FAQ for F-15 AFM Development

[CASoldier2014]

F15 in dcs clicklabel or not?

 

No.

[wilbur81]

F-15C FM work?

 

Hey, Gents.

 

Anyone out there aware of any work being done to further enhance the F-15C flight model/avionics at this time? I think the work they've already done on the current AFM is fantastic (though not perfect).

[Svend_Dellepude]

http://forums.eagle.ru/showpost.php?p=2379635&postcount=210

[SinusoidDelta]

http://forums.eagle.ru/showpost.php?p=2379635&postcount=210

 

Could you expand on the meaning of referenced post?

[wilbur81]

Could you expand on the meaning of referenced post?

 

^^^

Ditto

[Svend_Dellepude]

Hey, Gents.

 

Anyone out there aware of any work being done to further enhance the F-15C flight model/avionics at this time? I think the work they've already done on the current AFM is fantastic (though not perfect).

 

The FM is still being worked on. While I'd love to give detailed reports, unfortunately that won't happen without permission.

 

I was trying to answer Wilbur81. Maybe it makes more sense this way.

FM still being worked on, but dunno about avionics. :thumbup:

[wilbur81]

High Alt. Performance

 

Some of you have probably seen this video, but fascinating stuff!

 

 

I am most intrigued, though, by what you see from min. 14:10 through 16:28. I tried to fly a similar speed and altitude profile today with the F-15C in DCS because I thought as I was watching this video earlier today, "Man, the DCS -15 is more of a pig at that altitude/airspeed than this real-life Viper that has significantly less wing area." After watching, I'm pretty sure that, though the AFM on the Eagle is fantastic up to about 20K, it's turning performance (max G capability) at anything above about 30K is really poor. At Mach 2 and about 41K with the Eagle, I could only get about a 5.9 G pull, and that only being a very momentary spike of performance...not sustained turning like you see in the real life video. Would love to see the Eagle AFM with a more realistic high alt., turning performance...unless the Viper really does have an edge here?

 

I know the air is thin up there, but again...that video seems to show that Viper handling surprisingly nicely at those altitudes.

 

Side note: ironically, it does appear that the DCS Eagle's roll rate is too high at altitude. Anyway, I still LOVE what they've accomplished with the F-15 AFM!

[GGTharos]

The AoA is not treated correctly as altitude increases. The devs know.

[Weta43]

edit - thread moved on while I had the page open :)

[SinusoidDelta]

Sounds like every plane out there!

 

It's really not. We're seeing 200dps at low AoA. Very NOT like the Bitburg roll.

 

Yes, a lot of research has been done, and every time it's done the CAS gets an upgrade to stop it from happening.

The Bitburg roll is an interesting example, but the end it is said to 'not be well understood', and in any case if you do read the research you'll find that the eagle doesn't enter what they call a 'true departure' too often, even when they're trying for it.

 

In hindsight I agree, they are dissimilar. I didn't know the roll rate in DCS was 200dps. I actually have read the research on uncommanded roll and departure in the F-15, quite extensively. The Bitburg Roll had multiple contributing factors. These factors result in lateral asymmetries, producing transient yaw acceleration, yaw and wing rock. This is amplified with low fuel and carrying stores. In this sense I think the AFM issue is quite similar.

 

My gut says yes, but I'm not sure it's really testable (or at least easily testable). You could turn the CAS off, but in theory the horizontal stabilizers can still be physically rigged to deal with it.

 

As you're aware, AFCS is not modeled properly in the AFM. CAS off flight is wildly inaccurate compared to the real data I've seen.

 

Some of these things you can log with lua. Frankly unless you're an F-15 pilot though or you're trying to match public empirical research, you're probably not doing anything that's very useful. That's not to say it can't happen, just that it's rare. There's also a lot of data that's simply not available.

 

I'm not a test pilot :( I'm just an engineer who looks for problems to solve, sometimes I end up creating them:lol: I did come up with a solution for data logging (Not involving Tacview). That being said, there is a plethora of useful empirical data, it only needs sorted through and correlated to DCS flight test data.

 

I still see people coming around complaining that 'this FM sucks, the F-15 can't climb straight up!' Usually they don't even know what the -1 is :)

 

I think the FM is very, very good. It just needs refinement and I'm excited for future developments. Furthermore, most people don't realize the -1 isn't the only manual. ;)

Edited July 16, 2015 by SinusoidDelta

[wilbur81]

The AoA is not treated correctly as altitude increases. The devs know.

 

Good to know that they know. :-) It'd be great to see it fixed! It never feels right to have to come down below 20K in an F-15 to do very basic ACM at moderate G levels. The muted AoA up high also makes missile evasion tough if you're stuck at 'airline-altitudes'.

[SinusoidDelta]

Some of you have probably seen this video, but fascinating stuff!

 

 

I am most intrigued, though, by what you see from min. 14:10 through 16:28. I tried to fly a similar speed and altitude profile today with the F-15C in DCS because I thought as I was watching this video earlier today, "Man, the DCS -15 is more of a pig at that altitude/airspeed than this real-life Viper that has significantly less wing area." After watching, I'm pretty sure that, though the AFM on the Eagle is fantastic up to about 20K, it's turning performance (max G capability) at anything above about 30K is really poor. At Mach 2 and about 41K with the Eagle, I could only get about a 5.9 G pull, and that only being a very momentary spike of performance...not sustained turning like you see in the real life video. Would love to see the Eagle AFM with a more realistic high alt., turning performance...unless the Viper really does have an edge here?

