Rudder control?

Rob,

The first thing you need to come to grips with is that the rudder (unlike in a boat) is NOT used to turn the aircraft! Each [set] of control surface acts on a different axis. The elevator acts on the pitch (lateral) axis which runs horizontally from wingtip to wingtip, the ailerons act upon the roll (longitudinal) axis which runs from nose to tail and the rudder acts upon the yaw (vertical) axis which runs through the cabin roof and exits the bottom of the aircraft.

All 3 axes meet at the center of gravity of the aircraft and can change with different loadings.

It is the roll axis, controlled by the ailerons, which causes an aircraft to turn as by rotating around this axis the differential angle of attack and hence lift in each wing causes the aircraft to turn. Notice I neven mentioned rudder.

I will now. The rudder, controlling rotation around the yaw axis, serves to keep the tail following the nose as the aircraft is describing an arc in the sky when in a turn. When the tail is not following the nose, the aircraft is said to be either slipping or skidding depending on where the tail is with regards to the nose (left or right). This is known as "uncoordinated" flight as rudder movement is supposed to be coordinated with aileron movement in the appropriate proportion to keep things in line. The performance instrument is the very low tech inclinometer (the ball in the glass tube) on either the older turn and bank gyro indicator, the newer turn coordinator gyro indicator or the newest "glass panel" with a graphic representation of the inclinometer which gets its inputs from accellerometers mounted remotely somewhere in the aircraft.

So there you go. Although there was considerable technical information presented here I hope I made it clear and in an understandable manner. I apologize if all I did was add to the confusion.

Planeflyr

 

In planes equiped with yaw dampers, we do not use the rudders that much whle hand flying. We do when side-slipping or forward slippiing the airplane
or stopping dutch rolls at altitude with a loss of the yaw dampers.

I recommend Bill Kirshner's book, The Student Pilot's flight Manual and Advisory Circular AC 61-23C, Pilot's Handbook of Aeronautical Knowledge

it would be a good idea to have your written passed before enbarking on any fomal flight training.

The deflection of the down aileron creates more lift and in doing so more drag which in turn yaws the nose adversely or opposite to the vector of the horizontal component of lift the wings created by being tilted by the ailerons

Coordnated use of the rudder corrects this conditon knows as "adverse yaw" caused by aileron drag. You can feel this in your seat the slipping or skidding condition. Apply too much rudder and you have a skid and too little a slip.

Minimizing the effect of Adverse yaw

Two methods are common:

Frise ailerons

Frise ailerons are designed so that when up aileron is applied, some of the forward edge of the aileron will protrude downward into the airflow, causing increased drag on this (down-going) wing. This will counter the drag produced by the other aileron, thus reducing adverse yaw.

Unfortunately, as well as reducing adverse yaw, Frise ailerons will increase the overall drag of the aircraft, and therefore they are less popular in aircraft where minimizing drag is important (e.g. in a glider)

Differential ailerons

As it is the downwards deflection of an aileron that causes aileron drag, a simple way of eliminating adverse yaw would be to rely solely on the upward deflection of the opposite wing to cause the aircraft to roll. However, this would lead to a slow roll rate - and therefore a better solution is to make a compromise between adverse yaw and roll rate. This is what occurs in Differential ailerons. The down-going aileron moves through a smaller angle than the up-going aileron, reducing the amount of aileron drag, and thus reducing the effect of adverse yaw. The De Havilland Tiger Moth biplane is one of the most famous aircraft that uses this method of roll control to avoid adverse yaw problems.

Paul

 

That's jes' what I was going to say but those other guys beat me to it. A hundred years ago when I was a student, I learned " rudder" but before that I learned spins and spin recovery. Earlier, I learned stall recovery, you know, push the stick forward when the airplane starts to shake. One day the instructor said that we were going to do deep stalls and proceded to allow me to pull the stick into my gut , leave it there and try to keep the airplane level.Naturally, I reverted to the ailerons which are absolutely useless in a stall and we went into a spin. " Okay, we're going to learn how to prevent that but first , we are going to learn how to do spins and to recover from them." He showed me that my lack of knowledge could get me into a spin and I needed to know how to survive them so we did spins that day. The next day we started what he called" rudder exercise stalls". We did the stick in the gut thing with cruise power and I learned how to work the nose as it fell through the stall by using quick and aggressive rudder inputs. Failure to do so resulted in a quick spin from which I recovered and returned to the exercise. It wasn't long before I could leave the stick and power alone and roller coaster the airplane with its nose in the air and keep it straight with rudder. My old L-3 had Frise ailerons and it was a beautiful flying little airplane. I could pull the nose up and walk it around at speeds below what the airspeed indicator could indicate. It would spin but it would pop out on its own as did the Stearman. The PT-19 was another story.

