F-22 DSI?

Unread postPosted: 21 Sep 2017, 00:13
by rhoads56
Hey all,

I've been wondering why the F-22 wasn't designed with Diverterless Supersonic Inlets (DSI) similarly to the F-35, rather than a traditional BL diverter?

My two theories are:

1) The tech just wasn't available during the initial design phases.

2) There is some limit on speed that the DSI imposes that would render it impractical for the F-22.

Any input? My apologies if this has been brought up before...

Thanks!

Rhoads

Re: F-22 DSI?

Unread postPosted: 21 Sep 2017, 00:28
by wrightwing
The F-22 and F-35 are optimized for different speed ranges.

Re: F-22 DSI?

Unread postPosted: 21 Sep 2017, 00:45
by rhoads56
wrightwing wrote:The F-22 and F-35 are optimized for different speed ranges.


Yes, I just wonder if the DSI tech was mature back then or not. Is DSI less favorable for supercruise well above M1?

Rhoads

Re: F-22 DSI?

Unread postPosted: 21 Sep 2017, 06:26
by scat
The DSI development was a direct result of the experience with the F-22 inlet. It was found that the F-22 inlet configuration was complex and difficult to manufacture with boundary-layer diverter and various bleed air holes, ducts and doors. With the advent of Computational Fluid Dynamics (CFD), engineers could instead design a bump that actually divert the boundary layer flow away from the inlet opening without being ingested into the inlet duct and by the engine. The use of DSI resulted in a much simpler and lighter inlet design that also provide some signature benefit. The basic concept was thoroughly flight tested in a modified F-16 Viper during the early to mid 1990's to provide risk reduction for later F-35 application.

Re: F-22 DSI?

Unread postPosted: 21 Sep 2017, 17:24
by zhangmdev
I am go for 1). DSI design requires huge amount of CFD simulation. Basically put the inlet and bump into virtual space, build a mesh around them, with millions and millions of nodes connected to each other. Then solve the pressure on each node with some mathematical magic. Repeat different inlet/bump configurations under different condition (mach numbers, ect). Until find the best one.

Generally the finer the mesh is, more accurate the result is supposed to be. But finer mesh will have a lot more nodes, way more memory and computing hours. Pre-mid-1990s computers (ancient technology comparing what is available now) were not capable enough for this kind of work.

Re: F-22 DSI?

Unread postPosted: 21 Sep 2017, 18:34
by scat
One can view two photos of the Viper test aircraft with the DSI modification in the Hall of Fame Gallery within this site;

http://www.f-16.net/aircraft-database/F ... file/1450/


11 Dec 1996 [act] 83120 USAF USAF 416 FTS F-16C Block 25



F-35 Inlet Installed
Modified inlet as an X-35 test bed with General Electric F110-GE-129 engine. This inlet resembles the airflows that are created when flying with the X-35. The flight test program consisted of twelve flights flown in nine days in December 1996.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 16:14
by SpudmanWP
Here is the CodeOne Magazine article about the F-16 testbed for DSI.

http://www.codeonemagazine.com/article.html?item_id=58

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 17:43
by scat
Can someone teach me how to insert a photo into a post? I have no luck at all. Copy & paste does not work. What is the Img button for?

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 17:54
by SpudmanWP
If the image is on the web (like imgur.com), then put the url of the image between the [img] brackets.

Code: Select all
[img]http://www.google.com/intl/en_ALL/images/logo.gif[/img]


If the image is coming from your computer, then use the "upload attachment" process located below the text window.

When you are entering text in a post, you will notice a "BBCode" url on the right, click it and there are instructions.

faq.php?mode=bbcode

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 18:16
by tacf-x
As others have mentioned, it's due to the fact that the F-22 is an older plane that was designed back when the industry was making the transition from primarily relying on classical analytical theory (ie pencil and paper calculations) to primarily using computer-based numerical methods such as Finite Volume or Finite Difference solution schemes for assessing the aerothermodynamic properties of intake designs. The ubiquity of CFD numerical methods that could be run on personal computers from the 1990s onwards basically made it possible to cheaply design and analyze a specifically contoured bump that could generate surface pressure distributions that could passively force boundary layer air away from the inlet without the use of a diverter or splitter plate.

CFD was in use during the F-22 design era but was mainly relegated to rudimentary verification of a few aerodynamic aspects here and there. For the F-35 CFD was crucial to the design of the DSI as the precise shape of the bump was something that needed to be perfected at minimal cost in order to work to an acceptable degree of effectiveness.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 19:23
by wrightwing
rhoads56 wrote:
wrightwing wrote:The F-22 and F-35 are optimized for different speed ranges.