 

I know the air is thin up there, but again...that video seems to show that Viper handling surprisingly nicely at those altitudes.

 

Side note: ironically, it does appear that the DCS Eagle's roll rate is too high at altitude. Anyway, I still LOVE what they've accomplished with the F-15 AFM!

 

That video is chock full of extremely useful performance figures. He pulls 5G at 41k at M1.5. He does bleed speed off rapidly though.

[Svend_Dellepude]

He was actually at 2.0M when he started maneuvering and ended at 1.0M.

Completely different A/C though and I don't know if we ever see his load out and fuel, but he probably only has the wingtips loaded.

[SkateZilla]

Why are we comparing videos of F16s to the F15 PFM?

 

They are no where near the same performance wise.

[GGTharos]

They are both supersonic fighters and both fly like supersonic fighters.

[SinusoidDelta]

In the Raytheon Cup 2013 video you can clearly see him maneuvering and the altimeter reading 50k ft around 1:20.

 

http://m.military.com/video/aircraft/jet-fighters/f-15-eagle-2013-raytheon-trophy-video/3547422373001/

 

Edited August 4, 2015 by SinusoidDelta

[wilbur81]

...that's why

 

Why are we comparing videos of F16s to the F15 PFM?

 

They are no where near the same performance wise.

 

Because the F-15 should perform just as well or better than an F-16 (in real life at least) at extreme altitudes due to its SIGNIFICANTLY larger wing area, that's why. Also, someone mentioned loadouts.... try flying the F-15C in DCS absolutely clean at altitudes above 30K... it is still an unstable pig compared to a real life F-16 (and F-15C apparently). But, as GG said, "the Devs know" and hopefully they're working on it.

[Ktulu2]

In the Raytheon Cup 2013 video you can clearly see him maneuvering and the altimeter reading 50k ft around 1:20.

 

Great video :thumbup:

[strikeeagle]

Because the F-15 should perform just as well or better than an F-16 (in real life at least) at extreme altitudes due to its SIGNIFICANTLY larger wing area, that's why. Also, someone mentioned loadouts.... try flying the F-15C in DCS absolutely clean at altitudes above 30K... it is still an unstable pig compared to a real life F-16 (and F-15C apparently). But, as GG said, "the Devs know" and hopefully they're working on it.

 

Very unstable! I've had 2 rides in the back of this thing and the real jet does not fly like this. Hell, the Strike sims at SJ don't fly like this. You just can't simulate a PRCA or ARI for a computer sim/game.

 

Those dudes that fly/fight in the 15 hammer the crap out of the stick during a fight...you can't (or I can't) do that w/this sim w/out it flopping around like a fish.

Edited August 4, 2015 by strikeeagle

[SinusoidDelta]

Very unstable! I've had 2 rides in the back of this thing and the real jet does not fly like this. Hell, the Strike sims at SJ don't fly like this. You just can't simulate a PRCA or ARI for a computer sim/game.

 

Those dudes that fly/fight in the 15 hammer the crap out of the stick during a fight...you can't (or I can't) do that w/this sim w/out it flopping around like a fish.

 

Why can't the PRCA or the ARI be simulated?

[pr1malr8ge]

Very unstable! I've had 2 rides in the back of this thing and the real jet does not fly like this. Hell, the Strike sims at SJ don't fly like this. You just can't simulate a PRCA or ARI for a computer sim/game.

 

Those dudes that fly/fight in the 15 hammer the crap out of the stick during a fight...you can't (or I can't) do that w/this sim w/out it flopping around like a fish.

 

No but others on this forum seem to think the eagle in game has no modeling issues *caugh //RAGE *caugh..

 

Thanks for confirming what I have said already. I have had a family member whom is a former F15C driver state the same thing. It is not even close to the real thing in that flight envelope..

[GGTharos]

In fact I have worked with cofcorpse to improve the PRCA. I don't know how much improvement will go into the ARI, but hopefully enough to make the feels better (and in particular, the flying :) ). This is one of those required-dev-time-to-do-this-vs-other-stuff things.

 

Not @SinusoidDelta: There's no point in further complaints. The problem is known, understood, and hopefully will be fixed in a future release. Just might not be the 'next' release.

 

Why can't the PRCA or the ARI be simulated?

[Svend_Dellepude]

In the Raytheon Cup 2013 video you can clearly see him maneuvering and the altimeter reading 50k ft around 1:20.

 

http://m.military.com/video/aircraft/jet-fighters/f-15-eagle-2013-raytheon-trophy-video/3547422373001/

 

Really really nice video you posted there SinusoidDelta. :thumbup:

[strikeeagle]

Why can't the PRCA or the ARI be simulated?

 

As complicated as the PRCA is, the components that make it work, the air data inputs that it uses, and it's hydo-mechanical inner workings...how can it be accurately simulated for a game? I think it's cool how the developers go about getting data to attempt to simulate the jets flight characteristics, but I don't think those components can be simulated. The REAL flight sims don't fly 100% like the real jet, but both DCS and the real sims have one thing in common that's missing...feel/feedback.

[SinusoidDelta]

I'd love to have a go in a professional simulator. You've flown the eagle in real life as well? What 'feel'/feedback' was the sim missing as opposed to the real thing?

 

Regarding the PRCA, IMO the CSBPC could be simulated in Matlab or Labview. The flight control system is a bunch of block diagrams in the virtual sense. I'm not saying it would be a walk in the park to simulate but it's far from impossible.

Edited August 4, 2015 by SinusoidDelta