For perhaps most people engaged in model airplane flying today, it is hard to imagine a time when having even a single
channel of remote control was considered a giant leap in capability. Commercially available rudder-only (RO) systems
came on the scene back in 1950s or so, and were common up through the 1970s. The earliest systems used tube amplifiers
and lead acid batteries, but by the time they disappeared from the pages of modeling magazines transistors and nickel
cadmium (NiCad) batteries were the norm.
At first, simply successfully taking off, flying around a bit, and landing successfully was considered quite feat.
As time went on and pilots became more adept and equipment became more reliable, that was no longer good enough. There
is something about a model airplane that begs for aerobatics, and those aero pioneers were not about to let only a
single control- rudder - stop them from performing loops, rolls, inverted flight, and even Immelmann turns. This story
from the July 1957 issue of American Modeler is a tutorial on how to become a rudder-only aerobatic pilot.
You Can STUNT Your Rudder Plane
Most R/C plane kits include written instructions for building the plane and some go quite thoroughly into preliminary
balance. But they leave you right there with nary a word on aerobatics. In one way this is understandable, for many
builders have no particular interest in stunting-at least in the beginning. Just as well, too, for it is smart to
learn how to control your new R/C model in gentle turns. Better to get thoroughly familiar with its action in general
before you start to get violent.
Incidentally, it is always good practice to go through the AMA R/C Pattern Event maneuvers rather than just making
aimless turns in the air; you'll find it sharpens your control quite a bit to have some definite goal to attain, like
producing several perfect pattern sequences in a row.
now let's say that you have learned to control your plane pretty well, and are starting to "throw it around" a bit.
You'll be surprised at what you can do in this line with just a rudder control plane. Beginning R/Cers can learn to
do very acceptable loops, rolls, Immelman turns, etc. we tell you how in just a moment.
First, a quick review of trim requirements. Every design has its own angular setup of wing and stab, proper location
for CG, motor offset and down thrust.
But almost every plane is different; even planes made from the same
plans may require different balance.
Hidden warps, unnoticed fin offsets, even lopsided fuselages play their dastardly part here. Rudder planes normally
are adjusted to fly under full power in a moderate and steady climb, with no "scallop" or swooping action. See Dwg.
Your trim should be such that when the engine cuts, the plane goes into a smooth glide, likewise devoid of swoops.
If it glides nicely, but climbs tab steeply, it is probable that you need more down thrust; add this a little at a
the model glides straight, but tends to turn under power unless you keep giving, opposite rudder, you should look
to your engine offset-which means that you point the engine to one side or the other, away from a straight ahead line.
Dwg. B illustrates both down thrust and offset. The latter usually is needed to the right, since torque reaction to
the direction of prop rotation tends to roll the model to the left under power; by pointing the prop slightly to the
right. you can compensate.
Models seldom need up thrust, or left offset. But we have flown one requiring the latter, so you can't make hard
and fast rules here. One other point: if you change the size or pitch of the prop, you will usually find a different
offset (and sometimes down thrust as well) is required. This is entirely normal. In any case, before you go in for
stunting, try and get the plane to climb evenly and travel in a straight line.
While a model will fly nicely, and climb at a reasonable rate, with a given size of engine, it is often necessary
to increase the power, to get real stunt ability. Yet - sad to say - some models won't stunt well. even if way over-powered;
they just weren't designed for it.
best stunting, of course, a light weight model is the thing: keeping the wing loading down is the surest way to success.
If you have a heavy model and just can't get it to loop, it may be necessary to substitute next larger size engine.
Before you do, though, try the easier tricks, such as different sizes of props, hotter fuels, anything that will enable
your engine to put out more power.
R/Cers generally use larger props on their engines than will allow the latter to develop maximum power. So try
the next smaller prop diameter, or put on a narrow-blade prop if you have been using wider-bladed ones. Heavy planes
usually fly faster; if you have made changes to your plane that give a weight increase, you might find it necessary
to use a higher-pitched prop to retain a good climb. If so, it would probably be smart to use the next smaller diameter,
to allow the engine to turn up at an efficient speed.
flight in windy weather, some modelers keep a special shim to slip under the trailing edge of the wing, or to give
a bit more positive angle to the stab. This makes the model fly flat and fast and "bore" into the wind without excessive
climb. But don't forget to remove the shim if there is no wind next time you fly, or the model may make a long and
shallow power flight right into the ground!
One other necessity for good stunting is a fuel tank and feed system that will allow top engine power in any position.
Pressure tanks or those that have a swivel on the outlet tube have been found satisfactory.