Yes, I just wonder if the DSI tech was mature back then or not. Is DSI less favorable for supercruise well above M1?

Rhoads

In other words, the inlet designs used in the F-22 and F-35 differ, due to the speed range that they're optimized for, not due to available technology. The F-22's super cruise speeds are near the max limits of DSI, and its top speed exceeds those limits.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 20:06
by scat
It is generally acknowledged that Lockheed Martin F-35 is the first aircraft to apply the DSI technology after a thorough developmental effort that culminated in the F-16 flight test in the mid 1990's. Nonetheless, Chinese Chengdu fighters J-10B, J-17, and J-20 all have been observed to have adopted also the DSI in recent years. The J-17 DSI was shown in a photo below. It has been a puzzle to me why the J-17's DSI is full of bleed air holes. Was the DSI design deficient such that corrective measure was needed? Of course, the Chinese are more sensitive about the J-20, and no close-in photo of the DSI has been seen in public to my knowledge. Maybe someone in this Forum can shed some light on this matter.

Image

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 20:32
by scat
I guess that I just do not know how to post a photo in this forum!

If interested, someone can Goggle "Diverterless Supersonic Inlet" and look at the thousands of photos of DSI. Most of them are of the Chengdu fighters.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 21:10
by disconnectedradical
scat wrote:It is generally acknowledged that Lockheed Martin F-35 is the first aircraft to apply the DSI technology after a thorough developmental effort that culminated in the F-16 flight test in the mid 1990's. Nonetheless, Chinese Chengdu fighters J-10B, J-17, and J-20 all have been observed to have adopted also the DSI in recent years. The J-17 DSI was shown in a photo below. It has been a puzzle to me why the J-17's DSI is full of bleed air holes. Was the DSI design deficient such that corrective measure was needed? Of course, the Chinese are more sensitive about the J-20, and no close-in photo of the DSI has been seen in public to my knowledge. Maybe someone in this Forum can shed some light on this matter.

Image


Image

This is a decent image of the J-20's inlet. The bump itself doesn't seem to have holes, but there are porous plates right behind the intake.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 21:30
by sprstdlyscottsmn
That's either a photoshop of the best picture of the J-20 I've seen, referring solely to the quality of the image.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 21:45
by wrightwing
sprstdlyscottsmn wrote:That's either a photoshop of the best picture of the J-20 I've seen, referring solely to the quality of the image.

Looks like a photoshop to me, too.

Re: F-22 DSI?

Unread postPosted: 22 Sep 2017, 21:58
by disconnectedradical
sprstdlyscottsmn wrote:That's either a photoshop of the best picture of the J-20 I've seen, referring solely to the quality of the image.


Apparently, it's a promotional image from a Chinese movie, which the PLAAF may be using for promotional/propaganda purposes.

Here are other images of the J-20's bump.
Image
Image

Re: F-22 DSI?

Unread postPosted: 23 Sep 2017, 01:35
by wrightwing
That looks far more refined than the Su-57.

Re: F-22 DSI?

Unread postPosted: 23 Sep 2017, 22:46
by rhoads56
wrightwing wrote:
rhoads56 wrote:
wrightwing wrote:The F-22 and F-35 are optimized for different speed ranges.


Yes, I just wonder if the DSI tech was mature back then or not. Is DSI less favorable for supercruise well above M1?

Rhoads

In other words, the inlet designs used in the F-22 and F-35 differ, due to the speed range that they're optimized for, not due to available technology. The F-22's super cruise speeds are near the max limits of DSI, and its top speed exceeds those limits.


Makes sense. But it seems there are differing ideas. Some are saying the DSI tech just wasn't mature when the F-22 was under development and you're saying the contrary and that it purely has to do with speed. Can you discuss why the DSI does not perform well at the F-22 supercruise speeds? Couldnt one design a specialized DSI for higher mach numbers?

Re: F-22 DSI?

Unread postPosted: 24 Sep 2017, 01:12
by scat
The timeline is very clear:

1. The YF-22 was designed 1984-88 with the present inlet configuration.
2. The F-22 FSD started in late 1991.
3. GD/Fort Worth joined Lockheed in 1993.
4. The GD/Fort Worth development work on DSI was between 1990 to 1996, and DSI was chosen for JAST.
5. JAST program was between 1994-1997 with the down-select of Lockheed and Boeing to go forward in 1997.
6. Northrop and BAE that were in the McAir losing JAST team joined the down-selected Lockheed team to go-on for JSF program.
7. Lockheed Martin was formed with the addition of Martin Marietta & others in 1997.
8. Boeing bought McAir & Rockwell in 1998 and joined forces for JSF competition.
9. LM Aero-Northrop/Grummann-BAE team beat Boeing for JSF in 2001 after flyoff.

