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  < Back to Table Of Contents  < Back to Topic: Automotive … Planes and Trains Too

article number 279
article date 10-17-2013
copyright 2013 by Author else SaltOfAmerica
Learn To Fly a Helicopter in One Easy Lesson. A 1946 Introduction to this New Contraption.
by C. B. F. Macauley & Joseph S. Dunne
   

From the June, 1946 issue of Air Trails Magazine. Original title: How to Fly a Helicopter.

THE HELICOPTER IS NOT IMPOSSIBLE TO FLY, BUT ITS COMPLEXITIES DEMAND BETTER COORDINATION, JUDGMENT THAN THE CONVENTIONAL PLANE’S.

COMPARATIVELY speaking, helicopters are more difficult to fly than airplanes; however, anyone call fly one if he takes the time to learn. A great deal of progress already has been made, and much more is promised for the simplification of helicopter operation. As they exist today, it is safe to state that anyone who can fly an airplane can also learn to fly a helicopter.

The AAF and the Coast Guard have trained a large number of pilots to fly helicopters. Some of the trainees had only fifty hours previous time in light-planes. These men learned to fly the helicopter in the prescribed time and have flown successfully since.

The average solo time is between five and eight hours; and additional instruction brings the total course of training to approximately twenty-five hours. Included with the flying training is considerable ground school instruction on the fundamentals of rotary-wing theory, mechanics of the helicopter, etc.

The helicopter has all the controls that an airplane has—plus one. To understand their functions a simple explanation is required. Keep their use and application straight in your mind and you will have no difficulty. There are three groups to consider: horizontal, vertical, and directional or turning control.

As you sit in the cockpit you find conventional rudder pedals at your feet. With them the fuselage can be turned to the right or left for directional control. Between your knees is a conventional stick—exactly as in an airplane. In helicopter circles it is called the azimuth stick (these days it is called the cyclic). It governs the direction and the speed of horizontal movement.

   
Helicopter controls. These days the Azimuth Stick is called the cyclic and the Pitch Stick is called the collective. The Tail Rotor Control Pedals are sometime called rudder pedals but there is no rudder: instead there is a tail rotor which is effective at all speeds. Currently, helicopter rudder pedals are often called Anti-torque Pedals.

The new control is found at your side. It is a lever, pivoted behind the seat so that it works up and down. This is the pitch stick. (These days it is called the collective: your engine throttle is still located on it.) It is linked to the overhead rotor in such a manner that the pitch angle of the rotor blades can be regulated from the cockpit. This permits absolute control of vertical ascent or descent.

The old familiar throttle is gone. You will find a motorcycle handgrip on the pitch stick. That is the throttle.

To correct for the torque that exists between the overhead rotor and the fuselage, a propeller is mounted at the end of the tail boom. Its thrust opposes the torque thrust on the fuselage.

By varying the pitch of this tail rotor to a greater or lesser degree, the fuselage can be made to turn to the right or left. This is accomplished through operation of the rudder pedals.

   

To regulate vertical ascent or descent, the pitch angle of the overhead rotor blades is varied. In operation this is extremely simple. To ascend you pull the pitch stick up. To descend push it down.

There is only one catch to this proposition: when the pitch is changed the throttle must also he changed. The two must always be very closely coordinated in order to maintain constant r.p.m.

In a normal course of training one learns to do this as one proceeds with the use of the other controls. In a very few hours the average student has mastered throttle operation. From that point on the throttle becomes part of the pitch stick.

In this discussion we will assume that the student has learned throttle coordination, and we will speak of pitch changes.

To achieve horizontal movement the pilot operates the azimuth stick and causes the overhead rotor to tilt in the desired direction. This “borrows” a portion of the lift and changes it to horizontal thrust.

Assuming that the engine has been started and warmed up, let’s take an imaginary flight and observe the operation of the controls.

We have engaged the rotor to the engine by increasing the r.p.m. to the point where the centrifugal clutch “throws in.” The rotor is turning lazily above us. We are sitting side by side, almost completely surrounded by Plexiglass. About all that interferes with our visibility is the small instrument panel before us.

The engine, behind us, purrs with a deep reassuring sound, and the fuselage trembles slightly. We now “rev” up the rotor by turning the throttle. The tachometer on the instrument panel indicates that we have reached flying r.p.m. We hold the azimuth stick in neutral, slowly pull tip the pitch stick. Gently we rise from the ground.

If the fuselage has any tendency to turn, we correct it with application of rudder pressure. If we are inclined to drift horizontally, a slight pressure on the azimuth stick corrects it.

We are now hovering about four feet in the air. It is easy to grasp the function of the pitch stick now. Pull it up and we rise like an elevator. Push it down and we descend. We can stop descending anywhere we wish. The reaction is virtually instantaneous.

