F-22 vs PKA-FA thrust vectoring

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vilters

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Unread post27 Jan 2018, 16:25

Everything you put on an airplane has a weight, a technology, a MTBF, and can ground an aircraft.
The end question is a balance : Advantage versus disadvantage.
Is that last 1% of performance worth the weight, maintenance, failures, operational status?

If the primary mission is BVR?
Are we gonna put a lot of weight; risk and effort in WVR?

In brief : Trust vectoring is for airshows and not required for BVR.
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milosh

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Unread post27 Jan 2018, 18:52

tailgate wrote: Now the Russkies decided for some reason that they “neede” 3d tvc for the PAK. I can tell you from this pilot’s perspective that you aren’t hiding those tailpipes from anything!, especially in the rear 180 degree corridor. The heat signature would be extreme and from what I see, all the “stealth” is frontal only. Not sure how that benefits you with the ability of today’s sensored platforms?


New engine and new nozzle, nice comparison from first flight test (new engine and old engine):
http://imagehosting.io/images/2017/12/06/Izd30mf.jpg
Last edited by milosh on 27 Jan 2018, 19:05, edited 1 time in total.
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rheonomic

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Unread post27 Jan 2018, 18:55

zero-one wrote:Someone correct me if I'm wrong. I talked to a military journalist once and he said that the Raptor doesn't need TVC for yaw control because of its canted tail design.

The canted tails capture the high pressures generated by the vortecies in the chined forward fuselage allowing the vertical stabilizers to affect control at near zero airspeed or even when falling belly first.

This is why the F/A-18 and F-35 can still do Flat spin maneuvers even without yaw TVC.


Essentially if you design the aero properly and have sufficiently sized control effectors you can maintain control power pretty well over a large part of the envelope.

For the F-22 in particular the verticals are huge, which 1) helps maintain directional stability and 2) results in more rudder area and thus more control power.

basher54321 wrote:Partly I think because this AFAIK only applies to the FA-18E/F, not the FA-18A/C. The Super was designed with a goal to elliminate the high AoA handling issues the Legacys had - which required an increase in control surface size and a full up fly by wire system (the magic that brings it all together).


As far as I remember the legacy Hornet always had a full authority digital FBW FLCS.
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Unread post27 Jan 2018, 19:50

rheonomic wrote:
As far as I remember the legacy Hornet always had a full authority digital FBW FLCS.




Quite possibly yes (assuming the first As didn't start Analog) - anyway according to the US Navy part of the success of the increased level of control is down to higher integration of the FCS in the Super Hornet. The Legacy had a fly by wire system sitting along side a conventional hydraulic setup - but the Super ditches all that in favour of FBW only so there were some major changes in the Super not just in the coding.
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rheonomic

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Unread post27 Jan 2018, 20:08

basher54321 wrote:
rheonomic wrote:
As far as I remember the legacy Hornet always had a full authority digital FBW FLCS.




Quite possibly yes (assuming the first As didn't start Analog) - anyway according to the US Navy part of the success of the increased level of control is down to higher integration of the FCS in the Super Hornet. The Legacy had a fly by wire system sitting along side a conventional hydraulic setup - but the Super ditches all that in favour of FBW only so there were some major changes in the Super not just in the coding.


This paper from NAVAIR makes it seem like the main changes were 1) additional control effectors and 2) allocation of the control effectors (vs mixing e.g. ailerons and aym HT for roll, sym HT for pitch, etc. as done classically) to ensure reconfigurability and sufficient multi-axis control power, and 3) redesign of the CLAWs for better perofrmance at high AOA etc.: Operational Lessons Learned from the F/A-18E/F Total Flight Control Systems Integration Process

(only skimmed it so far but looks like a very interesting paper)

Also it looks like the legacy Hornet was FBW but had a mechanical reversionary mode that was removed in the Super.
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XanderCrews

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Unread post27 Jan 2018, 23:16

The 3D VC on the flankers and what now looks like Pakfa is one of those examples Id like to mention to the Russia Stronk krew when they start going on about the brilliant simplicity of Russian design.

I have no clue why it isn't a much more simple 2D that would also take away some learning curve and vastly simplify the handling but here we are

One could even question why it's there at all really. The F-22 has it for the prime reason of very high altitude cruising in thin air.

That ain't the Flanker but whatever
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XanderCrews

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Unread post27 Jan 2018, 23:22

vilters wrote:
In brief : Trust vectoring is for airshows and not required for BVR.


Explain the F-22 vilters.
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vilters

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Unread post27 Jan 2018, 23:32

I don't have to.

The F-35 "explains" the F-22. No Trust vectoring any more.
For the mission?
It is not worth its weight, maintenance, reliability, the trouble.

For the F-22?
If they could do it all over again?
Be sure that "weight" would go to fuel.
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XanderCrews

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Unread post27 Jan 2018, 23:58

vilters wrote:I don't have to.

The F-35 "explains" the F-22. No Trust vectoring any more.
For the mission?
It is not worth its weight, maintenance, reliability, the trouble.

For the F-22?
If they could do it all over again?
Be sure that "weight" would go to fuel.