It is obvious that DSI was not in anyone's mind in the 1980's. LM Aero considered using DSI to only meet JSF/F-35 performance requirements. Whether DSI is suitable for the super-cruising requirements of ATF will be a very complex question at this stage of the game.

Re: F-22 DSI?

Unread postPosted: 24 Sep 2017, 03:20
by johnwill
Your time line is very clear, but remember GD/Fort Worth was a 1/3 partner along with Boeing and Lockheed in the YF-22 and F-22 programs. F-22 FSD could have benefited from DSI development work at GDFW. All of which makes me guess lack of DSI on F-22 was a performance decision, not a technology decision.

Re: F-22 DSI?

Unread postPosted: 24 Sep 2017, 04:19
by scat
The F-22 FSD contract award was in the Fall of 1991, and the first flight of the development aircraft was scheduled and executed in 1996. It would a stretch and be very risky to decide on a major inlet change when the DSI development work was just underway simultaneously.

In addition, the F-22 teaming agreement was a rather strange animal in that every major system on the aircraft was assigned a lead team member and the other two team members only have support engineering roles. Therefore, the team lead actually had major say so on the final design of the system. Interesting enough, even though GD/Fort Worth was assigned the mid-fuselage including 95% of the inlet duct for design and fabrication, the inlet lip region actually was assigned to Lockheed Marietta and was considered to be a part of the forward fuselage.

Whether DSI was ever being considered by the F-22 FSD team will be anyone's guess. Personally, it is doubtful.

Re: F-22 DSI?

Unread postPosted: 24 Sep 2017, 13:24
by scat
Here is one of the photos that I have been trying to upload for the last few days.

Re: F-22 DSI?

Unread postPosted: 24 Sep 2017, 21:07
by disconnectedradical
The J-20's DSI bump always looked a bit weird to me, since it almost seems like the bump isn't quite large enough to properly divert that boundary layer. But then again, these are things that's hard to eyeball, and maybe CFD and windtunnel testing showed that it's enough.

On the other hand, having porous plates on the DSI bump of the JF-17 seems to defeat the purpose of a DSI in the first place.

scat wrote:The F-22 FSD contract award was in the Fall of 1991, and the first flight of the development aircraft was scheduled and executed in 1996. It would a stretch and be very risky to decide on a major inlet change when the DSI development work was just underway simultaneously.

In addition, the F-22 teaming agreement was a rather strange animal in that every major system on the aircraft was assigned a lead team member and the other two team members only have support engineering roles. Therefore, the team lead actually had major say so on the final design of the system. Interesting enough, even though GD/Fort Worth was assigned the mid-fuselage including 95% of the inlet duct for design and fabrication, the inlet lip region actually was assigned to Lockheed Marietta and was considered to be a part of the forward fuselage.

Whether DSI was ever being considered by the F-22 FSD team will be anyone's guess. Personally, it is doubtful.


Interestingly, based on drawings of the EMD F-23, it seems like it would've had a DSI bump as well.

Re: F-22 DSI?

Unread postPosted: 25 Sep 2017, 03:57
by scat
A few years back, I was surprised to find the attached close-in photo of the J-17 DSI. In this case, bleed air holes were observed to be quite extensive both inside and outside of the inlet cowl. In fact, they were densely populated behind the DSI bump. If the DSI was designed properly, no bleed-air holes or porous plates is necessary as in the F-35 inlet.

That was the reason that I asked whether anyone came across a close-in shot of the J-20 inlet because its DSI also appeared to be funky...small as compared to the size of the inlet and asymmetrically located closed to the top of the inlet. a close-in image will reveil whether bleed air holes are also necessary for J-20. If so, the Chengdu design team must have a different design philosophy on the DSI. I just do not understand why the porous plate is necessary at all.

Re: F-22 DSI?

Unread postPosted: 25 Sep 2017, 05:04
by disconnectedradical
From what I can tell, the J-20 inlet doesn't seem to have porous plates around the DSI bump, but there's a porous hexagonal grid on the outside of the cowl right behind the intake. The F-22 also has porous plates right behind the intake inside the inlet.

Re: F-22 DSI?

