J-15 carrier fighter thread

[Blitzo]

29940 kg = 20440kg (empty plane armed with 2xR-27 + 2xR-73) + 9500kg (full internal fuel tanks) . Theoretically , plane could takeoff in this configuration from 195m launch point , but I don't think Russians ever attempted that (could be wrong but there is no proof) . Btw , Su-33 with 4 AAMs would be standard scramble configuration .

33000kg = 19600kg (empty plane without missiles) + 9500kg (full internal fuel tanks) + 3900 kg (weapons) . Well , if you believe Su-33 could takeoff with that , then I have a bridge to sell you ...

Clearly you haven't been following the previous few posts at all, where it has effectively been shown that the Su-33 could take off with such loads.
From A Fomin's book, Su-33 could take off with 28 tons from 105m, and 32 tons at 195m, likely under no headwind. From the magazine, it corrobates A Fomin's stats implying that performance is attained at 0 knots headwind, and also says that with 25 knots headwind the Su-33 could take off with MTOW (33 tons) from all the positions.

So yes, I do believe Su-33 can take off with 33 tons from a ski jump, so I'll take a look at that bridge, thank you very much.

Mig-29K internal fuel is somewhere around 4450 kg (5670 l ) . Su-33 has 9500 kg (12100 l) .

Empty Mig-29K is 12700 kg , empty Su-33 is 19600 kg . Full fuel / empty weight : Mig-29K 0.35 , Su-33 0.48 . These are your proportions . I believe that Mig-29Ks engines are more efficient then Su-33s , therefore it needs less fuel - higher proportion of takeoff weight could be given to weapons .

What makes you think the Mig-29Ks engines are more efficient than Su-33s, and what makes you think that even if they are more efficient, that they would be more efficient to the point where it will effect the proportional load the Mig-29K can take off with at certain conditions.

And you still haven't clarified what you meant by Mig-29K having proportionally larger wings, which is what I was asking about.

As for lift , I would say on the first glance that Mig-29K body generates more lift (I could be wrong tho ) .

So basically you have no idea and you're eyeballing just like the rest of us. I can say that I think the Su-33 generates more lift, that its engines are more efficient, so it can take off with more proportionally relative to the Mig-29K. But I would have no proof for that, the same way you don't have proof for your claims.


Look, clearly it is impossible any of us to argue whether Mig-29K or Su-33 is more weight efficient at take off. That is the entire point I'm getting at.
We don't have the resources or the specs at hand to calculate or derive such conclusions.
That is why the only logical and reasonable stance to hold the null hypothesis, which is that both would have similar maximum take off weights proportions dependent on the conditions that both are taking off in.

 

[Totoro]

Issue I have with those scans is just what sort of magazine is that? are those their own calculations? or they got them from an official source? if so, which one?

While it can be just a simple mistake, notwithstanding to the numbers themselves, the inclusion of r77, kh65 and kh31 in the armaments list is highly suspicious. Contrary to some popular opinions online, there is no evidence su-33 was ever integrated with ANY guided weaponry save for r-73 and r-27. Also, looking at the timeline of its design and production, as well as the russian history through the 90s and 2000s where little to no investment was made anywhere, it's highly suspicious those weapons were indeed ever integrated on su-33.

while inclusion of headwind could indeed be one possible explanation - i offer another one: If the magazine numbers are by someone who knows his physics, while they may reflect true limits of the aircraft launches, they may not include safety margins. And those margins are something that operational su33 would always use in real world conditions. Loadouts and fuel quantities wouldn't be calculated on moment by moment basis, depending on where the wind blows, if it will turn away this minute or the next, will it add or substract from the ship's speed, whether the sea is relatively calm or it's causing ship to pitch and therefore possibly lower the objective angle of the ramp etc.

real world planning will always go on the safe side and use predetermined classes of fuel and armament loadouts. Even just a 10% safety margin (lets remember that usaf likes a 20 minute loiter time around base margin for their fuel allowance) would amount to 3 or so tons of difference.

On another note, we do know that taihang has some 5% more thrust than engines on su33 (and probably ones on j15). We also know there are bits of info about m1 variant of al31 being available or even ordered by chinese, and those are roughly the same thrust as taihang.

We suspect j11b is lighter than su27s, as per one jane's article. further differences in construction and newer, lighter electronics may possibly increase that still from the alleged 700 kg. coupled with stronger engine, some reengined j15 circa 2020 may quite plausibly be able to carry a whole ton of fuel/ordenance more.

