Tu-160 "White Swan"

Composites are strong but not 1:1 replacements for metal. Even the most recent ones are still too brittle. The use of composites in
wings proves nothing. Wing dimensions allow for more flex from even brittle materials. Compact objects requiring shear deformation
and other load related distortion may not do so well.

The vaunted weight savings with composites only apply if they are used conservatively. A multi-layer composite structure that
has the right range of load bearing and shear resistance characteristics may be much heavier than simplistic atomic weight
comparisons would imply. Seems to me like the center box section would be very heavy if made out of composites. So
why not use Aluminum?

It's important to note that metals (tempered steel especially) function basically as springs. They are good at absorbing energy.

If a metal takes enough force, it will start to deform, but it will keep its structural integrity up to a certain point past that

If a ceramic or whatever material takes enough force, it will simply crack and break

Composite materials are not some super material with no problems of their own.

Composites can have all sorts of problems including de-lamination and the fact that they suddenly snap without warning.

Being able to flex in one direction or another might be useful, but it also might not... I would guess a centre box section holding the mechanism for the wing sweep is something that needs to be very strong and relatively light.

If the original design in that regard works I don't see any reason to change it except to replace it with a more sophisticated fixed design that offers lift for takeoff and landing from reasonably sized runways but also low drag for high speed flight.

The Tu-160 is a big plane that already had composite materials in its design so improving those and also adding more should be a good thing but remember these things need to operate in arctic bases, so don't ruin the design.

GarryB wrote:Composite materials are not some super material with no problems of their own.

Composites can have all sorts of problems including de-lamination and the fact that they suddenly snap without warning.

Being able to flex in one direction or another might be useful, but it also might not... I would guess a centre box section holding the mechanism for the wing sweep is something that needs to be very strong and relatively light.

If the original design in that regard works I don't see any reason to change it except to replace it with a more sophisticated fixed design that offers lift for takeoff and landing from reasonably sized runways but also low drag for high speed flight.

The Tu-160 is a big plane that already had composite materials in its design so improving those and also adding more should be a good thing but remember these things need to operate in arctic bases, so don't ruin the design.

The box section experiences load distortions more complicated than any wing or fin. It is the juncture of the body and the wings so has
at least twice the number of bending and shear modes, and on top of that the full load of the wings and the body is riding on it. Showing off
with composites in this critical part is asking for trouble.

Showing off
with composites in this critical part is asking for trouble.

My thoughts exactly.

If they want to be super modern and ground breaking then creating a wing design that does not need to sweep to allow takeoffs from reasonable length runways, but also high dash speeds would be much more impressive...

There haven't been that many changes in wing design... taken to the very core... the straight wing of WWII like the Yak-3 subsonic planes was standard, with sweeping it back of the wing necessary as speeds approached the speed of sound as with the MiG-15 and 17. The MiG-19 achieved supersonic speed with a straight swept wing but with an extreme sweep which increased takeoff and landing speeds so the delta wing and tail surfaces of the MiG-21 tried to mix reasonable runway length with supersonic speed with a shorter runway... then they went for exotic solutions like solid rocket boosters to shorten takeoff run and of course lift jets for STOL and VSTOL, and at the same time swing wings. The swing wings prevailed but were not the ideal solution, which came in the form of the MiG-29/Su-27 wing and lifting body shape to allow short take off and landing with supersonic speeds.

In bombers they went from swing wing back to subsonic in the flying wing design...

Cold is not a problem for composites are they have been used for decades on planes that take off in 40C and operate at -40C.

Not all parts of an aircraft are subjected to outside temperatures in flight... the fact that the F-35 has problems operating in the cold in Japan suggests that operating in the Arctic at much much lower temperatures would be a serious problem...

I understand the west is happy to build enormous air conditioned and heated hangars for their planes... the Germans keep their tanks in tents to prevent them getting too cold too, but that is just not practical in Russia. They might be building the hangars but there are times when the aircraft will spend time sitting outside for whatever reason so they have to be able to take it.

If they had the wing box tooling available, I would agree, just build it. But since they don't and have to fully reconsider this structure, for 3 units a year composites, may offer an opportunity, or Al Li, or a combination of composites, alumunim and steel.

