?
The PD-24 remains more enigmatic due to the fact that official information regarding it is exceedingly scarce.
Nevertheless, the PD-24 is now being more frequently associated with civilian aircraft in Russian aviation discussions, as opposed to military transports. The engine is most likely associated with medium-sized widebody aircraft programs and future stretched versions of the MC-21 family, according to the most credible speculation.
The MC-21-500 model, which is proposed with PD-24 engines, is of particular importance. The PD-14 is presently employed in the standard MC-21. Therefore, the introduction of a significantly larger PD-24 would result in a significantly more capable and heavier aircraft configuration. A market segment between traditional narrowbody aircraft and genuine long-range widebodies could potentially be occupied by such an aircraft.
This implies that Russia may be investigating an aircraft familial structure that is comparable to the strategies employed by Airbus and Boeing. In such a framework, the PD-14 would provide power to standard narrowbody aircraft, the PD-24 would support larger stretched civil variants, the PD-26 would serve medium widebody aircraft and transports, and the PD-35 would be reserved for exceptionally large aircraft and strategic heavy transports.
If this interpretation is accurate, the PD-24 may be a PD-26 that is significantly weaker. Rather, it may be optimized in a different manner, despite the relatively close thrust figures.
The Main Technical Distinction Between PD-24 and PD-26
The primary issue at hand is not just a disparity in thrust of two tons. The optimization philosophy that underpins each engine concept is the more critical concern.
It is probable that a PD-24 that is primarily intended for civilian aviation would prioritize reduced maintenance costs, extended service intervals, quieter operation, and a lower overall engine weight. Efficiency is of paramount importance to civil airlines, as their profitability is contingent upon the economics of fuel consumption and maintenance over thousands of flight cycles.
In contrast, a PD-26 that is designed for military transport aircraft or heavy widebody platforms may prioritize entirely different characteristics. Designers may prioritize the following: extreme reliability during overload situations, optimum takeoff performance, durability under harsh operating conditions, operation from less-developed airfields, and greater thermal margins.
Consequently, the two engines could conceivably coexist, although their thrust categories appear to be similar on paper. This would be comparable to the manner in which Western manufacturers create multiple engine variants based on a common technological foundation, while simultaneously optimizing them for specific purposes.
The Reasons Why Russia May Not Want Both
The most significant challenge to the concurrent development of both engines is likely not engineering capability but industrial capacity.
Russia is currently confronted with major challenges in the process of increasing the production of the PD-14 family. Production expansion efforts are still being impacted by manufacturing bottlenecks, supply chain constraints, and sanctions-related restrictions.
This reality is of paramount importance when discussing two engine programs that are wholly distinct within the same thrust category.
Simultaneously developing the PD-24 and PD-26 would necessitate separate certification campaigns, distinct nacelle designs, numerous testing programs, expanded supply chains, duplicated engineering teams, and additional manufacturing infrastructure. At a time when Russia’s aviation sector is already under duress, each program would require substantial financial and industrial resources.
In such circumstances, it may be economically unfeasible to introduce two engine families that overlap.
The Most Effective Argument in Favor of a Single Engine
The PD-26 is presently advocated for by the most compelling industrial argument.
The PD-26 seems to be in harmony with the broader PD-35 ecosystem, which is the reason for its compatibility. The PD-35 was designed as a scalable platform, as Russian industry discussions consistently underscore, rather than a single isolated engine. Russia could achieve significant economies of scale in production and maintenance operations if the PD-26 directly shares the PD-35 gas generator.
This commonality would facilitate long-term production planning and decrease research and development expenses. Spare parts inventories, maintenance training systems, turbine technologies, and manufacturing processes may be shared among various engine variants.
PD-24 could potentially become unnecessary in this scenario. Engineers could opt to de-rate the PD-26 electronically or mechanically for aircraft that necessitate less performance, rather than developing a distinct engine family. This method is strikingly similar to the strategies that are often used by Western engine manufacturers.
The Most Effective Justification for Maintaining Both
Nevertheless, there is a compelling argument in favor of maintaining both engines.
Civil aviation economics is the foundation of that argument.
A PD-24 that is exclusively designed for civilian airline operations has the potential to provide substantially improved fuel efficiency and lower operating costs than a de-rated military-oriented PD-26. Airlines evaluate engines on the basis of their long-term profitability, which encompasses fuel consumption, maintenance costs, reliability, and engine lifetime over thousands of operating cycles.
The priorities of military aircraft are significantly different.
However, a specialized civil-oriented PD-24 may still be strategically viable, despite the overlap in performance, if Russia genuinely intends to establish a competitive domestic widebody ecosystem or expand the MC-21 family into larger aircraft categories.
This is particularly critical due to the fact that Russian airlines are already grappling with challenging economic conditions, restricted fleet flexibility, and operational challenges associated with sanctions.
The Most Likely Result
At present, the most probable scenario is that only one engine family in this propulsion category will ultimately achieve large-scale serial production in the near-to-medium term.
The PD-26-class derivative, which is derived from the PD-35 core, is the most likely candidate.
The rationale is straightforward: the aviation sector in Russia is placing an increasing emphasis on the simplification of manufacturing through industrial consolidation. A scalable PD-26 platform has the potential to simultaneously power military transports, future twin-engine widebodies, upgraded Il-96 derivatives, and conceivably several other aircraft categories.
In the interim, the PD-24 is at risk of becoming excessively specialized unless a significant civilian aircraft program is formally initiated in conjunction with it.
Therefore, the debut of PD-26 engines on the most recent Tupolev widebody model may serve as an early indicator of the current inclination of Russian industry leadership.
The Debate’s Strategic Significance
The debate between the PD-24 and PD-26 is ultimately about much more than just engines.
It is indicative of the overarching objective of Russia’s aviation strategy following the imposition of sanctions.
Russia must choose between consolidating resources into a few scalable industrial platforms for multiple aircraft categories or developing many specialized aviation products with limited production volumes.
The PD-26 concept is an ideal match for the second approach due to its emphasis on industrial efficiency, scalability, and commonality.
The PD-24 is a more specialized approach that is designed to optimize civil aviation efficiency.
In the past, Soviet aviation commonly favored designs that were highly specialized and specifically designed for specific missions. Nevertheless, the economic realities, sanctions pressure, and manufacturing limitations of contemporary Russia are causing it to appear increasingly compelled toward industrial consolidation.
In the end, the industrial realities may ultimately determine the victor of the PD-24 versus PD-26 debate more decisively than sheer engineering performance.