The intent of this page is to list new developments and news that may be of interest. A related page is the Bug List page, where I collect all notices of problems people might have in using the programs and work-arounds, if possible. If you report a bug, I will put your notice on the bug list page.
2021 April 7
With the latest release of gfortran (9.3), some bits of code that gave warning messages are now flagged as fatal errors. Panair and Digital Datcom have fallen victim. I have made fixes to the source code for both of these programs that should enable you to compile without fatal error. You may download
I do not think we are out of danger, though. The next versions 10 and 11 of gfortran are planning for more modifications and we will have to adapt with the times. I think we are headed for a modern Fortran without statement numbers.
15 September 2020
There is now a link that allows you to download all of the programs in one archive file (ZIP format). Go to the order page to use this link. This is now the standard way to distribute the software.
22 December 2018
Starting in January 2019, the standard way to distribute the complete set of programs by mail will change from CD to USB flashdrive. This reflects the technological shift in computer hardware away from CD drives. I will still make a CD for anyone who prefers this format.
8 November 2018
The file atmos.zip has been updated to incorporate the revised version of atmos76.f90 which had an error. This new version of atmos.zip can be downloaded from atmosdownload.html.
18 July 2017
I have put a link to the corrected tables that make up the appendices to the book Theory of Airfoil Sections on the main page. The tables have been on the site since 2001 and have been a popular item, but you had to look around to actually find them. Now, it is not so much of a scavenger hunt.
6 July 2017
The tables program for the standard atmosphere that was written for Python 2 has a problem when run with Python 3. I have fixed tables.py so that it now runs properly with Python 3, but the unfortunate side effect is that it no longer runs with Python 2. I have added tables2.py which does exactly the same calculations under Python 2. The package atmos.zip may be obtained from the download page for Atmosphere.
For those interested, there is only one line in the program that is different
between the versions. It is in the procedure that does a binary search for the
atmosphere layer that contains the altitude of interest.
The table index is recomputed from earlier estimates with the
k=(i+j) / 2
which, in Python 2, will use integers i and j to compute a new integer k using integer arithmetic. For example, if i=4 and j=7, k will be computed as 5 (integer). But with Python 3, this calculation would yield 5.5 (floating point) and this will be deemed unusable as a table index. The way to get the desired result in Python 3 is with the command
k=(i+j) // 2
which will return 5 as desired.
16 January 2015
Still more entries on the Sources of Aeronautical Software page.
6 January 2014.
There are some new entries on the Sources of Aeronautical Software page.
3 October 2013.
I have made some improvements to the Line Intersection program as a web application. The program now displays the results in graphical format. This page is an example of a web application that includes input with error checking, self-contained calculation, and graphical display of the results, all within a single HTML 5 file of 267 lines with no external files or procedures used outside of the web browser. I encourage you to examine the source code and use it as a guide for your applications. The Line Intersection program page has a link to the new HTML page.
14 August 2013.
21 April 2013.
There is now one Table of Contents page replacing the separate pages for released programs and those that are "in progress". This supercedes the message of 15 March 2009.
5 January 2013.
There is an error in the source code to the Celestial Coordinate Transformation package, CELEST. The best way to correct this is to download a new copy of celest.zip from the CELEST program page. Thanks to Nathaniel Cook for finding this error.
7 October 2012.
I have made predictions of the trajectories of various balls falling from high altitudes in preparation for the Red Bull team attempt to have a human achieve supersonic speeds in a jump from 36 km altitude. The link to my calculations is from the Atmosphere page or you may go to the Falling Objects page directly from here.
26 September 2012.
The files containing the DATCOM reference manual have missing pages! See the page fixedDatcomDocs.html for instructions on getting a good copy. Thanks to Steve Peterson for spotting this.
30 June 2012.
There is now a page of references for the program called Aircraft Motions or by its code ATC. Many thanks to Robert Clarke of Dryden for tipping me off to the references and the authors, Ralph Bach and Rodney Wingrove of NASA Ames.
19 June 2012.
Back in March of 2009, I promised that I would continue to make executables for people with older Macs if they contacted me for a special order. My standard disc has executables for Macs with Intel chips. The disk on my old iMac with the G5 chip has gone belly-up and I don't plan to replace it. So, I am afraid I must retract my promise. I can always get you a file from an old master disc, but it will be from an older source code. You will be frozen in 2007. Sorry about that, but it is time to upgrade.