 

[thunderchief]

Btw , one more thing about supposed 33 000 kg MTOW for Su-33 .

Max thrust from Su-33 engines is 2x 125.5kN = 251 kN . With mass of 33 000 kg , this would give acceleration of 7.61 m/s*s , disregarding friction and air resistance . If we take 195m takeoff length and round it to 200 m (to give us little bit more speed ) , exit speed would be something like 55.2 m/s = 199 km/h . Therefore , you would need very strong head wind to achieve minimal speed (in 240 - 250 km/h range , possibly more for fully loaded airplane)

If you repeat same calculation , but for 29940 kg , acceleration would be 8.38 m/s*s , exit speed would be 208 km/h , still a tight spot . And for 26000 kg (stated normal takeoff mass ) acceleration would be 9.65 m/s*s , exit speed 223 km/h . Calculate ship speed and headwind and you will get your answer about Su-33 capabilities

 

[Blitzo]

Issue I have with those scans is just what sort of magazine is that? are those their own calculations? or they got them from an official source? if so, which one?

While it can be just a simple mistake, notwithstanding to the numbers themselves, the inclusion of r77, kh65 and kh31 in the armaments list is highly suspicious. Contrary to some popular opinions online, there is no evidence su-33 was ever integrated with ANY guided weaponry save for r-73 and r-27. Also, looking at the timeline of its design and production, as well as the russian history through the 90s and 2000s where little to no investment was made anywhere, it's highly suspicious those weapons were indeed ever integrated on su-33.

while inclusion of headwind could indeed be one possible explanation - i offer another one: If the magazine numbers are by someone who knows his physics, while they may reflect true limits of the aircraft launches, they may not include safety margins. And those margins are something that operational su33 would always use in real world conditions. Loadouts and fuel quantities wouldn't be calculated on moment by moment basis, depending on where the wind blows, if it will turn away this minute or the next, will it add or substract from the ship's speed, whether the sea is relatively calm or it's causing ship to pitch and therefore possibly lower the objective angle of the ramp etc.

The rather specific nature of the stats (the full thing includes endurance for very specific missions such as CAP at various ranges, loiter, etc), makes me think they are not based on the author's own calculations.

I wonder if they might be sourced from original Russian stats (which is why the magazine uses Su-33 and russian munitions rather than J-15 and chinese munitions), possibly acquired from Ukraine with the original T-10K prototype SAC got their hands on? The real question is whether these stats are gained from tests or derived from stats.
The fact that Su-33 was never integrated with some of the weapons in question may be simply a matter of Su-33s being tested with dummies for those weapons, but they never got along to integrating them. Unfortunately that is an assumption on my part, and it is of course equally likely that the loadout stats are derived from known test results.

Unfortunately I'm not sure what the original magazine is. But it doesn't sound like the kind of stats someone outside of the industry can simply calculate, or indeed reveal, without some kind of consent.



As for safety margins, I make the assumption that safety margins are included, seeing as the previous stats are included with safety margins presumably intact as well. (And none of the loadouts exceed 33 tons, which is the claimed max safe take off weight from all three positions at 25 knots as well).


But what is your opinion on A Fomin's stats for 28 tons and 32 tons at 105m and 110m? Headwind or no headwind? My position is already pretty clear on this matter, and I use the magazine's similar conditions as a backup for my stance.

 

[thunderchief]

From A Fomin's book, Su-33 could take off with 28 tons from 105m, and 32 tons at 195m, likely under no headwind.

I dispute that with my own calculation above

What makes you think the Mig-29Ks engines are more efficient than Su-33s

They are new design , with some improvements in technology . Compare ranges of Mig-29K and Su-33 .

And you still haven't clarified what you meant by Mig-29K having proportionally larger wings, which is what I was asking about.

Wing loading . Mig-29K has lower wing loading .

 

[Blitzo]

Btw , one more thing about supposed 33 000 kg MTOW for Su-33 .

