PAK-FA and FGFA Thread

Gaur · Post by **Gaur** » 25 May 2010 02:10

^^
Done.

Viv S · Post by **Viv S** » 25 May 2010 04:14

indranilroy wrote:yes, the aircraft will have its longitudinal axis stay horizontal (or whatever angle decided), but wouldn't the plane loose altitude unless the axis is an angle to the ground where the thrust's vertical component balances the weight of the craft (which has already been discussed by Shiv)?!

Actually its not really the vertical component of the thrust that balances the weight of the craft but the lift from the wings. But all the same, fighter aircraft have a symmetrical wing, so they probably will lose altitude at a zero degree angle of attack.

Indranil · Post by **Indranil** » 25 May 2010 04:17

Viv S wrote:
indranilroy wrote:yes, the aircraft will have its longitudinal axis stay horizontal (or whatever angle decided), but wouldn't the plane loose altitude unless the axis is an angle to the ground where the thrust's vertical component balances the weight of the craft (which has already been discussed by Shiv)?!
Actually its not really the vertical component of the thrust that balances the weight of the craft but the lift from the wings. But all the same, fighter aircraft have a symmetrical wing, so they probably will lose altitude at a zero degree angle of attack.

HUH!!! Please read my post and the condition that I was discussing again.

shukla · Post by **shukla** » 27 May 2010 20:02

Live demo.. PAK-FA test flight in Siberia.. (Apologies if posted earlier)

[youtube]Wx1Z4KJCpOU&feature=player_embedded[/youtube]

Awesome..

shiv · Post by **shiv** » 27 May 2010 20:41

Raman wrote: Instead the fins produce a yawing moment (with respect to the aircraft's frame of reference), which points the rear end of the aircraft down (with respect to the earth's frame of reference). This produces a vertical component of engine thrust that counteracts the gravitational force. Of course, this is a dynamic situation, so the rudders must be kept deflected to keep the aircraft "trimmed" for that attitude of flight.

In fact this is what I said earlier when I asked the question

shiv wrote:I have seen videos of aircraft doing a fly by in an attitude of 90 deg roll where the pilot deliberately rolls 90 degrees and actually points the nose slightly upwards (i.e away from the side of roll and towards the sky) so that the loss of altitude in with the plane on its side is somewhat compensated - albeit temporarily.

So you are saying that this is engine lift caused by a yaw that is prevented by tailfin trim from making the aircraft gain altitude despite the nose up, tail down attitude. That sounds reasonable. But a tailfin is surely generating lift that is causing the airflow to lift the tail and force the nose down, and that lift is counteracted by tailfin trim. The engine merely maintains forward speed to generate fin lift. Would an aircraft with a huge vertical tailfin not generate some lift in this situation? The lift toward the tail end would cause a nose down attitude, but the trim would prevent the nose from going down. Large fins are big surfaces that generate forces and in a 90 deg roll the forces generated can be lift.

My question really was if largish vertical tailfins would generate some lift at 90 degree roll and that lift could be greater than the lift produced by canted tailfins allowing a plane with unstealthy vertical fins to maintain altitude better at 90 deg roll than a plane with stealthy canted tailfins.

negi · Post by **negi** » 27 May 2010 21:42

There is a catch there in practice the AC will never be flying at exact 90deg bank because afaik all the military fighter AC have anhedral or even polyhedral wings which would mean even if the fuselage is tilted at 90 the wing surface itself be at some angle to the vertical axis and some miniscule lift will be produced , also unlike the main wing the vertical tailplane airfoil imho is symmetrical about the chord so it will never generate any lift in its neutral position (it is not meant to do that in first place). During a extreme banking maneuver the tailplane will be used for correcting the nose attitude and the lift will still come from the wings.

Viv S · Post by **Viv S** » 27 May 2010 22:39

indranilroy wrote:HUH!!! Please read my post and the condition that I was discussing again.

Hmm... my post was a bit tangential to the issue, sorry.

But, even in the event the aircraft is banked at 90 degrees, tilting the aircraft's axis to horizontal will still result in the aircraft losing altitude, unless the aircraft has a very high T/W ratio(in excess of the cosecant of the angle with the horizontal). The vertical component of thrust is just too small to balance the weight of the aircraft.

Raman · Post by **Raman** » 28 May 2010 01:13

My question really was if largish vertical tailfins would generate some lift at 90 degree roll and that lift could be greater than the lift produced by canted tailfins allowing a plane with unstealthy vertical fins to maintain altitude better at 90 deg roll than a plane with stealthy canted tailfins.

Note that only forces acting "at" the center of gravity will provide any translational effect. Since the fins are aft of the center of gravity, they can only provide a rotational force. If they do provide any "lift" at all, you can see that they will only succeed in putting the nose down even further. If anything, you want the fins to produce a "negative lift" to push the tail down and keep the nose up, which will provide some thrust component to counteract gravity.

