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Analysis and Comparative Study on the Different

Kinds and Number of Spokes of Rotors on Helicopters

For the Completion of the

Physics Course in the

Fourth Year Level

Submitted by:

Enrico M. Bola

Lemuel A. Carandang (L)

Charlie Sheen D.C. Concepcion

Curt Marvin B. Cruz

Inna Felicia I. Agoncillo

Rochelle Angelica Andasan

Camille Angela S. Ayento

Jeremi Elaijah M. Barretto

4th Year Matapat

S.Y. 2010 2011

Submitted to:

Ms. Jenny Rose Apuntar

Physics Mentor


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CHAPTER 1

The Problem and its Setting

I. Introduction

Our group has decided to focus on the study of rotors of a helicopter. We chose this topic

because we want to know how helicopter rotors work by means of theoretical and

mathematical basis. We also want to figure out the different functions of rotors in a helicopter.

Lastly, we want to find out how helicopter rotors differ from other kinds of aircraft rotors.

The history of rotors was researched and developed by Juan Dela Cierva. He became

successful with his invention of fully articulated rotor systems and it is widely used today. Then

came another inventor who tried and tested two bladed rotor system and it is now used in

many remote control model helicopters.

Several improvement made by Cierva was the system of hinging each blade to hub, to flap and

adjust unequal lift forces bringing the aircraft sped into forward flight. There were also pioneers

like the Autogiro who designed rotors for a safer landing of helicopters. Others have created

different designs of rotor systems and they fell under three basic types: the articulated, the

semi-rigid, and the rigid rotors (or a combination of these three types)

II. Statement of the Problem

This study will focus on the analysis and comparison of the different shapes and kinds of rotors

on helicopters. Therefore, our group prepared the following questions to keep this research

consistent, effective and functional.

1. What are the differences among the given kinds of helicopter rotors?

2. What is the relation of the rotor to the body being lifted and to the force exerted?

3. What would be the effect of the number of spokes on the flight of the helicopter?

III. Hypothesis

The inferences are as follows:

1. The given kinds of helicopter rotors differ on their effectiveness and capacities. They are of

different blades, structure and movement.


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2. Since all rotor systems require turning of the blades along their span-wise axis, owing to the

action of the pilot's controls, probably the most effective would be the airfoil shape.

3. The larger the rotor, the easier for it to lift the body depending on the combination of all

forces acting on it. (e.g. Normal force and Gravitational force)

IV. Research Paradigm

V. Scope and Delimitation

The study will cover mainly on the different kinds and number of spokes of rotors used on

helicopters. Basically, a helicopter's main rotor or rotor system is a type of fan that is used to

generate both the aerodynamic lift force that supports the weight of the helicopter and thrust

which counteracts aerodynamic drag in forward flight. A helicopter rotor is generally made up

of two or more rotor blades. Helicopter rotor diameters are also relatively large as this gives

much better energy and propellant efficiency for the speeds at wqhich helicopters fly.


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This study is related to equilibrium, momentum, aerodynamic lift force and impulse. This

research will be configured by means of a toy plane and an improvised rotor system. This

research does not cover the size of the plane. Rather, it would focus on the size of the rotor.

The experiment will be conducted by using a toy plane with a constant weight to determine and

have a comparative analysis regarding the effectiveness of rotors of different kinds. The study

will not cover the kind of plane. A fixed plane would be used which is a toy helicopter for

effective and efficient study.

VI. Significance of the Study

This research aims to help people realize how crucial or how lethal the number of rotor in a

helicopter is. This study also aims to know the difference of having three or more rotors

supporting the helicopter. This study would also inform the people especially the students how

the design of a rotor could affect the flight of the helicopter. This will also serve as a source of

information for those aspiring physicists since the movement of the rotors shows exactly how

uniform circular motion and how the second condition of equilibrium works. This project also

targets those aspiring Aircraft designers by helping them know how the number of rotors

should be compatible to the design of the helicopter.

VII.Definition of Related Terms

Aerodynamics the branch of mechanics that deals with the motion of air and other gases and

with the effects of such motion on bodies in the medium.

Drive Shaft a mechanical component for transmitting torque and rotation

Thrust a reaction force describe quantitatively by Newton's second and third laws. When a

system expels or accelerates mass in one direction, the accelerated mass will cause a

proportional but opposite force on that system

Blade Pitch Refers to turning the angle of attack of the blades of a propeller or helicopter

rotor into or out the wind to control the production or absorption of power.

