The 5th Generation Fighter challenge [FAR]

[RocketTurtle]

How do you guys recommend fixing this aircraft? It stalls whenever I turn, even with the elevators set to 12 deg deflection.

I'm really new to this, so be gentle.

[CrisK]

How do you guys recommend fixing this aircraft? It stalls whenever I turn, even with the elevators set to 12 deg deflection.

I'm really new to this, so be gentle.

This is not a bad design. If you post the craft file I'll take a look and give you specific advice. I'm sure others will as well!

[RocketTurtle]

This is not a bad design. If you post the craft file I'll take a look and give you specific advice. I'm sure others will as well!

As you wish. Thanks

https://www.dropbox.com/s/ycdz9njswo8qvru/pls%20dont%20die.craft?dl=0

Edit: just noticed that the vertical stabilizers were angled inward slightly, you may want to fix that.

Edited July 20, 2015 by RocketTurtle

[Halsfury]

I'm back, still have a lot of work so I'll be in and out over the next little while updating the main page as I go.

[FourGreenFields]

As you wish. Thanks

https://www.dropbox.com/s/ycdz9njswo8qvru/pls%20dont%20die.craft?dl=0

Edit: just noticed that the vertical stabilizers were angled inward slightly, you may want to fix that.

The wings aren't clipped properly. They cause each other to stall.

'Twas a very quick fix.

Gonna try to improve the design a little, and then upload both with just the wing fix, and improved version.

[RocketTurtle]

The wings aren't clipped properly. They cause each other to stall.

'Twas a very quick fix.

Gonna try to improve the design a little, and then upload both with just the wing fix, and improved version.

Oh. Whoopsie. I clipped them like that to keep the Mach 1 wave drag area low. Thanks though.

[FourGreenFields]

Oh. Whoopsie. I clipped them like that to keep the Mach 1 wave drag area low. Thanks though.

After fixing just the wings it had about 0.01m² less wave drag area though

Anyway: https://www.dropbox.com/s/41qduwj130neylr/pls%20dont%20die%20wingfix.craft?dl=0

And the variant with more fixes: https://www.dropbox.com/s/bzk92c6vz0z02kx/pls%20dont%20die.craft?dl=0

Changelog (might've forgoten one or two changes):

- Inner intakes rotated for lower wave drag

- Slight repositioning of rudder and elevator for lower wave drag

- Rotated rudders to add dihedral effect - found to also decrease yaw instability at Mach 4, haven't calculated at any other speed.

- Increased Mass/Strength of wings

- Added strut between wings and outer intakes

- Increased brake torque of rear gear legs

- Decreased elevator deflection from pitch 100% of 12° to pitch 90% of 12°. Can still easily reach critical AoA at all speeds.

- Slightly moved the wings forming the middle part of the fuselage back for lower wave drag

- Turned the "spoilers" at the rear into actual spoilers. Have succesfully tested them at up to Mach 0.7 at ground alt.

- Elevator no longer also used as aileron. Roll rate still high enough imho.

IIrc wave drag area about 0.57 at Mach 1, but already deleted the design, so can't check.

Other thoughts:

- Structural instability of wings + intakes and control surfaces (rudder) still an issue.

- Gear legs need reinforcements to tolerate slight slipping without causing a leathal crash

Edited July 20, 2015 by FourGreenFields

[Darth Lazarus]

I'm back, still have a lot of work so I'll be in and out over the next little while updating the main page as I go.

take your time budy

[RocketTurtle]

After fixing just the wings it had about 0.01m² less wave drag area though

Anyway: https://www.dropbox.com/s/41qduwj130neylr/pls%20dont%20die%20wingfix.craft?dl=0

And the variant with more fixes: https://www.dropbox.com/s/bzk92c6vz0z02kx/pls%20dont%20die.craft?dl=0

Changelog (might've forgoten one or two changes):

- Inner intakes rotated for lower wave drag

- Slight repositioning of rudder and elevator for lower wave drag

- Rotated rudders to add dihedral effect - found to also decrease yaw instability at Mach 4, haven't calculated at any other speed.

