Lesson Nine - Secret of the Perfect Step Turn
A Lesson from, Vern Kingsford, DPE
Of all the maneuvers required of the student float plane pilot to learn and demonstrate during the few hours spent earning his SES rating, the step turn is one of the most uncomfortable and difficult. We could call this lesson “Step Turns Made Simple.” Or to plagiarize from a few book titles, “Step Turns for Dummies”.
For illustrative purposes, the step turn I am about to describe will take place in light winds, 6 to 8 knots. In this discussion the wind effect will not be discussed. You must be aware of extra care while turning from a downwind step taxi to upwind.
Before you start any step taxi or turn, keep at a conscience level this sage advice; “Don’t EVER step turn or step taxi unless you really NEED to.”
To perform a step turn proficiently requires a basic understanding of Newton’s laws of motion. A step turn is started from a stabilized step taxi. In this case we are step taxiing into a slight headwind. Your aircraft is step taxiing straight ahead. You’ve stabilized the speed, you are on the step. Your speed is at the minimum necessary to maintain the step. (Perfect!)
You decide you want to alter the heading of your aircraft, that is, change direction. Turning left or right is different. You put some pressure on the rudder in the direction you want to go and position your ailerons into the turn. You have observed in previous practice that the turn tightens in both directions. You don’t know why, but add a little opposite rudder anyway to compensate, avoiding the tightening tendency. (For the moment I will disregard this fact and save it for a later lesson)
You start the step taxi turn. Immediately the feeling of skidding takes place, you feel as if the airplane is going to tip over to the outside of the turn. This feeling of tipping towards the outside of the turn is caused by centripetal force. As you begin your turn Newton’s laws of motion enter the equation.
During your step taxi straight ahead, the aircraft (Mass) was stable. (Not accelerating, not decelerating) Newton observed in his first law that a body in motion, tended to remain in motion, in the direction of motion, until acted upon by an outside force. This tendency to continue in motion is called inertia. Inertia is energy, specifically kinetic energy. Energy is created by our object (in this case the aircraft) that is in motion.
Your airplane is a Super Cub. It weighs 2000 pounds (STC’d on Whipline floats - we’re legal). You have 2000 pounds of mass moving straight ahead at about 25 MPH. It wants to keep going straight ahead, period…and this is where the typical pilot begins to lose it.
You’ve been told, “Stay ahead of the airplane.” What exactly does that mean? It means, knowing the eventual future effect of what you are doing now.
YOU want to turn. So you exert some force on the rudder in the direction you hope to maintain your step taxi turn, you place your ailerons in the direction of your turn, AND… immediately, instantaneously, at the very moment you start to change heading you destabilize your step taxi. You diverted some of the energy that was keeping your aircraft in motion while going straight ahead. Surely but slowly your Super Cub starts to fall off the step. You notice the nose start to rise, so you put a little forward stick in, (Law of primacy) which just makes things worse. Now half way through the turn you hear funny sounds from the prop, sounds like aaahhrrrgg. You lost it!
Here is the Secret, It’s this SIMPLE to do a step turn properly.
First, define and memorize this word: simultaneously! It means existing or occurring at exactly the same time.
AT EXACTLY THE SAME TIME, Not before, not later. Simultaneously!!!
You will be required to perform many tasks with this word, simultaneously, at a conscious level of your thinking. So, again you start your step taxi turn from a stabilized step taxi. This time, you simultaneously, at exactly the same time, you apply rudder pressure, you also add some power!
How much power? My rule of thumb about required power is: The tighter the turn, the more power is required. During a real tight turn all available power will be needed. Don’t try it until you have lots of experience. I put a wing in the water once. I was quick on the rudders and throttle and didn’t capsize.
For a gentle, medium step taxi turn, usually about 200 RPMs is good. Be flexible, “be ahead of the airplane,” use the amount of power needed. Adjust power as required. You’ve learned that at the moment the nose on the aircraft starts to come up you add a little more power. I say, “Blow it down.” You’re ahead of the aircraft. You now know why what is happening, is happening. If you had paid better attention in science class you would have an easier time.
As you complete the step turn, you now know the airplane to accelerate because of the extra power used in the step turn.
To avoid lifting off, you reduce the power, smoothly, simultaneously, so you will not over speed.
You now know “The Secret” of properly executing a step turn. It’s this SIMPLE to do a step turn properly: simultaneously add some power and be ahead of the airplane. Fine tune the power as you complete the turn. It is simply that simple. Newton would understand.
To Review: Secret of a perfect step turn. Keep at a conscience level; “Don’t EVER step turn or step taxi unless you really NEED to. “Simultaneously add some power as you start the turn, more is better than not enough, you can reduce it. Go to this web site; Newton’s Laws of Motion. http://www.grc.nasa.gov/WWW/k-12/airplane/newton1.html
Now YOU Know the Secret of a perfect Step Turn. Go practice. “Practice does not make prefect, Only perfect practice makes perfect.”