Enhance FAA Coded Instrument Flight Procedures

This program augments a provided coded instrument flight procedures (CIFP) database with more accurate localizer bearings for flight simulators.

Background

The Federal Aviation Administration (FAA) CIFP file is released every 28 days and is the basis for all digital navigation products like GPS databases, ForeFlight, etc. It can also be used in flight simulators like X-Plane in order to provide the most up-to-date navaids, waypoints, and procedures.

The ARINC 424 specification defines fields for localizers to provide an accurate bearing, but unfortunately this field is not included in the FAA's public CIFP release. This results in simulators displaying localizer courses that are significantly different from the actual path (hundreds of feet off).

It turns out that a reasonable estimate can be made for the localizer bearing by computing the bearing between the final approach fix (FAF) and the localizer unit itself. This data is present in the FAA CIFP file, and this program makes use of that data to augment every localizer with a more accurate bearing.

Install

To install this package, you need to install Go on your system. The following commands are for Unix-like systems. I am very sorry if you use Windows.

1. Fetch the repository.

   go get github.com/wallaceicy06/enhance-faa-cifp

2. Build the code from source. This will install the program under $GOPATH/bin.

   go install github.com/wallaceicy06/enhance-faa-cifp

3. Make sure that $GOPATH/bin is in your $PATH.

   export PATH="${PATH}:${GOPATH}/bin"

Usage

To use this program, you need to have a CIFP file in the ARINC 424 format. The FAA publishes the CIFP for download on their website.

1. To process your CIFP file and output the results to a new file, run:

   enhance-faa-cifp --output=/path/to/FAACIFP_enhanced /path/to/FAACIFP18

2. If you would like to use this data in X-Plane, locate your X-Plane install directory, and place the file in the "Custom Data" folder with the name earth_424.dat. The following is an example, but your paths may differ:

   cp /path/to/FAACIFP_enhanced "${HOME}/Library/Application\ Support/Steam/steamapps/common/X-Plane\ 11/Custom\ Data/earth_424.dat"

By default, the program removes duplicate localizers that are specified for airports that use another airport's localizer on one of their approaches (e.g. KVNY LDA-C). The reason these are removed is that it causes unpredictable behavior when using the localizer in X-Plane. If you would like to turn this functionality off, set the remove_duplicate_locs flag to false:

 enhance-faa-cifp --output=/path/to/FAACIFP_enhanced --remove_duplicate_locs=false /path/to/FAACIFP18

Help

You can print the help for the program by running:

enhance-faa-cifp --help

Known Issues

This is a project that will likely encounter a handful of known issues as users test it in practice. The ones I am aware of are listed below:

• Some localizer bearings are more than 5 degrees off the original one published by the FAA. The ones I have detected are IBRL, IPIA, IVVS, and IYKM. A warning is logged for these localizers, but the new (potentially incorrect) value is persisted. See issue #1.

Side Note For Pilots

I wrote this enhancer because I discovered the bug myself while practicing the ILS 28R at KMOD in X-Plane. I popped out of the clouds to see that the runway was offset hundreds of feet to my left. Having flown the approach in real life, I know that this is not accurate. This project was my deep dive into learning why that error happened, and to offer a potential fix.

You can read more about my process solving this bug in my blog post.

Contributing

Contributions to this repository are welcome, within the scope of the problem of enhancing the CIFP data. Please submit bugs/suggestions to the issues section and I will get back to you as soon as possible.