McMullan Aircraft Design

McMullan Aircraft Design

Birth of an Airplane

JayBird Design Page

Page 1

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Updated August 30, 2004

Click Here to download the Volo View Viewer. This viewer is essential for you to be able to view the drawings of the JayBird airplane.

IMPORTANT: All drawings, photos, and information presented on these web pages are the sole property of Jay S. McMullan and are © 2002. Nothing on these pages can be copied or reproduced in any way without the written, expressed permission of Jay S. McMullan and/or his assigness.

In this series, I will show how the very beginnings of an aircraft come into being. Before the preliminary steps can begin, the following decisions must be made:

1. What will the airplane be used for?

2. How many people will the aircraft be required to carry?

3. What type of power source will the airplane use?

4. What kind of speed will be required of the airplane?

5. How much range will the airplane be required to reach?

6. How much money am I willing to spend on this airplane?

7. Am I capable of building the airplane or having someone build it for me?

8. What materials will the airplane be built out of?

Once these, and possibly many other, questions are answered, you can move on to the preliminary design phase. Some of the things that must be determined in the preliminary design phase are:

1. Wingspan, chord width, wing planform and wing aspect ratio.
2. Engine and propeller requirements.
3. Landing gear configuration.
4. Seating arrangements.
5. Wing placement.
6. Etc, Etc, Etc.

My book, Preliminary Design - Modern Aircraft Design for the Non-Engineer goes into much more detail than will be shown on this web site. The book will discuss, in detail, each of the considerations that must be made in the preliminary design phase of an airplane. Included with the book is spreadsheet software that will greatly simplify the aircraft's preliminary design phase. Many times when just one calculation is changed, each previously calculated part of the airplane must be re-calculated. By using the spreadsheet, the aircraft designer can plug in one new number and the software will make all the necessary changes in the calculations that have already been made. The JayBird Rx2T began as a conceptual aircraft for the book Preliminary Design - Modern Aircraft Design for the Non-Engineer but has since turned into a real aircraft project for me. You will notice that I do not work on the airplane everyday. This whole thing began as a mental exercise for me. I hope to someday complete both the Vortex Magnum and the JayBird Rx2T. I also hope that my book and this web site may be of some help to you if you are designing your own airplane.

NOTICE

The drawings shown below are not detailed drawings. Please download AutoDesk's DWF Viewer and then click on the drawing you want to see. With the DWF Viewer, you will be able to zoom in and out on the complete drawings to see much more detail and keep up with the progress of the design of the JayBird aircraft.

August 26-27 - Studied sliding canopy design and worked on the design of the wing spars. The wing spar design must be determined before the fuselage design can be completed. Once that is done, how the fuselage and the wing are joined must be determined. There are a couple of considerations here. Do I want each wing panel to be able to be detached? I also could design the airplane so that the fuselage detaches behind the trailing edge of the wing and the wings are permanently attached to the fuselage.

I do want a tapered wing which makes designing the spars and other things more difficult but it will also give more speed to the airplane. The wing will have 5 degrees of dihedral and 2 to 3 degrees of washout. I had originally decided upon 2 degrees but I noticed that the Falco has 3 degrees. I'll have to check into that further.

There are two drawings linked below. You will have to use the Volo Viewer from AutoDesk to be able to view them closely.

The first drawing is of the fuselage structure. Some of the formers will have to be moved and beefed up when I determine the wing spar design. Notice that the canopy slides forward to open. This may change later.

The second drawing is the beginning of the wing spar. You will also see the airfoil for the root and tip of the wing.

Click on the Image to view with Volo View

Drawing 1 - Fuselage Construction - August 27, 2002

Drawing 2 - Wing Spar and Wing Rib Construction - August 27, 2002

August 26-27 - I have been working on the spar design for the airplane and building 2 degrees of washout into the wing. I want to carry the fuel in the wing and I think I have found a way to carry some of it there. I may still end up carrying some fuel in the fuselage which I drastically don't want to do for two reasons: 1. It just isn't safe. If the fuel is in front of the pilot and passeger, it can be thrown all over them if there is an accident. Even if there is a leak in the tank, it can end up in the fuselage. 2. The wing spar won't have to carry the extra weight of the fuel if it is carried in the wing. Fuel weighs in at 6# per gallon.

I noticed that the Falco uses 3 degrees of washout in its wing but most other planes I have looked into have 2 degrees. After rotating all of the ribs, I think I will stay with 2 degrees. After talking to the author of one of the books I use on aerodynamics, it seems that it is pretty hard to precisely determine what the washout should be. There are just too many factors to be calculated. So, I am sticking with the 2 degrees. Use the VoloViewer and you can see the wing ribs combined to show the degrees of washout.

Drawing 3 - Wing Construction - August 28 - Sept 2, 2002

Drawing 4 - Fuselage Construction - August 28 - Sept 2, 2002

December 19, 20 - With the wing having 2 degrees of washout, I drew the ribs. One view shows the ribs as they would appear from the side of the airplane, the other with the ribs stacked one on top of another, aligned at their centers. The stacked view will give you a greater understanding of washout or "wing twist". Now comes the tedious task of measuring and drawing the wing spars, leading edge, trailing edge, flaps and ailerons. All of these tasks are very slow but will pay off in the long run when everything fits perfectly.

The drawing above, shows the different parts of a wing made with plywood wing ribs. The wing's spars will be constructed from clear vertical grain Douglas fir. The next thing I have to do is scale each wing rib and draw it with the spars and flaps or aileron. Once the ribs are drawn, ribs can be cut from plywood. The computer drawings can also be cut on a CNC machine.

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All information, images, photos, etc. unless otherwise noted are ©
by Jay S. McMullan. DO NOT copy in any form without the written, expressed
permission of Jay S. McMullan and/or his designees.