They have built a new factory to make Tu-160s from scratch which includes a forge to make the titanium centre structure. I would expect a forge that size will be able to be used to wield other materials as well... the justification for building it was because they are going to build another 50 odd Tu-160s and such a forge could also be used in the construction of the PAK DA as well... and I suspect a new MiG-41 might benefit from one piece large section Ti structures being formed in one piece...

Even steel has vastly improved in 40 years. Point is, replicating the old structure is just as, or maybe even more complex then just designing a new one from a clean sheet with the 40 years of additional knowledge they have.

Obviously they will revise the design.... if they didn't it would have been in mass production 5 years ago, but they needed to digitise the design and then upgrade it... they did it the way they did everything else... upgrade existing bits as far as possible while working on a major upgrade... and in the back ground work on the from scratch replacement... ie T-72 upgrades, T-90AM, and T-14.

Except with the White Swan you end up with Tu-160M, Tu-160M2, and PAK DA.

going through my photos and found this. the Tu-134UBL a Tu-160 crew training version, with Tu-160 nose cone, although i always found that the nose cone of the tu-22 and tu-160 vermy similar, and due to the size of the Tu-134 to me it looks more like a variant of the Tu-22 or vice versa.

When they talked about upgrades for their big bombers they often mentioned unification of as much as possible.

Part of that would include radar and engines, though that was only to replace the NK-25 in the Backfire with the NK-32 of the White Swan to improve commonality across the types... I don't remember reading about any plans for the NK-32 to be used on the Bear or anything....

They did talk about the self defence avionics suite and radar and weapons being unified though...

Links to a veritable treasure trove of Tu-160 info and photos, 551 pages in total (unfortunately in Russian but still their is plenty for mono-lingual types like me).

http://www.aviationunion.ru/Files/Nom_2_TU_1.pdf
http://www.aviationunion.ru/Files/Nom_2_TU_2.pdf

Big_Gazza wrote:Links to a veritable treasure trove of Tu-160 info and photos, 551 pages in total    (unfortunately in Russian but still their is plenty for mono-lingual types like me).

http://www.aviationunion.ru/Files/Nom_2_TU_1.pdf
http://www.aviationunion.ru/Files/Nom_2_TU_2.pdf

That book is incredible indeed

UAC about the new Tu-160M

https://zen.yandex.ru/media/id/5ddfbc8b9515ee00ac9e370a/belyi-lebed-letit-v-buduscee-5f4903d61a067118d6299e0e

Chinese praise the Tu-160: https://rg.ru/2020/09/03/kitajskoe-izdanie-nazvalo-bombardirovshchik-tu-160-hudshim-koshmarom-nato.html

The Kuznetsov NK-32 engine production capability was almost lost thanks to Yeltsin's comprador regime. One of the key reasons it was saved was that it was used
for the development of a gas turbine to propel LNG fuel locomotives.

The NK-32 has a hybrid design that is not a run of the mill jet engine. The wikipedia page on it is idiotic. Turbofans are not designed to operate at 20 km but the NK-32
can operate at such an altitude.

It looks like a derivative of the NK-32 will be used to re-engine An-124 cargo aircraft now that Motor Sich has been run into the ground by Banderatards and their NATzO
patrons.

kvs wrote:

The Kuznetsov NK-32 engine production capability was almost lost thanks to Yeltsin's comprador regime.   One of the key reasons it was saved was that it was used
for the development of a gas turbine to propel LNG fuel locomotives.  

The NK-32 has a hybrid design that is not a run of the mill jet engine.   The wikipedia page on it is idiotic.   Turbofans are not designed to operate at 20 km but the NK-32
can operate at such an altitude.  

It looks like a derivative of the NK-32 will be used to re-engine An-124 cargo aircraft now that Motor Sich has been run into the ground by Banderatards and their NATzO
patrons.  

Originally, but the PD-35 will likely supersede it in replacing the Motor Sich engines in the An-124 fleets. Will likely supersede them in the PAK-DA's, unless they decide to make them supersonic with thrust-vectoring down the road.

magnumcromagnon wrote:Originally, but the PD-35 will likely supersede it in replacing the Motor Sich engines in the An-124 fleets. Will likely supersede them in the PAK-DA's, unless they decide to make them supersonic with thrust-vectoring down the road.

The text (at least translated) is misleading, the idea is to create a high-bypass engine based on the NK-32, since its gas generator already has the needed size. PD-35 is way bigger.