- Increased Mass/Strength of wings

- Added strut between wings and outer intakes

- Increased brake torque of rear gear legs

- Decreased elevator deflection from pitch 100% of 12° to pitch 90% of 12°. Can still easily reach critical AoA at all speeds.

- Slightly moved the wings forming the middle part of the fuselage back for lower wave drag

- Turned the "spoilers" at the rear into actual spoilers. Have succesfully tested them at up to Mach 0.7 at ground alt.

- Elevator no longer also used as aileron. Roll rate still high enough imho.

IIrc wave drag area about 0.57 at Mach 1, but already deleted the design, so can't check.

Other thoughts:

- Structural instability of wings + intakes and control surfaces (rudder) still an issue.

- Gear legs need reinforcements to tolerate slight slipping without causing a leathal crash

Not sure I can even consider this design mine any more. Thanks!

Edit: Also, I have no idea what that red statistic means, but how do I make it, well, green?

Edit #2: Also, when I try to make turns, it stalls, and one wing drops. I feel like this designs needs a major overhaul... are the wings too small?

It also isn't exactly a plane I'd want to take into combat above mach 1.

Edited July 20, 2015 by RocketTurtle

[CrisK]

As you wish. Thanks

https://www.dropbox.com/s/ycdz9njswo8qvru/pls%20dont%20die.craft?dl=0

Edit: just noticed that the vertical stabilizers were angled inward slightly, you may want to fix that.

Here's my take on your craft.

Here's what I changed:

There was far too much fuel. The mass of the aircraft was roughly twice what it needed to be, and the mass was shifted towards the rear of the aircraft.

The clipped wings added weight and drag, and did not provide any additional lift. I removed the extra pair of wings and replaced them with control surfaces.

I added a communotron to extend the front hub. I think that's the look that you were going for.

The FAR settings for the control surfaces were causing your craft to stall constantly. I optimised them.

I set up some spoilers so that it can land safely.

The rear canard shifted the center of lift too far behind the center of mass. They were really hurting your design.

The structural intakes cause drag and serve no function. But they look cool, so I kept them.

I added struts to reinforce the structurally risky areas. The craft no longer flexes.

I added drogue chutes so that you perform short landings. For example, on the island or KerbinSide's aircraft carrier.

I added basic action groups. Press 1 when you want to use the drogue chutes. Press 5 when you go transonic and press 4 when you're below mach 0.8 again.

With these very minor changes I think that you have one of the nicest light fighters in this competition. It's a good design! It's stable up to Mach 4.

The main limiting factor in your design is the stock wings and control surfaces. They suck. The stock swept wings especially suck. If you replace the wings with B9 procedural wings then it performs amazingly well.

Javascript is disabled. View full album

Edited July 20, 2015 by CrisK
Added a link.

[Hodo]

Not sure I can even consider this design mine any more. Thanks!

Edit: Also, I have no idea what that red statistic means, but how do I make it, well, green?

http://i.imgur.com/QpqefXf.png

Edit #2: Also, when I try to make turns, it stalls, and one wing drops. I feel like this designs needs a major overhaul... are the wings too small?

It also isn't exactly a plane I'd want to take into combat above mach 1.

The red number is the sideslip stability of the craft at .35mach at sea level. Means your craft is a bit unstable at landing at take off speeds or more accurately will slide sideways a bit at those speeds. Nothing to major, check at different speeds at altitudes.

[FourGreenFields]

The rear canard shifted the center of lift too far behind the center of mass. They were really hurting your design.

Only after you modded the design though. Even with them it wasn't all that stable before.

@RocketTurtle: As said, it still easily reaches critical AoA at any speed. Elevator authority was very high. And yes, wing loading wasn't the best (which Crisk's reduction of fuel load should've changed).

[RocketTurtle]

Here's my take on your craft.

