How do I design a stable, but "maneuverable" fighter aircraft?

[SpaceToad]

Hey guys! I am trying to better design my fighters, but they wont fly well at all without SAS, and even then, the moment you center the stick, the SAS oscillates a little! What can I do to fix this? How can I better design my aircraft?

[dafidge9898]

1 hour ago, SpaceToad said:

Hey guys! I am trying to better design my fighters, but they wont fly well at all without SAS, and even then, the moment you center the stick, the SAS oscillates a little! What can I do to fix this? How can I better design my aircraft?

The F-16 is unstable but maneuverable. The SAS always oscillates a little, and it can be annoying. If you wan't to build a stable craft, put the CoL behind the CoM, have the wings right on top of the CoM, and the stabs far behind it. If you want to build an unstable craft, don't do that. Instability means maneuverability most of the time. The Sukhoi fighters are incredibly maneuverable, but unstable. We've lost a few F-15s to unrecoverable spins. The Cessna 172 that I fly, cannot even get into a spin. A higher wing loading (weight/AreaOfWing) means lower maneuverability, a lower one means higher maneuverability, but at the cost of airspeed. So if you wan't a very maneuverable plane that doesn't kill its airspeed in one turn, put lot's of swept wing, big control surfaces, and big engines. But be careful, it might just flip over. Even if the CoM is infront of the CoL, it can still flip over.

And regarding SAS oscillations: if you're cruising, you can just decrease the control input of the control surfaces. However, this will make it less maneuverable. Real world fighters sort of do this; not to keep the plane from oscillating, but to keep overly aggressive high speed maneuvers from putting the pilot into G-LoC or tearing off the wings. You can fly without SAS, but you have to be very gentle and careful with your input. 

Edited August 2, 2016 by dafidge9898
About SAS oscillations

[Me1_base]

Make CoM within CoL and the control surfaces more far away from the CoL.The coefficient of pitching momentum should be 0 and will be near stable without sas

[SpaceToad]

16 hours ago, dafidge9898 said:

The F-16 is unstable but maneuverable. The SAS always oscillates a little, and it can be annoying. If you wan't to build a stable craft, put the CoL behind the CoM, have the wings right on top of the CoM, and the stabs far behind it. If you want to build an unstable craft, don't do that. Instability means maneuverability most of the time. The Sukhoi fighters are incredibly maneuverable, but unstable. We've lost a few F-15s to unrecoverable spins. The Cessna 172 that I fly, cannot even get into a spin. A higher wing loading (weight/AreaOfWing) means lower maneuverability, a lower one means higher maneuverability, but at the cost of airspeed. So if you wan't a very maneuverable plane that doesn't kill its airspeed in one turn, put lot's of swept wing, big control surfaces, and big engines. But be careful, it might just flip over. Even if the CoM is infront of the CoL, it can still flip over.

And regarding SAS oscillations: if you're cruising, you can just decrease the control input of the control surfaces. However, this will make it less maneuverable. Real world fighters sort of do this; not to keep the plane from oscillating, but to keep overly aggressive high speed maneuvers from putting the pilot into G-LoC or tearing off the wings. You can fly without SAS, but you have to be very gentle and careful with your input. 

Thanks for the input! Ill give it a try and report back.

(P.S. I wish I could afford aircraft maintenance costs, I wish I had my own 172  )

[dafidge9898]

11 minutes ago, SpaceToad said:

Thanks for the input! Ill give it a try and report back.

(P.S. I wish I could afford aircraft maintenance costs, I wish I had my own 172  )

It's not my own 172, it's with a flying group. The group owns the 172 and uses it to train students with volunteer instructors.

[SpaceToad]

4 hours ago, dafidge9898 said:

It's not my own 172, it's with a flying group. The group owns the 172 and uses it to train students with volunteer instructors.

Thats great! Are you a CFI?

[Rocket In My Pocket]

4 hours ago, dafidge9898 said:

It's not my own 172, it's with a flying group. The group owns the 172 and uses it to train students with volunteer instructors.

Cessna buddies! 

I fly a 172 with a friend a couple of times a month, we rent it from a flight school.

What a fantastic plane right? Simple, reliable, tried and true. If I was going to own a plane, it'd definitely be the humble Cessna, she's not flashy...but she'll get you where you're going in one piece.

[dafidge9898]

13 minutes ago, SpaceToad said:

Thats great! Are you a CFI?

Oh my goodness, no. Not yet, at least. I'm one of the students. Headed off to Embry Riddle in two weeks where I will hopefully get my CFI rating, as well as a degree in Aerospace Engineering!

 

7 minutes ago, Rocket In My Pocket said:

I fly a 172 with a friend a couple of times a month, we rent it from a flight school.

What a fantastic plane right? Simple, reliable, tried and true. If I was going to own a plane, it'd definitely be the humble Cessna, she's not flashy...but she'll get you where you're going in one piece.

Nothing like a good Cessna. My profile picture is actually from my first solo in a 172N. 

[foamyesque]

Aside from the suggestions above, which are all good, use an all-moving tail approach for your elevator (or all-moving canards, more or less equivalently). The standard canard is by far my favourite control surface for this reason, since, with zero-trim, it's a perfectly functional stabilizer, but it can allow for extraordinarily high-g turns by throwing your CoL in front of your CoM during the turn. I've pulled out of a straight down 1km/s dive to level flight 30m ASL in about two seconds :v

Edited August 3, 2016 by foamyesque

[Firemetal]

Moar struts. Col directly behind Com. Panther engines.

[SpaceToad]

19 hours ago, dafidge9898 said:

Oh my goodness, no. Not yet, at least. I'm one of the students. Headed off to Embry Riddle in two weeks where I will hopefully get my CFI rating, as well as a degree in Aerospace Engineering!

Thats awesome! My dad graduated from Embry Riddle Daytona, and instructed there for a while. He's now a UAL captain. Hopefully I'm next in the chain for flight instruction

[Hydrothermalventclam]

First off, for my fighter jets, I always use SAS, except when maneuvering.  When I design my planes, I try to keep the COL pretty close to the COM, but still behind it.  I also always use the thrust vectoring engines with afterburner, because they have a great vectoring range, and are reasonably powerful.  Also, if you deactivate some of the control surfaces, and generally use each control surface for only one action, then your planes will have less problems when you are maneuvering.  This is one of my best fighter jets.  The canards in the front, coupled with the tail fins give it pretty amazing maneuverability, and it flies very well with SAS on.