The Art of landing.

[martinborgen]

Hello all.

I currently have some troubles landing my spaceplane. I either come in too hard or too fast (not having enough runway to break on). I've played quite a bit of flight sims, so this shouldn't be too hard, but I don't have my joystick anymore, so I might be hampered by needing to use keyboard.

HOwever, when I come from orbit, I find it hard to line up with the runway. The cockpit view is not that good, and the externals are not much better. As I don't have the luxury of landing legs, or circle the airfield, I find a lot of error in descent speed is made trying to align.

A way would be to place probes, giving markers similar to a real runway approach. But how to place these so that they're correctly aligned?

[Dedjal]

Place flags at both ends

[Pecan]

HSI and ILS mod - http://forum.kerbalspaceprogram.com/threads/85353-1-0-2-NavUtilities-ft-HSI-Instrument-Landing-System-v0-5-1-RC-1-%2AJune-2015%2A

[Xyphos]

build a 2-kerbal rover in SPH

drive rover PAST the end of the run way, in the grassy area

plant a flag named "AIM HERE"

drive rover to other side, PAST the run way, in the grassy area

plant a flag named "YOU MISSED IT"

line up the flags and profit.

[Red Iron Crown]

I find chase view to be best for landing planes. I keep a small rover parked just off the west end of the runway for alignment from afar (I could put some mroe further out but I'm lazy).

Landing gear brakes are pretty weak, try supplementing them with airbrakes as well for more effective stopping once down.

[martinborgen]

Yes, I have been thinking of placing flags, however, upon switching to my spaceplane, the loading bugged and all parts separated. Strange, but happened three times.

However, do you find one flag at each end suffice? Some more during the final approach might be handy, no?

[Edax]

The navball is a handy guide. Since the runway runs perfectly EAST/West, the 90/270 degree marker is your target that you want the prograde marker to line up with. Cross check that by eyeballing the runway, if your coming in too left, compensate by making sure the prograde marker has moved to the right of the 90/270 degree marker. It can be an easy mistake to think you've adjusted your heading by using the rudder, cause of where the plane is pointed, but make sure the prograde marker has moved to where you want it. When your very close to the runway and aligned, you want to make sure your prograde marker is dead on the 90/270 degree marker so that you'll run off the runway. You also want to make sure your airspeed is less then 75/ms when you touch down and parachutes do a wonderful job of slowing you down when your on the runway.

Edited August 10, 2015 by Edax

[Fearless Son]

I either come in too hard or too fast (not having enough runway to break on).

Question for you: have you adjusted your brake torque? I ask because I find that the default brake torque is often too slight to make a short enough landing in most circumstances, and I find it is a good idea to up the torque in order to help bring it to a controllable stop. A caution when doing this though, make sure that the rear wheels receive much more torque than the front. I prefer to leave the front torque alone and double the back torque from default, usually. If you have too much torque up front and not enough in back, you might find your plane flipping over its nose.

On that note, the new(ish) A.I.R.B.R.A.K.E.S. part is brilliant for this. Place a few of these near the back of your plane above the center of mass, make sure they are disabled for pitch and yaw, and just activate them like you do the wheel brakes. They can help to shed unwanted airspeed before you touchdown without throwing off your approach. Use them carefully to get down to a controllable gliding speed as you are coming in, and they help you slow down more quickly once you have made contact with the airstrip too.

[GraviTykillz]

A.I.R.B.R.A.K.E.S.

This makes all the difference for me in sheading speed.

[Alshain]

Yes, I have been thinking of placing flags, however, upon switching to my spaceplane, the loading bugged and all parts separated. Strange, but happened three times.

However, do you find one flag at each end suffice? Some more during the final approach might be handy, no?

Don't put your flags ON the runway, it is cleared when you launch. You need to go well beyond the ends of the runway, you can usually see where the runway model ends, it's pretty obvious as the grass kind of changes color and elevation.

[martinborgen]

Oh, yes, A.I.R.B.R.A.K.E.S. are there - eight of them. Break torque was eventually maximum on rear wheels.

I asked because this aircraft in particular has quite small lift - it's a rocket SSTO with wings on it (starting weight 380 tons, landing weight ~80t). It relies mostly on body lift. Landing speed was at about 275 m/s, and that's where I will do my next modifications - more wings, or chutes, or retro thrusters. However, to get the first aircraft down safely, I needed several tries, and hence I started thinking of these problems when waiting for my plane to burn through the atmosphere.

Now the aircraft is down, although I had to stop right after the runway and just before the water.

[Mat2ch]

Retrorockets! If you're really coming in this hot, try using Sepatrons just before you touch down.

[MaverickSawyer]

Hmmm... perhaps you should look into RealChute. There's a drag chute option you can use that won't deploy until you hit the ground.

Also, sounds like you need to have some more nose up on final if you're hitting the runway at 275. Using the Adjustable Landing Gear will give you low-profile gear that can reach out quite a ways.

[pandaman]

Landing speed 275 m/s ! That seems a bit quick, as in not too far off supersonic! Try and touch down well below 100 m/s and, if you can, try for less than the impact tolerance on your landing gear (60 iirc). As others have said try airbrakes, and drogue chutes too if you can't slow down enough otherwise.

[A_name]

Considering your flight profile I would recommend ditching a runway landing all together and coming down on parachutes.