Here's what I changed:

There was far too much fuel. The mass of the aircraft was roughly twice what it needed to be, and the mass was shifted towards the rear of the aircraft.

The clipped wings added weight and drag, and did not provide any additional lift. I removed the extra pair of wings and replaced them with control surfaces.

I added a communotron to extend the front hub. I think that's the look that you were going for.

The FAR settings for the control surfaces were causing your craft to stall constantly. I optimised them.

I set up some spoilers so that it can land safely.

The rear canard shifted the center of lift too far behind the center of mass. They were really hurting your design.

The structural intakes cause drag and serve no function. But they look cool, so I kept them.

I added struts to reinforce the structurally risky areas. The craft no longer flexes.

I added drogue chutes so that you perform short landings. For example, on the island or KerbinSide's aircraft carrier.

I added basic action groups. Press 1 when you want to use the drogue chutes. Press 5 when you go transonic and press 4 when you're below mach 0.8 again.

With these very minor changes I think that you have one of the nicest light fighters in this competition. It's a good design! It's stable up to Mach 4.

The main limiting factor in your design is the stock wings and control surfaces. They suck. The stock swept wings especially suck. If you replace the wings with B9 procedural wings then it performs amazingly well.

http://imgur.com/a/EfFv9

Thanks. I know the stock wings suck, but I wanted to keep the craft stock.

But thanks for the changes. I'll test out the plane now.

Also, the wave drag area is almost 1 m^2.

Is there any way I can bring this closer to the .5-ish it was before?

Edit: I just flew it, and it's still not quite there yet. It can only pull 7 ish G's...

I think I'm just really bad at this, lol.

Edited July 20, 2015 by RocketTurtle

[CrisK]

Only after you modded the design though. Even with them it wasn't all that stable before.

@RocketTurtle: As said, it still easily reaches critical AoA at any speed. Elevator authority was very high. And yes, wing loading wasn't the best (which Crisk's reduction of fuel load should've changed).

No, even before I modified the design the balance was poor. FourGreenFields, this conversation reflects a difference in opinion on what a fighter should be. None of your designs could really be considered fighters because they're not maneuverable. They can move quickly in a straight line, but they'd be easily outmaneuvered by the other designs in this thread.

Now, you could make the argument that interceptors like the YF-12 are the way of the future.

Thanks. I know the stock wings suck, but I wanted to keep the craft stock.

But thanks for the changes. I'll test out the plane now.

Also, the wave drag area is almost 1 m^2.

Is there any way I can bring this closer to the .5-ish it was before?

Why are you so concerned with the wave drag? If you really want to minimize it:

1. Use the offset tool to push the external tanks closer in.

2. Use the offset tool to push the wings further into the body.

3. Move the wings forward.

4. Rotate the RAM intakes.

5. Remove the intakes on the wings.

You're not bad at this. It really just is the crappy stock wings that are holding you back. Here's a version of your plane with a simple delta wing using B9 procedural wings and adjustable landing gear. Your design looks darned good with B9 wings, and it flies very well. It's also stable up to Mach 4 at any altitude under around 20km.

Edited July 20, 2015 by CrisK

[FourGreenFields]

No, even before I modified the design the balance was poor. FourGreenFields, this conversation reflects a difference in opinion on what a fighter should be. None of your designs could really be considered fighters because they're not maneuverable. They can move quickly in a straight line, but they'd be easily outmaneuvered by the other designs in this thread.

If a fighter can pull enough Gs to cause LoC at normal combat speed it's maneuverable enough. Prob already more than it needs. Roll rate matters ofcourse.

"Turning doesn't win battles" <- Spitfire pilot about his advantage over Focke-Wulf Fw 190s which were a LOT less maneuverable (better roll rate though) than Spits, but were roflstomping them all day. 190 wasn't an interceptor. You don't need turn rate to dogfight. Just enough to point your guns at a target, and prevent being shot if you overshoot.

Only reason I could imagine turn time and possibly supermaneuverability to matter in dogfights, is evading incoming missiles. But I have no experience with guided weaponary.