So now the question is if un-canted fins provide more aerodynamic authority than canted fins. I would say that it shouldn't make a difference. The sizing/placement of the fins would have been performed by the designers to ensure that there is sufficient control authority for all points in the envelop by moving the fin or altering its size (i.e., ensuring that tail volume coefficient is the same).

One can make this even more academic by forcing all other parameters to stay the same and only change the angle of the fins. I don't think there is a blanket answer even for this artificial situation because it is not a question of whether the canted fin does "less" than an uncanted one --- only that the canted fin has sufficient aerodynamic authority to keep the aircraft pointing in the right direction for all points of the envelop.

In practice, this is probably not a big concern unless you're designing an airplane for aerobatics, competitions, etc. For the most part, the 90 degree roll position is a transient position, and steady turns (even very sharp ones) are done with a roll of less than 90 degrees to let the wings do the lifting, if altitude preservation is important.

nachiket · Post by **nachiket** » 28 May 2010 01:31

negi wrote:also unlike the main wing the vertical tailplane airfoil imho is symmetrical about the chord so it will never generate any lift in its neutral position (it is not meant to do that in first place).

negimullah is right. If the vertical tail fin had an unsymmetrical airfoil shape like the wing it would produce a continuous yaw movement when upright that would make it impossible to fly the aircraft.

Raman · Post by **Raman** » 28 May 2010 02:12

^^^

But that is assuming that the local flow around the fin is exactly aligned even when the aircraft is rolled at 90 degrees. That is false: if the aircraft does nothing else, it will experience (at the least) a side-slip effect (in local aircraft frame). If the aircraft is trimmed for steady flight, the fin will be deflected through a yaw. You describe a situation that could only exist as a transient. However, by definition, the aircraft must be experiencing a roll, etc., which means that the flow will not be aligned exactly.

This whole discussion is quite academic.

shiv · Post by **shiv** » 28 May 2010 06:17

Raman wrote:
This whole discussion is quite academic.

Absolutely. The only "experience" I have of this however is with model aircraft with a conventional set of foreplanes and tailfin. If the model is launched unpowered at an attitude of 90 deg roll the primary movement observed initially is mainwing lift that causes the plane to appear to turn to one side (due to a pitch up from mainwing lift) . What happens next is totally dependent on whether the intial attitude was less than 90 deg roll or more. If less the model tends to right itself. If more than 90 deg it rolls over and nosedives to the ground unless it has altitude when it ends up completing the second half of a loop.

Maintaining a razor sharp 90 deg roll and straight flight (as in an airshow) takes some doing. I expect the tailplane will need trim to prevent mainwing lift from causing the plane to "pitch up" (which is sideways in 90 deg roll). And while it is IMO impossible to maintain altitude in this attitude, I just wonder what is the contribution of body lift and tailplane lift that might make different aircraft designs less or more capable of generating lift while doing this.

Craig Alpert · Post by **Craig Alpert** » 29 May 2010 04:10

UPDATE ON FGFA

AW: What is the latest from fifth-generation fighter aircraft (FGFA)?

A.N.: Negotiations are currently progressing for concluding the Preliminary Design (PD) contract. The PD contract is expected to be signed shortly, and this phase is estimated to be completed in 18 months. The PD phase will be the preparatory phase during which the transfer of documents, drawings, training, etc. will take place for enabling the joint design, development and manufacture of the FGFA. The conclusion of the PD phase will lead into the R&D phase, which is estimated to be of 102 months’ duration.

NRao · Post by **NRao** » 29 May 2010 06:07

Craig Alpert wrote:UPDATE ON FGFA
AW: What is the latest from fifth-generation fighter aircraft (FGFA)?

A.N.: Negotiations are currently progressing for concluding the Preliminary Design (PD) contract. The PD contract is expected to be signed shortly, and this phase is estimated to be completed in 18 months. The PD phase will be the preparatory phase during which the transfer of documents, drawings, training, etc. will take place for enabling the joint design, development and manufacture of the FGFA. The conclusion of the PD phase will lead into the R&D phase, which is estimated to be of 102 months’ duration.

18 months for PD. There must be a typo for the 102 months of R&D? Else the FGFA will come out after 10 years?

NRao · Post by **NRao** » 29 May 2010 06:12

For a "India Thought Leaders" series, that too for AWST, these are very bland questions.

Viv S · Post by **Viv S** » 29 May 2010 11:24

Craig Alpert wrote:UPDATE ON FGFA

"A.N.: (a) SU-30MKI : The present schedule will be completed by 2015-16. Additional orders are anticipated from IAF, and this will keep the production line active till 2017-18."

