Questions about using yawing and tip stalls

[SkyEye]

Hi all! I took a break from RC about 4 year ago but am revisiting it now through the Phoenix Flight Sim v.6, I have a DX6i. When I stopped flying all those years ago I had progressed to where I was starting to get pretty comfortable flying 4 channel planes but that's about when I stopped. (Too many repairs).

I have been really trying challenge myself and push myself to become a better pilot. I started with the Apprentice and did circuits around a runway, challenging myself to make it look smoother, land with shorter distance etc. I then started challenging myself to use yaw more with my turns. I had always heard in general that you're supposed to do this to help turning somehow. I found that with some practice I could smoothly use both aileron and rudder to turn the plane, and it looks smoother of a turn. I then advanced myself to a T-28 Trojan on the simulator, which is a plane I actually own (in parts now). Yawing on the Trojan is feels more responsive, which I thought was due to the low wing design and that it was a common tendency on 'warbirds' in general (idk if you would consider the Trojan a warbird). I made the hypothesis that yawing is used primarily with a turn at low speeds. It seems that yawing produces less drag than banking into a turn with aileron. In addition, yawing gives you the option to keep your wings more level to keep lift up. Is this correct? Tell me what I need to know. I am really looking to learn as much as I can about how to fly. I also noticed the difference with yawing between high and low wing planes but couldn't make any conclusions.

My next question was about tip stalls. I am not sure if the simulator is accurate in showing stalls but overall it seems like stall characteristics are pretty mild in the sim. I have been trying to recreate stalls to learn basically what situations not to get in where stalls are likely and to teach myself what to do in stalls, but tip stalls remain something that I can't figure out. Why do tip stalls happen? Again, I am looking for any knowledge I can get so please let me know what you think. With stalls especially, let me know any information that you think might be useful (I know to push the nose down so you don't have to mention that one).

EDIT: I posted that and then I was like "Maybe it's just when the wingTIP stalls?". Tip - Stall. I'm a genius. I still look forward to your wisdom however.

Thank you!

 

[Merv]

.......I made the hypothesis that yawing is used primarily with a turn at low speeds. ......Why do tip stalls happen?

The only times I use the rudder is in a knife edge, stall turns or in a spin. Some use it for a cross wind landing.

Tip stalls happen when you are flying too slow. The wing doesn't have enough air moving over it to generate lift. It's very seldom that both wings quit at the same time. One will quit before the other. Tip stalls can be fun when you are several hundred feet in the air and you can accentuate them with the rudder. You can get some great spins . When they happen 10 feet off the ground, it's usually rebuilding time.

 

[SkyEye]

The only times I use the rudder is in a knife edge, stall turns or in a spin. Some use it for a cross wind landing.

Tip stalls happen when you are flying too slow. The wing doesn't have enough air moving over it to generate lift. It's very seldom that both wings quit at the same time. One will quit before the other. Tip stalls can be fun when you are several hundred feet in the air and you can accentuate them with the rudder. You can get some great spins . When they happen 10 feet off the ground, it's usually rebuilding time.

Yeah, I had flown for like 3 years before I stopped and I never used to use rudder at all. I only picked it up to learn more about it really. I do not know if they are considered tip stalls but I saw a stall where the plane's tail rocked down violently as if the cg was super far back, and then the wing tipped over. Good to know about tip stalls, thank you!

 

[Merv]

.....as if the cg was super far back, .....

Moving the CG aft will increase the tip stall. Likewise moving CG forward will reduce tip stall. It will make the plane more stable.

Move the CG to get the stability you prefer, some like it very stable, I like a bit of instability.

 

[whackflyer]

The only times I use the rudder is in a knife edge, stall turns or in a spin. Some use it for a cross wind landing.

Tip stalls happen when you are flying too slow. The wing doesn't have enough air moving over it to generate lift. It's very seldom that both wings quit at the same time. One will quit before the other. Tip stalls can be fun when you are several hundred feet in the air and you can accentuate them with the rudder. You can get some great spins . When they happen 10 feet off the ground, it's usually rebuilding time.

