The T-50 (PAK-FA) Thread

[PAKFA]

[PAKFA]

[PAKFA]

[PAKFA]

[aaron886]

I'm sure it was exciting in the cockpit. Looks like he was up at a pretty good clip at time of failure. Probably a long runway, but still some of the most tense moments in aviation happen on takeoff roll.

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airliners should really have chutes

[Vekkinho]

Runway was wet on sunday, perhaps engine had too much to drink that day.

[RvETito]

airliners should really have chutes

 

They have waaay more effective devices to stop them on ground such as thrust reversers, ground spoilers and very effective brakes. I've been on board on a 737 during test flight few times and part of the flight was a real rejected take-off. I can tell you one thing - it kicks bad, you and the airframe. But it stops like a b.tch.

[Sov13t]

What does it need 2 exhausts for?

 

АЛ-31 series engines use "turbostarters" to spool up the turbines, they are located on the engine itself and each engine has an independent turbostarter...

 

It would be my guess that the АЛ-41 [117S] that is installed on the T-50 uses the same approach.

 

Picture here: http://koavia.com/gtde.htm

[aaron886]

Strange approach... I suppose it increases readiness time but I find it hard to believe even if both engines could be started simultaneously that the jet would not still have to wait just as long for other systems to start up.

[Sov13t]

Strange approach... I suppose it increases readiness time but I find it hard to believe even if both engines could be started simultaneously that the jet would not still have to wait just as long for other systems to start up.

 

Both engines can definitely be started simultaneously (procedures outlined in 27 manual), of course in scramble type situations only.

 

Otherwise left first - right second as it will be easier to pinpoint faults in systems should one of the engines throw a malfunction.

 

Now, the exhausts on the 27 are located differently... so I could be wrong with the PAK-FA location... but they look rather convincing [to me at least].

[Frostiken]

what inlet design? what exactly do you think is problematic?

The inlets are straight "box" style with exposed engine fanblades. First, the duct itself is making a nice big flat reflective surface from the sides, but most importantly...

 

Engine fan blades are the single most obvious reflector of radar energy from the front and rear aspects of an aircraft. Due to the fact that radar waves bounce you can get some feedback at angles off of them too.

 

The F-117A had special screens fitted over the ducts to try to reflect most of the radar energy away from the fanblades, while on the B-2 they're hidden deep inside. Both of these aircraft also have their exhausts inside the airframe itself to both serve to hide the fanblades as well as diffuse the hot gasses to present a smaller IR profile.

 

The F-22 and the F-35 have very obvious serpentine-shaped ducts (the F-35's inlet duct is incredibly short and uh... yeah, Crew Chiefs are going to *hate* jumping tubes on that thing) to hide the fanblades from front-aspect radar acquisition, and while the F-35's engine is hardly stealthy from the back, the F-22's thrust vectoring nozzles were designed to minimize the RCS from the rear.

 

In the case of this Russian beast it has no such features. I can swallow that new engines may be bolted on, but you can't just redesign that inlet duct. If that thing is flying towards you, you *will* see it.

[Vekkinho]

I second that, I've seen T-50 over at MAKS and to be honest it just proved my doubts.

 

Current engines used, be it -31 or -41, are huge radar/IR beacons. I saw the compressor blades spinning as she taxied in front of public.

 

"True stealth" engines of the future simply ask for nacelle redesign, pretty much most of the fuselage needs redesigning in order to fit new curved inlets.

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@Frostiken

Just what I wanted to hear :D

 

I was under the impression that it was something that requiers huge math models to simulate, and hours of lab testing to plot reflection grahps.. I even hear something about a thousand page book on how electromagnetic waves interact, worthy of a Nobel prize. Yet some people are just naturally gifted :) I am so amazed by this that... well, you can see my signature ;)

 

Thrust [sic] me, it's not that simple.

[Pilotasso]

The nacelles themselves are reflectors from the side aspect. The final model should be more angular instead of having tubular shaped nacelles. S-shaping will be a challenge at the very least. They will have to make huge compressor blockers to compensate for this, and all that it implies for loss of power.

Edited August 30, 2011 by Pilotasso

[GGTharos]

You don't need to read a 1000-page book on any sort of physics to determine that where there's smoke, there's usually a fire.

 

I think the better thing to say here is that this is a demonstrator and not the finished product.

 

@Frostiken

Just what I wanted to hear :D

 

I was under the impression that it was something that requiers huge math models to simulate, and hours of lab testing to plot reflection grahps.. I even hear something about a thousand page book on how electromagnetic waves interact, worthy of a Nobel prize. Yet some people are just naturally gifted :) I am so amazed by this that... well, you can see my signature ;)

 

Thrust [sic] me, it's not that simple.

