F-15s Unrealistic slow speed handling

[jc005e]

You've already had one thread on this topic locked (yesterday no-less).

 

Pretty sure you're about to feel the force of an unhappy moderation team considering you haven't even bothered to bring hard data to this thread (again).

 

 

Yeah... A room full of eagle fanboys , I already knew ALOT would disagree. I know you guys want your precious F-15 to stay the way it is because you can easily get kills and easily out maneuver misses when your plane is literally unbreakable.

[jc005e]

F-15 skin damage MAKS 2011 sunny:

 

 

LMAO an F-15E strike eagle.. Much more heaver , less of a Thrust to weight.. Those turns weren't even the same as i was doing with the F-15C , i would love to see an F-15E attemp such maneuvers and a low altitude high alpha pass like i did with the F-15C.. in my video, The plane would probably just fall out of the sky.

[jc005e]

I am also posting another video with wing tanks , AGIAN i can still attempt a slow speed low altitude high alpha pass and the pitch rates are still similar to that of an F-18 or F-16. I also manage to pull more than 9g with the tanks on , Plane doesn't even break or anything... Lol so agian i can see why many of you eagle fanboys don't want this plane to change.

 

I would love to see how you guys fight if they ever created a damage model when over stressing the air frame too many times... FOX 3!! with a split S and bam!! a wing snaps off:megalol:

[jc005e]

TRUST ME i know i wont win with you eagle fan boys but F-15s is no way should be performing like this at lower altitudes and slower speeds. They way the f-15 is designed theirs just no way. UP HIGH is where its best maneuverability should be not LOW and SLOW. Its needs a fix.

[Yurgon]

[...] i would love to see an F-15E attemp such maneuvers and a low altitude high alpha pass like i did with the F-15C.. in my video, The plane would probably just fall out of the sky.

 

Well, you're right, obviously. If you've never seen it, it can't be true. :music_whistling:

 

The thing is, and some posters already hinted to this... if you want the flight model corrected, ED can't really go by "I've never seen this, so it must be wrong!"

There is hard data out there, there are performance charts, and if the FM is off as much as you suggest, it should take only a few minutes to back this up with real life data.

 

The result would probably be an improved simulation for everyone.

 

Most fortunately, ED doesn't code FMs by people's gut feeling, though (at least not to my knowledge).

 

Edit:

 

I would love to see how you guys fight if they ever created a damage model when over stressing the air frame too many times...

 

Interesting you should bring this up right after commenting on the F-15E display video.

 

The g-limits, to the best of my knowledge, don't mean "pull more than the limit and the wing snaps off". It's more like "stay within the limits and the airframe can have a service life of X years".

 

When something snaps off the vertical stabilizer of the F-15E in the airshow video, I always imagine the crew going...

"Did you feel that?!"

"Yeah, what was that? Did we lose the stabilizer?"

"I... uh... nope, it's still there."

"Yeah, looks okay. You wanna abort?"

"Well... we probably should."

"Yeah, we probably should. So?"

"Foxtrot Uniform Charlie Kilo it! :D"

 

I've never seen an F-15 tossed around like that, and like you so appropriately pointed out, it's a heavy F-15E.

 

Ultimately, I'm saying that when DCS pilots fly the aircraft at the edge of the envelope, it doesn't mean it outperforms the real thing. Maybe it just means real pilots don't usually get that close to the edge - if for no other reason, then because they value their careers and their lives.

 

But, again, simply prove DCS got it wrong and it'll get fixed eventually.

Edited August 17, 2017 by Yurgon

[DarkFire]

Yeah... A room full of eagle fanboys , I already knew ALOT would disagree. I know you guys want your precious F-15 to stay the way it is because you can easily get kills and easily out maneuver misses when your plane is literally unbreakable.

 

Read my posting history and tell me again how I'm an Eagle fan boy. FYI I have 3K hours in the Su-27 over the history of DCS and probably 1.5 hours in the Eagle. But whatever, I'm done here. Believe what you want to believe. :dunno:

[BuzzU]

TRUST ME i know i wont win with you eagle fan boys but F-15s is no way should be performing like this at lower altitudes and slower speeds. They way the f-15 is designed theirs just no way. UP HIGH is where its best maneuverability should be not LOW and SLOW. Its needs a fix.

