gliding - Max Distance

[davidpsummers]

If you are doing an unpowered decent with a space plane, is there any guides on what do to do to get maximum distance from your glide?

[bewing]

Don't let your AoA go over five degrees, and maintain your speed and altitude as long as possible.

ie. don't hit the brakes until you are absolutely sure you can make it.

 

Edited August 9, 2018 by bewing

[mystifeid]

Normal aircraft get the best glide from the best lift/drag ratio (or commonly referred to as best LD). I suppose you could try turning on aerodynamic forces (F12) and maintaining an angle of attack (AoA) that maximizes lift and minimizes drag. If successful and with some experience in a plane you could stop using F12 (in that plane).

Also this wind tunnel mod might be worth looking into.

Edited August 9, 2018 by mystifeid

[mystifeid]

So you got me thinking about old gliding stories. One of my favorites has always been the not-so-ordinary Gimli Glider. Nice that it was able to be written up with such humor afterwards and well worth a read if you are not already familiar with it.

[Snark]

Incidentally, if you're comparing different designs and looking to evaluate their glide ratios, you may find this little mini-mod helpful:

It doesn't do much... all it does is, while you're in flight and gliding, it displays the glide ratio next to the navball.

Even though it's labeled "1.3", I believe it ought to work just fine in KSP 1.4.5.

[davidpsummers]

Not really comparing.  All my planes glide "reasonably" well.  It is mostly, if I have come in short, what can I do to compensate.  

5 degree of AoA sounds right.  I know that over 15 you actually loose lift?

Not sure what to maintain speed.  You need to stay above the stall speed.  Slow means less drag, but it means you cover less ground?

 

I'll look at the mod.  (I'm actually using 1.3)

Edited August 11, 2018 by davidpsummers

[bewing]

23 minutes ago, davidpsummers said:

 I know that over 15 you actually loose lift?

Around 30 degrees is max lift, but also very high drag. Above 30 you lose lift. (Of course, FAR changes all of that if you are running modded.)

0 to 5 degrees gives good lift with minimal drag -- and if you are short, it's more about minimizing drag than about creating lift. Because if you are short, that means you have many kilometers still to cover -- which means you need speed. Lift just gains you a little extra altitude -- which won't get you very far if you don't have any speed. And maximizing speed while minimizing drag means "stop your descent as high as you can". If you are too low, and also short -- you just aren't going to make it, unless you have some engines and fuel to burn.

 

Edited August 11, 2018 by bewing

[XtraChrisP]

On ‎8‎/‎10‎/‎2018 at 9:21 PM, davidpsummers said:

Not really comparing.  All my planes glide "reasonably" well.  It is mostly, if I have come in short, what can I do to compensate.  

5 degree of AoA sounds right.  I know that over 15 you actually loose lift?

Not sure what to maintain speed.  You need to stay above the stall speed.  Slow means less drag, but it means you cover less ground?

 

I'll look at the mod.  (I'm actually using 1.3)

A couple things to remember: You don't stall at an airspeed, you stall at an Angle of Attack (AoA).  Generated lift is proportional to the lift coefficient times the square of the velocity.  Lift coefficient rises with AoA, until you reach a critical AoA after which it starts to drop off: your wing stalls.  As you AoA rises, so too does your drag.  At some point, usually around 5 degrees (depending on the airfield), your maximum L/D is achieved.  This is the AoA you have to hold to get your best glide distance.  I guess what I'm trying to say is don't get too wrapped around the axle with holding an airspeed, really you only need to concern yourself with AoA.  Please note that all AoA indications, both in the AeroGUI and the NavBall are based off the nose of the aircraft.  If you placed some incidence in the wings, you need to add or subtract that from your indications.

So, once you figure out your best glide and maintain that, just know that there is nothing you can do, short of firing up the engines, to extend your glide.  My advice to you would be plan on coming in a bit long and holding a sub-optimal glide slope.  If you hold this and realize that you're coming in long, you can always dump some speed or altitude.  If you're coming in short, you can pitch over into your best glide to extend it.  If you're still short, well...