Swash Plate- a device that translates input via the helicopter flight controls into motion of the

main rotor blades.


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CHAPTER 2

Review of Related Literature

Helicopters

Most aircrafts can only fly forward, but can helicopters can fly backward and forward, as well

as straight up or down they can even hover on one spot. Helicopters can do all of these

because they both get lift and thrust from their spinning rotor blades. These have an airfoil

shape and work rather like overhead propellers, screwing the helicopter through the air.

Parts:

Rotor Head Movable control rods in the rotor head allow the pilot to change the pitch (angle)

of each blade as well as the tilt of the whole rotor unit. The rotor head is driven by the

helicopter's engine.

Rotor Blades The rotor blades are long, narrow airfoils. More curve above than below. The

difference in air pressure above and below the spinning rotor blades creates lift.

How Helicopters Fly

Using the cycling pitch control, the pilot can alter the tilt of the main rotor unit to make the

helicopter fly in different directions. Tilting the rotor unit forward, for example, makes the

helicopter fly forward. Using the collective pitch control to change the pitch of the rotor blades

varies the amount of lift the steeper the pitch, the greater the lift.

Bibliography:

Kingfisher Books, 1992. How Things Work; Planes, Gliders, Helicopter and Other Flying

Machines p. 22-23. New York: Grisewood & Dempsey Inc.

More Rotors, More Speed

The ability of a helicopter to hover and land almost anywhere makes it an enormously useful

machine. But helicopters have their limitations, particularly when it comes to flying fast. In a

recent series of test flights, a new type of chopper has begun smashing speed records.


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The X2 is an experimental helicopter being developed by Sikorsky, an American company, at a

test-flight centre in Florida. It recently flew at more than 430kph (267mph), according to a

report in Spectrum, published by the Institute of Electrical and Electronics Engineers. The

present record is held by a souped-up Westland Lynx helicopter, which managed 400kph in

1986. But most helicopters cant fly at anything like these speeds and are typically flat out at

270kph.

To make an official attempt on the record, Sikorsky will need to have the flight monitored by the

Fdration Aronautique Internationale, which compiles airspeed records. But that is unlikely

to happen until the X2 is going even faster. Later this year, Sikorsky hopes it will be zipping

along at more than 460kph. The company, however, is interested in more than just breaking

speed records. It plans to use the technology developed for the X2 in commercial helicopters.

What limits the speed of a helicopter is the same thing that allows it to hoverthe air flowing

over its spinning rotor blades. The rotor blades work like the wings of an aeroplane, with an

aerofoil shape providing lift. But unlike an aircraft, when a helicopter is flying forwards the air

passing over its rotor blades does so at different speeds. The air passing across the blade that

is advancing to the front of the helicopter and into the oncoming air is going faster than the air

passing over the blade that is retreating to the rear of the helicopter. And the faster the

helicopter goes, the greater this difference. At 300kph, the air passing over the advancing

blade could reach 1,100kph while that over the retreating blade would be about 500kph. This

difference in lift can make it hard to maintain level flight. And to make matters worse for the

pilot, as the tips of the rotor blades approach the speed of sound (around 1,200kph at lower

altitude temperatures), shock waves produce huge vibrations.

The X2 gets around these problems in a number of ways. First, it uses two counter-rotating

rotors that spin around the same axis, one positioned above the other. So in forward flight each


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rotor can produce an equal amount of lift on each side, thus providing balance. The idea has

been around for some time, but it proved difficult to make it work properly.

What has changed are technological advances in aircraft engineering and control systems.

Now, vibrations can be reduced using active control, which involves placing sensors around

the helicopter to detect the onset of vibration and then using force generators on various parts

of the frame to vibrate in such a way that they cancel out the original tremors. Advanced

computer modelling has also made it possible to design more efficient rotors. A pusher

propeller has been fitted at the rear of the X2 to provide extra oomph. According to the

engineers, this propeller can also be used to slow the helicopter snappily. And computerised

fly-by-wire controls allow the X2 to be flown relatively easily.

Sikorsky reckons that future helicopters built using the X2 technology would be extremely

versatile machines. They would dash to and from a medical emergency a lot faster. They

would also be very agile in flight, which would increase their capabilities in combat. Sikorsky

has already produced a simulator so that potential customers can experience what these fast

helicopters will be like to fly. Plenty of whirlybird pilots will be keen to get their hands on the

real thing.

http://www.economist.com/node/16990748
http://www.economist.com/node/16990748http://www.economist.com/node/16990748


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CHAPTER 3

Methodology

In this chapter, the group will show the procedures and materials that they will be using, in

order to prove the stated theories and statements on the previous chapters.