Try again. The F-22 has TV specifically for high altitude flight, and of course they are by extension used for BVR since the F-22 would be up in the thin air plinking away
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Unread post28 Jan 2018, 00:13

XanderCrews wrote:
vilters wrote:I don't have to.

The F-35 "explains" the F-22. No Trust vectoring any more.
For the mission?
It is not worth its weight, maintenance, reliability, the trouble.

For the F-22?
If they could do it all over again?
Be sure that "weight" would go to fuel.


Try again. The F-22 has TV specifically for high altitude flight, and of course they are by extension used for BVR since the F-22 would be up in the thin air plinking away


Sorry but he is right. The F-22s vectoring system was to originally include a thrust reverser. The decision for the 2D rectangular exhaust was determined by the requirements for thrust reverser. It was deleted for weight and cost reasons. Hindsight 20-20 the F-22 would have had a system more like the F-35 LOAN with thrust vectoring. After the requirement was abandoned and the rest of the aircraft design was essentially ready, now we have the current system.

https://books.google.com/books?id=uCI5K ... 6&dq=F-22+"thrust+reverser"&source=bl&ots=q-zHVGhP7b&sig=_vRURnvd_dDDsq6D1f_NfupxnSo&hl=en&sa=X&ved=0ahUKEwib18WmovnYAhWJqFQKHdkFBIkQ6AEIYTAJ#v=onepage&q=F-22%20%22thrust%20reverser%22&f=false

I would to see a pilot interview or quote that claims they need thrust vectoring for high altitude flight. The F-15 was certified to 80K and limited to 60K in service. Nothing I ever read claimed that the F-22s vectoring is for high altitude flight. Do you have a quote or article that supports this?
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Unread post28 Jan 2018, 02:12

H Bomb

Xander is correct that the primary purpose for thrust vectoring was high altitude, "where air is thin", trim control iirc. It was quoted many years ago in AFM or CA by a prominent USAF officer.
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Unread post28 Jan 2018, 02:46

I would to see a pilot interview or quote that claims they need thrust vectoring for high altitude flight. The F-15 was certified to 80K and limited to 60K in service. Nothing I ever read claimed that the F-22s vectoring is for high altitude flight. Do you have a quote or article that supports this?


The Eagle was cleared for said heights, but had to maintain high energy state for obvious reasons. The TVC allows for control of the aircraft in attitude and angular respects and even allows control when airflow spoils over normal flight controls.
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Unread post28 Jan 2018, 02:59

The Raptor was designed to dominate high up in the rarefied heights and TVC is a key feature allowing it to do so.


http://www.ausairpower.net/API-Metz-Interview.html

Kopp:

There is some debate in the fighter community about the relevance of thrust-vectoring in this day and age of Helmet Mounted Displays and 4th Generation heaters. What advantages do you see in having thrust vectoring, and how does it influence both instantaneous and sustained turning performance in the F-22A?

Metz:

Thrust-vectoring is often thought of in terms of the classic 'dogfight' where one aircraft is trying to out-turn his opponent at ever decreasing airspeeds. Whether a pilot should ever engage in these slow speed fights is a matter that is hotly debated within the fighter pilot community. Certainly, there is general agreement that it is best to not get slow - ever. With the advent of the helmet mounted sight, 4th generation heat seeking, off-boresight missiles the slow dogfight becomes even more dangerous. 'To slow or not to slow' are questions of tactics and best left to the expert fighter pilots of the future. The F-22's thrust-vectoring can provide remarkable nose pointing agility should the fighter pilot choose to use it. What is not widely known is that thrust-vectoring plays a big role in high speed, supersonic maneuvering. All aircraft experience a loss of control effectiveness at supersonic speeds. To generate the same maneuver supersonically as subsonically, the controls must be deflected further. This, in turn, results in a big increase in supersonic trim drag and a subsequent loss in acceleration and turn performance. The F-22 offsets this trim drag, not with the horizontal tails, which is the classic approach, but with the thrust vectoring. With a negligible change in forward thrust, the F-22 continues to have relatively low drag at supersonic maneuvering speed. . But drag is only part of the advantage gained from thrust vectoring. By using the thrust vector for pitch control during maneuvers the horizontal tails are free to be used to roll the airplane during the slow speed fight. This significantly increases roll performance and, in turn, point-and-shoot capability. This is one of the areas that really jumps out to us when we fly with the F-16 and F-15. The turn capability of the F-22 at high altitudes and high speeds is markedly superior to these older generation aircraft. I would hate to face a Raptor in a dogfight under these conditions.[/b]
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Unread post28 Jan 2018, 03:25

Tailgate flew the F-22 (and F-15,F-16), he knows what he is talking about here-
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Unread post28 Jan 2018, 05:45

Thanks for the support ADF, but no worries. The premise here is tvc allows the 22 to do lots of things throughout its flight envelope. High altitude flight control just being one. I always found myself in the 30-40k range though, the 22 had outstanding capabilities there.

I know that for along time, russkie engines were just not that reliable and required allot maint man hours to achieve just nominal longevity, one thing we had a good advantage in. I confess, I haven’t kept up........but unless they have really made significant progress in this area, I wonder how much more work adding 3d tvc has caused to the equation
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