How to slow down when landing in FAR?

[Streetwind]

Are these mid-wing or tailplane spoilers? Too far forward and you'll unbalance things. You can set spoilers on in the FAR analysis screens to check.

It's a tiny plane with a single, large swept wing (and a tailfin taped to the rear of the body). Both CoM and CoL are fairly far back. Spoilers are probably roughly lined up with CoL. I say "probably" because I can't check bcause I am not at my home computer right now. I am however pretty sure that I checked the stability derivatives for many different speed and altitude settings and they should be all green... I suppose I will check again later today when I get home.

[Van Disaster]

Technically, many atmospheric engines in real life have thrust reversal systems like this:

I wonder if there are mods that can do thrust reversal in KSP?

Some of the B9 engines have built-in thrust reversers. I have a suspicion the engine needs to be modelled with them in mind so there's a thrust transform pointing forwards too, but I don't know the details of how they're doing it.

"Some" - those ones do at least.

Spoilers need equal sized spoilers deflecting the other direction, and then they're stable - unless they're really small and the plane has enough pitch authority to cope, anyway, or they're mounted vertically which is an annoyance in FAR. For flaps for that rather nifty looking delta wing craft it might be better to set the ailerons up as flaperons instead of the elevators, they're nearer where I presume CoL to be, which would have the side effect of them working with drag & steering by yawing a bit also. To be honest although I out of habit set up airbrakes and flaps, for my larger spaceplanes which you'd think would need them - given landing speeds in the 130m/s range and deorbiting mass up around 200t for the biggest - I rarely even use flaps, I just let them slow down as they want.

Edited January 16, 2015 by Van Disaster

[Alshain]

I wonder if there are mods that can do thrust reversal in KSP?

Yes, Firespitter does. I'm not sure if you can do it in flight though. But Firespitter & KAX do allow you to make prop push planes like these

Edited January 16, 2015 by Alshain

[Alshain]

You guys mention flaps. I didn't used them. Should I dedicate control surfaces just for this function or is it okay to activate that for the pitch control surfaces?

I missed this question but Flaps prevent the control surface from acting as anything else. They must be dedicated. Also, flaps are useful but not always required. In your case the plane has a large wing surface compared to it's body, which also lifts, so your minimum safe speed is already pretty low.

Congrats

[Northstar1989]

Problem is, the spoilers stall when they reach full deployment angle - and when this happens, the plane immediately becomes excessively unstable. Almost feels as if the main wing stalls too (but FAR's visualization confirms this is not the case, it's only the spoilers that stall). It's gone to the point where I lost control and crashed despite still being above 100 m/s - and the plane in question has a takeoff speed of about 60!

You should probably reduce the deflection of the spoilers. The greater their deflection, the more they will destabilize the plane. You can reduce flap/spoiler deflection in the SPH with tweakables...

Alternatively, just try placing the spoilers further back (which will reduce their effect, but also destabilize the plane less). Personally, I recommend the reduced deflection if you're having difficulties landing, though...

I missed this question but Flaps prevent the control surface from acting as anything else. They must be dedicated.

Not unless this was changed in a very recent version of FAR (it's been a little while since I used flaps, due to the 0.90 part-count restrictions). Flaps can still be assigned pitch-control functions in the SPH. If their flap/spoiler deflection setting is less than the control-range, they can still be differentially actuated to act as aerlions as well (both flaps and spoilers are sometimes differentially actuated to provide roll-control in real life, so it's NOT unrealistic...) or deflected even further to provide some limited pitch-control (and possibly yaw-control if at an inclined angle).

What setting a control surface as a flap does is provide a *minimum* deflection that the control surface deflects to, that you can't go below. Whether you can actuate the control surface further depends on the relative values of the control-surface-deflection for pitch/control/yaw vs. the flap/spoiler deflection settings...

Yes, Firespitter does. I'm not sure if you can do it in flight though.

You *CAN* reverse thrust it in-flight with Firespitter engines (propellers, and certain B9 jets that use Firespitter code). You can do it manually (by right-clicking) if it's a centrally-mounted propeller (I wouldn't recommend doing this for an outboard engine unless you have thrust set very low, in which case it can be used to cause your plane to turn more quickly. Otherwise you sill probably go into a flat spin...) or with Action Groups set to reverse outboard propellers in symmetric groups... (or asymmetric groups if you want to crash)

Regards,

Northstar

Edited January 16, 2015 by Northstar1989

[Alshain]

Not unless this was changed in a very recent version of FAR (it's been a little while since I used flaps, due to the 0.90 part-count restrictions). Flaps can still be assigned pitch-control functions in the SPH. If their flap/spoiler deflection setting is less than the control-range, they can still be differentially actuated to act as aerlions as well (both flaps and spoilers are sometimes differentially actuated to provide roll-control in real life, so it's NOT unrealistic...) or deflected even further to provide some limited pitch-control (and possibly yaw-control if at an inclined angle).

