Any way to make my fighter more maneuverable?

[drtricky]

So I am building a fighter for the Top Gun AI challenge, and its current problem is that it has below-average maneuverability in high (250+ m/s), mid (250-100 m/s) and low (<100 m/s) speed turns when compared to the other smaller fighter designs.

Below are pictures of my abomination fighter:

Spoiler

Has ~1700 units of fuel. All panther engines are set to afterburning mode (excluding the one whiplash in the middle that has no such setting)

 

My question is: Can I make my aircraft more maneuverable (besides reducing size, because I like it big!), or have I hit the limit on how maneuverable a plane of its size and mass can be? I also cannot move the CoL any more any more forward into the CoM, as then the plane becomes too prone to stalling in turns (especially when it has expended its missiles). Does anyone know if there is anything I can do about this?

Edited January 17, 2016 by drtricky

[Boris-Barboris]

I don't see FAR, so you can always just spam wings and control surfaces. Where there is one wing, there can be three. Same for control surfaces.

Yes, there is a fundamental problem with large planes, they will never be as maneuverable as small ones. Their inertia characteristics grow faster with size than CLs and control authorities.

Edited January 17, 2016 by Boris-Barboris

[T-Bouw]

You could try to move weight more towards the center of the plane. That will help for maneuverability.

Use shorter wings for the same reason. That will certainly improve rolling.

[AeroGav]

What is meant by Maneuverability?    So far the thread is responding as though the OP means roll and pitch rate.    Or are we talking about the number of Gs that can be pulled at these airspeeds in both a sustained and transient manner?

 

[ForScience6686]

Better maneuverability = col on com.  Other than that you're trying to make a airliner a fighter so you will struggle.  Add more thrust as you should expect to lose speed in high g turns.  

[drtricky]

10 hours ago, Boris-Barboris said:

I don't see FAR, so you can always just spam wings and control surfaces. Where there is one wing, there can be three. Same for control surfaces.

Hiding one part completely within another is forbidden, and I know that I could stack wings, but that is generally looked down upon.

 

8 hours ago, AeroGav said:

What is meant by Maneuverability?    So far the thread is responding as though the OP means roll and pitch rate.    Or are we talking about the number of Gs that can be pulled at these airspeeds in both a sustained and transient manner?

 

Yeah, I should have mentioned that that is what I meant by maneuverability.

 

4 hours ago, ForScience6686 said:

Better maneuverability = col on com.

 

I mentioned in the OP that if I move the CoL any closer to the CoM, then the plane becomes too prone to stalling in turns after expending its missiles

[Starhawk]

I would suggest reaction wheels.

There may, however, be a problem at some point with joint strength.  If it's too maneuverable and you try to pull too many gees you may find the craft simply comes apart at the seams.

Happy landings!

[ForScience6686]

I understand, however you seem to want a bomber to fly like a fighter.  Dropping your payload should not shift your com, as that will change flight characteristics, for the worse according to you.  That's not how you would design such a craft.   dropping your payload should increase performance.  

Sometimes we expect too much from our designs.  I've been there myself, but I'm pretty sure my advice is still valid.

 

[drtricky]

16 minutes ago, ForScience6686 said:

I understand, however you seem to want a bomber to fly like a fighter.  Dropping your payload should not shift your com, as that will change flight characteristics, for the worse according to you.  That's not how you would design such a craft.   dropping your payload should increase performance.  

Dropping the missiles actually shifts the CoM back, which does makes the aircraft more maneuverable. Unfortunately, the issue that arises then is that it stalls too easily when making turns with its shifted CoM.

[Van Disaster]

The secrets to maneuverability are to keep as much mass in the centre as possible so the craft has low turning moment, as light overall as possible so it has low inertia, and as much lift and control surface as you can fit without murdering your cD. Generally less is more, the minimum size IRL is generally set by trying to fit all the equipment & fuel in and still be a good shape.

Small is beautiful. Notice how it's mostly wing!

[Plusck]

2 hours ago, drtricky said:

Dropping the missiles actually shifts the CoM back, which does makes the aircraft more maneuverable. Unfortunately, the issue that arises then is that it stalls too easily when making turns with its shifted CoM.

I have far less experience with planes than rockets, but I'd say the double wing design is what's killing you. The non-control surface of the rear wing is bound to resist any tight turns and act like the feathers on an arrow, but then simply stall when you push the turn any tighter. Almost all of the front wing is ahead of your CoM; however that is where your missiles are mounted so releasing them will necessarily move the CoM even further back.

Finally, it looks like half of your front wing's control surfaces are ahead of the CoM, and half are behind. I don't know what the game makes of that (does it even try to use them to control pitch?) but it makes them useful only for roll. If those control surfaces are used for pitch control, they will merely increase the drag of the wing and maybe even precipitate a stall.

So the only real solution that I can see is to abandon the double-wing arrangement. CoM should be centred on your wing, and the sweep of the wing will put CoL just behind CoM. Then you can load the wing with weapons without changing the distribution of weight. Control surfaces at the rear should provide 100% control, as should the canards. Anything less than 100% is simply going to resist your turns, then stall as soon as their max AoA is exceeded.

[Aethon]

What ForScience said.  Center of lift nearly on top of Center of mass.

[drtricky]

On 1/17/2016 at 1:48 PM, Starhawk said:

I would suggest reaction wheels.

There may, however, be a problem at some point with joint strength.  If it's too maneuverable and you try to pull too many gees you may find the craft simply comes apart at the seams.

I tested it, and my plane was able to resist ~26 gees of force in its tandem(?) winged fighter configuration (what is pictured), so I don't think structural integrity will be a problem. I'm not even sure if 26 gees of force is its limit 

On 1/17/2016 at 6:37 PM, Plusck said:

I have far less experience with planes than rockets, but I'd say the double wing design is what's killing you. The non-control surface of the rear wing is bound to resist any tight turns and act like the feathers on an arrow, but then simply stall when you push the turn any tighter. Almost all of the front wing is ahead of your CoM; however that is where your missiles are mounted so releasing them will necessarily move the CoM even further back.

Finally, it looks like half of your front wing's control surfaces are ahead of the CoM, and half are behind. I don't know what the game makes of that (does it even try to use them to control pitch?) but it makes them useful only for roll. If those control surfaces are used for pitch control, they will merely increase the drag of the wing and maybe even precipitate a stall.

So the only real solution that I can see is to abandon the double-wing arrangement. CoM should be centred on your wing, and the sweep of the wing will put CoL just behind CoM. Then you can load the wing with weapons without changing the distribution of weight. Control surfaces at the rear should provide 100% control, as should the canards. Anything less than 100% is simply going to resist your turns, then stall as soon as their max AoA is exceeded.

I tried removing a set of wings (while keeping CoL and CoM in roughly the same position), and the results was that while the plane was able to change the direction of its nose faster, the reduced wing area (combined with its mass, which was still over 40 tons) meant that the forward motion's ability to respond to the change of direction was much slower. Simply put, that made its maneuverability overall worse.

In the single winged config, I tried a comparison between using only canards and rear fins to change the aircraft's pitch, and also using the wing's control surfaces. The addition of the wing's control surfaces improved its ability to change its pitch. Roll rate was also obviously increased with usage of the wing's control surfaces.

Edited January 20, 2016 by drtricky