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By Anton Maneschijn 
INTRODUCTIONWhy would a person want to build his or her own aircraft? The answer to this question is two-fold:
Many thousands of aviation enthusiasts worldwide have created and built their own aircraft and have turned this unique hobby into a sport which we call Personal Sport Aviation. For many builders, an aircraft building project is a hobby and they enjoy the building process sometimes more than the actual flying of the aircraft afterwards. In the same way, many builders build an aircraft specifically to enjoy the flying part, and participation in the many different sporting events become their pastime. The sporting activities include navigation rallies, air races, precision flying and aerobatic competitions.
Personal Sport Aviation in South Africa has its roots in the early 1900's when many aviation pioneers built and flew their own aircraft. Some of the aircraft were more successful than others, and the competitions these aviators participated in proved the ingenuity with which the early contraptions were designed and built. 
Since the early pioneers, homebuilt aircraft were designed and built by many ordinary people and in the early 1960's, a group of enthusiasts, under the leadership of Mike Spence and Ton Maneschijn (Snr) formed the first South African Chapter of the American Experimental Aircraft Association. More aircraft were built and flown and the sport became well known amongst the aviation fraternity of the country.
With the advent of new designs such as the Ken Rand KR-2, the concept of kit-built aircraft became popular and several kit aircraft were imported from the USA. The late Sakkie Halgreen became the South African agent for the KR-2 kits and with several KR-2's under construction, the need for regular information-sharing get-togethers became evident. Sakkie responded by starting the regular "KR-Get-togethers" which proved very popular. After his death, Chris Eksteen continued with the Get-togethers and by the early 1990's, these functions were held on a quarterly basis. 
By this time, the Get-togethers were catering for the needs of builders of all types of aircraft and the builders started requesting more formal events. The concept of general homebuilder Get-togethers was born and in 1992, four such Get-togethers, or Fly-ins, were held, all of which drew substantial interest and support from aircraft homebuilders and newcomers to the sport.
The success of the Fly-ins sparked off the idea of a truly South African organisation that could cater for the particular needs of the aircraft homebuilder. Thus, in February 1994, The Aircraft Homebuilders of South Africa was formed with the objectives to promote and develop personal sport aviation in Southern Africa, and to serve the needs, and in particular the technical needs, of the homebuilders. The Aircraft Homebuilders have developed considerably since then and promote the sport actively to the general public through regular Fly-ins, lectures, workshops and media presentations. Technical assistance is given and the use of South African materials is continuously researched and promoted. With the increasing cost of imported aircraft and materials, building an aircraft with local materials, and getting support and motivation from a South African organisation, has made it possible for many aviation enthusiasts to become airborne for less than the cost of a new car. To import a kit from the USA has become the privilege of a few, and more and more homebuilders are taking up the challenge to do their own thing right there. Why build your own aircraft? Simply because it can be done, it can be done relatively cheaply and the enjoyment experienced throughout the construction and flying process is more than many other sports can offer you. If you like working with your hands, and if you are an aviation enthusiast, but cannot afford a factory-built aircraft, aircraft homebuilding is a hobby and sport you should seriously consider. Many other people like yourself have done it in the past, and many more will do it in the future! THE STEPS INVOLVED IN BUILDING YOUR OWN AIRCRAFT Building your own aircraft: What does it mean? Building your own aircraft is the process by which you create, from raw materials or a kit, a finished aircraft with which you can fly. There are currently more than 500 different homebuilt aircraft designs worldwide from which you can choose, or you can design your very own, unique aircraft. Whichever way you choose, you will have to use a set of plans and the necessary Materials to build the aircraft. 
The building process involves working with different types of materials, fabricating and forming them into components and parts which, once assembled, forms an aircraft. Because an aircraft is only as safe as it is designed and built, the workmanship must be of high standard. Provided that the correct procedures are followed and the appropriate materials used, any person with reasonable practical skills can build an aircraft.