Nope, been that way since I started using NEAR (around 0.24) and they work the same in FAR now that I use that. Flaps must be dedicated, Spoilers can be other controls too. You sure you aren't thinking of spoilers? You can set them to be pitch control but if the Flap option is enabled too they will not respond to pitch inputs.

[pincushionman]

…Problem is, the spoilers stall when they reach full deployment angle…

Thing is, in real life, that's exactly what spoilers do. It's supposed to be a controlled local stall. The resulting stall reduces lift over the affected wing chords, increasing downforce on the wheels and making the brakes work better. Stall also creates detached flow and a dramatic increase in drag, again at the affected chord. Such spoilers should not be placed ahead of ailerons and should not be deployed in flight.

There are spoiler systems that can be partially depoyed in flight to assist descent, though, so take that with a grain of salt.

I'm not sure how FAR and the game handle spoilers and stall, though.

[Streetwind]

Such spoilers should not be placed ahead of ailerons and should not be deployed in flight.

But I need something that will slow me down while in flight. I don't care about being grounded, I can slow down with wheel brakes fine... I just have an intense problem of being unable to shed speed on the final runway approach. The plane glides so well, it just won't slow down. It takes like a minute to lose 20 m/s in level flight at 1km altitude, and I might be coming in at 250 to 300 m/s and want to land at under 100.

So I need some way to kludge together an airbrake. It doesn't have to be elegant, so long as it has some amount of effectiveness and doesn't stall the whole wing...

[Wanderfound]

But I need something that will slow me down while in flight. I don't care about being grounded, I can slow down with wheel brakes fine... I just have an intense problem of being unable to shed speed on the final runway approach. The plane glides so well, it just won't slow down. It takes like a minute to lose 20 m/s in level flight at 1km altitude, and I might be coming in at 250 to 300 m/s and want to land at under 100.

So I need some way to kludge together an airbrake. It doesn't have to be elegant, so long as it has some amount of effectiveness and doesn't stall the whole wing...

So long as they're placed behind CoM, opposed spoilers or flaps [1] should not destabilise the plane, especially at subsonic speeds. But they do move CoL around, so it's wise to toggle them on in the SPH and look at the stability numbers.

However, the fastest and most effective way to slow down does not require any aircraft design tricks. The best way to slow is with S-turns; bank steeply and yaw/pitch the nose around until you've made a 90° turn, then do the same thing for a 180° turn back the other way, and repeat alternating 180° turns until you've slowed sufficiently. You can wash off a lot of speed very quickly by doing this.

[1] To clarify for some commenters: in the real world, assuming placement behind CoM, flaps deflect down (more drag, more lift) and spoilers deflect up (more drag, less lift). In FAR, both spoilers and flaps can be set to deflect in either direction, although the same surface can't go both ways. The difference is that spoilers toggle 100% on or off with a single action group, whereas flaps move on a four-point gradient with increased and decreased deflections controlled by separate action groups. Same results as real-world, but different use of names.

[Alshain]

Thing is, in real life, that's exactly what spoilers do. It's supposed to be a controlled local stall. The resulting stall reduces lift over the affected wing chords, increasing downforce on the wheels and making the brakes work better. Stall also creates detached flow and a dramatic increase in drag, again at the affected chord. Such spoilers should not be placed ahead of ailerons and should not be deployed in flight.

There are spoiler systems that can be partially depoyed in flight to assist descent, though, so take that with a grain of salt.

I'm not sure how FAR and the game handle spoilers and stall, though.

This functionality did not work for me until the absolute latest version. I only found out a few moments ago, but the last release fixed spoilers so they do in fact stall the wing, if placed correctly. Prior to that it always reported 0% (though it may be the reporting was corrected and it always created the lift dump). I am positive it showed a 0% stall when deployed in 0.14.5 and earlier.

- - - Updated - - -

But I need something that will slow me down while in flight. I don't care about being grounded, I can slow down with wheel brakes fine... I just have an intense problem of being unable to shed speed on the final runway approach. The plane glides so well, it just won't slow down. It takes like a minute to lose 20 m/s in level flight at 1km altitude, and I might be coming in at 250 to 300 m/s and want to land at under 100.

So I need some way to kludge together an airbrake. It doesn't have to be elegant, so long as it has some amount of effectiveness and doesn't stall the whole wing...

To do that, use two not in symmetry mode, but put them on the vertical stabilizer Right next to each other. Set one to a -45 spoiler deployment and the other to +45 spoiler deployment. Assign them to the same hotkey. The end result will be a shuttle style air brake. It doesn't alter lift because the vertical stabilizer isn't supposed to create lift. You can set them both to be yaw as well.

Edited January 17, 2015 by Alshain

[Van Disaster]

I asked ferram a while ago about spoilers as lift dumpers - he said something along the lines of if you stalled a surface it'd stall the wing directly behind it. I noticed surfaces not reporting being stalled in older FAR versions, not sure if that was just reporting issues or actually didn't stall.

