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Public Domain Aeronautical Software (PDAS)  

All of the programs are free to download, but you charge for a disc. Is there premium content? Why would anyone order a disc?

There is no difference between the source code of the programs. Also no difference between the sample cases and instruction files. The reference documents for each program are not included in the download, but are individually downloadable from the reference pages on the PDAS web site.

The CD or thumbdrive lets you have the entire collection on a disc along with the references. This saves you from having to make 83 downloads for the programs and hundreds of downloads for the individual references, leaving you with several hundred files to organize and file on your computer. The answer to the last question is that it is the best solution for someone for whom time is a more valuable resource than money. On the other hand, I don't suppose anyone is interested in every single one of the programs.

Also, I have not included the executable code for the programs in the download. I think it is always better for the user to compile the program for the target machine. The disc has these, but always compiled for the most generic machine. For example, some users have a single core cpu and 32-bit operating system, while others have quad-core cpus and 64-bit operating systems and lots of combinations in between. My distribution would have to be the most generic possible. If any user does not have a Fortran compiler, I can email them a generic executable for a given program.

How can I get a copy of the free gfortran compiler?

Go to the gfortran web site. From there, you can get a copy for Windows, Macintosh, Linux or several other platforms. The gfortran compiler is part of the Gnu CompilerCollection, and you can install the entire collection, thereby giving you Fortran, C, Java, and C++ compilers.

How can I get a copy of the free g95 Fortran compiler?

Go to the g95 web site. From there, you can get a copy for Windows, Macintosh, Linux or several other platforms.

How can I get a copy of gnuplot?

Go to the Gnuplot Web Page for instructions on downloading and installing a free copy of gnuplot. If you use Linux, be sure to get gnuplot-x11 and not the generic gnuplot.

How can I get a printed copy of DATCOM?

If you intend to be a serious user of digital DATCOM, you should get the manuals for the original DATCOM. You may download the entire set from this reference:
Fink, R.: USAF Stability and Control DATCOM.. AFWAL-TR-83-3048. McDonnell Douglas Corporation, Douglas Aircraft Division, for the Flight Controls Division, Air Force Flight Dynamics Laboratory, Wright-Patterson AFB, Ohio. October 1960, revised November 1965, revised April 1978.
If you are thinking about having these documents as hard copy, you may wish to read my printed DATCOM Manual page that discusses your options.
If you have a disc from 2012 or earlier or loaded the DATCOM reference document from this site in the past, be warned that there are missing pages. Go to fixedDatcomDocs.html to get a new copy of the entire document with the missing pages restored.

What does the variable SWAFB stand for in DATCOM?

Short answer: I don't know. Obviously, this was intended to be used for something, but it was never implemented. I have scanned the entire source code and can assure you that it is never used on the right hand side of a = statement or in a subroutine or function call. Several users have been a little worried because it appears in some examples. If anyone has any inside information, I will include it in the documentation.

What version of PanAir is distributed on the CD-ROM?

This version of PanAir is known as the ht2 version and is the last public domain version dated 1993. The Boeing Company has continued the development of PanAir, but not for public release.

Panair input is too difficult and Panin is incomplete and has errors. Isn't there an input procedure for Panair that has a graphical user interface?

People have wanted this for years, but no one has stepped up and taken on the task. There is a new company, called Hegedus Aerodynamics that is in the process of developing such a product. You may download the current version of this product from their web site.

I see that you have some pages labelled as XHTML + MathML. What is this?

I think that MathML is the upcoming way of presenting pages on the web that contain mathematical expressions. Go to my MathML page for more information.

How can I get a copy of the NASA report on the geometry of the NACA airfoil sections?

In December 1996, NASA published a new report outlining the theory behind the NACA airfoil sections. It is designated TM-4741 and you can download a copy (PDF, 293 KB) from this server. There is a copy on the CDROM as well as a copy of the source code.

How can I get a copy of NACA Report 1135 with Equations, Charts and Tables for Compressible Flow?

You can download a copy (PDF, 12.9 MB) from this server. There is a copy on the CDROM.

When I try to run a program, it says that I cannot open a certain file (usually a .out file). What is wrong?

The most likely reason this happens is if you are trying to run the program from the CD-ROM and have set the default drive to the CD-ROM. The problem is that the program is trying to open an output file on the default device. Now, you cannot create a new file on the CD-ROM. It is possible to run from the CD-ROM, but you must leave the default drive set to a hard disk.

I copied a file from the CD-ROM. Now, when I want to modify it, my editor says that I can't. What's wrong?

All files on a CD-ROM are read-only. Sometimes, depending on how you do the copy, this attribute gets carried over to the copy of the file. If this happens, bring up the Properties page for the file and uncheck Read-only. (Right-click to get Properties). This should never happen on Linux or Macintosh.

