On Tuesday, IXEG gave us an update on the current predicament with VNAV and FMS data issues for their X-Plane 737 Classic. For those unfamiliar with the reports; the most prominent being related to descent FMS entries, some users experienced bugs during the later stages of flight at various airports and approaches.
Tom Kyler, a developer with IXEG, goes into lengthy detail in his X-Pilot forum post. This problem has been compounding over a long period of time. The root of the issue can be traced back to differences between Navigraph’s XML format dataset and Aerosoft’s equivalent, “…Aerosoft had additional XML types that Navigraph didn’t have…and for which I didn’t have code to handle.” says Tom Kyler. This discrepancy kicked off a slew of back-and-forth patchwork in what the developer calls ‘band-aids’, some quick fixes meant to accommodate the differences in code. It seemed as if every solution would bring forth new problems to tackle. This misunderstanding between code and database, as well as some inhibiting ‘band-aids’, explains the seemingly random experiences between pilots. Whether the pilot would encounter issues or not was dependent on the route being flown and other variables such as approaches, runway selection, and transitions.
Side by Side comparison of Navigraph and Aerosoft’s XML data. This example is from Boston’s Logan Intl Airport (KBOS)
With the advantage of hindsight, Tom explains how they better understand the XML differences now and can make some small adjustments to vastly increase the consistency of the software. One method that will be implemented to help keep the software on track; if you select a STAR that is associated with a runway, or has any runway transitions, the FMC will warn you to select a runway (unlike its real-life counterpart). This fix should keep the issues grounded while the team says they are weighing their options for a more permanent solution of Aerosoft’s and Navigraph’s data. The team is convinced the next step will be switching to the XP11 navdata format.
To read more about IXEG’s situation and other possible solutions going forward, please see the original X-Pilot forum post.
