Warringah Radio Control
Society Incorporated
(Incorporated under the Association Incorporation Act 1984)

 Learning to fly
- by Charles Peake - (A posthumous thanks again to our much beloved Charles for this evergreen advice)
TAILDRAGGER TAKE-OFF
The essential characteristic of the taildragger is that the tail must be allowed to rise in the early part of the takeoff roll, and the aircraft permitted to gain flying speed with the fuselage more or less horizontal.
Most models have a much higher power to weight ratio than a full size aircraft, and this may allow the propeller to literally drag the model off the ground in the  three point attitude.  If this happens, the wing is already almost stalled, aileron control may be almost non-existent, and the torque effect can simply roll the model into the ground.
This can be avoided by ensuring that full power is not applied until the tail is up.  Open the throttle slowly, or hesitate at about half throttle, until the tail lifts.
Torque effect will be much more evident than in the trike ( tricycle undercarriage), especially while the engine is accelerating and the tail is rising.  Any swing must be corrected quickly, before a ground loop can develop.  Be careful not to over correct, which may cause a ground loop in the opposite direction.  [Alan Place explained that a ground loop is when the aircraft swerves off the runway, and not as the unwashed like me might expect, a tail over nose flip].
The further forward the main gear is positioned, the more pronounced the ground looping tendency.  The latter can be corrected with up elevator, but this requires precise elevator timing, as it must not be held in long enough to cause the model to lift off with insufficient speed, as is described earlier.  In a sense you have to learn to  fly the tail  first, while the model is gaining speed for lift-off.
As you can deduce, main gear positioning is critical.  The optimum position generally sums to be as follows; with fuselage horizontal (tail up), the axles should be vertically below the wing leading edge.
There were no sketches with the original article.  The drawings are from an article by George Vale in RCM&E, vol 40 issue 5, in which he refers to his rule of thumb for wheel location
Taildragger requires 1 wheel diameter ground clearance when level
Main wheels should be at least 30 degrees in front of C/G

IT WON’T TAKE OFF!

The two most likely causes are [a] poor u/c design and/or [b] not enough power.

TRICYCLE GEAR

Wheels should be big enough for the worst runway surface.  (George’s mower crew can’t be as good as ours ‘cause he finds on grass the practical minimum diameter is 63 mm!  We can comfortably handle 40 mm although he does go on to say)......With 50 mm or smaller wheels, the U/C acts like an anchor on landing and may do more harm than good.
Main wheel track of 1/4 to 1/5 of wing span is about right.  The U/C legs ought to allow prop clearance by one wheel diameter.  They should also allow the model to put its tail down far enough for the wing to reach its maximum lift angle of attack [AoA] which is also the stalling AoA.  At this point the main wheels should be touching the ground just under the centre of gravity [cg]
You can decide this on the drawing board and decide whether to lengthen the leg or sweep up the rear of the fuselage.  If the main wheels are too far back, the tail has to provide a lot of downward force to lift the nose into the take off attitude.  If the model cannot get up enough speed to develop that much tail force it can’t possibly take off.
With the main wheels too far forward, nothing much happens except that the model can be left sitting on its tail with the nosewheel in the air.  Undignified.
The main wheels should not be too close to the nose wheel in the fore and aft direction, see sketch.  If the triangle becomes too flattened, the model is likely to nose over on landing.  Keep the wheelbase to at least 50% of the track but preferably about 60% of the track.

TRICYCLE GEAR SHOULD GIVE AT LEAST 1 WHEEL DIAMETER GROUND CLEARANCE

MAIN WHEELS SHOULD BE DIRECTLY UNDER REARMOST C/G POSITION WHEN MODEL IS IN TAKEOFF ATTITUDE

TRICYCLE GEAR WHEELS SHOULD FORM A BROAD TRIANGLE WITH THE WHEELBASE ABOUT 60% OF THE TRACK

LANDING

The taildragger has the capability of two distinct types of landing -the three pointer, and the wheeler .
The former consists of allowing all three wheels to touch the ground simultaneously, while in the latter the main wheels touch down first and the tail wheel lowers to the ground as speed decreases. Before the days of undercarriages, the ability to perform consistent three pointers was considered one of the marks of good airmanship.
The initial squeeze of elevator during landing is called flaring. To achieve a three pointer, the elevator is moved progressively up as speed decreases, with the wheels just above the ground, until the aircraft actually stalls.
This, of course, must take place with the wheel no more than a few inches above the ground, so that the aircraft settles gently on to it.
Too high, the aircraft falls with disastrous results. Too low, and the aircraft will bounce due to the combination of undercarriage spring and upward moving elevator, and may stall at the top of the bounce with, again disastrous results.
The wheeler is similar to landing a trike type, except that some further back stick is necessary after the initial flare to ease the wheels down, and back stick pressure must be released on touchdown to avoid flying off again, since the aircraft still has flying speed.
Once speed has reduced, and the wheels are firmly on the ground, the tail lowers itself (more or less). Rudder control may have to be used to maintain direction during the landing roll to avoid ground looping.
As you can see landing a taildragger well, probably requires more skill than the now conventional tricycle gear. But it often requires a lot of words to explain something which is essentially fairly simple, and to be aware of a problem is the first step to overcoming it.
The best that any instructor can do is point the way . He can describe what the aircraft does in response to the controls, explain why it happens, demonstrate what various manoeuvres look like, and take over control when necessary.
He cannot transfer to the pupil the ability to perceive quickly what the machine is doing, and make the necessary control movements in response.
To a large extent the pupil must teach himself by a fairly long period of careful attention and practice.
So with care and patience, it is quite possible to teach yourself to fly, although a good instructor shortens the path somewhat.

