@#$&*(^ airplanes -- how do they work?

[Spricigo]

2 hours ago, Catbus said:

Totally disagree. As I mentioned, I've been successfully using the rocket equation and delta-v maps to design multistage rockets that go exactly where they need to with just enough fuel to get there, if not on the first try then on the second or (at most) third. (Usually the fault isn't in the basic design but rather is because I forget to put on solar panels or RCS thrusters.) Maybe I'm spoiled by the predictability, but the amount of sheer guesswork involved in designing planes, compared with the near-total absence of guesswork in designing rockets, has been frustrating to me.

I think you missed his point in a few ways. But more relevant:

How good a particular design is in VAB/SPH means nothing. Is when you fly it that you can evaluate how effective it really is. Its when you fly a design that you may spot thing that are not self-evident in the VAB and you build experience over time.

So a novice consulting deltaV charts and using some formulas may be able to build an effective ship for Mun landing and return after a few tries. A more experienced play do it in the first tries without the need to consult deltaV charts. An even more experienced do it without consulting charts, estimating the results, fly the mission  without the assist of maneuver nodes and with a ship that is 10% cheaper....then someone do a Eve landing and return using only Solid Rocket Engines.

What actually seem now like a lot of guesswork is just some simple aspect that are not exactly self evident (and some even counter-intuitive). But you like the experience to see then as it.

14 hours ago, Catbus said:

Though I'd still like to see an equation for how much lift is needed per ton of mass, or how much fuel it takes to circumnavigate Kerbin . . .

Sadly there is not a simple answer for 'how much wing I need?'. Let's take an real life example, those iconic aircrafts:

Spoiler

 

 

The first one have 18m² wing area and max take-off weight 13t, the other have 90m² and 18t.

KSP planes are not that different. (actually KSP replicas of both crafts are common) There is several ways to design a functional plane and anyone advocating some "true way" is just boasting his preferences.

For what is worth I tend have less than 1lift for ton, ~4/1 between main wing and tail (very rarely use canards), almost always have a few degrees of wing incidence and often TWR>1. The purpose of my planes, with very few exceptions, are either science collection in Kerbin or delivery of a payload/crew at LKO.

[XLjedi]

I have 3 or 4 decent aviation only planes; or at least so I think?  You can maybe take a look at how I set them up if you like.  Just follow the "My Designs" link in my signature below.

I generally follow these rules...

1. I display the center of balance and center of lift gadgets and basically try to keep COB slightly ahead of COL.  If these two get reversed at any point during your flight the plane is gonna be difficult to control.  When you let off the throttle, the plane needs to fall nose first to the ground.
2. If I'm looking for performance or a VTOL jet, then thrust to weight ratios are also of interest and I like the Engineering Redux mod for this info, TWR of 1.0 or higher tends to be a funner plane to fly.
3. For runway tracking I'm looking to maintain pretty close to a center track until the recommended rotation speed.  I find that I can usually fix and/or improve runway tracking by:
   • First and foremost make sure all of your gear are attached at a perfect 90° before moving them around.  ...and some of the Mk2 fuselages seems to be notoriously bad as anchor points in this respect.  ...and let's not even discuss a Mk2 fuselage radially attached to another Mk2 fuselage, you have to attach these things where the wings mount at perfect 180° and use the offset gadget to move them carefully into their final position or they compound error and translate it into what you think are well placed landing gear.   Somtimes to shore up the tracking, I might attach the gear where you might attach a wing, and then rotate it 90° and carefully move it around with the offset gadget.  Many times, this solves the problem.  Sometimes I allow some rotation on the main gear, but usually not more than a 10° to 15° camber. 
   • Next I would look to increase the distance from forward gear to main gear.   Move your forward gear all the way out to the nose; maybe past the nose even.  If it still won't track, I have to maybe consider a redesign at this point.  If it does track, then I start moving the forward gear back to see how far I can go before it gets loose again.
   • Mechanical Intervention - Dual vertical stabilizers, and maybe a couple small ventral fins get added as design modifications first. I've used split flaps in some of my designs (the FE-03 for instance) to create additional drag toward the rear of the aircraft to help stabilize it during takeoff and landing.  ...or even forward split flaps to help increase lift.  Speed brakes may be another option in this respect, and can also be used for additional yaw control.  But typically, it's more related to the first and second bullet above.   