 

 

Shouldn't you be on the Russian forum?

[jc005e]

Read my posting history and tell me again how I'm an Eagle fan boy. FYI I have 3K hours in the Su-27 over the history of DCS and probably 1.5 hours in the Eagle. But whatever, I'm done here. Believe what you want to believe. :dunno:

 

Well Sorry on my behalf. I did not take the time to view your profile and probably wont anyway. My main message is to ED and that they need to fix this planes flight model.

[jc005e]

https://youtu.be/X3tWj55aqL0

 

 

With tanks and still able to do aggressive pitches , Slow high alpha passes , over G turns ect...

 

This is the last of my post on regarding the F-15. ED Fix this toy plane :lol:

[Curly]

I could be wrong, but you never went over 20 degrees. The F-15 displays AoA in units (units = AoA + 10). I think your HUD showed 30 max. The video is very low quality though.

The conversion for AOA to units in the eagle is

AoA[units] = 0.7728*AoA[Degrees] + 12.22

 

I saw a max of 41 indicated on the hud giving a true a of 37 Degrees. The craft looked deeply stalled at that point at around 3:33.

 

The craft is stalled well before that earlier in the video. At around 3:24 it's at 33 units of Alpha and stalled.

 

The ability to generate more alpha in the stall is more likely the result of the Eagle greater than 1:1 thrust to weight ratio and excellent pitch authority due to it's large flight control surfaces. You are just able to slowly rotate the aircraft while the huge engines rocket you up.

 

Where the craft does actually stall it looks pretty much on the numbers from the flight manual

 

http://www.avialogs.com/viewer/avialogs-documentviewer.php?id=3704

 

page 247.

[GGTharos]

There is a lot more information/data out there, but I'll just stick to this for now:

 

http://www.dtic.mil/dtic/tr/fulltext/u2/a319164.pdf

 

PDF page 11. A very quick summary: This was early testing and research into F-15's uncommanded roll off tendencies at 30 degrees AoA or higher. The purpose of this research was to correct this roll-off, and they did so successfully.

 

This isn't about spiking to 30deg AOA, this is about flying at 30deg AOA for a number of purposes including a tree fight (like scissors but going so slow you can't roll ... rudders and pitch only, AFAIK) or maintaining position behind another slow aircraft's 3-9 line.

 

Well Sorry on my behalf. I did not take the time to view your profile and probably wont anyway. My main message is to ED and that they need to fix this planes flight model.

[GGTharos]

I didn't watch the whole thing ... your first 'aggressive pitch' manages a whopping 5.6g (well within structural tolerance, even with the 2 bags) and a spike to less than 37deg AoA which is less that what's recorded for defensive jinks (45+).

 

You don't even know what parameters to fly to demonstrate that there IS a problem, and would still be a demonstration of the missing DM and nothing to do with AoA ;)

 

PS: Low altitude improves AoA handling, not the other way around. Your remark regarding high/low altitude doesn't hold up. This aerodynamic fact (and others) hold up for all aircraft, not just the eagle.

 

https://youtu.be/X3tWj55aqL0

 

 

With tanks and still able to do aggressive pitches , Slow high alpha passes , over G turns ect...

 

This is the last of my post on regarding the F-15. ED Fix this toy plane :lol:

Edited August 17, 2017 by GGTharos

[mytai01]

It's just the whiskey talking

[mytai01]

You need to watch flight testing videos, my young Padawan...

[Gunny Highway]

This is a mis-characterization of the SU-27 and to Russian engineering. Which is pretty impressive and far from poor.

 

Its a matter of attitude. Russians think from a war time perspective which states stuff will get shot out of the sky and design accordingly. Cheap where they can afford it to be and expensive where it must be and easily replaceable under war time conditions is not a poor design choice nor poor engineering.

 

You are reinforcing my point. They poorly engineer things because they know it will get shot down anyway. F15C is engineered to kick A$$. Check its record. 102-0.

