How to NOT crash my plane?

[Matrazuchi]

Hi all, I just got drawn into playing KSP and it wasn't long until I built my first aircraft, trying to stick by whatever basic knowledge about winged flight I had... not much, if you're wondering.

So, here it is, my first flying craft, that seems to take off well (at about 60m/s), but I can't seem to be able to land it, no matter how slow I'm trying to put it down. I still don't master the skills to align it with the runway, so the landing is just on grasslands, but still... i can't understand why it's always blowing to pieces, even at very shallow descent angles and low speed (i tried speeds between 50m/s to 100m/s). It's not stalling and it's not going too fast... I must be doing something wrong.

Any "piloting" advice is more than welcome. Also, I was wondering if is possible to share a model, for whoever would like to try and fly it and give some feedback.

Thanks.

[18Watt]

First, welcome to the KSP forums @Matrazuchi!

Could be a lot of things going on, here's my first few guesses:

• Your tail extends behind the landing gear a long way (which is normal).  Is the tail hitting the ground when you touch down?
• Are your main landing gear attached to the engine pylons?  If so, I've had problems with that.
  • I have much better luck mounting the landing gear to the central fuselage.  You can then use the 'rotate' and 'offset' tools to position the landing gear where you need them.
  • The game will still think the gear is attached to the center fuselage.  Not sure why, but no matter how much I strut and auto strut, attaching the gear to wings or engine pylons often causes the wings or pylons to fall off during landing.
• Those tiny landing gear are not ideal either.  In general I find that whatever landing gear 'looks about right' is usually not adequate to support the weight I'm trying to land.
• However, early in the tech tree, you might only have that tiny landing gear.  So, you might want to adjust the spring and damping values of the main gear.  Try increasing the damping value, perhaps even max-out the damping.  Just taking a wild guess, I'd try setting the spring value of the main gear in the 1.2 - 1.5 range.
• Touch down as slow as you can, slower is better.  I'm guessing your only limit on how slow you can fly is eventually your angle of attack will be so high that you risk the tail hitting the ground.

[Matrazuchi]

@18Watt
Indeed my landing gear is attached to the engine pylons... that may be indeed the issue. I'll move them on the body and then manually offset them in the desired position.
Also, I will adjust the damping of landing gear springs. Should I increase or lower (or leave as is) the spring value?

My landing angles were very shallow, almost horizontal, which baffled me even more when I saw the thing blowing to pieces... I'll keep you updated if the above changes will help.

Thank you for the quick and valuable feedback.

[18Watt]

2 minutes ago, Matrazuchi said:

Also, I will adjust the damping of landing gear springs. Should I increase or lower (or leave as is) the spring value?

First, I suggest making one or two changes at a time.  It's tedious, but less confusing.  I'd start with mounting the gear to the center fuselage, then off-setting to the desired location, and see how that works.

Next, for spring and damper settings, once you select 'manual' for those, take a look at the default values.  I usually increase damping to start with, sometimes I just max out damping right away.  Maybe try 1.8 for damping.

The default spring setting is probably 1.0.  That is probably close to what will work, but you could also try adjusting that too.  For really light planes you would want to decrease the spring value.  For heavier planes, maybe increase the value to 1.2 - 1.5.  

I couldn't tell from the screenshot, but is one of your center fuselage sections also a fuel tank?  If so, the fuel in the center tank has a lot of weight.  If you are landing with a lot of fuel in the plane, that will affect how much energy the landing gear needs to absorb.

If you are touching down gently at speeds below 80 m/s, I suspect there is something going on with the design.  My first guess is that mounting the gear to the center fuselage will help.  Good luck!

 

[Matrazuchi]

@18Watt

My first successful landing! ... After moving the landing gear to the body and then shifting it manually in the desired position.

To answer your previous question: no, the body under the wings is a passenger section. The only fuel the craft carries is in the engines tanks.

 

[18Watt]

1 minute ago, Matrazuchi said:

My first successful landing!

Awesome!  And that's a great looking plane, by the way!

[Vanamonde]

That is the first step of landing gear and it is extremely weak. If you replace them with a later model I think that will solve most of your troubles. 

In other advice, you can simplify your design by removing one of those sets of horizontal canards. You are likely having difficult with over-steer from too much steering force. 

Other than that, landing is just plain difficult. Congrats on your flight. 

[Matrazuchi]

Just now, Vanamonde said:

In other advice, you can simplify your design by removing one of those sets of horizontal canards. You are likely having difficult with over-steer from too much steering force.

I added the canards (and the secondary one) to shift the center of lift forward, because the rudder is producing too much lift for such a small craft.
Yes, the landing gear seems to be incredibly weak, only one in perhaps 10 landings happens withoug incidents :))

[18Watt]

51 minutes ago, Matrazuchi said:

Yes, the landing gear seems to be incredibly weak, only one in perhaps 10 landings happens withoug incidents :))

All of the wheels in KSP are prone to frustration, and always have been.  You are not alone!  There are a few tricks to make them semi-functional.  

Hope this makes you feel better:  I've been playing KSP since it was pre-beta (about 10 years now?  Sheesh!).  I just figured out the trick of mounting landing gear to the center fuselage instead of wings a month or two ago.

Again, welcome to the KSP forums!  Don't hesitate to check in with questions.  There is usually somebody around who can point you in the right direction.  I'm actually not even close to an expert with KSP aero questions, but I can muddle my way through sometimes.

[Matrazuchi]

2 hours ago, Vanamonde said:

In other advice, you can simplify your design by removing one of those sets of horizontal canards. You are likely having difficult with over-steer from too much steering force. 

I removed the small canard and the manoeuvrability of the airplane improved considerably. Before, turning was a real pain, hence my difficulties to align with the landing strip...

[Leganeski]

Did you disable the brakes on the front wheel? When I first learned about that a few months ago, it helped tremendously with yaw stability during landings. (Before that, I had to resort to putting parachutes on planes because I simply could not get them to land going faster than 35 m/s without crashing.)

Similarly, leaving the steering enabled on the back wheels was causing my planes to roll out of control. It looks like you're using fixed landing gear for those wheels, so this would not apply.

[adsii1970]

20 minutes ago, Leganeski said:

Did you disable the brakes on the front wheel? When I first learned about that a few months ago, it helped tremendously with yaw stability during landings. (Before that, I had to resort to putting parachutes on planes because I simply could not get them to land going faster than 35 m/s without crashing.)

You can also reduce the brakes on the front wheel, too. I usually lower mine to 25%, that way I still get some braking but my craft doesn't spin.

I miss the wheels in 1.3.0.

[18Watt]

1 hour ago, Leganeski said:

Did you disable the brakes on the front wheel?

I actually leave the front wheel brakes enabled.  If there are yaw issues on landing, it's usually something else causing it.  If anything, I dial back the rear brakes to 95%, and increase the front brakes to 75% or more.  Which is unrealistic, I've never flown a real airplane with brakes on the nose gear.  But seems to work just fine in KSP.

 

[Vanamonde]

Does that model of wheel have brakes? 

[18Watt]

7 minutes ago, Vanamonde said:

Does that model of wheel have brakes? 

Good point.  Turns out the very basic nose-wheel does NOT have brakes, near as I can tell.

[FleshJeb]

Just to support you in your future endeavors, this thread has some excellent intermediate to advanced advice:

https://forum.kerbalspaceprogram.com/index.php?/topic/165435-basic-mk2-spaceplane-guide/