17 December 2011.
I have discontinued processing credit cards and will now exclusively use PayPal for online payments. You may still use your credit card for a purchase, but it will be through PayPal. For those who do not like to use PayPal, you may order a disc and pay by check by sending mail to PDAS at PO Box 1438, Santa Cruz CA 95061.
Since you can now download any program without charge and have the source code immediately, there should be no need for express shipments. This option has been removed from the PDAS store.
8 October 2011.
All of the programs in the collection are now downloadable free of charge. Each program page now has a hot link permitting you to download the program as well as instructions and test cases (if available). I will still offer the complete collection on CD-ROM as a convenience to those who want a secure archive to keep on the shelf.
28 September 2010.
All of the web pages have been converted to HTML 5. You shouldn't see any difference on a computer browser, but if you use a handheld device to browse the web, there is some better assurance that things will display properly.
26 March 2010.
There is a new version of the Panair user's manual available. None of the content is changed, but there is now also a set of bookmarks that make it easy to navigate the document and find what you are looking for. You may now search for arbitrary words or phrases as well. Many thanks to Peter Gasparovic for making this new version of the manual.
10 February 2010.
Version 15.0 is ready for distribution. There are several additions and improvements. The programs boom, celest, and tol have been moved from the in-progress category into general release. A number of new reference documents have been located and placed on the disc.
5 November 2009.
There are some examples posted for using the getmac program for computing the mean aerodynamic chord of an arbitrary planform. Go to the getmac page to see the link to these examples.
21 September 2009.
The documents for the segmented mission analysis program are now on-line and may be downloaded. Go to the NSEG page for links to these documents.
1 September 2009.
The document describing the Takeoff and Landing program has been found. Go to the TOL page for a link to this document.
2 June 2009.
The program documentation for the Space Shuttle Synthesis Program (SSSP) has been found. Go to the SSSP page for links to four good documents with lots of good background info on launch trajectories, space vehicle weight estimation, etc. Thank to Joe Huwaldt for locating these documents.
1 June 2009.
My Math Page with references to mathematics and mathematical software has been revised and all of those pesky broken links have been fixed. Thanks to Eva Lynch for some valuable help for some replacements for broken links.
7 May 2009.
Check the Bug List page for some info on wavedrag and wingbody.
18 March 2009.
Version 14.0 is ready for distribution. There are several additions and improvements. As of this release, I am compiling all of the programs with gfortran instead of my usual commercial compilers. The gfortran compiler is absolutely free, runs on Windows, Mac, and Linux and other platforms. I have received many comments and complaints that people could not modify some of the programs because they could not afford a Fortran 95 compiler. Many programs needed modifications to allow compilation with gfortran and I think we can now be assured that these codes are up to 1995 standards. I am also checking that all codes function properly with the g95 compiler (also free). See the FAQ page for more info about these free Fortran compilers.
15 March 2009.
I have a number of programs in the PDAS archives that appear to be of some value, but are lacking in some of the requirements for general release. As of today, I have decided to make them available, even though they have problems that prevent me from standing behind them with support. There is a link near the end of the Contents Page that will take you to a page describing these programs. All are available for free download so you may examine them. I am hoping that some of you will be able to locate the missing documentation or can decipher the input requirements from the source code.
15 March 2009.
Starting immediately, all of the executable files for the Macintosh are coded for the Intel chips. They will not run on older Macs with the Power PC chip set. Last year, they were compiled for the Power PC and Mac Intel people had to run them in legacy mode. Now they will run at top efficiency on the modern Macs. If you have an older Mac, this does not mean that I am abandoning you. I am keeping my G5 Imac running OS 10.4 for the indefinite future and I can still compile programs with g95 or with the Absoft F90 compiler. However, if you order a disc and want an executable for Power PC, be sure to tell me so I can make you an extra disc with these files. They will not be on the regular CD.
28 January 2007.
The CD-ROM now contains the full text of the 1500 page USAF DATCOM theory document which forms the basis for Digital Datcom. Also, the NASA documents for ORACLS and VASP are now on the CD-ROM.
2 May 2005.
There is a new page on the web site describing the use of the programs on a Macintosh system. These programs are console applications and run under Terminal.