[AndytotheD]

I knew this was bait

[BuzzU]

You are reinforcing my point. They poorly engineer things because they know it will get shot down anyway. F15C is engineered to kick A$$. Check its record. 102-0.

 

 

+1

[lunaticfringe]

TRUST ME i know i wont win with you eagle fan boys but F-15s is no way should be performing like this at lower altitudes and slower speeds.

 

USAF F-15 instructors dictate 230 knots and 30 units AoA at 5000' AGL.

 

But hey- random person on the internet without any documentation whatosever says he's never seen it done at an airshow; I don't know about anybody else, but *I'm* convinced.

Edited August 17, 2017 by NineLine
edit for 1.2

[The Black Swan]

Jc005e have you actually taken the Su-27 to its max to compare?

[David OC]

Are all these accusations that get started around here about FM's, with no real proper research or evidence in hand, is this because of lack of understanding just how these FM's are created for DCS?

 

DCS is basically a simulated wind tunnel, there is no faking of performance when building up AFM or PFM level Flight models. They either work across the flight envelope or they don't work and something is out somewhere, this is why it can take so long for aircraft to leave beta, they need to be tested and tested some more until very mature, that's why the F15 was created, to help mature ED's new technology for new jets such as the F18.

 

Quote by EvilBivol-1 Belsimtek/TFC Associate

 

"We break the aircraft down into sub-elements (including breaking the rotor blades/propeller blades/wings/stabilizers into sub-elements like the root, mid-section, trailing edge) and apply physics equations to each element in real time to determine the forces and moments acting on it at any point in time.

 

To be short, AFM is built from the ground up. We don't build behaviors to match desired performance. We build a physical model as correctly as possible and then check it against known performance characteristics."

End Quote

 

You can read the full post here

 

Here are some more good example of what goes into creating these FM works of art.

 

F14 AIM-54 Phoenix CFD Whitepaper. WOW cRazy weapon modeling.

 

 

(Mirage) 2000 Update on the flight model.

 

DCS Flight Model explanations by Wags.

 

F16 High Fidelity Flight Dynamics and Tech/Academic Initial Demonstration.

 

 

The thing the valued researcher can not do is to obtain real blade tip log from the simulation, but I can.

This log obtained form in vitro tool is for 280 kph and the collective pitch rotor AoA close to the simulation. Later I can obtain it just from the simulation that uses just the same calculation model as the tool.

Of course, the REAL TIME model used in Ka-50 (for average PC of 2005, by the way) did not use true aeroelasticity and detailed wake model as non-real time models used in the references by Kamov company...

 

But it does use true aerodynamic and mechanical simulation of each blade using the shortest dt we can afford.

 

But the result of it is quite good for the real time, single PC simulation.

If the simulated helicopter performs the same aerobatics as real without blade collisions - it's a good FM, right?

 

 

 

 

The complete post can be found here

 

 

Love that one above, A simulation in DCS of a calculation tool that does simulations.

 

.

Edited August 17, 2017 by David OC

[MiG21bisFishbedL]

[VampireNZ]

...I don't know about anybody else, but *I'm* convinced.

 

Yes - but that is because you are a lunatic....living out there on the fringe! :thumbup:

 

But yea I am with you - I love reading on the interwebs how aircraft are 'supposed' to fly hehe.

[NineLine]

TRUST ME i know i wont win with you eagle fan boys but F-15s is no way should be performing like this at lower altitudes and slower speeds. They way the f-15 is designed theirs just no way. UP HIGH is where its best maneuverability should be not LOW and SLOW. Its needs a fix.

 

You once again brought an argument based on opinion on how you feel the F-15 should or shouldnt act. (and a very low-rez video)

 

You need to show real data that something is wrong, you can compare with what real world sources are available out there, if its so off, it should be easy for you to do. That said, open another thread without something to back it up again, you will be venturing into 1.4 territory. ED and BST will stand behind their product, its been tested by actual Eagle drivers, so you need to do your homework to bring change.

 

Right now this thread is just going to go in the toilet... so when you are ready to provide hard data, try again.

 

Thread closed based on Rule 1.4.

 

Here is a low-quality vid as well... least it has a decent soundtrack though...

 

Edited August 17, 2017 by NineLine