The program on this disc gives coordinates for NACA airfoils, but I am interested in a [... airfoil name ...]. Can you help?

The best source for help is the Airfoil Data Site.

What airfoil is used on the [... airplane name ...]?

I once started a list of airplanes and the associated airfoils. Then I ran across The Incomplete Guide to Airfoil Usage and was amazed at the depth of coverage. There are hundreds of airplanes in the list with the corresponding root and tip airfoils. I quietly threw my meager list away and now consult this page. You can all thank Dave Lednicer for maintaining this list and send him any info you may have for additions to the list.

NASA has written hundreds, maybe thousands of flight simulator programs. Why don't you put some of these on the CD-ROM?

The simplest answer to this is that Flight Sims tend to be very graphical and this will tie the program to one platform. In addition, there are numerous commercial products that are better value to an end user than a research code from NASA. If you want a flight simulator that you can look inside and modify to your needs, have a look at the FlightGear open source flight simulator. If you want more information on commercial flight simulators for the PC, you might begin at the AvSim site or the Thirty-Thousand Feet page. There are many add-in or add-on files for setting up simulators for a particular airplane or scenery - even cockpit gauges.

I want to get copies of the books Fluid Dynamic Drag and Fluid Dynamic Lift by Hoerner. They do not seem to be available in bookstores. Can I get copies through PDAS?

No, not from me. But if you write

Hoerner Fluid Dynamics
PO Box 21992
Bakersfield CA 93390
661-665-1065

you should find out the current price, etc.
I think you can order through Amazon, also.

What book should I read to learn about [... aeronautical topic ...]?

The best thing I can do is to refer you to Dan Raymer's book list. He has collected a most comprehensive list of important books for aero folks with comments, etc. His whole site is worth a visit.

Why don't you put a copy of Theory of Airfoil Sections by Abbott and von Doenhoff on your disc?

Simple. It is copyrighted and I will get myself sued. However, there is a copy of NACA 824 on the disc. This report by Abbott, von Doenhoff and Stivers was the prototype of the book. The report has some interesting material that is not in the book. The disc also has a copy of NACA Report 452 by Theodore Theodorsen with a thorough treatment of airfoil theory that overlaps much of the material in the book. You should be aware that there are many typos in the numerical tables in the three appendices to the book. There are corrected pages at this web site. Anyway, you should all buy a copy of Abbott and von Doenhoff. The inexpensive Dover edition is a bargain among the expensive textbooks of the modern day.

How can I get a job in the aviation industry in the USA?

I get asked this a lot and I really don't have a good answer. If anyone can help me out with a reference or a web site that deals with this question, I would really appreciate it.

How can you make the best approximation of pi, using only six decimal digits?

So, what does this have to do with aeronautical engineering? Probably nothing, but I will share this way to win a free beer now and then. Most folks will answer this with 3.14159, but you can amaze them with the fact that 355/113 is 3.14159292... which is better than 3.14159. But, to really top them all, you can use the fact that

Sqrt(Sqrt(2143/22)) = 3.14159265...

Can I use my credit card to order a copy of Public Domain Computer Programs for the Aeronautical Engineer on disc?

All purchases and donations are now handled thru PayPal. PayPal allows you to use all popular credit cards to charge your purchase.

How can one place orders from outside the USA without using PayPal or a credit card?

To place an order from outside the United States, you should go to a major international bank and have them write you a check to Public Domain Aeronautical Software (PDAS) for $99 US. They will charge you the equivalent in local currency plus money exchange fees. An alternative approach is to get an International Money Order, usually through a local post office. If you are willing to accept the small risk of your letter being lost in the mail, you may send the cash equivalent of US $99 in your own currency. I like to get pounds and euros. As for other currencies, maybe you will inspire me to visit your country.

I want to use a non-postal carrier, such as UPS or FedEx. Is this possible?

The simple answer is yes. But, of course, it costs more to do that. Send me e-mail and I will tell you what it will cost. If you are in North America or Western Europe, you have to be in an fantastic hurry, because most people receive their discs in about five days. In other parts of the world, I can appreciate that the local mail service sometimes leaves a bit to be desired. The prices vary from location to location, but expect to pay an additional $80 for air express to eastern Europe, Middle-east or Asia and $40 to North America or western Europe.

Why do you put a low value on the disc on the customs declaration form for non-USA shipments?

The value that should be declared is the cost of sending another package if this one is lost or destroyed in the mail. From this point of view, the value is the cost of the blank disc plus the envelope and wrappers - about $5 at most.

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Public Domain Aeronautical Software (PDAS)