Granted though, my designs lack climb rate. That'd be important, but doesn't get rewarded with points. Same for E-retention in dives and turns, zoom climb abilities, and acceleration in dives.

Roll rate could be imroved, but isn't vital.

(That all being said, this assumes that dogfighting is still a thing. Being able to pick your fight (climb rate, speed, possibly service ceiling) is definitly important though)

Also, I don't trust SAS. And didn't want to bother tuning the AoA limiter to work properly. So I made sure all my designs are flyable without SAS and AoA limiter.

[RocketTurtle]

Why are you so concerned with the wave drag? If you really want to minimize it:

1. Use the offset tool to push the external tanks closer in.

2. Use the offset tool to push the wings further into the body.

3. Move the wings forward.

4. Rotate the RAM intakes.

5. Remove the intakes on the wings.

You're not bad at this. It really just is the crappy stock wings that are holding you back. Here's a version of your plane with a simple delta wing using B9 procedural wings and adjustable landing gear. Your design looks darned good with B9 wings, and it flies very well. It's also stable up to Mach 4 at any altitude under around 20km.

http://i.imgur.com/SC4Nc6B.png

http://i.imgur.com/1oUvPfg.png

Thanks. I guess I'll probably make a stock and a B9 version. But a lower wave drag area would make the plane faster, no?

If a fighter can pull enough Gs to cause LoC at normal combat speed it's maneuverable enough. Prob already more than it needs. Roll rate matters ofcourse.

"Turning doesn't win battles" <- Spitfire pilot about his advantage over Focke-Wulf Fw 190s which were a LOT less maneuverable (better roll rate though) than Spits, but were roflstomping them all day. 190 wasn't an interceptor. You don't need turn rate to dogfight. Just enough to point your guns at a target, and prevent being shot if you overshoot.

Only reason I could imagine turn time and possibly supermaneuverability to matter in dogfights, is evading incoming missiles. But I have no experience with guided weaponary.

Granted though, my designs lack climb rate. That'd be important, but doesn't get rewarded with points. Same for E-retention in dives and turns, zoom climb abilities, and acceleration in dives.

Roll rate could be imroved, but isn't vital.

(That all being said, this assumes that dogfighting is still a thing. Being able to pick your fight (climb rate, speed, possibly service ceiling) is definitly important though)

Also, I don't trust SAS. And didn't want to bother tuning the AoA limiter to work properly. So I made sure all my designs are flyable without SAS and AoA limiter.

Maneuverability is extremely important still. Despite all the "experts" saying that fights will be fought BVR, these BVR missiles can't keep up with the advancement of jamming and countermeasure technology. BVR missiles have hit rates in single digit percentages. And when jets are flying at Mach 2 towards each other, it goes from BVR to visual range in a matter of minutes. Let's say, hypothetically the F22 engages with an Su-35. The F22 fires its long range armament, however the 35 dodges the missiles with ease. Or maybe, the 35 uses its radar jamming tech. Whatever it is, it will turn into a within visual range fight quickly, and then maneuverability really matters.

[CrisK]

If a fighter can pull enough Gs to cause LoC at normal combat speed it's maneuverable enough. Prob already more than it needs. Roll rate matters ofcourse.

"Turning doesn't win battles" <- Spitfire pilot about his advantage over Focke-Wulf Fw 190s which were a LOT less maneuverable (better roll rate though) than Spits, but were roflstomping them all day. 190 wasn't an interceptor. You don't need turn rate to dogfight. Just enough to point your guns at a target, and prevent being shot if you overshoot.

Only reason I could imagine turn time and possibly supermaneuverability to matter in dogfights, is evading incoming missiles. But I have no experience with guided weaponary.

Granted though, my designs lack climb rate. That'd be important, but doesn't get rewarded with points. Same for E-retention in dives and turns, zoom climb abilities, and acceleration in dives.

Roll rate could be imroved, but isn't vital.

