How do you land a VTOL?

[katateochi]

OK, yes, vertically, got it....but what I mean is before the vertical bit.  How do you kill your horizontal speed when approaching the landing site?

My approach is to cut the power to the horizontal engines, throttle up the vertical engines and pull up.  This works but I end up gaining a lot of altitude. On some designs I've put lots of air brakes and while that works I don't like the aesthetics of it and you don't see RL VTOLs turning into some kinda airbrake porcupine just before landing. 

Annoyingly most of the youtube vids that I can find for VTOL landings just show the vertical bit, or are demos of the craft just going up and then coming back down again. Not to many that show the approach to landing, but I don't imagine something like a harrier ends up climbing several hundred meters as it does it's approach. 

I guess I am looking for the kinda movie-style or bird like landing of coming in with a swoop and dropping neatly down. But my attempts at a graceful swoop send me soaring up way higher than I'd like to be and then there's a long slow vertical descent. Maybe the answer is have much less lift on the craft? 

So what is your approach for graceful VTOL touchdowns?

[Rocket In My Pocket]

I do it similarly, kill the horizontal engines, engage the vertical, pop air brakes. (Most real life VTOL's do indeed have airbrakes they deploy when taking off/landing. Usually just one though.)

I guess the only real difference is I prefer to circle my landing spot in vertical mode, shifting my thrust outwards as a I make the circle to kill vertical velocity.

Graceful VTOL landings are tough in KSP due to extremely slow jet engine spool times. I've had a few that looked good but more often that not it's pretty awkward due to the slow throttle response.

F35B with airbrake deployed:

Spoiler

 

Edited November 2, 2017 by Rocket In My Pocket

[Helmetman]

Well, even going 10, 20, 30 m/s you will still have considerable lift effect. Combined with vertical vectored engines and a pull up it is not remarkable that you will climb. It could also be due to the fact that you have spent most of your wet mass? And now the vertical engines are actually OP at full throttle.

Using my own VTOL aircraft I generally use airbrakes/spoilers to decelerate. Then I lower the throttle to 33-66 percent when approaching close to the runway at the lowest airspeed.
I don't quit the horizontal engines right of the bat, rather, I spool up the vertical engines at said throttle levels then I will start pitching up slowly and gently as speed keeps bleeding off.
Then close to stall speed I maximise throttle while cutting the horizontal engines and immediately level off while keeping a slight pitch to bleed of the 10-30m/s horizontal speed that's left. Then gently sink down to the surface. Speed numbers are examples but can be much higher ofcourse. It depends per vessel.

I use vernors for low airspeed rotational control. Usually by canceling gimbal on the vertical engines as they're often to close to the COM.

 

[Geschosskopf]

On 11/2/2017 at 10:29 AM, katateochi said:

So what is your approach for graceful VTOL touchdowns?

I use @allista's amazing Throttle Controlled Avionics mod.  Solves all VTOL problems, plus does quite a few other very useful things.  One of the best mods ever IMHO.

Another trick I've picked up from using TCA is to use the tiny Jetwing engines from @Angel-125's Buffalo (which is available by itself or included in his Pathfinder) for my VTOL's RCS system.  That way, I only need jet fuel, no need for mono.  Tell TCA the Jetwing jets are your attitude control and everything is perfect :).

Things get a little more complicated if your VTOL is high-speed and/or uses 90^ pivoting engines (such as from @SuicidalInsanity's Mk 2 Expansion).  Then you generally have to do the main slowdown prior to entering hover manually with thrust-reversers and/or airbrakes.  But once you get reasonably slow in the vicinity of the LZ, pop the engines into VTOL mode (if necessary), engage TCA, and all is simple after that.