How to teach turning (Revisited)
I've been reading the thread on how to teach turning with some interest.
Naturally every CFI will have their own approach to this issue.
I have respectfully pasted in below for you some notes from a lecture I gave to aerobatic instructors at a seminar I did many years ago where we were concentrating heavily on basics.
It is my intent to perhaps inject some personal perspective into this very important question based on personal experience gained over many years of teaching people to fly.
I hope the information is of some use.
------------- From 1961 Reading Air Show Reading Pa.
First of all, let me begin by saying that one of the first things any good flight instructor does with a new student when introducing turns even in small airplanes is to get them used to flying the airplane with outside visual cues. The objective here is to get the pilot's attention about 90% outside the cockpit and the other 10% on the panel to peripherally cross check the accuracy of what's being done physically with the aircraft using those outside visual cues. This means for example that you learn to estimate say a 20 degree bank angle by visual reference to the horizon and you put the airplane in that 20 degree bank doing a visual angle estimate with the horizon and peripherally check what you did by a quick glance at the attitude indicator, or artificial horizon you have installed in the airplane.
Notice I didn't mention the turn and bank. There's a reason for that. In attitude flying which is what we are talking about here, one of the first things you should be doing is learning to "READ" the quality of your turn entries, turn maintenance, and turn exits, by visual reference to the horizon rather than using the ball on the turn and bank.
This is very easy to do once you realize there are 3 possible types of turn entries and exits, 1. Perfectly coordinated,2. a slipped entry or exit, and 3. A skidding entry or exit.
In attitude flying, you use the NOSE of the aircraft as your "ball". Every time you enter or leave a turn you watch the nose of the aircraft. The literal definition for a coordinated turn entry or exit can be defined by using the exact amount of rudder required to match the rate of roll the ailerons are producing as you are entering or exiting a turn.
Now how does this equate to the nose on the horizon. It's simple really. Lets discuss what the rudder does for a second. When you enter a turn, the down aileron produces induced drag as it increases the lift on the high wing. So if you are turning left for example, the left aileron is up and the right is down. What's happening here? Well, that outside wing because that aileron is deflected down is now producing more lift than the left wing so the airplane banks left. Remember, when that right aileron goes down it physically changes the camber of the wing creating more lift on that side. Increased lift means increased induced drag, and what does that drag do? It wants to yaw the airplane to the right! Well, we're rolling into a left bank to turn left so the last thing we want the airplane to do is yaw to the right.
ENTER the rudder!. It's the rudder that kills the adverse yaw to the right that that down aileron is producing. Now you say.........well FINE! But how much rudder do I need to be using to correct that yaw and make the turn entry coordinated?
The answer is staring you right in the puss. It's out there on the horizon right directly over the nose.
As you roll into the turn for the first 5 degrees or so, you want that nose to be PINNED solidly in place on the horizon. If you used no inside rudder with your aileron, that nose would be yawing to the right on you, and that's NOT what you want to happen.
Now understand that as soon as you split your lift vectors into two parts (it's the horizontal component of the two vectors that will be producing the turn, the other part opposing gravity) that nose will start to move sideways with you as the bank starts producing a turn. What you want to do is to PIN that nose out there on the horizon for the first few degrees of the turn, then watch it go with you as the airplane starts turning. You NEVER...and I repeat it again for clarity......NEVER want to see that nose slewing the OTHER WAY, in this case to the right. ( I am omitting a deliberate slip entry where in some cases you actually WANT the yaw and accept it entering a slip). It is important to note here as well that in aerobatics, we consider cross control as coordinated IF cross control is what is desired as in a slip, knife edge flight, a slow roll, or killing the lift on the outside wing in a hammerhead for a few examples) Remember, we're talking PRIMARY visual coordination here and that means a non crossed control input as in level turn entry and exit.
Now, back to our left turn entry as we are watching the nose. If the nose does slew right on you as you enter the turn, even a tiny bit, you haven't used enough inside rudder to offset the adverse yaw and your rate of turn is not enough for the bank you are creating. You are SLIPPING the entry! Now you can check this by referencing the ball as a lot of pilots are unfortunately taught to do, and this takes your visual cue off the horizon, but you shouldn't have to look at the ball. You should be both feeling the turn as coordinated and seeing it verified by what the nose is doing on the horizon outside the airplane. THIS is attitude flying.
