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Russia’s new SU T-50 fifth generation fighter gets new engine and new name

Advanced fighter jet now being tested with new engine and being referred to as “SU-57”

Certain Russian publications have in recent weeks begun referring to Russia’s new fifth generation fighter – hitherto known as the “SU T50” (a designation designating a test aircraft) – as “SU-57”, suggesting that this may be the aircraft’s name when it enters service with the Russian Aerospace Forces.

This has not so far been definitely confirmed.  Moreover the name has a much higher number – “57” – than might have been expected.

Russian fighter jets are given numbers depending on their place in the sequence of aircraft designed by a design bureau that enter service.  Thus the “SU-7” of the 1950s is obviously an older aircraft than the “SU-27” of the 1980s, with the difference in the numbers indicating the number of designs the bureau – in this instance the Sukhoi bureau – has developed between the two aircraft.

This is not a rigid rule, and it is complicated by the fact that the Russians tend to use odd numbers for fighter aircraft with a crew of one and even numbers for aircraft with a crew of more than one, though this is not a rigid rule either.

As it happens we know that between the entry of the SU-7 into service in the 1950s and the appearance of the SU-27 in the 1980s the Sukhoi bureau designed and brought into service the following aircraft: SU-9, SU-11, SU-15, SU-17, SU-20, SU-22, SU-24 and SU-25.

The surprisingly large difference in the number used for the last Sukhoi fighter jet to enter service – SU-35 – and that allegedly used by the final version of the SU T50 – SU-57 – may indicate the great number of failed and abortive projects in which the Sukhoi bureau was involved during the crisis years of the 1990s and early 2000s, only some of which are known about.  However the reported name – “SU-57” – could be wrong, or – more plausibly – it might be an unofficial name used by the Sukhoi bureau, in which case the name the aircraft will eventually be given by the Russian Aerospace Forces might be completely different.

In view of this uncertainty I will stick to using the SU T50 designation for the time being.

What is beyond doubt is that the SU T50 is now about to start testing with its new engine, which is in fact its definitive engine which has been specifically designed for it.

There is very little information about this engine, with the Russians not even disclosing its proper name (the Russians refer to it in open publications as “item 30”).

What is however known about this new engine is that it is entirely new, that is the first completely new engine for a fighter jet designed in Russia since the USSR’s fall, that it has been developed by the Saturn Engine Design Bureau in Rybinsk (the design bureau responsible for all engines used by Sukhoi fighter jets since the 1950s) and that it is significantly more powerful than the AL-41F1 engine the SU T50 has been flying with up to now.

The AL-41F1 is in fact an advanced derivative of the AL-31 engine developed in the 1970s for the SU-27 fighter.  The SU T50 has up to now being flying with this engine because in a break with traditional Russian practice the Russians initiated development of the SU T50 some years before the new “item 30” engine was ready.

The new “item 30” engine is said to be far more powerful and far more efficient than the AL-41F1, as is to be expected of a wholly new engine having no connection to the AL-31/AL-41 family of engines which have their roots in the 1970s.

The best indication of how much more powerful and efficient the new engine is has been provided in a detailed description of the SU T50 provided by the official Russian news agency TASS.

This puts the thrust ratings of the AL-41F1 at 8,800 kgf and at 14,500 kgf when using an afterburner. By contrast the thrust ratings of the new “item 30” engine are put at 11,000 kfg and at 18,000 kgf when using an afterburner.

This is a very significant increase in thrust.  It is likely that the new engine is also significantly lighter and more fuel efficient than the older AL-41F1.

Apparently the SU T50 is already capable of supersonic flight with its current AL-41F1 engines even when they are being used without afterburner – what is known as “supercruise”.   Obviously the flight performance of the SU T50 will increase very considerably once it is powered by the new engine.

Recently there has been uncertainty as to the precise date when the SU T50 will enter service.

There are reports that on 23rd March 2015 Russian Deputy Defence Minister Yury Borisov visited the factory in Komsomolsk-on-Amur in Russia’s Far East where Sukhoi fighters are built and told the workforce that the Russian Aerospace Forces would delay entry of the SU T50 into service because the highly effective SU-35 and SU-30 fighters already in service and being built at the factory offered a more cost effective solution to their current needs.

Borisov is supposed to have said that the Russian Aerospace Forces would initially only buy one squadron of 12 SU T50 aircraft using the current AL-41F1 engine – to be delivered apparently next year ie. in 2018 – and would instead buy more SU-35s and SU-30s, with total orders for the SU-35 and the SU-30 being put at 98 aircraft and 116 aircraft respectively.

Full service entry of the SU T50, and large orders for the aircraft, would in the meantime be delayed until the “item 30” engine is ready, with all SU T50 aircraft entering front line service with the Russian Aerospace Forces using only this engine.

This makes sense.  It should not be seen so much as an economy measure – as most commentators suppose – but rather as a response to the earlier than expected availability of the “item 30” engine, whose development seems to have gone smoother and faster than expected.

Given the availability of the new engine and the dramatic improvement in performance it offers, it makes perfect sense to delay service of the SU T50 until the new engine is fully ready and is being produced in quantity.

In the meantime it also makes sense to build more of the current highly potent and fully perfected SU-35s and SU-30s rather than accept into service an incomplete SU T50 whose performance is compromised by use of the older AL-41F1 engine.

Apparently the plan now is for the SU T50 to begin entering service in quantity with the new engine in 2021 with the initial order being apparently set at 60.  The Aerospace Forces will use the intervening period to familiarise themselves fully with the new aircraft by working out on the test squadron of 12 which will be provided to them next year.

This is consistent with the conservative Russian approach, which in contrast to the US avoids pressing into service new aircraft or weapons systems before they have been fully perfected and all the bugs in them have been ironed out.

This approach is not only effective in performance terms – since it ensures that new aircraft and weapons systems are fully combat capable when they enter service – but has repeatedly been shown to be more cost effective as well.  Suffice to say that many of the US’s recent procurement disasters have been caused by the over hasty entry into service of advanced new weapons systems before their technology has fully matured, and before all the problems connected with them have been ironed out.

In the meantime all comparisons between the US’s F-22 and F-35 fighters and the SU T50 using its current AL-41F1 engines – which is to say nearly all of them – are now valueless since the SU T50 will not enter service with these engines.

A more valid point critics of the SU T50 programme can make is that the Russians are bringing their fifth generation fighter much later into service than the Americans.  Suffice to say that the F-22 Raptor’s entry into service was in 2005, whilst the SU T50 is not now expected to enter service before 2021.

This delay is the direct result of the massive disruption to Russia’s aerospace industry caused by the crisis of the 1990s and early 2000s.  The fact the Russians have only now successfully matched their fifth generation fighter with its definitive “item 30” engine – in stark contrast to their historic practice, which is to develop the engine first – is a reflection of this disruption, which their industry has only now finally overcome.

The one big advantage for the Russians from this delay is that their SU T50 fifth generation fighter will be a significantly more modern aircraft when it enters service than its closest US analogue: the F-22 Raptor.  As a result the SU T50 will be able to benefit from the very considerable advances in technology which have taken place since the first fifth generation fighter – the US’s F-22 Raptor – entered service in 2005.

I will finish with a video of the highly impressive flight display the SU T50 flight put on at the recent MAKS 2017 airshow in Moscow in June this year.  Note that the aircraft is flying with its current AL-41F1 engine.  What sort of flight display it will put on when it is flying with its definitive “item 30” engine one can only imagine

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