Aircraft building is also not limited to the realm of men, and many women have built and flown aircraft with great finesse. Even teenagers have tackled homebuilt projects and in the USA, many schools have aircraft building programmes as part of their school syllabus. An aircraft building project usually takes some time and the financial investment required is spread over the duration of the project. Stated in another way, the project progresses as you can afford to buy materials, an engine and instruments. Unless you purchase a kit, there is thus no need for a large amount of cash initially. This allows you to progress at a rate that is comfortable for you and your family. And of course, your family can also be involved in the project. With their participation, they will appreciate your achievements and motivate you to complete the project. Rules and Regulations As with any other sports, there are rules and regulations that govern personal sport aviation. In South Africa, these rules and regulations are controlled and enforced by the Civil Aviation Authority (CAA), which is a part of the Department of Transport. The normal Air Navigation Regulations apply to the flying of a homebuilt aircraft, and the construction of such an aircraft is regulated by a CAA Document, Document LS/1. Doc. LS/1 caters for amateur-built aircraft, microlight aircraft, gliders, gyrocopters, veteran aircraft, motorised gliders and research aircraft. It consists of rules and regulations applicable to aircraft that may not be issued with a Certificate of Airworthiness, such as commercial aircraft. Homebuilt aircraft may not be used for remuneration purposes and may only be used for recreational and sport flying. The builder/owner of the aircraft may receive flight training on the aircraft and passengers may be carried at their own risk. However, homebuilt aircraft cannot be allowed to be built without ensuring that they are airworthy. Thus, an inspection system is in place through which the homebuilt aircraft is inspected at various stages. The inspectors, called Approved Persons, inspect each substructure of the aircraft before it is closed and does a final inspection prior to the first test flight. Any building faults can thus be eliminated before the aircraft is flown. The Approved Persons are experienced in aircraft construction techniques and assist homebuilders with technical advice, when required. On completion, the Approved Person also assists the homebuilder with the completion of the necessary forms to get permission to test fly the aircraft. Once the aircraft has completed the test flight programme, the Approved Person again inspects the aircraft, after which a Permit to Fly is issued. The aircraft is then inspected on an annual basis to ensure that it remains in an airworthy condition. Selecting the Right Project Once you have decided to build your own aircraft, you have to decide what type of aircraft you would like to build. The options are varied, and the first choice would be to select an existing aircraft. Existing aircraft have been tested in real life and most problems have been eliminated. The original designer would have improved the aircraft to the point where it is safe for any other person to build and fly such an aircraft. The designer would also have compiled a set of construction plans, from which you can build your own aircraft. The majority of these aircraft exist in the USA and you would have to get a list of the available aircraft plans before you can select a particular aircraft and order the plans. The next option is to select a pre-manufactured kit from the many kits that are currently available. Most of the kits come from the USA and Europe, and you would have to follow the same route as with the plans. The third option is to buy a partly-completed project from someone who has decided not to complete the aircraft. There are such projects available, but you may be limited to a design that might not be quite what you wanted. The last option is to design your very own, unique aircraft. This is a longer process, but allows you to design an aircraft that suits your needs exactly. The design process is time-consuming, but any person with highschool maths, and access to the services of an aircraft design engineer, should be capable of designing a sport aircraft. The aspects to consider in the selecting process includes deciding on the type of aircraft you want, for what purpose you want to use it, how many seats it must have, how many engines you want, and what type of materials you want to work with. The most common materials include aluminium, steel tube structure with fabric covering, wood and fibreglass. Many aircraft use a combination of these materials, although one particular material is usually used extensively for the structure. Where to Get Information Any aircraft building project is largely based on information, from the set of plans to the technical advice required to simplify the building process. Technical information can be obtained from Approved Persons and other Aircraft homebuilders. By attending Fly-ins or joining an organisation such as The Aircraft Homebuilders of South Africa, you can make contact with people who have already built aircraft and get much valuable information from them. Dedicated sport aircraft magazines contain many articles