   
First commercial helicopter license (NC-I H) was granted recently to Bell Aircraft for model 47, above. Note the blur of the tail rotor mounted on a boom at the rear of the helicopter. It is controlled by the “rudder pedals”.

It should be mentioned also that when the pitch is changed, with the accompanying throttle adjustment, the torque varies so that a slight compensating pressure on the rudder pedals is needed. This action soon becomes automatic.

Can we ascend to perhaps several hundred feet and hover? Yes, if there is a breeze blowing. In a dead calm it is not so easy. There is still some controversy concerning the cause, but it is a well-known and accepted fact that when a rotor system moves through air, its efficiency is increased. Hence the desirability of a breeze.

Also, it is always easier to hover near to the ground because of the “cushion” effect. This effect is due to the downwash from the rotor’s pushing against the ground.

From a hovering position it is simple to demonstrate the use of the azimuth stick. To go forward, push forward. By applying a slight pressure in that direction we begin to creep ahead. The same principle applies to backward and sideward flight. By applying a back pressure we can come to a stop. Continue the pressure and we begin to move backwards. The amount of pressure applied governs the speed at which we move.

While hovering we can check the operation of the rudder pedals. Press right rudder and we turn to the right. We are pivoting over a spot on the ground. The same applies to the left. The amount of pressure applied regulates the speed with which we turn.

The rudders are essentially for additional anti-torque control and are seldom used during flight. Only when operating above or below normal cruising power is it-necessary to use them.

To take off we started from hovering flight. First we applied a slight pressure on the azimuth stick. As we began to creep forward we applied a little additional pitch for more lift and to increase forward speed. We were now flying along a few feet above the ground.

Suddenly we began to climb! As we picked up speed we caused air to flow through the rotor system: our efficiency was increased and we started climbing automatically.

   

Now, an explanation of why the helicopter started climbing without increasing pitch or throttle is in order. When a rotor system moves through the air laterally, at whatever angle, its total lift or thrust is proportionally greater, with equal power, than when it is stationary in relation to the air.

Thus, with a given power and pitch setting, when the helicopter starts moving laterally in any direction from a hovering position, it will start climbing. To level off and remain at constant altitude, therefore, pitch and throttle are reduced.

Or to explain it another way, if the helicopter is hovering stationary with relation to the air, and a sudden breeze were to start blowing at 10 mph, or more, the helicopter would start climbing until it again came to a stop in relation to the air mass.

For this reason, it is possible to take off a helicopter at high altitude or with a heavy overload which would render it unable to rise from the ground vertically by causing it to taxi along the ground a few feet before rising into the air. This technique often is employed under conditions of extreme heat and very still air which prevents a true vertical ascent. The length of run required under such circumstances is only from about 25 to 50 feet.

This phenomenon is sometimes, referred to as “translational lift,” although engineers are reluctant to use this term because it does not accurately describe what takes place. But for general purposes it conveys the idea and probably will be used frequently until a better descriptive phrase is coined.

Forty mph is a desirable forward speed for climbing, so we continue to apply forward pressure on the azimuth stick until we have reached it. If we are not climbing fast enough we can pull up the pitch lever some more.

Our rate of climb and our forward speed regulated, we can now settle back and wait until we reach our desired altitude.

How will we level off? Simple. Push the pitch stick down a small amount, continue to hold 40 mph with the azimuth stick, check the altimeter.

How about increasing airspeed? Easy. More forward pressure on the azimuth stick. BUT—it will be necessary to find a new pitch setting or we’ll lose altitude.

There you have it—the proper relationship between the azimuth stick and the pitch stick. One controls horizontal movement while the other controls vertical movement. When one is changed the other must be readjusted.

We are now flying at 600 ft. and 60 mph. Suppose we experiment with the controls. If you have flown airplanes it should be easy for you to hold the helicopter “straight and level.” If you have not, it will help to use some spot on the helicopter windshield as a reference point. Something that you can compare to the horizon. This will aid you in maintaining the craft in a constant attitude.

The helicopter fuselage changes its attitude (relative to the ground) as it changes airspeed. At high speeds it flies tail high and nose low. At low speeds it assumes a more level position. Then by watching the attitude it is fairly easy to hold a constant airspeed.

   
The power required to maintain a straight-and-level flight and a stabilized airspeed. From the 2012 FAA Aviation Maintenance Technician Handbook – Airframe.

Here is one more hint before you actually take the azimuth stick. There is a short time lag in the reaction of this control. It is only a split second but it can confuse you. Remember to wait for the result of each correction.

Now take the stick. Hold it lightly yet firmly. Notice that it has no particular pressure on it and that it moves freely in all directions.

Move it forward slightly. Notice the time lag. The nose dips down a bit more and we begin to pick up speed. We are now flying at 80 mph. Hold the attitude constant and check the speed by making occasional references to the airspeed indicator.