[4c Hajduk Veljko]

Level of "expertise" on stealth design is simply amazing on this forum. Let me remind you that the "stealth" shape research and scientific work originated in Russia. They know very well how to properly implement stealth in a balanced way.

[Frostiken]

Let me remind you that the "stealth" shape research and scientific work originated in Russia.

 

And the study of flight originated with the French and the Dutch.

 

 

And fission research originated in Germany.

 

 

And space exploration originated in Russia.

 

 

And you say stealth technology did too?

 

 

I like this game :)

 

 

Level of "expertise" on stealth design is simply amazing on this forum.

 

I resent that comment - I guarantee you that I'm far more qualified to comment on subjects of radar and stealth features than you will ever be.

Edited August 30, 2011 by 159th_Viper
Rule 1.1 - Profanity.

[GGTharos]

Let me remind you that the "stealth" shape research and scientific work originated in Russia.

 

I disagree with that. A particular piece of mathetics that stealth research ended up being based on originated in Russia. The research or stealth itself, as we know of it today, originated in the US. RUssia wasn't known of it.

 

They know very well how to properly implement stealth in a balanced way.

 

I'm certain the science doesn't escape them, but I don't think their level of expertise is at the same level as that of the US, who have been building stealth aircraft and weapons for decades now. I would expect that a lower budget aircraft wouldn't really be meant to be a competitor to the F-22 for example, but more against the F-35, and even there ... it's just a you get what you pay for thing.

 

That said, I still think what we see here isn't the finished product. As far as the engines go, I expect they'd use radar blockers in the intakes, maybe for kick-down-the-door phase (assuming the inlets don't get re-designed). After that, who needs'em anyway?

Edited August 30, 2011 by GGTharos

[sobek]

Level of "expertise" on stealth design is simply amazing on this forum. Let me remind you that the "stealth" shape research and scientific work originated in Russia. They know very well how to properly implement stealth in a balanced way.

 

I don't know why people treat stealth like it is some sort of occult magic.

 

Maxwells laws that govern the propagation of electromagnetic waves are well established in the scientific community, and while it might be hard to design the features of a plane so that it reflects as little energy as possible at a broad range of frequency bands back to the emitter(and still be able to fly), it is not impossible to determine that a feature is not stealthy by purely looking at it, if the 'unstealthiness' is very obvious.

[Frostiken]

Especially if we're calling into question the stealthiness of fan blades which has been a known problem with stealth aircraft since they've existed - as I tried to point out with the clumsy stupid screens they fit on the F-117A :P

 

While installing baffles in the intakes could very well be an option for the T-50, the drop in engine power would be significant.

 

Also I think I figured out how those mysterious missile bays on the wings work:

 

 

:D

Edited August 30, 2011 by Frostiken

[GGTharos]

It would be, but you might not care if you're dealing with a non-stealthy opponent :)

[tflash]

I don't know why people treat stealth like it is some sort of occult magic.

 

Maxwells laws that govern the propagation of electromagnetic waves are well established in the scientific community, and while it might be hard to design the features of a plane so that it reflects as little energy as possible at a broad range of frequency bands back to the emitter(and still be able to fly), it is not impossible to determine that a feature is not stealthy by purely looking at it, if the 'unstealthiness' is very obvious.

 

As long as you don't think that something that looks stealthy is therefore stealthy. Compare an F-104 starfighter and an F-35 in frontal view and then say to me which one "looks" the more stealthy to you.

 

It is fantastic that YOU know the laws of propagation so well that your Mark 1 Eyeball helps you out where the US needed major advances in computing power to actually be able to achieve this. I guess they will call you, no, they should have done so already! :D

[GGTharos]

Which part of 'aligned edges, unexposed rivets, lack of corner reflectors, and lack of right angles reduce rcs' is difficult for you to understand? :D

At the same time, which part of 'visible engine fan blades produce a large RCS, as does the radar dish when pointed at the right angle' happens to cause issues with comprehension?

 

There are basic rules, we can make gross judgements by rules of thumb that are known. If they did something new and sneaky, that'll be something interesting to learn! :D

 

As for the F-104 vs. the F-35, I'm not sure what makes it difficult to determine at a glance that one was designed for stealth, and the other not - we're not looking at a (visibly) new generation of stealth here, like B-2/F-22/F-35 vs. the F-117.

 

As long as you don't think that something that looks stealthy is therefore stealthy. Compare an F-104 starfighter and an F-35 in frontal view and then say to me which one "looks" the more stealthy to you.

 

It is fantastic that YOU know the laws of propagation so well that your Mark 1 Eyeball helps you out where the US needed major advances in computing power to actually be able to achieve this. I guess they will call you, no, they should have done so already! :D

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What part of "those are just simplifications for the Discovery Channel" don't you understand? :)