I found the comment about some derivative being used for the An-124 a bit strange and people here have filled in the details. The D-18T does not resemble
the NK-32 in any fashion and any replacement for it would be starting from scratch. The PD-35 is supposed be based on a scalable design and would be
a high bypass turbofan so it make sense to use it instead of an NK-32 derivative.

The thing is that re-engining the An-124 is to basically replace the Orc engines... they don't need to be super powerful or super efficient... they just need to offer the right level of power and be Russian.

In the long term the PD-35 is actually too powerful... remember the Ukrainian engines being replaced are about 23 ton thrust engines, so replacing four 23 ton thrust engines with a total of 92 tons thrust, with either two PD-35s with 70 tons of thrust or four PD-35s with 140 tons of thrust does not balance... it will either be under powered or over powered.

Keep in mind that the 6 engined An-225 has 138 tons thrust so actually using four PD-35s on the An-225 would be a good plan as it reduces weight and complication by removing two engines but retains the thrust of all 6...

The NK-32 of the Blackjack has a dry thrust of something like 14 tons and full AB thrust of 25 tons... using AB on a transport simply does not make sense but it is a low bypass turbofan engine... so essentially changing the front fans to make them 2-3 times bigger means the rear hot turbojet section sucking through vastly more cold air would dramatically increase thrust but would reduce the exhaust velocity... in other words the thrust might be 25 tons thrust without afterburner but the engines would now be way to wide to fit inside a Blackjack and certainly would render the aircraft subsonic only even if they could be adapted to fit.

Essentially what they might be talking about is using the hot section of the NK-32 to drive a high bypass turbofan to get a quick simple 24-25 ton thrust non afterburning high bypass jet engine... wont have amazing performance but should be good enough to replace the Ukrainian engines.

They wont need to use it on anything else... it could be kept on An-124s and exported to other operators of the aircraft that also now can't get Ukrainian engine parts...

When the PD-35 is ready and other models like a PD-24 or whatever is needed they can put it on Slon and Il-106 type transports that will essentially eventually replace the An-22 and An-124 in Russian service... the replacement engines could be made for export too to support operators of the An-124 as well...

kvs wrote:I found the comment about some derivative being used for the An-124 a bit strange and people here have filled in the details.     The D-18T does not resemble
the NK-32 in any fashion and any replacement for it would be starting from scratch.     The PD-35 is supposed be based on a scalable design and would be
a high bypass turbofan so it make sense to use it instead of an NK-32 derivative.  

The An-124 (and probably also the new il-106) needs an engine with about 23-24 tons of takeoff thrust (but it could benefits of a bit more thrust, and in the past motor sich proposed a D18T modification with 25-26 tons of takeoff thrust).

The PD35 will  not be ready before at least 6 years and even if it is a scalable design the PD24 will be less of a priority, and will be available later. (They need anyway to design and test a new engine, even if they could save a bit of time by reusing the solutions from its smaller (PD14) and bigger brother PD35).

Concerning the NK32 derived engine, as it was mentioned in another thread, it should be in development already since several years ago and a variant of it should go on the Pak-Da subsonic bomber).
In a few articles from last year and from early 2020 also it was mentioned that such engine should start ground tests around the last quarter of 2020...

Another NK32 derived engine, called NK-23D should also be in development (or was proposed) and it is not clear how much commonality there is between this one and the Pak-Da engine.
It wouldn't need to be started from scratch anyway.

At least,  not the whole of the engine...

Well, if the core (in this case  IP and HP compressor, Combustor, and HP and IP turbine) is of the acceptable size, they need to probably upgrade a bit the materials and some minor redesign (to get some increase of operating temperatures for the HP compressor and turbine) and  probably some changes to the combustor as well.
A few stages must be added to the LP turbine (since it operates at a lower speed, having a bigger fan, and maybe also there they could introduce some new lighter materials (like intermetallic ti-al for LP turbine blades, probably already considered also for PD14 and PD35).

The fan needs of course to be completely new, going from a multi stage very low bypass fan (needed for supersonic speed) of the NK32 to a large single stage fan (maybe a scaled up version of the PD14 fan, if perm motors and Kutznetov exchange information)...