that are useful to homebuilders and can be obtained from the USA or Europe (no such magazine exists currently in SA, although the Newsletter of the Aircraft Homebuilders serve this purpose to a large extent). Engineering type information can be obtained from Technical Libraries, such as the Engineering Libraries of universities, technikons and colleges. Where to Get the Bits and Pieces With the plans and information you need, you are now ready to start building. Sourcing the correct materials can be a daunting task if you do not know where to look for the materials. Again, contact with other homebuilders is crucial, since they have already researched and sourced appropriate materials. Materials specified by USA and European plans are usually only available in those countries and unless you can find a suitable local alternative, you will have to import the necessary materials. South African materials are totally suitable for aircraft building purposes, provided that you ensure, by means of an engineering check, that the materials will perform in the same way as those specified in the plans. Obviously, if you design your own aircraft, you will ensure that you use local materials as far as possible, since the imported materials are usually very expensive (even though there is a wider variety available in the USA and Europe). Many local materials have already been used in homebuilt aircraft and most microlight aircraft produced in SA are built with local aluminium products. The important factor is, though, to make contact with Approved Persons and other homebuilders to find out what materials can be used, and where to source the materials. Getting Started... You have now decided to build your own aircraft. You have selected the type of aircraft and you have a set of plans, your own design or a kit. Now you have to get started. The first step in the building process is to plan your project. It is important to plan your building time and to inform your family of your plans. Your family must be involved in your project right from the beginning and should understand the end objective. With their cooperation and participation, you will be able to progress with your project without having to interrupt the building process. Remember also to plan your project so that you can sustain a steady work rate. Too many projects have failed in the past because the builder started off at a high pace and lost interest because of a lack of energy. The first component you should build must be a small structure and typically, one of the tail surfaces should be selected. Once you have completed this structure, an Approved Person must inspect your workmanship and advise you on possible areas for improvement. Continue then with the building process, but remember to allow for adequate storage space for the completed components. (If you are building in your garage, it becomes awkward if you complete the fuselage and find that you do not have sufficient space to build the wings. Usually, you would first build the wings and hang them in the roof.) During the building process, you might encounter problem areas which you did not anticipate initially. By consulting other builders or Approved Persons, you may find an easy solution, or you will solve the problem yourself. If you need to modify any structural component, you will first have to analyse the problem and present your modification to an Approved Person before you can implement the modification. This will ensure that the structural integrity of the aircraft is maintained. Remember also that you will one day be in a position to assist other builders with their projects. There is much satisfaction in helping somebody who is struggling with a problem you have encountered in the past. For this purpose, it is important to keep a Builder's Log of the work you do on your aircraft. The Builder's Log is a summary of all the work you do on the aircraft, and includes the materials and sources you have used. Peculiar problems you have encountered, with their solutions, should be sent to the Technical Committee of the Amateur Aircraft Section of the Aero Club of SA. This committee files the information per aircraft type for use by other builders. Finally, prepare yourself mentally for the building project. The project may take anything from several months to several years to complete, and your ultimate goal is to complete your own aircraft. With the right frame of mind, you will persist and finish your own creation. Attend the regular Fly-ins and draw on the motivation from other builders, and keep in contact with those builders and your Approved Person to maintain a high level of enthusiasm throughout the project. In this way, you will ensure that you complete your aircraft and enjoy the fun of participating in a very unique sporting activity. DESIGNING YOUR OWN AIRCRAFT Many aircraft, commercial and military, start off as sketches on restaurant servettes. Aircraft designers become artists when they start working on a new design, and until they have a definite picture of what the new aircraft should look like, they will not touch a calculator. You, too, can bring out the artist in you and create your own aircraft. Again, this is how most homebuilt aircraft come into existence and the creations that have taken to the air during the past few decades can claim