[Fearless Son]

Wow, yeah, 275 m/s is pretty fast for a landing. I would say you should try and get down below that before touching down. And yeah, you need that speed to maintain your lift, but once you are lined up and on track for the runway you need to deliberately induce a controlled stall to shed both speed and altitude. Not sure how aggressively you can flare your descent without knowing the shape of the craft (tail dragging can turn a controlled landing into a crash) but you certainly sound like you have enough aerobreaking capacity built into the plane itself.

I would say try to get the plane lined up, like you will do a narrow overshoot of the runway, and get down to your minimum cruising speed for that altitude. Then as you approach the runway (might need to experiment with timing here) nose up a bit, and activate the airbrakes on full. If you have done it right, the plane should slowly start loosing both speed and altitude until it hits the ground rear wheels first.

You mentioned parachutes. Might be worth considering as well. Place a couple of the small diameter aerodynamic stack chutes on the rear of the plane, and trigger those when you hit the ground. Pretend that you are landing on an aircraft carrier and you need them to kill your velocity as you hit touchdown.

[GoSlash27]

I always shoot my deadstick landings for 5° angle of attack rather than a set speed. Getting set in the glide to assure you'll get there with decent speed means a steeper descent path. If you're going long, then s-turn to bleed off energy, but whatever you do don't allow yourself to go short. It's like carpentry; you can always cut excess wood off, but you can't get it back on again...

You should drop yourself into the final with some excess speed (but not 275 m/sec!). Just flare just before touchdown and ride the 5° AoA. The speed will bleed off and drop you into a nice gentle landing.

As for the markers, I personally use marker drones, but flags can work just as well. I set them at 5km, 10km, and 20 km west of the runway. Use the latitude in the map screen to get the lineup and something parked on the runway to get the distance.

This will give you reference points for lineup that are so clear you can see them from orbit. As a bonus, you can check your altitude as you pass over them as checkpoints during your descent.

Best,

-Slashy

Edited August 10, 2015 by GoSlash27

[ajburges]

The navball is a handy guide. Since the runway runs perfectly EAST/West, the 90/270 degree marker is your target that you want the prograde marker to line up with. Cross check that by eyeballing the runway, if your coming in too left, compensate by making sure the prograde marker has moved to the right of the 90/270 degree marker. It can be an easy mistake to think you've adjusted your heading by using the rudder, cause of where the plane is pointed, but make sure the prograde marker has moved to where you want it. When your very close to the runway and aligned, you want to make sure your prograde marker is dead on the 90/270 degree marker so that you'll run off the runway. You also want to make sure your airspeed is less then 75/ms when you touch down and parachutes do a wonderful job of slowing you down when your on the runway.

Pedantic: there is a couple seconds difference in latitude between the two ends. It's not much, but it points southwards which adds to the inclination you get from it being 3 minutes south of the equator.

- - - Updated - - -

Being constructive:

I find glide slope is heavily dependent on the craft. One of mine had a 20° slope! Of course, that may be because I like a faster glide.

Regardless, I find gliding in boring. Most my craft have enough wing loading and control authority to pull out of a 200 m/s dive to level flight. Unless your craft is less aerodynamic than a brick, 200 m/s should give you a couple of klicks of near level flight. This requires non-trivial lift however. A minimal lift rocket may not be able to control a dive.

The runway is the friendliest landing surface in the game. Even so, I like to touch down with less than 160 m/s.

[SpacedCowboy]

Parachutes!

[ajburges]

I use the trajectories mod to guage decent above 18 km. Reentry has too much ranges too early for flags to help and if my reentry is good, I can maul the plane into a great (all parts survive) landing on the runway.

Did I mention Jeb is a huge fan of my space program? (at least until we get stock flight computers)

[martinborgen]

So, I tried with flags, and to see slowest speed where this contraption could go. Turns out it's about 175 m/s (at 10 degrees AOA). Here's some pictures for you - however I find the throttle hard to control while keeping the AOA and landing, so I botched this landing.

Anyways, here's some pictures of the madness;

http://imgur.com/a/DGQRK

Edited August 11, 2015 by martinborgen

[cantab]

Yeah...that's still about 390 miles per hour! The Space Shuttle landed at 215 mph, most airliners land at about 160 mph. It sounds like you may have simply built something unlandable.

[martinborgen]

I have landed it a few times, but it's hard with keyboard controls. I haven't tried KSP with a joystick yet, but from my flight sim experience, I think it should be much easier with a stick and throttle.

I find the hard thing is learning how KSP flight works.

Edited August 11, 2015 by martinborgen

[Vegetal]

Ok dude, I land perfectly 99% of the time. The secret? Use locked view, it's the best. Combine it with navhud (mod) and you know perfectly where your plane is going. Having a joystick helps too, but I make do with a xbox gamepad.

You need to give yourself some room to adjust your speed for landing, I usually don't land over 100m/s, so take your time, use the air brakes and come in smooth.

[Edax]

Sounds like you simply need more lift. More lift means you can say aloft at slower speeds. I recently built a SSTO biplane that can still fly/glide at 40m/s before stalling (extra wings means extra lift, duh), and it makes landing VERY gentle. I can't see you picture but in general, you need more wings and winglets.

Edited August 11, 2015 by Edax