Up until now, if you had only a three channel trainer, you still could get recognizable results on the maneuvers studied so far. Some pilots can even get recognizable horizontal rolls, having only the rudder as the rolling mechanism. But that is straining it. For this maneuver you really should have ailerons. A flat bottom airfoil is okay, but a semi- symmetrical is better, and a fully symmetrical is best. This maneuver involves rapid revolutions about the longitudinal axis. One moment you are upright, the next upside down, and soon you can hardly keep track of where you are. And yet this is an exciting maneuver to have in your repertoire, and worth every bit of the trouble necessary to learn it.
Putting a plane into a continuous series of axial rolls is achieved by applying full aileron, to the right seems comfortable for most pilots, and then while holding full aileron, the elevator stick is moved fore and aft to create applications of up and down elevator at the right moments. To master this maneuver, these suggestions are offered: 1. Get a proper roll rate by adjusting the amount of full throw in your ailerons.
Three complete revolutions in faster than five seconds is too fast, and if they take much longer than eight seconds, that is too slow which means you'll have more trouble keeping the flight path straight. 2. Practice this maneuver in a climbing mode. After you have the knack for proper elevator timing, gradually bring the flight path into a level axis, parallel to the ground.
Learning this maneuver in the climbing attitude is what turns this plane crasher into a pussycat.
The trick of the maneuver is to learn the proper amounts of up and down elevator to apply, and to learn the proper timing of that application to coincide with alternate upright and inverted position of the aircraft. If you are off on your elevator timing, the maneuver can "slice or hook," to use a golf term, that is to curve right or left from a straight flight path. It can also lose altitude if the timing of the elevator is off too much.
Taking first the amount of elevator application most planes require more down elevator while the plane is inverted, than up elevator while it is rolling through the upright phase of its rotations. The flat bottom airfoil can require full down elevator. The relative for/aft center of gravity will also affect this aspect the more nose heavy, the more down elevator while inverted. The exact amount of up or down you will have to determine with practice. Taking next the timing the goal is to begin applying some elevator as soon as the wings are 45 or more degrees off level though you can skip applying up elevator going into the first revolution.
Thus your first application of elevator becomes down as the plane has passes through knife edge and is coming into its first inverted position. You smoothly slide forward on the elevator stick, timing your application so that the maximum amount of down you are going to apply occurs exactly at full inverted. As the plane revolves through that position and starts coming through 45 degrees, you start easing up, so that you are entirely off down elevator and sliding onto up elevator by the time the plane has revolved through knife edge and is flying 45 degrees upright. As the plane is exactly upright you should be applying maximum up elevator.
If your maximum application occurs while the plane is still tilted, you will induce a turn, which, of course, will curve the flight path. It is a common mistake while learning this maneuver to develop a rhythm, and you're doing pretty well, and them all of a sudden one time the flight path hooks or slices on you. What happened was you came to depend on the rhythm, not the timing of max up/down with exact upright/inverted flight, and your rhythm got slightly off time, so the max was occurring in tilted flight.
So concentrate, and practice your elevator application to achieve maximum elevator application adequate to keep your plane in a steady upward climb, without curving right or left. As you gain confidence, allow the climb to be steadily lowered until you can hold perfectly level flight while rolling.
While called a downwind maneuver, as a sport flier you will find it works well upwind, too. Be sure to practice coming from the right and the left. Don't become a flier addicted to one direction. As always, center it on yourself by beginning soon enough to get upside down of the second roll right opposite yourself. A crisp end is made by rapid release of the aileron at the end of the third roll.