Edited July 25, 2017 by XLjedi

[GDJ]

Sounds like you have all the advise you should need Catbus. Feel free to ask more if the need arises.

[Catbus]

I just want to call everyone's attention to this mod: Kramax Autopilot 1.3

If you have a plane that will fly, this mod will land it, 10 times out of 10. I'd put it in the must-have category along with MechJeb and Kerbal Alarm Clock.

Speaking of planes that will fly, I decided to try making some Kerbal planes based on the real planes that used the engines that Kerbal engines are based on. My first one, using a Juno engine, is a replica of the Messerschmitt Me-262. Oh, man. It flies like butta. Like butta.

[Kryten 2X4B 523P]

27 minutes ago, Catbus said:

I just want to call everyone's attention to this mod: Kramax Autopilot 1.3

If you have a plane that will fly, this mod will land it, 10 times out of 10. I'd put it in the must-have category along with MechJeb and Kerbal Alarm Clock.

Speaking of planes that will fly, I decided to try making some Kerbal planes based on the real planes that used the engines that Kerbal engines are based on. My first one, using a Juno engine, is a replica of the Messerschmitt Me-262. Oh, man. It flies like butta. Like butta.

 

Got a stock version? That appears to use Mechjeb parts on it. Love to give it a go but I  dont want yet another mod :-)

[Catbus]

Oh . . . the only MechJeb part on it is MechJeb. Can you load the craft without it? If not, I'll upload an all-stock version.

[Spricigo]

40 minutes ago, Catbus said:

I just want to call everyone's attention to this mod: Kramax Autopilot 1.3

If you have a plane that will fly, this mod will land it, 10 times out of 10. I'd put it in the must-have category along with MechJeb and Kerbal Alarm Clock.

Speaking of planes that will fly, I decided to try making some Kerbal planes based on the real planes that used the engines that Kerbal engines are based on. My first one, using a Juno engine, is a replica of the Messerschmitt Me-262. Oh, man. It flies like butta. Like butta.

 

I like the course guidance feature of Kramax and I'd love to have in as a standalone mod.  No autopilots in my must have category but info is always welcomed.

12 minutes ago, Kryten 2X4B 523P said:

 

Got a stock version? That appears to use Mechjeb parts on it. Love to give it a go but I  dont want yet another mod :-)

Actually it uses Pilot Assistant, not Mechjeb. Pilot Assistant is more geared towards atmospheric flight and planes. 

 

Edited August 4, 2017 by Spricigo

[Catbus]

No, what Kryten meant is that the Messerschmitt replica craft file includes a MechJeb unit, which I didn't think to remove before uploading it. It has nothing to do with the autopilot mod I linked to.

Edited August 4, 2017 by Catbus

[Spricigo]

Just now, Catbus said:

No, what Kryten meant is that the Messerschmitt replica craft file includes a MechJeb unit, which I didn't think to remove before uploading it. It has nothing to do with the autopilot mod I linked to.

D'Oh!

BTW 3 hints about craft sharing:

1. KerbalX  and spacecraft exchange

2. pure stock craft are accessible to more people.

3. Images and flight instructions

[Bottle Rocketeer 500]

@Catbus I have a plane on KerbalX that flies pretty well, and I routinely fly it between Kerbin City and KSC. You can get it here.

[Kryten 2X4B 523P]

13 hours ago, Catbus said:

Oh . . . the only MechJeb part on it is MechJeb. Can you load the craft without it? If not, I'll upload an all-stock version.

 

Not played about with craft file editing, but managed to do so without breaking it and got rid of the MJ part :-)

Had a play with the plane this morning - I like it! Control surface authority settings could do with being toned down a bit as its majorly twitchy, but its easy to take off / fly / land under SAS, and a pretty good stock replica of the original. Ground clearance for the landing gear is a bit tight, but thats a feature of the original.

 

Nicely done!