Deploy those tail fins!

[NewtSoup]

I've often wondered what the deploy function was for on winglets and tail fins.  They didn't seem to have much use at all.  So I've never, ever bothered binding that function to an action group.  

This is my current "Science Plane" - It's got an octo for stability control - a load of science bits a couple of engines and two tail fins, the reaction wheel is not necessary, I just like it for making "on the spot" turns instead of faffing around taxiing in a circle.

 

Its ugly but it flies pretty well and it does the job.  The wing section at the front is for a kerbal to stand on when they climb out of the cockpit.  As long as you are doing less than 80m/s you don't get blown off the wing.  Though I wouldn't recommend "let go"  or "climb out" or you will disappear into the distance which is why everything can be reset from the cockpit door - no the wing is to stand on to take surface samples when landed really.

Anyway back to my point - I've always had to slow down to do EVA's in flight and to reset the science stuff.  This has led me to wish I had air brakes.  Today though I thought "I wonder?" so I went back to the SPH and bound the deploy function to RCS toggle because I only have basic action groups available right now.

Lo and Behold a PAIR, you must have 2 or things will go very bad for you, a PAIR of  fins turn in on each other and produce a massive amount of drag working just like an air brake!.  This resulted in my first ever successful landing at the abandoned island air field.

 

As you can see the tail fins are turned inward this allows me to really control my speed on approach to a runway and indeed on the runway itself to aid in braking.

I would highly recommend this kind of setup (2 fins or winglets ) to anyone making planes because it's just so useful.

The first deployables you get are in Aviation  ( Tail Fin ) and Flight Control ( AV-8 Winglet) - Obviously you need Aviation for making planes anyway but there may be a use for deployed winglets in aerobraking maneuvers.

[Capt. Hunt]

"Deploying" just actuates the control surface either up or down depending on the tweakable.   I've found it handy for flaps on approach as well as airbrakes.

[Dark Lion]

I stumbled onto this a completely different way, but I digress, we mustn't overlook the fact that the fins of yours are higher from center, aiding the nose up too! This force is much greater applied with low-attached forward canards, of course, where you can get even bigger-booty-birdies with lower thrust-to-weight ratios out of the water if you need to. Used in combination... and just perfectly placed, your birds might just land themselves safely!