(That all being said, this assumes that dogfighting is still a thing. Being able to pick your fight (climb rate, speed, possibly service ceiling) is definitly important though)

Also, I don't trust SAS. And didn't want to bother tuning the AoA limiter to work properly. So I made sure all my designs are flyable without SAS and AoA limiter.

You're arguing for an interceptor or a reconnaissance aircraft. Again, that may be the way of the future - there's merit to that argument. However, any of the fighters in this thread can outmaneuver your designs by a wide margin.

Thanks. I guess I'll probably make a stock and a B9 version. But a lower wave drag area would make the plane faster, no?

Maneuverability is extremely important still. Despite all the "experts" saying that fights will be fought BVR, these BVR missiles can't keep up with the advancement of jamming and countermeasure technology. BVR missiles have hit rates in single digit percentages. And when jets are flying at Mach 2 towards each other, it goes from BVR to visual range in a matter of minutes. Let's say, hypothetically the F22 engages with an Su-35. The F22 fires its long range armament, however the 35 dodges the missiles with ease. Or maybe, the 35 uses its radar jamming tech. Whatever it is, it will turn into a within visual range fight quickly, and then maneuverability really matters.

Your design can already reach Mach IV with ease, at which point it explodes.

Modern fighters operate between mach 1 and mach 2. There's no practical reason to go faster than that. The Eurofighter and Raffale supercruise at around 1.4-1.5, and the F22 supercruises at 1.8.

Designing your fighter to be better in the transonic to supersonic ranges will lower its maneuverability. It comes down to what you value more - the ability to go really fast in one direction, or the ability to maintain Mach 0.8-1.2 and be highly maneuverable.

[RocketTurtle]

You're arguing for an interceptor or a reconnaissance aircraft. Again, that may be the way of the future - there's merit to that argument. However, any of the fighters in this thread can outmaneuver your designs by a wide margin.

Your design can already reach Mach IV with ease, at which point it explodes.

Modern fighters operate between mach 1 and mach 2. There's no practical reason to go faster than that. The Eurofighter and Raffale supercruise at around 1.4-1.5, and the F22 supercruises at 1.8.

Designing your fighter to be better in the transonic to supersonic ranges will lower its maneuverability. It comes down to what you value more - the ability to go really fast in one direction, or the ability to maintain Mach 0.8-1.2 and be highly maneuverable.

Well maneuverability doesn't matter much for this challenge, so normally I'd say speed, however my plane can only pull 7.5 G's, and it disassembles itself if you turn above Mach 1... so...

[FourGreenFields]

You're arguing for an interceptor or a reconnaissance aircraft. Again, that may be the way of the future - there's merit to that argument. However, any of the fighters in this thread can outmaneuver your designs by a wide margin.

Actually, I'm arguing that a fighter doesn't need to be that maneuverable. Not sure whether my designs are maneuverable enough, but being able to out-turn the opponent isn't nessecary. You just need to avoid the enemy being able to turn any dive on his 6 into a head on pass.

This is based on experience with WWII era air combat sims. If the opponent is on your 6, you need to turn alot tighter to avoid getting hit*. If you are on his 6, it's enough to be able to pull the lead (and that's what my "Flying Pencil" might not be able to do if the enemy does a break turn while out of fireing range).

If it developes into an actual dogfight you can use BnZ and energy fighting techniques to get on a tighter-turning target's 6 (rope a dope, yoyo, or simply zoom climb until the enemy can no longer follow, then dropping back down). And a good BnZer/E-fighter usually has the advantage of being able to pick his fights.

Being able to pick fights + being able to get on target's 6 vs being able to get on target's 6. I know what I'd choose.

*EDIT: This is meant as in "you'd need to turn so tight that you'd need to sacrifice so much other performance to achieve it, that it isn't worth it". Better do evasive maneuvers 'till you can dive away.

