| |
|
Автор: Donald R. Crawford
Издательство: Crawford Aviation
Год издания: 1981
isbn: 0960393404
Количество страниц: 218
Язык: english
Формат: PDF (scan)
Размер: 10 Мб
Каталожный номер: 92208
|
Published to help the beginning designer through some of the preliminary phases of aircraft design. The nomogram and design procedure described in this book are aids I developed as a result of a design study for "Crawdad" — an ultralight foot-launched motor glider that I hope to build. In the process of learning about aircraft design I discovered the various useful performance and design nomograms of Raoul Hoffman, a noted practical aerodynamicist of the 30's and 40's. His alignment charts were useful because I could obtain answers to involved problems in aerodynamics by drawing straight lines connecting the related aircraft performance parameters. With this background, I was inspired to seek a single nomograrn that I could use to make parametric studies for future designs. With the aerodynamic relations contained on a single graph, the calculation could then proceed in a systematic manner, since the answers from one graphical construction would be automatically available as data for the next. An attractive feature of the nomogram is that it is "preprogrammed" so that we don't have to worry about exponents and conversion factors in the equations. All of the governing aerodynamic relations are built into the design of the scales and we can dispense with the tedious algebra Finally, by using a plastic template and a graphical construction technique, we can simplify the task of finding the rate of climb versus airspeed. One part of the template is used to find the gliding sink rate and the other part gives the rate of climb produced by the engine brake horsepower lifting the weight of the airplane with an efficiency corresponding to that of an idealized propeller. Using each part of the template as a French curve having the mathematically correct shape, we can immediately draw the two curves and subtract to find the rate of climb. The intersection of the curves gives the maximum level speed. The template is positioned using the reference points obtained from the graphical calculation with the nomogram. Then, we can use the reference scales on the template to make rapid parametric studies for the effects of altitude, weight, drag, brake horsepower, propeller diameter, and airplane size. The book began as an instruction pamphlet for the use of the nomogram, but it has evolved into the present handbook, with the detailed sample calculation, parametric study and theoretical background. The governing equations are tabulated for the convenience of those who want to program them on a computer and a sample listing for a FORTRAN computer program for the performance analysis is given in Appendix E. However, the answers obtained from the nomogram and the graphical construction of the rate of climb curve are adequate in the preliminary design stages. Although the computer will give greater numerical accuracy, the approximations of the governing equations do not justify keeping accuracy greater than two or three digits. The book is written for the homebuilder as well as for the beginning aerodynamicist. The first part of the book is devoted to practical considerations and is meant to be self-contained. The Airplane Performance and Design Nomogram can be used without really having to understand the details of the aerodynamic analysis of Part 2, which can be deferred until a working knowledge of the design process is established. In this way, the homebuilder or novice engineering student can gain confidence and experience by working with practical examples before trying to study the mathematics of aerodynamics. The book and nomogram will be especially useful as a supplementary text to aid the student with his (or her) preliminary aircraft design project.
Ключевые теги: самолеты |
|
ПОСТУПЛЕНИЯ
РУБРИКАТОР
Комментарии (0)