Sukhoi PAK FA

[p2prada]

Grid fins folded:

The wings also fold, don't have a picture though.

 

[Payeng]

Not necessarily operational , even though it can be designed for the purpose current models do not fold and got 4 fixed screw for the joints, in that above picture two screws are not applied....

neither current model wings nor the fins folds but can be modified to work so, more over the wings are of fixed type and do not move for an aerodynamic maneuver.

 

[p2prada]

Yeah that's right. It is not required on current gen aircraft.

But the R-77 was always designed for internal bays. Su-47 and Mig 1.44 have always had internal bays. Not sure if the Mig 1.44 bays were used because they were covered by panels. But you can say R-77s have at least been physically integrated to the Su-47, if not fired already.

All they need to do is get the wings to fold.

 

[Payeng]

I dont know how credible it is but I have found some switchblade concepts.

US.

Russia

 

[Payeng]

^^ Actually I got it searching this switchblade

 

[Payeng]

I think with the passage of time, weapon compactness, delivery technique, inventory management (weapon bay) will change a lot current internal weapons seems just being covered by doors,where as future weapons should be based on maximum utilisation of space and design for a given performance.

 

[Payeng]

I wonder what makes the Russian designer let the engine exposed.

Other designers do not apply this phenomenon.
as for Rafale

or say the F-22

even our Tejas engine is not exposed

and not even the F-35 which need to move its nozzle downward for a vertical landing, it opens up when only necessary to do so.

 

[p2prada]

It is not exposed. The engine fits into a casing that is simply a different colour as the rest of the airframe. The engine is well inside the fuselage, only the nozzles are exposed and that's fine.

Without the casing, you can't place the engine.

F-15

 

[Payeng]

Yeah should be a casing but seems like without RAM treatment coating or the regular body cover and seems like bare metal exposed.

 

[p2prada]

We are yet to see the end product after all.

This is a F-35 without the external jacket and RAM coating. Maybe the T-50 is like this today with all the exposed rivets.

Everybody is waiting for the fourth prototype. We are hoping to see major changes like a new engine. Hopefully the Russians don't disappoint.

 

[Payeng]

I dont think a design is modified unless their is a flaw in design, while the first prototype is released base on a wind tunnel freezed design, but a highly anticipated modified engine as per rumour and new, I am curiously waiting for the new engine.

 

[Twinblade]

Yeah should be a casing but seems like without RAM treatment coating or the regular body cover and seems like bare metal exposed.

Almost all aircraft have cold air vents, cooling ducts and heat exchanging systems to keep the engine temperatures under acceptable limits.

Cooling vents in f-16:-

However in F-15 and Su-27 family, the temperatures still run high despite those measures.
Quoting Flateric's replies on the same topic at keypublishing -

Calculations of the airframe and systems temperature were performed by engineers Gladyshev and Tochilina (she was in charge of the fuel system temperature calculations). As a result "The Index of the temperatures of Object T-10" authored by Vladimir Gladyshev was released as a working document in the early stages of designing the Su-27. It allowed design bureau departments to consider the impact of temperature factors for the choice of materials and strength calculations for the airframe.

Calculations showed that the maximum speed of flight, corresponding to M = 2.35, at an altitude of more than 11 km, airframe skin heats up to 140 - 150 ° C, the temperature of glass windshield reaches 143 ° C, intake duct walls are heated to 175 ° C. In this case, the engine is heated up to 550 ° C in the afterburner area, while in the area of the nozzle feathers - up to 1100 ° C. That required usage of the titanium alloys in the construction of the engine compartment, the installation of heat protection screens on the walls of the tank #4 and the ventilation system to prevent possible explosions in the engine bay in the event of leakage of hydraulic fluid and fuel.

Su-27 Fighter Vol.I: Beginning of Story by Ildar Bedretdinov et al.

Also, the aft body of both f-15 and su-27/30/35 is made of titanium which seems to have a poor adhesion to paint at elevated temperatures and since Titanium forms a stable oxide on the surface, leaving it unpainted will not make it corrode. Hopefully with the newer engine either a more effective heat exchange system might be incorporated in Pak-fa or maybe something more ingenious might be incorporated.

 

[J20!]

Flat nozzles like F-22 has nothing to do with stealth, but supercruise.

Even round nozzles can have saw tooth arrangement and provide lower RCS returns.

This is a stealth optimized nozzle of the F-35.

There are a couple of issues with that argument.

1. Both the B2 and the F117 employ flat nozzles öptimised"for stealth. Both are subsonic, thus your supercruise argument is quite void there.