to be anything from classic art, to modern art, to comic art! Almost any conceivable variation of aircraft design has been built and yet, designers come up with new designs every day. But surely, the design of an aircraft is not just about drawing pretty pictures and dreaming dreams? It isn't! The proper design of an aircraft is an engineering exercise that requires a clear, logical mind, with reasonable mathematical capability, and a good measure of common sense. Practical aptitude is a definite advantage, but is not essential (you will just take a little longer to find the best way to design and build your aircraft). Provided you have these qualities, or know somebody with these qualities, you can easily be on your way to become an aircraft designer. General Layout The first step in the design process - after, of course, you decided to design your own aircraft - is to work on and select an appropriate General Layout of the aircraft. The General Layout is usually a three-view drawing of the aircraft, showing the front, side and plan elevations of the aircraft. At first, you will only be able to do freehand sketches of these views as you will not have accurate dimensions of the aircraft. This first freehand sketch will more often than not be changed many times before you will be satisfied with the draft layout of your design. Remember to draw new sketches every time you want to make a change, rather than to change the original drawing. This will help to keep a record of the development of the design and will also guide you to areas that may need improvement. Once you are satisfied, you can give your final sketch a title, the title being a Draft General Layout. Of course, if you have a name for your aircraft, include that on the paper as well, and remember to date, sign and copyright all your design papers, should you one day decide to market your aircraft. Only now are you ready to continue with the engineering part of your design project. Performance Prediction The first engineering step you will take is to predict the performance of your design. For these calculations, you will need the main dimensions of the aircraft, as well as estimates of the weight and engine power of the design. Here previous knowledge of aircraft comes in very useful, but if you are a newcomer, the best way to get a "feel" for the dimensions, weights and power, is to consult literature and compare these figures of existing aircraft. You will quickly pick up a trend which you can use as starting values for your aircraft. Performance prediction includes calculating the stalling speed of the aircraft, determining a more accurate wing size, calculating the maximum and cruising speeds of the aircraft, determining the rate of climb, estimating the take-off and landing distances of the aircraft, and estimating the range of the aircraft. The first set of calculations will probably not give you realistic answers, and you would have to adapt your initial estimates and repeat the calculations until the answers are realistic and satisfy your requirements. By now you will have a much more refined design and you can already start doing a proper engineering three-view drawing of your aircraft. In the meantime, you can also continue with the next step in the design process. Aerodynamic Design In the beginning, there were the Wright Brothers, and in the beginning Aerodynamics was still a weird and wonderful fantasy. So, the Wright Brothers had to sweat it out with test model after test model until they realised what aerodynamics meant. Any flying aircraft is a three-dimensional body that moves in a gas (air), and has six degrees of movement freedom (seven if you include Murphy's Law!). Thus, if not stabilised, an aircraft can move linearly in any direction (vertical, forwards and backwards, and sideways), as well as rotate around any of three axes. Complete uncontrollable motion will result, and unless we do the necessary aerodynamic design, our aircraft will go the same route. In this step, you will determine the sizes of the control surfaces and you will check for stability of the aircraft under all normal flying conditions. The wing profile will also be selected and various other aspects will be considered that will have an influence on the aerodynamic performance of the aircraft. To get you in the right mood, you will also start designing the propeller for your aircraft (unless you wish to use a jet engine!) With the performance predicted and the aerodynamic design optimised, you should be able to complete the engineering three-view drawing of your aircraft and you are now ready to start the structural design of your project. Structural Design Why do we need to design the structure of the aircraft? Well, if your house is built without a foundation, the forces of nature will very quickly see to it that your house is demolished. In the same way, an aircraft is subjected to forces of nature and you need a strong enough structure to withstand the battering of these forces. Now you can say, "Yah, but I just build it real strong and I will never have a problem!". That is quite true, because the aircraft will be so heavy that you will never be able to take off! The whole idea is to design a strong enough (not too strong!) structure that is as lightweight as possible. Each kilogram of unnecessary weight will require extra power to lift off the ground. This is where structural design becomes important. By designing the structure properly, you can ensure a lightweight and strong structure, and you can also ensure that you use materials that will cost the least. Flight Envelope First of all, we need to establish what loads will act on the aircraft. This we do by establishing a flight envelope that describes the outer limits of the performance of the aircraft. For this we need the maximum and stall speeds, as well as the structural loading factors for the design. The loading factors are selected from the following:
Wing Structure Next we determine the loads on the wing and proceed to design the wing structure. This will include the spars, ribs, attachments, skins and hinges for the wings, ailerons and flaps, as well as wingtips and any other attachments that may be located on the wing. The wing is subjected to torsion, bending moments and shear forces, and is designed to take the maximum loads as determined in the flight envelope. Fuselage Structure The fuselage structure is as important as the wing, and many designers have come short because they neglected the fuselage. The fuselage is usually more difficult to analyse than the wing, yet, a well analysed fuselage can be optimised substantially. Remember that provision must be made for the safe protection of the occupants during an accident. Empennage Structure The empennage, or tail surface, structures are designed to carry the full loads of the controls during flight. You would not want to fly into an aerobatic manoeuvre and find that some of the control surfaces have started taking an early departure! Undercarriage The design of the undercarriage is rather important, simply because, if you don't have an undercarriage, you cannot take off or land! The undercarriage must be robust enough to handle all types of landings, and in particular, hard landings of up to 4 g's. Powerplant Design You will have selected a particular engine type that you will want to use in your aircraft (if you are designing a powered aircraft), but you still need to design the engine mount and the associated structures, as well as the cowlings that will cover the engine. Also, you will need to consider the routing of the various controls that will be required for the engine. Systems Design You will have several systems to design and these include the instrumentation system, electrical system, the fuel system, a hydraulic system (if you have one), a pneumatic system (if required) and most important, the control system of the aircraft. The sizes of components, type of components required and routing of cables, wires, and plumbing will need to be established. Detail Design Once all the previous steps have been completed, and optimised for performance, strength and cost, the detail design can be completed, which will include exact sizing of all components, bolts, nuts and other parts, as well as doing detail drawings of all the structures and components. With this total design pack, you can approach an aircraft design engineer to check your design, even if you yourself are one. With the design checked, you can proceed to plan the construction of the aircraft, procure materials and start building. However, the design process will never be entirely completed because there will always be improvements and changes that can be incorporated in your design. It is thus important to maintain your design pack in an "open" mode, so that you can continuously update and change it. Only after the successful completion of the test flight programme of the prototype, can you start considering selling sets of plans to other homebuilders. And certainly, you will have to be quite sure that your design is fully optimised before you can start producing kits to sell to enthusiasts who want to get airborne quickly. (Note: if you buy plans or kits, check that they represent successful, flying prototypes, unless you are prepared and keen to do some design and development work yourself.) Enjoy your design work! Your achievements will fly for themselves! Technical Data Sheet A Technical Data Sheet is a list of aircraft particulars which forms a base from which you can design an aircraft. It is also the technical specification of the aircraft. The following is a blank Technical Data Sheet which you can use.
Anton Maneschijn has been involved in aviation for most of his life: his father, Ton Maneschijn, was one of the founders of amateur-built aircraft activities in South Africa in the early 60's. Anton has a BSc (Mechanical Engineering) degree and has, on the aeronautical side, 12 years experience in military aviation, lecturing and amateur-built aircraft design and construction. He is the author of "Guidelines for building your own aircraft", a starter's booklet, and "An Introduction to Experimental Light Aircraft Design", a 300-page enthusiast's guide. He has been President of the Aircraft Homebuilders of South Africa since he founded the organisation in 1994. In January 1998, he was elected the Chairperson for the fourth year running of the Technical Committee of the Amateur Aircraft Section of the Aero Club of SA. He is the 1997/1998 CIACA delegate from South Africa, and recently he has been involved in the investigation into sportifying flight simulation on personal computers. |