 

Good thinking , Rob. Forget the glass markers and learn how and when to use rudder. It can be your friend. I have seen too many spamcanners fly ( drive ?) with their feet on the floor because the 172 did a good enough job in a turn without any piloting.

 

Hey Rob,
At this point in your training, the VERY LAST thing you should be watching is the Instruments.
Forget all about them for now, and concentrate on the sight picture out the windshield.
See what the control inputs are doing to the airplane.
The horizon will tell all!
You are in the Basic Aeronautic mode of learning, or should be....
Watching the panel will only make it difficult to fly the plane.
The Instruments do NOT reflect the actual attitudes instantly.
Watching the panel will only put you, behind the plane.
Your most important job, is to stay ahead of the plane.

And learning to fly "out the window" may save your life one day, if there's an electrical failure.


**Whatever you do don't depend on the "Glass Panel" for anything. **

(**Attributed to a posthumous word of advice from ex baseball celeb.... Cory L.)

 

Furthermore in reference to rudder input vs's aileron input.I was taught while stall/spin training (an acrobatic course)
;if the ailerons are used instead of rudder to "correct" as you would in a car you will CREATE the spin (being that you are now totally uncoardinated.) :0

This is a VERY important reaction to un-learn as most (or at least some) reactions are learned through driving automobiles etc....

REMEMBER POTENTIAL SPIN OR SPIN GET THEM LEGS MOVING !!!

NOT AS MUCH OF AN ISSUE AT 10K (ALTITUDE IS YOUR FRIEND)
BUT AT LOW ALTITUDES IT IS NOTORIOUS FOR A LOT OF AVIATION STALL/SPIN FATALITIES.

MY355

 

Rob:
You darn well should not be doing anything at 1,200 ft that could result in a spin -- no altitude to get out of it.

At least that's my humble opinion.

 

1200 feet is plenty of altitude to recover from a spin if the corrct procedures are used in something like a 172 or a Cub or a Stearman or even a 182. They come out quickly. A T-6 or a PT-19 would a push but most of the Spamcans are a piece of cake.

 

Good advice in this thread. I would advise against stalls (and especially spins!) at 1,200 feet AGL, but then I'm a pretty conservative guy. The fact is, you have to work to get a 152 or 172 to spin (well, only tried it personally in a 152 but I imagine the same goes for a 172).

I used to do spins for fun in a Citabria, that spun pretty nicely. I think you could probably recover from one started at 1,200 feet, but I'd rather be watching from the ground for that one!

I would also especially agree with the comment above about looking out the window, not at the glass!

One historical comment about rudder: I have read that in the early days (pre-WWII), rudder was used as the primary turning control with aileron used mainly to correct for adverse yaw, basically the opposite of today.

 

Practicing stalls and slowflight maneuvers at 1200 above ground is too low for a student pilot. Reading Aviation Safety accident reports section and reading NTSB Reporter will open your eyes to the risk taking that becomes statistics that should not have happened. Keep that head looking through the windshield while low to the ground and close to an airport(unless you are instument flying). Three things that are of NO use to pilots: the runway behind you, the sky above you, and the fuel left behind.
N Dennis

 

I have always done stalls and slow flight practice at 2,500 feet or above, preferably around 3,000 feet.

As for rudder, usually you trail it a bit. A good thing to try: next time, turn the airplane using aileron only and watch carefully what the nose does. You'll see that the nose will start to go opposite to the turn, slightly. That is "adverse yaw."

You want to use the rudder to counteract that and keep the nose turning smoothly with the airplane. Different airplanes have different amounts of adverse yaw. Some of them require a great deal, some almost none. As I recall, the 172 doesn't have a lot of adverse yaw, but it's noticeable if you look for it.

My explanation isn't all that good (it's been a long time since I've given much primary instruction), but try it in the airplane and you'll see what I mean.

 

Rob,
the FAA requires you to be able to glide to a suitable landing area without damage to or harm of people/property, in the event of an engine failure...
Given the glide ratio of a 152, or 172.... (it's in the Pilot's Operating Handbook)
How long do you want to have, before hitting the trees/ building /ground ???

Time enough just to say OH! SH*T!!!
Time enough just to say Uh oh! we're going to have to land NOW!!!
Time enough just to look around for something with a nice large flat area?
Time enough to look for someplace nicer than the tree stumped field you're over... as you descend at 500 ft/min

Well that's why, altitude... is your very best friend.

