Turns at altitude

[Razor235]

I've been doing a lot of high altitude (~16-20 km) and high speed (~1000-1500 m/s) flying, but I cannot figure out how to turn without completely losing control of the aircraft. I've been descending to below 10 km in order to turn, but I'd like to be able to save fuel and time by not having to descend. Is there a specific trick to doing this?

[thescientist]

If your aircraft gets ot of control when you try to turn, probably:

1. You have too much control (high torque/too many big control surfaces)

2. Bad stability at high speed

3. CoM shifted due to lower fuel level than liftoff (but your case looks to not be this one)

4. Heavy fingers

The solutions are:

1. and 4. Press caps lock and take it easy*

1.b Reduce your control surfaces and your torque-devices (SAS, ASAS and such)

2. Shift your wings a little backward

3. Rebalance fuel with RMB+Alt on two tanks and pressing "in" or "out"

*remember that the faster you are, the slower your craft turn with higher load on structure - So do your 180° turn just after liftoff, not while you're flying at mach 3!

Edited May 15, 2014 by thescientist

[Vanamonde]

It is almost always helpful in diagnosing problems like this to see pictures of the craft in question. Can you post some?

[Kasuha]

To turn (e.g.right) in thin air at high speed:

- roll right

- turn your plane ~20-45 degrees in the direction you want to turn

- keep the prograde marker directly below center of your navball (see image below)

- watch your prograde marker slowly follow your nose. Continue turning, keeping 20-45 degree distance.

- control your vertical speed by pitch and roll

- when your prograde marker is at intended heading, turn the plane back and level

Do not expect it to go fast.

If you need to make fast turn, go down to thicker atmosphere, turn, and ascend again.

Edited May 14, 2014 by Kasuha

[Razor235]

Alright guys, thanks for the suggestions, I'll make sure to try them.

It is almost always helpful in diagnosing problems like this to see pictures of the craft in question. Can you post some?

It's been happening to pretty much every high-speed plane I've designed (swept and delta winged). But, for the sake of an example:

I have a hunch that for this particular craft it might have something to do with the canards providing too much control. However, it has happened on craft without canards. Unfortunately I can't access those right now, but I'll see if I can't find them.

[DeMatt]

I think the simplest explanation is that, at high altitude, you don't have a lot of air to push against and make your turn. Think of it this way: when you drive a car slowly, you can make a really tight turn with the steering wheel all the way over. Drive that same car at highway speeds, yank the wheel over, and you've got a pretty fair chance of flipping it rather than turning.

Take it gently, and don't even bother trying rudder turns. You can try adding more wing surface (not control surface), and see if that helps.

[Vanamonde]

It's possible that you have too much control authority and are rotating the ship faster than the airflow can match attitude. I'd suggest trading the front canards for a fin-and-elevator arrangement, or doing without forward planes at all.