Beyond the 280 already on order?

shiv · Post by **shiv** » 29 May 2010 20:44

Raman wrote: Note that only forces acting "at" the center of gravity will provide any translational effect. Since the fins are aft of the center of gravity, they can only provide a rotational force. If they do provide any "lift" at all, you can see that they will only succeed in putting the nose down even further. If anything, you want the fins to produce a "negative lift" to push the tail down and keep the nose up, which will provide some thrust component to counteract gravity.

So now the question is if un-canted fins provide more aerodynamic authority than canted fins. I would say that it shouldn't make a difference. The sizing/placement of the fins would have been performed by the designers to ensure that there is sufficient control authority for all points in the envelop by moving the fin or altering its size (i.e., ensuring that tail volume coefficient is the same).

One can make this even more academic by forcing all other parameters to stay the same and only change the angle of the fins. I don't think there is a blanket answer even for this artificial situation because it is not a question of whether the canted fin does "less" than an uncanted one --- only that the canted fin has sufficient aerodynamic authority to keep the aircraft pointing in the right direction for all points of the envelop.

In practice, this is probably not a big concern unless you're designing an airplane for aerobatics, competitions, etc. For the most part, the 90 degree roll position is a transient position, and steady turns (even very sharp ones) are done with a roll of less than 90 degrees to let the wings do the lifting, if altitude preservation is important.

OK. Great! Thanks for the reply.

kash · Post by **kash** » 04 Jun 2010 20:26

Can one say that the PAK FA is/will be the most advanced fighter??

considering some wired facts.. i guess the PAK FA has an upper hand.. [am considering only American and Russian birds.. also this is jus a mere observation and a "casual" view from my end]

Starting from the times of the P 51.. the Americans had a technological edge.. then the Russians lead the race with the Mig 15.. followed by the American F 86.. The F 86 was outclassed by the Russian Mig 21.. then came the turn of the Americans to lead.. the came up with the F 14 Tomcats.. So the Russians responded with the Mig 29.. The Americans took back the lead in the form of the F 15.. Russians made the Flankers to outclass the F 15's... so the Americans come up with the Raptor!! and have been ruling the skies ever since!! and now the Russians are developing the PAK FA.........

so history might just repeat!!

shiv · Post by **shiv** » 04 Jun 2010 21:02

Half fairy tale. Half rhetorical narrative.

KumarG - your note has a whole bunch of skewed facts apart from being wholly incomplete. By BRF standards it is trash. You knew it was "casual" - please don't waste bandwidth. Sorry, but I am blunt. There is a newbie thread where you will be excused for writing trash.

Nihat · Post by **Nihat** » 04 Jun 2010 21:59

Viv S wrote:
Craig Alpert wrote:UPDATE ON FGFA

"A.N.: (a) SU-30MKI : The present schedule will be completed by 2015-16. Additional orders are anticipated from IAF, and this will keep the production line active till 2017-18."

Beyond the 280 already on order?

230 are on order, follow on is planned for but not officially ordered yet.

Raveen · Post by **Raveen** » 04 Jun 2010 22:30

KumarG wrote:Can one say that the PAK FA is/will be the most advanced fighter??

considering some wired facts.. i guess the PAK FA has an upper hand.. [am considering only American and Russian birds.. also this is jus a mere observation and a "casual" view from my end]

Starting from the times of the P 51.. the Americans had a technological edge.. then the Russians lead the race with the Mig 15.. followed by the American F 86.. The F 86 was outclassed by the Russian Mig 21.. then came the turn of the Americans to lead.. the came up with the F 14 Tomcats.. So the Russians responded with the Mig 29.. The Americans took back the lead in the form of the F 15.. Russians made the Flankers to outclass the F 15's... so the Americans come up with the Raptor!! and have been ruling the skies ever since!! and now the Russians are developing the PAK FA.........

so history might just repeat!!

Kumar, you do realize that none of those planes you mentioned were Russian but were in fact Soviet, honestly let's keep this stuff to the Noob section please

kash · Post by **kash** » 04 Jun 2010 22:35

@ Shiv n Raveen..

Agreed...

i chose to express my out-of-the-box thought that came over me.. i am very new to this place and am still in the process of getting used it..
any ways i shall make sure my posts have greater depth..

chiru · Post by **chiru** » 04 Jun 2010 22:39

@ kumar (kash) welcome to brf ..... its a good idea if you go check out the first page of each topic .....it contains extensive articles about that aircraft/tech ...so you can have decent groundwork done
@ shiv saar please ignore that unwashed abdul for a few days ...let him get to BR standards

and about the topic ...nothing to say ....waiting for the babus to sign the agreement with russia

shanksinha · Post by **shanksinha** » 06 Jun 2010 01:48

kash · Post by **kash** » 06 Jun 2010 08:24

well i searched the web and went through this forum... but not been successful..