You don't coordinate your turns with rudder?

 

[SkyEye]

@whackflyer Coordinating turns with rudder. That is the phrase I was looking for.

 

[Ketchup]

@whackflyer Coordinating turns with rudder. That is the phrase I was looking for.

I’m pretty sure that turns are coordinated like that just to combat adverse yaw. If you don’t have any adverse yaw issues then you shouldn’t need to coordinate much. I usually just mix in a bit of rudder on my tx for bigger planes that need it.

 

[Bricks]

If you want to use rudder start flying 3D planes if you cannot use rudder you will never fly 3D . Start by trying to make flat turns keeping the wings level and still making the turn, I have the opposite problem I have one heck of a time flying a plane without rudder, so use to flying 3D I am darn near lost without it. Learn to use rudder and keeping wings flat alleviates most tip stalls as they usually occur at slow speeds and inputting aileron will cause it as one wing tip will quit flying. This is where you see so many warbirds crash it is on landing and slow speeds instead of correcting with rudder ailerons are input instead.

 

[sprzout]

If you want to use rudder start flying 3D planes if you cannot use rudder you will never fly 3D . Start by trying to make flat turns keeping the wings level and still making the turn, I have the opposite problem I have one heck of a time flying a plane without rudder, so use to flying 3D I am darn near lost without it. Learn to use rudder and keeping wings flat alleviates most tip stalls as they usually occur at slow speeds and inputting aileron will cause it as one wing tip will quit flying. This is where you see so many warbirds crash it is on landing and slow speeds instead of correcting with rudder ailerons are input instead.

Rudder also can become a factor on landing.

Our flying field gets a bit of a crosswind in the afternoons and evenings; if you try to make your approach without pointing the nose a bit into that wind, you’ll find yourself drifting off into the dirt on the far side of the runway, or catching the weeds.

Crabbing into the wind, you can use the rudder to keep your nose at the right angle and kick it around. It’s a skill I learned while still going through training due to those afternoon winds...

 

[Taildragger]

@whackflyer I've recently been reading an interesting book called stick and rudder, and in it the author says that the rudder is only used to get into a turn, and to keep the nose lined up on landings.

 

[whackflyer]

@Taildragger yes that's true, but like @Ketchup said, it's also used to combat adverse yaw. On planes like my FMS Super Cub, I need to use rudder or it skids through a turn. Some planes like the FT-22 don't even have rudders, ie bank and yank. It depends on the plane.

 

[quorneng]

SkyEye
Most of the time you use the rudder to combat yaw not to create it.
When you bank a plane it is very likely to yaw adversely. You use the rudder to correct it as appropriate.
The problem with RC is that it is very hard to detect small yaw angles from the ground. The danger is by the time it is obvious other aerodynamic effects will come into play.
Of course of you are actually in the plane with a slip indicator in front of you it is easy to apply just the tight amount of rudder to ensure there is no slip.
The faster you are flying above the stall speed only smaller control inputs are needed so the effects of aileron yaw are greatly reduced. Most EDFs can fly quite happily without using the rudder in a turn.

As other have pointed out the rudder is used at other times to specifically combat or create a yaw. This can be during aerobatic manoeuvres or to correct the flight path when close to, or on, the ground when banking the plane would be inappropriate.
What is important is knowing the likely effects and consequences of how and when to use the rudder.

 

[Taildragger]

@Taildragger yes that's true, but like @Ketchup said, it's also used to combat adverse yaw. On planes like my FMS Super Cub, I need to use rudder or it skids through a turn. Some planes like the FT-22 don't even have rudders, ie bank and yank. It depends on the plane.

Whoops, I meant to combat adverse yaw when beginning a turn.