Unread postPosted: 25 Sep 2017, 13:24
by scat
As stated in my original post, the DSI development at GD/FW and the subsequent application on the F-35 were a direct result of the experience with the F-22 inlet. The prime objective was to eliminate most of the standard subsystems necessary to divert the boundary layer air away from the inlet and to prevent ingestion into the engine. These subsystems included the diverter, bleed air holes (porous plates), and pipes/doors, etc were heavy and complex to manufacture. The F-35 design was successful in the total elimination of these standard items while meeting the propulsion requirement of the aircraft.

Since the propulsion requirements of the F-22 are different, one must initiate an extensive study whether it is possible to do the same for F-22. This statement may also apply to the Chengdu fighters as well. Nonetheless, we are here to observe and discuss the differences of their DSI configurations from the F-35.

Re: F-22 DSI?

Unread postPosted: 25 Sep 2017, 19:54
by wrightwing
rhoads56 wrote:



Makes sense. But it seems there are differing ideas. Some are saying the DSI tech just wasn't mature when the F-22 was under development and you're saying the contrary and that it purely has to do with speed. Can you discuss why the DSI does not perform well at the F-22 supercruise speeds? Couldnt one design a specialized DSI for higher mach numbers?


It's not either/or, but inlet designs are largely based around specifications, as well as technology. Using DSI inlets would likely result in a lower top speed, for the F-22, than the design that was chosen. The F-35 was designed around a M.95 to M1.6 range. The F-22 supercruises faster than the F-35's maximum speed, and has a top speed in the M2.2 to 2.4 region. It's much more difficult to get >M2 with DSI inlets.

Re: F-22 DSI?

Unread postPosted: 25 Sep 2017, 23:46
by charlielima223
I'm just a layman when it comes to this...

As others have pointed out, the performance specs for the F-22 require a dedicated type of intake design. Given the fact that the F-22 was designed more for high altitude high speed flight wouldn't a DSI disrupt the airflow leading into the intake? From my understanding shock cones were movable structures to better regulate the super sonic shock cones and air into the intake thus leading to better high speed performance. If that is the case wouldn't the fixed position of the DSI hurt the F-22's high speed performance? How the F-22 with its S-Shaped inlet ducts is able to achieve supercruise of mach 1.5 and greater still blows me away.

Re: F-22 DSI?

Unread postPosted: 26 Sep 2017, 17:21
by rhoads56
wrightwing wrote:
rhoads56 wrote:



Makes sense. But it seems there are differing ideas. Some are saying the DSI tech just wasn't mature when the F-22 was under development and you're saying the contrary and that it purely has to do with speed. Can you discuss why the DSI does not perform well at the F-22 supercruise speeds? Couldnt one design a specialized DSI for higher mach numbers?


It's not either/or, but inlet designs are largely based around specifications, as well as technology. Using DSI inlets would likely result in a lower top speed, for the F-22, than the design that was chosen. The F-35 was designed around a M.95 to M1.6 range. The F-22 supercruises faster than the F-35's maximum speed, and has a top speed in the M2.2 to 2.4 region. It's much more difficult to get >M2 with DSI inlets.


This makes sense wrightwing. I guess I need to do further research to understand how the DSI works and why it's impractical for high-mach flight. Part of my question, looking back on it, was based on the fact that modern Chinese fighters, specifically the J-20, use DSI and have a similar combat role to the F-22. Hence my curiosity.

Re: F-22 DSI?

Unread postPosted: 26 Sep 2017, 19:29
by scat
I just want make two points crystal clear:

1. The DSI technology has not been developed in the mid 1980's when the F-22 inlet configuration was designed and chosen. It is obvious that the F-22 inlet has met all performance requirements of the ATF program. I do not believe that DSI was ever being considered for the Raptor in that time frame.

2. Here in 2017, almost thirty years later, someone can certainly perform an in-depth hypothetical study as to the appropriateness of using DSI for the Raptor to met all ATF performance requirements. However, this study needs to include all the knowledge base and the latest state-of-the-art techniques to bear. Whatever our discussions here maybe, they could all be personal conjectures and preferences at this stage.

F 22 DSI

Unread postPosted: 21 Jul 2018, 19:11
by bezsmexasvar
Any help trying to find where the list of lake maps from my navonics gold card on my dsi unit would help a bunch iv tried everything I can see ????

Re: F 22 DSI

Unread postPosted: 21 Jul 2018, 20:05
by botsing
bezsmexasvar wrote:Any help trying to find where the list of lake maps from my navonics gold card on my dsi unit would help a bunch iv tried everything I can see ????

Ehh, this thread is about a totally different "DSI" but let me help you anyway:

https://youtu.be/uJCjNZQWx9s