Now to the stunts themselves. A plane that is adjusted normally will drop its nose when held in a sharp turn. If
you hold the rudder full on for any length of time, a spiral dive will develop. Try holding the rudder hard to one
side (after you climb the plane to a safe altitude) and note the reaction. If the ,nose drops rather sharply, speed
builds up and the plane spirals down at an alarming rate, you are ready for some stunting. (See Dwg. C) If not, you
probably don't have enough rudder action.
To stunt, you must have a means of gaining excess speed, and in a rudder-only plane the only way this can be done
is via the spiral dive (note that this is not a spin; we've never seen a rudder-only plane spin-in fact many planes
with elevator control can't be made to do a true spin).
the simplest stunt is the Wingover, which can normally be accomplished by allowing the plane to gain speed in a 180
degree turn, after which it will be headed down at a moderate angle. It is then straightened out, whereupon it will
start to climb due to the excess speed. Just as it gets near stalling speed, With the nose pointed upward at a fairly
steep angle, you hit full rudder. This should bring it around 180 degrees again, and back down the original path,
as in Dwg. D.
Normally, the prettiest and cleanest maneuvers are made with an absolutely straight and level recovery after you
have finished the stunt; in a rudder plane, this is impossible, but you can kill the excess speed by holding just
enough rudder to let the plane turn without losing altitude (that is, not enough so that it will drop into a spiral).
Actually, since practically all stunts produce a loss of altitude, it is smart to use up your excess speed in a climbing
turn, to get back the height you have just lost.
Now let's try a Roll. Here again, lots of speed is required; normally hot planes can gain sufficient speed for
this in a half turn of spiral. So do your half turn, give opposite rudder to straighten out and start a climb, then
hit hard rudder again, just as the nose starts to rise. Dwg. E. Your plane should do what is generally called in R/C
circles a "rudder roll." Actually, this is a sort of horizontal spiral; just the same, it's very spectacular! For
this maneuver, you need lots of rudder action and a plane that really travels. Plenty of power is also a necessity.
A hot ship can do roll after roll, without losing altitude, though you can lose height, if you wish; the roll is a
fine way to bore upwind in windy weather, since the plane can be held level, or can be brought lower, while still
heading directly into the wind at fairly high speed.
It might be thought 'that a model would roll best by taking advantage of prop torque--that is, roll the opposite
way from which the prop turns. This might be helpful in some case, but it seems more important to roll in the direction
that the plane turns the more sharply-which isn't always with torque. Some planes will roll (and spiral dive, for
that matter) only. in one direction.
How about a Loop? Really very simple. You will probably need to hold the speed-gaining spiral dive for at . least
a full turn, and maybe two or three, for you'll need lots of zip to go up over the top. As you pull out of the spiral
with opposite rudder to straighten out the plane and start it climbing, you might need to apply slight rudder either
side to keep it arcing up in a straight 'path; applying slight rudder is all you can do, besides just waiting to see
if she has enough speed to get up over the top without stalling. Once over, you still keep neutral rudder (or give
slight corrective blips) till the plane has come back down to level again; it will be going at high speed here and
you may be able to do one or more additional loops without stopping! Dwg. F. Coming out of the last one, put 'er into
that climbing turn to get back all the altitude you've lost.
If you can do a decent loop and roll, you can combine parts of each to do two more maneuvers-the Immelmanurn and
the Split-S; actually these are exact opposites of each other. For theturn and the Split-S; actually these are exact
opposites of each other. For the Immelmann, do a good half-loop, then right at the top, hit hard rudder (, do a good
half-loop, then right at the top, hit hard rudder (Dwg. G). Plane should roll out without too much loss of altitude
and be flying level in the opposite direction from which it started the half-loop. Some craft have trouble completing
a loop because they don't have enough power (or are too heavy) to get up over the top, yet still retain flying speed;
such jobs often do nice Immelmann, though, tending to roll level as they lose flying speed near the top of the loop.
A Split-S is just the reverse (Dwg. H); you do a half-roll, then just as the plane is upside-down, hit a blip of
opposite rudder to bring it into straight ahead flight. It can go only one way - down - and will do the last half
of a loop. Some planes lose a surprising amount of altitude' in this maneuver, so do the first few high!
good pilot with a hot and maneuverable plane can do a very reasonable Cuban-Eight, but it takes split-second timing.
Check Dwg. I first. You go into it from the usual spiral dive, and work the controls as though you were doing an Immelman;
however, let the nose of the' plane fall quite a bit after you get over the top of the half-loop, before you roll
out. The plane will then be headed downward when you simply repeat the Immelmann with a delayed half roll, to complete
Once you have mastered these stunts, there's nothing much more we can tell you. Maybe you will
find a way to do outside loops with your Rudder-Only plane; if so, you tell us 1 .
As new techniques and ideas come along they'll be covered in "AM's" Radio Control news'n'views column each month.
Keep an eye on that department and advise us if you develop any new maneuvers. Think of having one named after yourself!