 

[SkyEye]

Thank you all for your replies. To be honest, I never really knew what adverse yaw was until just now. I've never flown a real plane and don't think I've ever noticed adverse yaw. I'll pay closer attention on the sim. @Bricks Yes that is how I started teaching myself to use rudder. I did flat turns like that and then learned to keep the wings level and then pushed myself to turn left to right then left again. @sprzout I wish I had understood more about aerodynamics and rudder usage back when I had my T-28 Trojan. I was much younger then and couldn't control the plane well in those afternoon winds you're talking about. So using aileron to turn ('bank and yank' sort of turn) is acceptable?

Also, for a right bank for example, you would apply left rudder?

 

[Ketchup]

Also, for a right bank for example, you would apply left rudder?

To combat adverse yaw, no. Check out this video on it to better understand adverse yaw:

There are some situations in which you would use opposite rudder compared to the ailerons, but they are usually more special things like knife edge or slipping.

 

[Merv]

You don't coordinate your turns with rudder?

No coordinated turns for me. I’m just a simple bank n yank flyer.
Coordinated turns make the airplane ride more comfortable for the passengers.

 

[Taildragger]

I feel like RC planes are smaller, so adverse yaw is almost not there. I'm not an expert though.

 

[Merv]

....I've ever noticed adverse yaw. ....Also, for a right bank for example, you would apply left rudder?

In the rc world, adverse yaw is much more pronounced. You can bank the plane but is continuous to fly more or less straight. It may even yaw in the opposite direction as you want.

In every turn there is a wing to the outside of the turn and a wing on the inside of the turn. Adverse yaw is when there is so much drag on the outside wing it prevents the plane from yawning. If you have this problem, the solution is making the up aileron go up more than the down aileron goes down. This will shift drag from the outside wing to the inside wing. Drag on the inside wing will pull the wing the correct direction.

If your aileron servos are on the top of the wing, the servos horns should point slightly rearward, by one tooth. If the servos are on the bottom of the wing, the servo horns should point slightly forward, by one tooth. This slight change will cause the up aileron to go up more than the down aileron goes down.

 

[CappyAmeric]

I always coordinate turns. It becomes instinctive.

Rudder is an invaluable control surface on any aircraft, from an Airbus A380, to a tiny 4 channel R/C plane. While most airliners can fly “feet flat on the floor” because flight computers coordinate turns for you - but on landing rudders are always used. Likewise, with any single engine propeller aircraft (any size) - P-factor in a climb induces “left turn” tendency requiring right rudder on every climb.

 

[Tench745]

Many planes, especially beginner RC planes can be flown without using rudder. That said, understanding rudder and using it will make you a better pilot; opening up new options like flying knife edge; making flat turns in gliders to conserve altitude; flying scale aircraft, especially WW I and II vintage; side-slipping to lose altitude quickly for small landing areas; and landing in strong crosswinds.

About tip-stalls: most people use the term incorrectly. Most people use the term "tip-stall" to refer to an aircraft's tendency to drop a wingtip when it stalls. This is just a stall. Many aircraft will drop a wingtip when they stall. In a properly designed wing the root of the wing will stall first and the stalled portion moves out toward the wingtip as the plane slows. Usually the wing will stop generating enough lift to hold the aircraft up before the stall propagates all the way to the tip. If you can keep the wingtips generating lift even at high angles of attack the aircraft will stay controllable throughout the stall and recover relatively easily.

In contrast, a tip stall is when the wing tip stalls before the root of the wing, making for violent and unpredictable stall behavior. If your airplane is tip stalling, it is a flaw in the design. Many FT planes have under-cambered wingtips because under-cambered airfoils stall at a higher angle of attack than flat-bottomed airfoils; this keeps the wingtips generating lift and control even when the rest of the wing has stalled.

Flight simulators generally do a bad job of simulating stall behavior. Stalls are usually very docile in flight sims. Accelerated stalls, such as when you pull sharply out of a dive, are rarely simulated. Flight sims also do a bad job simulating side-slips and forward slips, but that's not what you were asking about.