TOO MUCH TOO LATE!

A basic problem of most students might be described as  too much too late .  That is, not realising quickly enough what the machine is doing, and then overcorrecting on the controls.  Furthermore, it is as important to know when to take out a control deflection as when to put it in. For those brave souls who aspire to the model helicopter, this soon becomes even more painfully obvious than in the case of a fixed wing model.
Note that it was emphasised earlier that with ailerons especially, the aircraft continues to roll as long as the ailerons are deflected.  So in maintaining the wings level for straight flight, the ailerons must be allowed to centralise as soon as the wings are level.  Likewise, when you roll out of a turn to the wings level position.
When you roll into a turn, failure to reduce aileron deflection when the wings are at the desired angle of bank will allow the bank to increase and the nose to drop as described earlier.  This is the start of a  spiral dive , and it is important to understand that pulling the stick back under these conditions will only  tighten the turn , not make the aircraft climb.  Hence the injunction to get the wings level first.
The spiral dive should not be confused with the spin.  A spin occurs when one wing stalls before the other.  The aircraft begins to rotate about an axis somewhere between all the normal axes, with the wing on the outside of the spin continuing to lift, while the inner wing remains stalled. In this condition ailerons are ineffective in raising the low wing, and to stop the spin it is necessary to apply opposite rudder to reverse the inside/outside effect and stop the spin.
Since most trainers have to be forced to spin in the first place, and some may not even be capable of spinning, this is not usually of much concern to the student in the early stages, but try to find someone to show you what a spin looks like. Most models recover from a spin by themselves if the controls are allowed to centralise, and it is then a simple matter to pull out of the ensuing dive. This is not the case with the spiral dive, where the wings must be rolled level with aileron recovery.

THE ROLLER COASTER EFFECT.

If insufficient backstick is applied in a turn, the nose will drop and speed will increase.  When the wings are rolled level, this excess speed may cause the model to climb, perhaps quite steeply, depending on how it is trimmed.  This is often particularly marked with a flat bottomed or lifting aerofoil, and sometimes worries the student.  As long as the wings are held level, speed will decrease quite rapidly, the nose will drop and it may do this 2 or 3 times before it settles down to normal flight, which is why I have called it the Roller Coaster Effect.  (Often made worse by  pilot correction  during the period)
Too much backstick in the turn causes the model to slow down.  Stall speed is higher when turning and this is the condition when a high speed stall may occur, though usually only in models with high wing loadings.  The average trainer will just  waffle  and aileron control may become sluggish, which indicates less back stick is required.

USES AND EFFECTS OF RUDDER.

Deflection of the rudder yaws the aircraft around its vertical axis.  But like the secondary effect of the ailerons causing the nose to drop, the rudder has a secondary effect.  This is our old friend the  inside/outside  effect.
If the rudder is deflected to the left, the nose yaws to the left, the left wing is then travelling more slowly than the right wing and therefore generates less lift and the aircraft rolls to the left.  The same will be true of right hand rudder application, in fact the plane will have to be watched closely as often the yaw is barely visible, all the is seen is the rolling effect.  This can be quite useful.  The chief one is when the aircraft is so close to the stall that the ailerons have become ineffective, application of rudder in the opposite direction to a dropping wing will lift that wing.

HENCE THE SPIN RECOVERY BY USE OF THE RUDDER.

There is a manoeuvre called the  Falling Leaf  in which each wing is stalled in turn and recovered so it descends in a series of swooping steps like a falling leaf, a very pretty manoeuvre.

Because it is possible to control roll with rudder, it is possible to fly a properly designed model without ailerons at all.  Indeed, before the advent of modern sophisticated radio systems, this was the accepted method.
The main design requirement is more dihedral (the angle between the horizontal and the wings when viewed from in front or behind).
There are several advantages to the novice of  the rudder only  method.  Firstly, construction is simplified.  Secondly, the model is controlled on the ground by the same thumb you use in the air.  Thirdly, rudder as roll control stays with you right down to the stall, whereas aileron control may disappear as the stall approaches.
Further, if you treat the rudder as a roll control, ie plug the rudder servo into the aileron socket, you can learn quite a lot, especially about coming toward yourself, by taxiing. Without getting airborne at all.

A Small Simplification:
*In the pre-take off check it was mentioned that controls should be checked for full and free movement in the correct direction.  This may appear self-evident, but with the capacity of modern radios to reverse servo direction on the transmitter, it is by no means unknown for a model to take off with one or more servos reversed, with disastrous results.
*Finally, care, patience and attention to detail, are the hallmarks of the airman, as well as manipulative skills.  This is. as true of the model pilot as his professional brother.
*There are old pilots and bold pilots.  There are no old bold pilots.

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