Max thrust from Su-33 engines is 2x 125.5kN = 251 kN . With mass of 33 000 kg , this would give acceleration of 7.61 m/s*s , disregarding friction and air resistance . If we take 195m takeoff length and round it to 200 m (to give us little bit more speed ) , exit speed would be something like 55.2 m/s = 199 km/h . Therefore , you would need very strong head wind to achieve minimal speed (in 240 - 250 km/h range , possibly more for fully loaded airplane)

If you repeat same calculation , but for 29940 kg , acceleration would be 8.38 m/s*s , exit speed would be 208 km/h , still a tight spot . And for 26000 kg (stated normal takeoff mass ) acceleration would be 9.65 m/s*s , exit speed 223 km/h . Calculate ship speed and headwind and you will get your answer about Su-33 capabilities

Do your calculations include the effect of the ski jump?

Add in the ski jump, combined with 25 knots of headwind (46.3km/h), and things start looking convincing.

And of course speed the only factor in a takeoff -- lift/angle of pitch is just as important. That's the entire point of the ski jump, to enhance the latter.

 

[Blitzo]

I dispute that with my own calculation above

Well I dispute your calculations with the stats above

I hope you understand which one I trust more. Your calculations, or stats from a book specifically written from an acclaimed Russian aviation historian.

They are new design , with some improvements in technology . Compare ranges of Mig-29K and Su-33 .

The modernized Mig-29K uses newer RD-33 variants.
A modernized Su-33 would use newer Al-31 variants as well.

Wing loading . Mig-29K has lower wing loading .

wing loading is less important when we consider overall (i.e.: body) lift.
Btw, that is one of the common rebuttals against why calculating J-20s supposed maneuverabiltiy based off wing loading is incorrect, because it ignores body lift.

 

[Totoro]

i have zero desire to argue here, but my position on fomin's info is "we dont know know for sure but if i had to pick, id pick those values as operational ones, meaning always at least a little headwind".

No special reason for that, it just sounds right and sounds sane and practical. Plus he talks about various loadouts for first launch positions, 26 to 28 tons, which again sounds like he's stating exact operational choices, not some theoretical limits. taking off with no headwind would constitute a theoretical take off in my book, i don't think that's ever operationally done. and even if it has to be done, in a situation where sea is calm, no wind, and ship's propulsion has broken down, the safety margins i talked about earlier may still allow for a take off, as there's no additional ship pitch or sudden wind gusts to be concerned about.

All that being said, a 20 kt headwind sounds about right as a safe, prudent operational condition. but as we know, if one adds a bit of real wind to it, it can go twice that. so theoretical loads of su33 may easely be a few tons more.

also, calculations that don't take into account whole part of the "virtual air-strip" after the ramp, that don't take into account drag (Even if it is a small part of it all) and don't take into account difference between installed and uninstalled thrust are meaningless.

 

[thunderchief]

Do your calculations include the effect of the ski jump?

Add in the ski jump, combined with 25 knots of headwind (46.3km/h), and things start looking convincing.

And of course speed the only factor in a takeoff -- lift/angle of pitch is just as important. That's the entire point of the ski jump, to enhance the latter.

Ski jump effectively lengthens the deck . You have velocity vector pointing slightly upwards and then it moves downwards toward horizon . Therefore , by the time it goes parallel with horizon (as on carrier without ski jump ) you would accelerate a bit more . You could compensate effect of ski jump by adding few more meters to actual length of the deck . You may use around 300 m instead of 200 , for a angle of 20 degrees and speed of 200 km/h . For a 33000 kg load that would give you 243 km/h . But bear in mind I didn't calculate effects of friction and air resistance , and I assumed that engines give maximum stated thrust . As Totoro said , you need safety margins

 

[Blitzo]

Ski jump effectively lengthens the deck . You have velocity vector pointing slightly upwards and then it moves downwards toward horizon . Therefore , by the time it goes parallel with horizon (as on carrier without ski jump ) you would accelerate a bit more . You could compensate effect of ski jump by adding few more meters to actual length of the deck . You may use around 300 m instead of 200 , for a angle of 20 degrees and speed of 200 km/h . For a 33000 kg load that would give you 243 km/h . But bear in mind I didn't calculate effects of friction and air resistance , and I assumed that engines give maximum stated thrust . As Totoro said , you need safety margins

These calculations are entirely arbitary. How can we say say that a ski jump angle of 20 degrees can be equated to an extra one hundred meters on take off??

Furthermore, do any of us know what the take off speed for a fully loaded Su-33 is anyway? Because if we dont' even have that number then any other half assed calculations won't have anything to compare with in the first place.

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Basically what I'm saying is all the calculations so far are more or less meaningless.