Conversely, if you see that the nose is leading you across the horizon, you have too much rudder in for the amount of bank you’re creating (aileron) and your rate of turn is too high for the bank. You are now skidding the entry. Again, you can check this with the ball, but it shouldn't be necessary. The NOSE should be telling you everything you need to know about the quality of your turn.
An integrated approach to primary flying is fine, and should be used by instructors, but unfortunately many CFI’s start the student out with hevay concentration on panel references at the expense of outside visual cues and in my opinion anyway, this is a HUGE mistake. I’ve been advising instructors all through my career to keep the attention initially OUTSIDE the cockpit using instrumentation to VERIFY the quality of control input by the student with HEAVY emphasis on referencing the visual cues as prime in flying the aircraft.
Now lets talk about turns once established and how that affects the ball.
Basically you can split all turns into 3 distinct categories and each category has it's own individual behavior and affects the ball a bit differently. Knowing how all this interacts will help you tremendously as you maneuver the aircraft in turns using visual cues.
Cat. 1. Shallow banked turns 20 degrees of bank and under
Cat. 2. Medium banked turns between 20 and 45 degrees of bank
Cat. 3. Steep turns over 45 degrees of bank
As you fly, you will come to realize that the ball in the turn and bank indicator will act differently in the 3 categories of turn. Here's why!
Lets start out with a simple premise. For ALL turns, what you want to achieve is a coordinated entry, then neutralize the bank, and LET THE RUDDER STREAMLINE with the relative wind. This is handled a bit differently for all three categories of turn.
In a shallow turn under 20 degrees of bank. The dihedral effect of the wings will be attempting to return the aircraft to level flight after you establish the bank, neutralize the aileron and let the rudder streamline. This will be your first bout with the infamous ball being "out" on you in a turn. It's called under bank tendency.
What happens is that as the dihedral effect tries to bring the airplane back to level flight on you, in order to maintain your angle of bank and turn you find that you have to feed in some additional inside aileron to compensate. And what happens when you do this? That down aileron again is now causing a bit of increased lift and induced drag. So you take a peek at the ball and it's not perfectly in the dog house!!!! Are you uncoordinated? Not really. You're compensating to keep the airplane in your chosen shallow bank angle that's all, but if you look at the ball.........it's not dead center in the doghouse. No big deal, and it's perfectly normal.
ANYTIME you have ailerons in ANY other position but streamlined with the wing, you have some increased lift from the down aileron that has to be compensated for.
I should note that usually for shallow bank turn, you simply need a bit of additional aileron to hold the bank. No big deal, but don't look for a centered ball.
In a medium banked turn, between 20 and 45 degrees, in most airplanes with dihedral this is the most stable range of bank. Basically it's here where you can put the bank in, neutralize the controls, feed in required back pressure to increase the aoa to maintain altitude and see a centered ball. Everything is streamlined with the relative wind; no additional aileron is being used, and thus no down aileron. Ball centered.
Steep turns are the most troublesome to maintain. Here we have what we call over bank tendency. It's in steep turns where the fact that the outside wing is moving faster through the air than the inside wing begins to really cause you problems holding a specific bank angle. That outside wing is creating a LOT of excess lift because of the speed difference between the wings and the effect of that is to cause the aircraft to want to bank even steeper than you want to bank. You are now the opposite of a shallow bank and you now have to fight to keep the bank from getting steeper. You do this by the application of outside aileron. This naturally puts the left aileron down in your left turn and requires a bit of rudder correction for that. You guessed it..........no centered ball again!
Notice I've been talking only about turn entries and maintenance. For turn exits, the exact same things I've covered above apply.
If you consider everything I've said here it begins to become clear that even if you are holding in a minute amount of rudder in a turn, depending on the exact angle of bank, you will be seeing several behaviors from the ball in the T&B, but that NOSE out there will ALWAYS tell you if what you are doing with the airplane is coordinated, with the added benefit of having your eyes checking for traffic as you turn instead of glued to the panel. Learn to fly this way and the eventual result will be a pilot capable of perfect coordination through the application of correct control pressures in all axis' through 3 dimensional space............all done instinctively in response to visual cues alone!
The airplane is the best instructor you will ever have.
Dudley Henriques
President Emeritus
International Fighter Pilots Fellowship
Last edited by Dudley Henriques; 17th Nov 2009 at 18:42.