How to Land Off the Runway - Design and Technique

[peachoftree]

Landing is hard enough on the runway^{[citation needed]}, It may seem impossible to land off of it.

This guide is here to help.

There's A video at the end showing the whole landing process, but to understand it you should read the tutorial first.

First, there are a couple of mods that I think are super useful for landing off runway:

Adjustable landing gear - get a wider wheel base

Kerbal flight data - see your height above the ground next to the navball

Kerbal engineer - get your vertical speed

RealChute - adds drogue chutes so you can land faster

The craft I used to do this tutorial can be found at http://kerbalx.com/peachoftree/KSS-Galileo

Part One: Design

First and foremost, you need to have a wide wheelbase. What that means is that your back wheels are very spread apart. This means that the plane will be much less prone to tipping over when you land.

Secondly, you need to have your plane be able to fly at 110 m/s or lower, it does not necessarily have to fly well, just be able to reasonably hold itself up in the air, the best way to do this is to have large wings relative to your fuselage. If your plane takes off at 130-140m/s it should be fine.

The last design element that you'll need is airbrakes. It really helps slow you down faster once you're on the ground, and is also useful for your approach.

I recommend placing 4 airbrakes, 2 in front of the COM and 2 behind it. Doing this mostly cancels out any pitch effects from slowing down.

Part 2: Landing

Step 1: setting up

The best place to practice is probably the hills west of KSC. To speed things up don't bother with turning around mid air, instead just taxi off the runway until you're pointing west, and take off from there. Once you get up in the air, be sure to quicksave so you can quickly come back if you crash. make sure you have steering enabled on the front wheel, and reverse it if necessary.

Step 2. Picking a landing site.

For your landing site you want to find an area that is not that steep. However more important that slope is consistency, a very bumpy site that is flat overall is going to be harder to land on than something with a slope, but is consistent. Also never touch down going directly up a hill, the ground sloping up has the same effect as increasing your sink rate, making touchdowns invariably harder.

I picked the area just to the left of the group of hills that was directly in front of me. I did not choose a very good time to land, ideally you want the sun lower in the sky so that the terrain forms shadows with which you can judge the size of hills more easily.

Step 3. Approach

Once you get aligned with your landing zone, you should start your descent. Be sure to carefully watch your speed when as you come down. when you are 500 m above the surface you should be going at around 170 m/s, by the time you get down to 100m you should be going at 140 m/s. When you get to 100m turn on the airbrakes permanently (click the brake light) quicksave at 400m up in case you mess up the landing

Step 4. Pre touchdown.

This is the most critical step. As you get closer and closer to the ground, make sure you are steadily decreasing your speed. When you are 60m up start watching your vertical speed in kerbal engineer, it needs to be lower than 10m/s when you touch down. Watch the slope of the ground, if it is too steep, don't be afraid to light up your engines and keep going until you get to a flatter area. Right before your wheels hit the ground, if necessary, roll so that you match the sideways slope. When you are 10m above the ground you should be going around 100 m/s (preferably lower). maintain your vertical speed until your wheels hit the ground. If you have drouge chutes, now is the time to deploy them

Step 5. Slowing down

The brakes should already be on from the previous step. As you are rolling over the ground, the most important thing to watch is your side slip, or how far to the side you are from prograde. If this increases too much you will flip over. Remember when I told you to enable steering? this is where that will come in. The wheels in Adjustable landing gear adjust their steering coefficients with speed, so the faster you are going the less they will steer. This means it is safe to have steering on during landing. As you slow down keep pointing towards prograde. If you come over the crest of a hill, try to land on your back wheels, especially at higher speeds, at lower speeds it does not really matter if you land on your front wheel as long as you point prograde.

Step 6: Profit!

Please post feedback below, this is my first tutorial so tell me how I did.

Edited August 22, 2015 by peachoftree
Added RealChute

[damerell]

This was not very surprising, but an interesting read.

[Mister Dilsby]

Sticky! Well done

[peachoftree]

Thank you so much sal_vager this is amazing

[JTpopcorn]

Secondly, you need to have your plane be able to fly at 110 m/s or lower, it does not necessarily have to fly well, just be able to reasonably hold itself up in the air, the best way to do this is to have large wings relative to your fuselage. If your plane takes off at 130-140m/s it should be fine.

Correction on this, the plane needs to fly slow or simply use parachutes to land. My fighter ssto lands at 230m/s by deploying drogues.