Edited July 21, 2015 by FourGreenFields

[RocketTurtle]

Actually, I'm arguing that a fighter doesn't need to be that maneuverable. Not sure whether my designs are maneuverable enough, but being able to out-turn the opponent isn't nessecary. You just need to avoid the enemy being able to turn any dive on his 6 into a head on pass.

This is based on experience with WWII era air combat sims. If the opponent is on your 6, you need to turn alot tighter to avoid getting hit*. If you are on his 6, it's enough to be able to pull the lead (and that's what my "Flying Pencil" might not be able to do if the enemy does a break turn while out of fireing range).

If it developes into an actual dogfight you can use BnZ and energy fighting techniques to get on a tighter-turning target's 6 (rope a dope, yoyo, or simply zoom climb until the enemy can no longer follow, then dropping back down). And a good BnZer/E-fighter usually has the advantage of being able to pick his fights.

Being able to pick fights + being able to get on target's 6 vs being able to get on target's 6. I know what I'd choose.

*EDIT: This is meant as in "you'd need to turn so tight that you'd need to sacrifice so much other performance to achieve it, that it isn't worth it". Better do evasive maneuvers 'till you can dive away.

Problem is, your design has crappy E-retention, which in extremely important for BnZ. Your designs are fast, but nobody dogfights at mach 4+.

And maneuverability is, and always will be important. Good luck dodging a sidewinder in a flying truck.

[tetryds]

Okay guys, just be careful and keep the conversation civil, I will not tolerate personal attacks if they happen.

[FourGreenFields]

Problem is, your design has crappy E-retention, which in extremely important for BnZ. Your designs are fast, but nobody dogfights at mach 4+.

And maneuverability is, and always will be important. Good luck dodging a sidewinder in a flying truck.

Never tested that much. Mostly for the challenge. So if you say the E-retentionn is crap, I can't argue with it.

And the 2. is just my point. All of what I wrote was under the assumption of a dogfight without guided weaponary (which I did mention before). I had already expected that rockets might make agility more important.

[RocketTurtle]

Never tested that much. Mostly for the challenge. So if you say the E-retentionn is crap, I can't argue with it.

And the 2. is just my point. All of what I wrote was under the assumption of a dogfight without guided weaponary (which I did mention before). I had already expected that rockets might make agility more important.

I remember you mentioning your design had bad e-retention, did you not?

Sorry then, lol.

[Hodo]

Never tested that much. Mostly for the challenge. So if you say the E-retentionn is crap, I can't argue with it.

And the 2. is just my point. All of what I wrote was under the assumption of a dogfight without guided weaponary (which I did mention before). I had already expected that rockets might make agility more important.

I think I may have inadvertently started this debate and I am sorry about that.

But about your craft, even if under the non-missile engagements and gun only fights, your craft wouldnt fair very well due to its poor roll rate. Lets look at historical examples of great energy fighters, or Boom and Zoom fighters. The FW-190D9 by far one of the best BnZ fighters in history. It had a phenomenal roll rate better than anything the Allies had during the war. This aloud it to pull off surprisingly quick reversals and get the shot then climb away before anything could counter it.

Next we could look at the Me/Bf-109G6, again, another light weight aircraft that had a great roll rate, and actually could turn pretty decently under high speeds, but suffered at lower speeds. This mated with its power to weight ratio, it could pull itself out of most fights if it needed to. The 109G6 manual even said, "when in trouble point your nose towards the heavens and climb like a home sick angel." The G6 had a 4200fpm climb rate, when the next best allied aircraft could only manage 3700fpm.

Lastly we could look at my personal favorite, the P-47D Thunderbolt. That thing was a TRUE energy fighter. If the jug was caught low, it was dead. But if it had the altitude advantage it would kill anything in the air. And because the Thunderbolt accelerated in a dive like a brick dropped by god, it could retain that energy into a mild climb. But if you asked it to turn it would burn that energy faster than a forest fire through a kindling factory.

[RocketTurtle]

faster than a forest fire through a kindling factory.

That one's new.

But in all seriousness, I agree.