2. The F35's nozzle is not optimised for stealth. It is a compromise to accomodate the F35B's rotating VTOL nozzle. The saw tooth edges in no way make them better or even close to low RCS performance of the F22 in the rear sector. Flat nozzles are best for both RCS and IR emissions minimizarion.

 

[Payeng]

Some information regarding flat nozzle experiment
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19870010950_1987010950.pdf
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA801403
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930081831_1993081831.pdf

Although according to open source information research have shown that their is no substantial loss of thrust compared to a conical design but it is believed that for employing a flat nozzle one have to actually sacrifice some amount of thrust, after all it is open source.

 

[p2prada]

There are a couple of issues with that argument.

1. Both the B2 and the F117 employ flat nozzles öptimised"for stealth. Both are subsonic, thus your supercruise argument is quite void there.

2. The F35's nozzle is not optimised for stealth. It is a compromise to accomodate the F35B's rotating VTOL nozzle. The saw tooth edges in no way make them better or even close to low RCS performance of the F22 in the rear sector. Flat nozzles are best for both RCS and IR emissions minimizarion.

B-2's nozzles are a bit more different than F-22s of F-117s. It is a high bypass engine and the nozzles act as IR blockers.

F-117's nozzles act as IR blockers.

However the F-22's radar blockers are inside the tailpipe. Overall flat nozzles affect IR emissions, along with a combination of other techniques, but not as much in EM. F-22 can use a round nozzle, increase IR emissions slightly, increase thrust and still retain EM stealth. But will sacrifice some speed while supercruising. Maybe it won't supercruise at all.

The F-35's sawtooth nozzles do reduce RCS. The reason they are said to be non stealthy is because of the lack of a radar blocker in the tailpipe. You can say the IR signature on F-35 will be greater than F-22. I am not sure, but there is a chance the nozzles on F-35 may be more stealthy than F-22 while other aspects may give away the stealthiness of the F-35, like the lack of a blocker.

You can see that all 4 designs have their own advantages, you only choose what is best for you. There are other ways to reduce EM and IR emissions. So, any country will choose a different design to achieve the same.

The Americans chose flat nozzles for supercruise on F-22/YF-23 while they chose inlet design for supercruise on SR-71.

 

[Payeng]

Interestingly F-117 have irregular dog tooth edge

 

[Payeng]

B-2's nozzles are a bit more different than F-22s of F-117s. It is a high bypass engine and the nozzles act as IR blockers.

F-117's nozzles act as IR blockers.

However the F-22's radar blockers are inside the tailpipe. Overall flat nozzles affect IR emissions, along with a combination of other techniques, but not as much in EM. F-22 can use a round nozzle, increase IR emissions slightly, increase thrust and still retain EM stealth. But will sacrifice some speed while supercruising. Maybe it won't supercruise at all.

The F-35's sawtooth nozzles do reduce RCS. The reason they are said to be non stealthy is because of the lack of a radar blocker in the tailpipe. You can say the IR signature on F-35 will be greater than F-22. I am not sure, but there is a chance the nozzles on F-35 may be more stealthy than F-22 while other aspects may give away the stealthiness of the F-35, like the lack of a blocker.

You can see that all 4 designs have their own advantages, you only choose what is best for you. There are other ways to reduce EM and IR emissions. So, any country will choose a different design to achieve the same.

The Americans chose flat nozzles for supercruise on F-22/YF-23 while they chose inlet design for supercruise on SR-71.

p2prada the saw tooth nozzle of F135 might help in deflecting radar waves but is not considered as stealth even by Pratt & Whitney but they claim F-119 to have integrated stealth technology.

 

[p2prada]

Yeah. I already mentioned that. F-119 has a radar blocker in the tailpipe.

F-135 does not. So, it is not stealthy.

 

[Payeng]

Is their any official confirmation that the F-22 Raptor have a maximum speed in acess to M 1.9-2.0?

 

[p2prada]

It seems the F-22's speed is either governed or simply hidden. AFAIK, greater than Mach 2 speed is actually a self imposed restriction. F-15s had major restrictions as well.

It is more draggy than F-15 and will require greater power to move as fast. But I think less draggy if weapons stores are added on the teen.

There is no doubt the F-22 can manage Mach 1.6 for 40 minutes using supercruise, according to requirements. I think they mentioned something about a 200-400Km supercruise range with a combination of subsonic speeds for 1000Km.

Comparatively I think Mig-31 can do Mach 2.35 for a 700Km range.