[peachoftree]

Correction on this, the plane needs to fly slow or simply use parachutes to land. My fighter ssto lands at 230m/s by deploying drogues.

I was going for a minimal mod approach, but will add Real chute to the list of recommended mods

[FyunchClick]

Nice. Can I recommend putting the brake torque in the rear landing gear to a higher value than on your front gear (or disable at front)? That way your CoM will tend to want to be in front of your rear gear as that drags back harder, which should help manage side slip (thanks for that term as well didn't know it was called that).

[peachoftree]

Nice. Can I recommend putting the brake torque in the rear landing gear to a higher value than on your front gear (or disable at front)? That way your CoM will tend to want to be in front of your rear gear as that drags back harder, which should help manage side slip (thanks for that term as well didn't know it was called that).

I find that this doesn't really need doing because the back already has twice the torque on account of the fact that there are two wheels as opposed to one, providing the aforementioned stabilizing force.

[FyunchClick]

I find that this doesn't really need doing because the back already has twice the torque on account of the fact that there are two wheels as opposed to one, providing the aforementioned stabilizing force.

True enough, although they're also usually located a lot closer to the CoM, so I wonder if that doesn't give the front wheel a longer lever arm and thus any disturbing forces (because of side slip for instance) there more torque, and the rear gears stabilizing force less torque (torque being arm times force). It been a while since classical mechanics so I'm not sure if that makes sense? I did have several planes where the different ratios did improve stability.

Edited September 1, 2015 by FyunchClick
typo

[peachoftree]

True enough, although they're also usually located a lot closer to the CoM, so I wonder if that doesn't give the front wheel a longer lever arm and thus any disturbing forces (because of side slip for instance) there more torque, and the rear gears stabilizing force less torque (torque being arm times force). It been a while since classical mechanics so I'm not sure if that makes sense? I did have several planes where the different ratios did improve stability.

I don't think it does, because the rear wheels are much closer to the CM, they have much more of the planes weight riding on them. I suspect any sideslip on landing is because they are acting as a pivot. In fact, having the gear far forwards may even act as a stabilising force on account of their distance from the CM for the same reason that tailplanes are more effective the farther back you put them. I could be wrong though.

[Spark Plug]

Do you have any tips for the descent? Like how much should I pitch my nose down? or is gliding better than keeping my engine at half-thrust all the way down?

I find that I often lose patience as I slowly descend, especially if I feel I'm going to miss my target, and so I increase my (negative) vertical velocity by nosing down. When the time comes around to decrease my velocity, I can't pitch back up enough to do so, land on my front wheel and then blow up.

I'm currently re-learning how to land, given the new aero model and the fact that I haven't flown a KSP plane in months. Well, I never was very good at sticking my landings back then either, runway or not.

[peachoftree]

Do you have any tips for the descent? Like how much should I pitch my nose down? or is gliding better than keeping my engine at half-thrust all the way down?

I find that I often lose patience as I slowly descend, especially if I feel I'm going to miss my target, and so I increase my (negative) vertical velocity by nosing down. When the time comes around to decrease my velocity, I can't pitch back up enough to do so, land on my front wheel and then blow up.

I'm currently re-learning how to land, given the new aero model and the fact that I haven't flown a KSP plane in months. Well, I never was very good at sticking my landings back then either, runway or not.

your problem sounds like a lack of control. your center of lift and center of mass need to be very close in order for you to have the control authority to land. The thing to remember that as long as you are below around 170 m/s, your horizontal velocity does not matter, only your vertical. when you are just about to touch down flare the nose up as much as you can. This kills your vertical and horizontal velocity so you can land. I recommend having a quicksave on your descent to landing so that you can try a bunch of different profiles and see what works. Also airbrakes are the greatest, they negate the need to do s-turns on you descent allowing you to be lined up from a very long distance.

[arise257]

Pro tip: If you don't have airbrakes unlocked yet, you can still get your air-brake on.

In SPH:

On the tops and bottoms of your main wing, on the leading edge, place control surfaces. You have to offset them so that half their height is exposed on the top and bottom of the wing. Also, point them rearward, like they would face were they on the back edge of the wing.

Disable all control authority (yaw, pitch,roll) and map them to toggle on the brake button in the action controls.

Be sure to check that they deploy upward on the top side and downward on the bottom.

In flight:

Hit the brake button and be amazed as your control surfaces open up, increase drag, and slow your plane down. Since you mapped it to the brake button, when you're on the ground you can delight in the teamwork between your wheels and wings.