The only strange information (dated 2015) available in internet mentioned that, since they wanted to keep the same nacelle of the D18T, they will end up compromising the design and limiting the Bypass to a value of about 5,5 to1, the same as the old D18T, and with a specific fuel consumption slightly worse than the old D18T... but that does not make sense...unless we are talking about a solution that can be ready in a relatively short time and it is just a placeholder...

https://www.litmir.me/br/?b=547394&p=9

Anton Shatskiy, Deputy General Designer of OJSC Kuznetsov, said at a conference at CIAM that a unique turbine that can withstand long-term high-temperature conditions provides the NK-32 gas generator with a parametric and design reserve for creating a line of high-thrust turbojet engines on its basis for use on transport and passenger aircraft. The first in their series could be the NK-23D three-shaft by-pass turbojet engine with a thrust of 24 tf for the remotorization of the An-124 Ruslan heavy military transport aircraft.

According to Anton Shatskiy, “the task is to raise the An-124 aircraft with domestic engines in 2019,” but “if we are now talking about creating a scientific and technical reserve, carrying out research and development work,” then the creation of a new engine of this class may take 10 -15 years. Therefore, Kuznetsov offers an alternative solution - to make an engine for Ruslan with the maximum use of the already existing reserve for the NK-32 gas generator. At the same time, serious conditions are set for the engine specialists: “We must fit exactly into the dimensions of the D-18T nacelle, the nacelle must remain in the same length, approximately in the same mass, i.e. we have both geometric and constructive constraints, ”said Kuznetsov’s deputy general designer. Nevertheless, he believes that it is quite possible to meet such a tight deadline.


According to the presentation presented at the conference in CIAM, the NK-23D proposed for remotorization of Ruslans with a takeoff thrust of 24 tf (for the D-18T - 23.4 tf) will have a degree in cruise mode (height 11 km, M = 0.75) bypass 5.4 (for D-18T - 5.5) and specific fuel consumption 0.565 kg / (kgf • h) with a thrust of 5000 kgf. According to the official data of Motor Sich PJSC, the thrust and specific fuel consumption of the D-18T series 3 in cruising mode in the same conditions is 4860 kgf and 0.546 kg / (kgf • h).

Here it is not clear if this engine (NK23D)  will be related to the similar thrust engine in development for the Pak-Da or not....


It would be smarter to redesign the nacelle and allow the advantages of a higher bypass... in that case however this will mean that it will not be able to mount them in the existing an124 withoout modifying the pylons and the mounts as well...


By the way, if I am not mistaken Kuznetov has in the not so remote past, already did a comparable operation (but smaller in scale), when they improved the D30 engine with a bigger fan to increase a bit the bypass.

In another source they mentioned about a cruise SFC 0.570 lb/(lbf*h) for the D18T.

Unfortunately there are not many modern engine of this size with which to compare (only the Trent500 introduced in 1999), but if we take the latest generation, the best among the engine for narrow body airliners (takeoff thrust around 12-15 tons) have a cruise SFC of about 0,52 lb/(lbf*h) (for comparison the PS-90A has an SFC of about 0.595 lb/(lbf*h) and the IAE V2500 (western engine contemporary to the PS90) has a SFC of around 0,58 lb/(lbf*h).

If we go on the larger size, like the engine for the larger airbus and Boeing widebodies, with more than 40tons of takeoff thrust, we can find cruise SFC of around 0,48 lb/(lbf*h) .

If we interpolate we can imagine that an optimised latest generation high bypass turbofan for civilian use with a takeoff thrust of around 24 tons should end up having a cruise SFC between 0,5 and 0,51 lb/(lbf*h)

note

You have to compare cruise sfc (specific fuel consumption) if an engine with cruise SFC of another engine.

Sometimes takeoff SFC is reported instead, but if you do not pay attention the values could be misleading. Even if fuel consumption is much higher at sea level than at cruise altitude, the SFC is dependent on thrust, and the takeoff thrust is normally around 4 to 5 times bigger than the thrust at cruise level (the main reason is the higher air density at sea level).

The PAK-DA will be a high altitude aircraft like the Tu-160. So an NK-32 derivative engine makes total sense. It makes no sense for the An-124 which requires a high bypass turbofan without
any high altitude operational mode. As I posted the PD-35 is a target size of a whole class of engines that will include smaller thrust variants. Since the PD-14 is already certified, the "PD-35"
class is not that far off in the future so will overlap any re-engine need for An-124s. I just don't see how the NK-32 is a shorter path to a D18-T replacement, it will have to have every turbine and
"fan" stage totally redesigned.