We have increased our airspeed from 60 mph to 80 mph at the expense of our vertical thrust. We can now expect to lose altitude. If you check the altimeter you will find that it is slowly “unwinding.” It is now necessary to increase the pitch. This is easily adjusted; and by checking the altimeter we find that we are now maintaining our altitude.

   

The helicopter is extremely sensitive to lateral or sideward movements of the azimuth stick. It is seldom necessary to apply anything more than a slight pressure in the desired direction. Try it. Notice how easily we bank to the right or left.

Now hold a constant pressure to the right. We begin to move in that direction. Observe how the fuselage is following around. We are actually making a gentle banking turn to the right.

To stop turning, apply pressure to the left and then neutralize to hold us straight. It’s amazingly simple!

Try a turn to the left. It is just as easy! As you gain more experience you will find that you can execute very steep and sharp turns with ease.

The helicopter will turn on a dime if you want it to.

Can you make turns by merely pushing on the rudder pedals? No. Remember that the azimuth stick governs the direction of horizontal movement. The fuselage will follow the line of flight and normally you will have no occasion to use the rudders.

We’ll try a landing approach now. In normal practice we approach the landing spot at an angle of approximately 30 degrees, and we always come to a hover four or five feet above the spot where we intend to “sit down.”

Also, although it is not always necessary, it is helpful to land into the wind. We are flying into the wind now. Let’s choose that small grassy spot directly ahead of us.

   

First, we will reduce our airspeed—40 mph should be about right. Ease the azimuth stick back toward you very slowly. The nose comes up. The airspeed indicator drops quickly from 80 to 70, to 60, to 50. Now begin to neutralize the pressure on the stick. There! You have it ! Forty mph. Hold that airspeed.

Of course we have started to climb. We really want to descend, so we reduce the pitch.

Now hold the attitude constant and observe the angle at which we are coming down. If we are descending too steeply, increase the pitch slightly. If it seems that we may overshoot the field, reduce the pitch some more.

It is a simple matter to regulate the angle of descent. We will hold this approach until we are closer to the landing spot.

Now, at approximately 100 ft., the landing spot lies just ahead of us. Very gradually, begin decreasing the horizontal speed in such a manner that we will come to a gentle stop directly over the spot. Also, very smoothly, increase the pitch, and continue to increase it.

Observing the ground, regulate the pitch so that we will come to a stop about four feet in the air just as we approach the landing spot. This process of deceleration, executed smoothly, brings us to a hover directly over the spot where we wish to land.

We will pause here momentarily before actually landing. We can hold hovering attitude with pitch stick corrections, and correct for any drift with small pressures on the azimuth stick.

Now if we are hovering steadily and we wish to “sit down,” it is only necessary to make a small reduction in pitch. As we descend to the ground we are particularly careful about any horizontal drift; and as the wheels touch we make a further reduction in pitch to keep us down. We have landed.

When wind-milling, or auto-rotating, the helicopter descends at approximately 1,200 ft. per minute, depending on the amount of forward speed. During auto-rotation the pilot has full use of all the controls and he can steer the helicopter to the most logical spot for the landing.

As he nears the ground it is only necessary to ease the azimuth stick back and increase the pitch. This causes the helicopter to “flare out” or level off. The “flare out” is executed in such a manner that the ship comes to level flight a few feet above the ground. As forward speed is lost it settles until the wheels touch lightly.

Depending on the wind velocity and direction, contact with the ground is made while traveling forward at a very low speed. Usually, the helicopter rolls 20 or 30 ft.

   
During an autorotation, the upward flow of relative wind permits the main rotor blades to rotate at their normal speed. In effect, the blades are “gliding” in their rotational plane. From the 2012 FAA Aviation Maintenance Technician Handbook – Airframe.

In an extreme emergency where you have to land directly below you, it is possible to make a vertical auto-rotative descent. In this case, the rate of descent is faster than 1,200 ft. per minute; and also it is not possible to execute a flare-out. Even so, after numerous tests and calculations, it has been found that the helicopter in such a vertical descent would strike the ground at a speed of approximately 18 mph.

Considering the shock absorbing ability of the landing gear and of the structure itself, such a landing should not prove harmful to the passengers. In a normal course of helicopter flying training, the student learns and practices auto-rotative descents and flare-outs. He soon becomes so familiar with the maneuver that he almost enjoys it.

At the Bell Aircraft Factory, near Niagara Falls, complete auto-rotative landings have become routine. Such landings are so easily executed that they are almost standard procedure for the Bell pilots.

In this discussion we have observed the functions of the various controls in executing normal maneuvers. In learning to fly the helicopter, the technique and coordination necessary for the performance of these maneuvers can be mastered in a very few hours of dual instruction.

After you solo you will learn other maneuvers designed to improve your coordination, judgment, and precision. They are all fun to learn; and the helicopter, once mastered, is fun to fly.

Where can you learn to fly one? Outside of the Army and the Coast Guard, nowhere now. But you can’t buy one just yet, either.

   
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