Materials/Set-up:

In this experiment, the group will be using the following materials:

improvised helicopter toy (2, 3 and 6 spokes)

meter stick

a spool of thread

weighing scale

Procedure:

1. Complete and construct the materials needed.

2. Weigh the different helicopters. Record the measurement.

3. Let the helicopter fly for every kind of propeller.

4. Measure the maximum thread length consumed for its height and its distance covered with the

use of the meter stick

5. Repeat the procedure until all the samples are tried.

6. Record your results. Use the table below as record sheet.


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Chapter 4

Data Analysis and Interpretation

The study focused on the three kinds of rotors. In ascending order, the rotors used are as

follows: 2 spokes, 3 spokes and 6 spokes.

For the 2 spokes, the three trials came up with the following results:

Focusing on the height, the results gathered are quite accurate and precise. The first result

was the most accurate. Arranging it in an ascending manner: trial 2, trial 1 and trial 3. The

average height obtained is 1.15 m.

Focusing on the distance, the result obtained was 0.77 m.

Focusing on the velocity, from trial 1 to trial 3, the results is in descending order giving the

average of 0.77 m/s.

For the 3 spokes, the 3 trials came up with the following results

Focusing on the height, the results are quite far from each other. Based on the three trials,

we have gathered 3.66 m, 2.04 m, and 1.73 m respectively which has the average of 1.5

m.

For the 6 spokes, the three trials came up with these results:

Focusing on the height, from the three trials, the least height obtained was from the third

trial which is 2.06 m. The greatest height obtained was from the second trial which was

4.13 m. The average height obtained was 3.11 m.

Focusing on the distance, the least distance traveled was from trial 3 which is 2.66 m. The

greatest distance traveled was from the second trial which was 4.32 m. The average

distance traveled was 3.59 m.

Focusing on the Velocity, the least velocity obtained was from trial 1 which was 0.48 m/s.

The greatest velocity obtained was from trial 3 which was 0.92 m/s. The average velocity

obtained was 0.77 m/s.


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Data and Results:


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CHAPTER 5

Summary, Conclusion and Recommendation

I. Summary

The group obtained the following results by following the scientific process. The group was

composed of Enrico Bola, Lemuel Carandang, Charlie Sheen Concepcion, Curt Marvin Cruz,

Inna Felicia Agoncillo, Rochelle Angelica Andasan, Camille Angela Ayento, Jeremi Elaijah

Barretto.. the study was all about the comparison between the different number of spokes,

namely 2, 3, and 6. The materials used in the experiment are as follows: Meter Stick, Toy

Plane and the spool of thread. The procedure of data gathering is as follows: 1. Prepare all the

needed materials for the experiment. 2. Perform the experiment by using the helicopter and the

other materials 3. Measure or collect the date needed eg. Height, Distance and Velocity. 4.

Change the spoke of the helicopter from 2,3 and 6. 4. 5. Interpret the collected data and

information. The group have recorded the following results arranged in ascending order

(highest in height and in velocity).The result of the study is based on the interpretation done by

the group. From the whole process of experimentation and interpretation, the group can now

formulate their conclusions and recommendations based on the result and the interpretation of

the study.

II. Conclusion

From the data that the group have gathered, it proves that the number of spokes of the rotor

could greatly affect the flight of a helicopter. The greater the number of spokes, the less the

height, distance and velocity obtained. This would mean that a flying machine containing more

number of spokes could travel a longer distance. Therefore, we conclude that the effectiveness

of the kind of rotor differ on the kind of rotor and the number of spokes it has.

III. Recommendation

Helicopters have been modes of transportation, not for public use, but usually for the military

and hospitals. Helicopters have been used in various situations that involve great emergency

because of their efficiency and speed. It would be more advantageous if its speed and


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efficiency in carrying loads were maximized.

Based on the results of the experiment conducted, the researchers recommend that designers

of helicopters look into the design of the rotor and maybe consider adding spokes so that the

efficiency of the helicopter can increase.

If there will be others who would be interested to conduct this experiment, the researchers

suggest that they shouldnt limit themselves to the number of spokes provided by this

experiment. If there are available resources, those who wish to conduct this experiment may

use other numbers of spokes to achieve more accurate results.