In the dynamic world of aviation, software plays a crucial role in ensuring safety and precision. However, what happens when essential software like ICAO PANS OPS OAS isn’t officially provided for years? To answer that question there is a need to understand that in this case the rationale and formulas for the derivation of the OAS are not publicly available, we only had at some point the OAS constants printed in green pages within ICAO DOC 8168 Vol II (PANSOPS) for a series of predetermined parameters including distance from localizer to threshold and missed approach gradient just to name a few.

Over the years the printed constants were replaced by a software implementation (4D programming language) derived from the original coding (Fortran) with the aim to provide a more digitalized environment, the concept sounds good but the outcome was problematic as the company that made the conversion went to cease to exist and unlike opensource developments as this was proprietary there hasn’t been any updates for years if not at least a decade. At some point ICAO went through the process of doing a bid to update the software but that didn’t happen, and the current install media is the only thing we have available that allow us to check parameters provided by third party instrument flight procedure tools. Sure, we can double check the OAS tables against what the software gives but the real crux of the issues is checking the OAS constants for the values that are not provided in the tables and are thus derived from somewhere. Another example is the Collision Risk Model (CRM).

All the above create a very challenging scenario for all instrument flight procedure designers that rely on these critical tools for PANS OPS design, among other things:

  • Outdated Technology: Without any official way of cross checking the OAS constants provided by the automation tools that we may acquire we are designing based a bit more on faith rather than facts, we may just trust that the companies have somehow either reversed engineer the constant (not so difficult for mathematicians) or somehow have access to the original document that provides the Fortran code for the original OAS implementation. Without the software we have a situation where we are compromising in a way the effectiveness and the safety of flight operations.
  • Security Concerns: A lot of us have access to the last available version of the PANS OPS software and we run it on machines that were not designed to be able to use it, this could potentially pose a security risk and we may end up getting wrong or false calculations. Until now on my tests the values work OK for ILS CAT I, however for the APV I the last software available has an issue where the E’ value is not correct and deriving it for the 0.95 NM rather than the 1.0 NM shown on the OAS software is not so easy as one may think, this can lead to difference between software implementations.
  • Operational Challenges: Still in a lot of places around the world many instrument flight procedure design offices (IFPDO) rely on using the outdated OAS software install as it either provides an independent way to verify the constants provided by the automated software purchased are OK or in many cases the constants are used to produce the actual drawings in CAD or GIS software. I have to say that I use it myself for these purposes and I even use it when I am providing classes as you can almost see the tears in students’ eyes when you tell them they will need to revert to deriving the constants from the OAS constants and applying all the adjustments from DOC 8168 Vol II rather than the software.
  • Dependency on Legacy Systems: Users might be forced to continue relying on outdated technology or resort to alternative solutions that may not fully meet the standards set by the aviation industry. This dependency on legacy systems can impede progress and innovation in flight operations.
  • Need for Potential Workarounds: As there is no news on any new implementation we are being in a way forced to accept the status quo, this means we either use the old software as it is and try to run it despite not being coded for modern computer architectures or we need to accept at some level without any questioning that software vendors that provide PANS OPS software are providing the correct implementations. Don’t get me wrong, I for one do not expect any software vendor to on purpose provide wrong software but as there is no real independent way to check the results we can’t say things are right or wrong, even if two different software provide the same results we don’t know if their understanding is in line with the underlying principles on which the original OAS software was developed.

However, notwithstanding all the above I decided to create a video where I explain how you are able to install and run the latest version of the PANS OPS OAS software that ICAO released if you happen to have a copy of it. Many users around the world have access to it but can’t make it run due to the nature of the new operating system updated.

The Challenge: No Official Support

For aviation professionals and enthusiasts alike, gaining access to ICAO PANS OPS software has been a challenge due to its absence on official channels for an extended period. Through the video tutorial, you’ll discover how to install the software and configure it to run on Windows 64 bits. The step-by-step installation guide allows anyone to navigate through the installation process and makes emphasis on crucial factors to allow it to launch such as granting administrator rights and compatibility mode settings, ensuring a seamless installation experience.

Please note that this software was originally coded to run on 32 bit and not 64 bits, this has a potential effect on how calculations are performed but in my opinion until now I haven’t seen any difference except the installation requirements. As instrument flight procedure designer, you are encouraged to make your own analysis, and the tutorial just provides insights into making the software work a 64 bit machine without any guarantee about the correctness of the provided results.

One thing that is very important to mention is the OAS software has a difference on how the APV I constants are calculated, and it also contains the option for APV II which as a concept has been removed from PANS OPS. If you require the software you will need to request to your local authority or see if someone has a copy willing to share, I think ICAO should disclose the code as opensource for the community to be able to implement it without any licensing restrictions, but for the time being things are like this.


If you read all this congrats! Most people will just want to go directly to the link to watch the video and be able to see if they can make their OAS software installation work!

Watch the tutorial on how to install the ICAO OAS PANS OPS software now:

#AviationTech #ICAO #PANSOPS #SoftwareInstallation #AviationEnthusiast #Tutorial #FlightSafety ✈️

Categories: PANSOPS

1 Comment

Ville · January 27, 2024 at 11:55 pm

I would like to teach for my student the proper way to assess planification, cartography and obstacles assesment for aircraft in general , drones, rockets , missiles etc….
As an engineer for engineers and pilots

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