Flap+control combos work fine, I'm literally staring at them working fine.

[starikki]

One realistic solution would be adding drag when gears are lowered. Hope FAR could do this in the future

[Van Disaster]

IIRC landing gear has no physics, so I suspect that isn't going to happen. May be some way of kludging hybrid parts so there's a combined airbrake/gear, I don't know though.

[starikki]

IIRC landing gear has no physics, so I suspect that isn't going to happen. May be some way of kludging hybrid parts so there's a combined airbrake/gear, I don't know though.

is there a air brake module? I tried to put a chute module on, but created more mess than usefulness.

[Van Disaster]

You can turn any control surface into an airbrake, just right click it & push the spoiler button. It won't do anything else but be a spoiler though, so don't use your ailerons...

[starikki]

IIRC landing gear has no physics, so I suspect that isn't going to happen. May be some way of kludging hybrid parts so there's a combined airbrake/gear, I don't know though.

I find the solution!!

Firespiter's FSwheel module has function to set drag when deployed.

I modified a landing gear from KAX, to make the landing gear slightly smaller and lighter to fit a light aircraft, and a bit higher drag when deployed (some thing like 0.5).

And now I can land a light trainer aircraft at even 5 degree glide slope with no spoiler! Even need to add thrust when approaching at 3 degree slope.

This is now very realistic and convenient, I'm happy now

[Hodo]

That's cool but my light craft could already do that without spoilers or air brakes. I think my current slowest landing light craft is about 45m/s.

[Northstar1989]

Nope, been that way since I started using NEAR (around 0.24) and they work the same in FAR now that I use that. Flaps must be dedicated, Spoilers can be other controls too. You sure you aren't thinking of spoilers? You can set them to be pitch control but if the Flap option is enabled too they will not respond to pitch inputs.

No offense, but you're wrong. I was using non-dedicated flaps just the other day on a suborbital spaceplane model I'm working on (basically, it pushes just outside the atmosphere, and then deploys a rocket which circularizes- as wings don't do any good outside the atmosphere...) They worked FINE for me. So, I'd check that you're following my instructions carefully. Try something REALLY drastic, like setting pitch authority to 45 degrees, and flap deflection to only 5 degrees. That should make whether the control surfaces are actuating REALLY obvious to you. My guess is you'll find I was correct all along...

Regards,

Northstar

[Northstar1989]

A picture is worth 1000 words, and so I respectfully present *proof* that control surfaces can act as both flaps and elevators:

Notice the control surfaces on the rear of the plane which I have opened the context menu for. They are quite clearly flaps (though currently undeployed) as they have a "Flap Setting" detail showing their deployment status on the context menu, but they are also currently deflected upwards (the opposite direction a flap would deploy) to help push the tail down so the spaceplane can keep its nose up as it climbs towards the upper atmosphere...

For what it's worth, that was actually a *suborbital* spaceplane- it deploys a cargo at the very edge of the atmosphere (this is in RSS 6.4x, so approx. 91 km) which then circularizes using its own fuel/engines. A *true* spaceplane in RSS 6.4x is virtually impossible without OP'd/unrealistic mods (the exception to this *MIGHT* be using KSP-Interstellar and Microwave Beamed Power, a technology that actually exists in real life and several teams of engineers are trying to get NASA to switch over to instead of chemical rocketry, which allows spaceplanes by raising ISP to 850-1000 seconds...)

Regards,

Northstar

Edited January 23, 2015 by Northstar1989

[Van Disaster]

That's cool but my light craft could already do that without spoilers or air brakes. I think my current slowest landing light craft is about 45m/s.

I think I have something relatively heavy ( in terms of our stuff anyway ) that'll stay in the air at 70kts IAS - needs rather large flaps to do that. I must experiment with leading edge extensions.

[Mighty1]

And another solution for a stock part game, only with FAR is to do a 360 deg turn. Do an agresive turn an you shall bleed speed very fast.

[Axelord FTW]

To do that, use two not in symmetry mode, but put them on the vertical stabilizer Right next to each other. Set one to a -45 spoiler deployment and the other to +45 spoiler deployment. Assign them to the same hotkey. The end result will be a shuttle style air brake. It doesn't alter lift because the vertical stabilizer isn't supposed to create lift. You can set them both to be yaw as well.

http://spaceflightnow.com/shuttle/sts114/040219delay/shuttlelanding.jpg

http://cloud-4.steamusercontent.com/ugc/39738595551173810/798A747B4A348DFB9ED86575F5617D2F5D0459EB/1024x576.resizedimage

Okay, now THAT is nice.

I don't do airplanes much but I still fiddle with them from time to time (it would be a waste to ignore them, be they lonely) and I tried to setup spoilers but I had a hard time getting things right.

I'll use that design, thanks.