I wanted to know if the PAK FA has a 3D thrust vectoring or 2D??
Also do u think the IR signature would be more compared to the F 22..??

chiru · Post by **chiru** » 06 Jun 2010 11:45

^^^ currently it has the mki nozzle(ie 2D TVC but in the mki style V orientation) ...i dont expect this to change unless Russia gets the fifth gen engine .... IR signature will be similar to the mki CURRENTLY ..this may change though

Gaur · Post by **Gaur** » 06 Jun 2010 13:48

^^
No, PAK-FA is using 117S as its interim engine and 117S has full 3d TVC.

NRao · Post by **NRao** » 06 Jun 2010 21:15

Whatever the PAK-FA is using, it is using. However, do not expect any of these to be in the final product. We should expect a lot of changes - governed by the funding (note that the "PAK-FA" has been funded by Sukhoi) (I expect Sukhoi to rely on Indian funding to make progress).

On the engine, specifically, the head of Sukhoi has stated that it will take 5 years - WITH PROPER FUNDING - to come up with an proper engine for the PAK-FA. I read that as a hint for India to fund. Just my take.

sawant · Post by **sawant** » 06 Jun 2010 22:53

KumarG wrote:... so the Americans come up with the Raptor!! and have been ruling the skies ever since!! and now the Russians are developing the PAK FA.........

so history might just repeat!!

Thats like Keynes said "... in the long term we are all dead" ... so does that mean we stop eating..or living ! Conflicts occur when one power perceives itself to be technically superior to the other and has the confidence to pre-empt.. Hence the need to play catch-up and reduce that miltary gap... any way as far as india is concerned, we have to play catch up in many areas, hence any such developmental effort as the FGFA is good education...

chiru · Post by **chiru** » 07 Jun 2010 08:19

Gaur wrote:^^
No, PAK-FA is using 117S as its interim engine and 117S has full 3d TVC.

gaur saar i too was surprised but it has the al-31 nozzle here is my proof

A provision has been made for using the thrust vector control nozzle similar to that of the AL-31FP

http://frontierindia.net/npo-saturn-fin ... -for-su-35

the 3D TVC will come with the fifth gen engine ...the only 3D tvc is used by Klimov, saturn does not hav a production 3D tvc nozzle including the 117S

...it was found on the now defunct su-37 ...dont know what happened to that

kash · Post by **kash** » 07 Jun 2010 08:44

yeah as of now the Mig 29 M OVT used the 3D tvc nozzle from Klimov.. I had read that the designers of the Raptor din go for the 3D tvc nozzle because of the IR signature issue...
But i reckon the end product PAK FA will have it as the Russians rightly believe[info from an interview during the display of the Mig 29 M ovt] that the days of dogfighting haven gone..

shiv · Post by **shiv** » 07 Jun 2010 08:47

KumarG wrote: the designers of the Raptor din go

What is Raptor dingo? An extinct Australian dog?

kash · Post by **kash** » 07 Jun 2010 09:12

^^^

there is a space between Din and go... when there is a space.. it means its not one word.. they are separate words..

shiv · Post by **shiv** » 07 Jun 2010 09:44

KumarG wrote:^^^

there is a space between Din and go... when there is a space.. it means its not one word.. they are separate words..

So what does din go mean? Make a noise before leaving? The designers of the Raptor made lots of noise before leaving?

Carl_T · Post by **Carl_T** » 07 Jun 2010 10:14

didnt go.

shiv · Post by **shiv** » 07 Jun 2010 10:17

Carl_T wrote:didnt go.

Oh T.IDUTFT.

Raja Bose · Post by **Raja Bose** » 07 Jun 2010 10:20

shiv wrote:
KumarG wrote:^^^

there is a space between Din and go... when there is a space.. it means its not one word.. they are separate words..
So what does din go mean?

Din goes to Raat ofcourse. Elementary.

woohoo! my first post in PAK-FA dhaaga!!

kash · Post by **kash** » 07 Jun 2010 11:09

shiv wrote: So what does din go mean? Make a noise before leaving? The designers of the Raptor made lots of noise before leaving?

No "SAAAAAR" it means Din't go..
i am surprised to know ur so particular about the language!!
oh sorry.. my bad.. "YOUR"..
By the way what is SAAAAR??? i have hear of Sir..

Rahul M · Post by **Rahul M** » 07 Jun 2010 11:12

kumar, this is not a kid's forum. do not use sms-speak.

kash · Post by **kash** » 07 Jun 2010 12:02

Rahul M wrote:kumar, this is not a kid's forum. do not use sms-speak.

Well alright.. wont use it again..

chiru · Post by **chiru** » 07 Jun 2010 12:50

rahul OT alert ...i know kumarG im speakin to him now ...its a small misunderstanding onlee SHIV saaar please ignore this guys he is just a third your age please cease and desist ill ask him not to post trivial stuff ,as per BR standards