3000 ft + for practice, and for distance, depends on topography of the land.
(i.e. towers, stacks, High rise buildings, mountains, etc.) You have to maintain certain distances from all ground objects, both horizontally, and vertically. Again..... altitude is your best friend.
And double it..... if you're crossing over water

In a word.....Coordinated.
(In english... both together, at the same time)


I'll have to disagree with Switches statement, too..... any student's practicing of ANY maneuver below 3000 ft, is asking for trouble.

And, to clarify, I'm not speaking here, of a "Pro", fine tuning his airshow act....with the correct procedures being used to recover from some unusual attitude....

Learning something as apparently simple ... as a steep turn, (45°) brings into the picture such unthought of items (by the neophyte) as airspeed, Load factors, accelerated stalling, secondary stalls, and recovery altitude, or how much altitude you're gonna lose, before there's enough air flow ( to produce lift ) over the wing before the airplane can even begin to recover, and oh yeah....radio calls to tell them where to send the ambulance....and pick up the pieces
.

Not to even mention what the if's.... like a door pops open...the engine quits...or another plane suddenly appears directly ahead....and the "what if" becomes extremely distracting....

Don't think it CAN'T happen.... I've seen the other plane coming at me during takeoff! .....and have had the door pop open. Reporting both, right here on this forum.

Ya just don't want to bet your life on these things, in such an intensely concentrative practice environment.

But hey.... I don't want to scare you....





.

 

Charlie, I wasn't encouraging any student to do spins below 3000 ft. I'm saying that it is possible to recover if you use the right procedures and don't rush the prosess. I was in a Cub on the downwind when the instructor asked me to look out and see if we had good airspeed before turning on base. It appeared to me that we were scooting right along and I said yeah, we're moving right along. he said okay, I'll just bank around here and enter base when all hell broke loose. The airplane was on its backand in a spin before I knew what had happened. As he recovered from a one turn spin he was talking calmly and telling me that this is how some students kill themselves when they don't look at how fast they are going over the ground instead of looking at the airspeed indicator. AND you don't make steep banking turns when you're on the downwind. I'll never forget seeing trees coming up like green spears and I'll never forget that lesson.
I saw a kid enter a spin inadvertantly and got the nose straight and yanked back on the stick, entered another spin, and repeated the process one more time before he hit. Lesson: Don't rush the control inputs.

 

Hey, Switches,
We're on the same page....
Well... all, except for "groundspeed".....Unless, I somehow misunderstood you.. ? Or I missed something somewhere.... Which IS entirely possible....

Since when does groundspeed matter during maneuvers? (with exceptions for "ground referencing" maneuvers, and touchdowns...)

I wouldn't want to, but theoretically, I could be in a 90 knot headwind, in a 152, and be travelling backwards over the ground, and still have sufficient airspeed to bank 45° ..... NO??? What have I missed?

(Agreed on steep downwind turns, due to a lack of altitude, for accelerated stall..... recovery, )

I know you've done some show work, and recovery is possible with correct proc's.
Was just making sure "The new guy" didn't think this was protocol for a low time student..

Hey Did I ever tell you the time I was in a row boat, doing really tight turns, in only 3 feet of water???

Left oar forward, Right oar backwards... And NO rudder!!

Boy!! Did I get into a spin!!!


.

 

Charlie, the instructor was making a point that APPARENTairspeed can kill you. Only actual airspeed is what you should fly by. Down wind low to the ground can give a low time student a feeling of speed when the relative airspeed is quite low. The steep turn onto base rolled the wings over to zilch air flow from leading edge to trailing edge and it stalled........Fast. This guy taught by harsh example and I can thank him for saving my skin too many times when I reverted to what he pounded into my head. With him, you didn't " ride " , you flew. Upside down in a Stearman? When we were on a cross country he asked me which way the wind was blowing. I noticed some clouds passing by and I pointed to the tail of the airplane. Faster than you can pee your pants, we were inverted." Now you look up there or down there and find something that tells you where the wind is coming from!" I couldn't at the time and the engine started to miss and backfire so we rolled upright. He allowed that there wasn't much to gage so we had a quick talk about measuring drift and watching check points. No OMNI, GPS, or anything else but sectionals and ground checks. Florida has no section lines . Nothing but swamps and lakes so navigation had to be a constant checking of drift, headings and reading the charts. The greatest time of my life.

 

Switches, I should have known better.

Now See There???
I just knew I musta missed sumptin.....somewhere..!
Now that you've filled me in, and brought me up to par...
Guess I'll have to rescind the previous disagreement.

 

That's a safe way to learn, Rob. What kind of RC planes are you flying? I used to fly big gas free flights when I was a kid. I wish you good things in your training.
Switches