Aviation Obstacle Data – What’s the deal?

Every day thousands of aircraft take-off, fly en-route and approach to different airports around the world, all of them operate under the premise that no matter where they are flying all of the States operate in a similar fashion abiding by ICAO. In this respect is means that each day pilots load up in their FMS all the procedures that have been published by official means in the AIP, loaded in an FMS and a chart produced. However how can you be certain that the information used is correct, the process and the updates.

As hard as it may sound as there are differences in the state of development between countries the same difference also shows up with respects with the instrument flight procedures that each day are followed religiously, without any questioning about if they are correct, updated or needed to be adjusted.

One of the additional things that needs to be done are engine-out procedures which include performance calculations, the critical part in this sense is that the responsability is shifted from the State to the Operator to make this part as it’s logical the State can’t know the aircraft used, the performance and other data required. However the State has a very critical role in doing two things:

• Publish an Instrument Flight Procedure that abides by all of the ICAO SARPs and that is continuously updated
• Make available the obstacle data

Annex 6 is very explicit in that the Obstacle data shall be provided to enable to operator to develop procedures “Take-off. The aeroplane shall be able, in the event of a critical engine failing, or for other reasons, at any point in
the take-off, either to discontinue the take-off and stop within the accelerate-stop distance available, or to continue the takeoff and clear all obstacles along the flight path by an adequate vertical or horizontal distance”

A reference is made to go to Annex 4 (Aeronautical Charts) and Annex 15 (Aeronautical Information Services) for methods of how to present the obstacle data. Now many times the issue is that the data is presented only in charts, have you ever seen the AD sections mentioning “go to this chart” ? There are many problems with that approach.

I want to highlight the issues with not providing the adequate data in a machine readable format (AIXM, CSV, XLS, shapefile, KML whatever you choose is better than paper or PDF)

1. You are asking the users to extract the information from paper or PDF maps which if we think about it are not that exact to get the absolute precision required. The map may be printed at a wrong scale (specially true if printing options are not taken into account correctly). The PDF may be converted to an image and then georeferenced to be used within a CAD or GIS to extract the data but that may be done incorrectly, loss of quality, precision, etc
2. There are cases where the obstacles that are present in one AIP section are not present on the chart itself and viceversa that leads to the question what is the correct data anyway. This also speaks about the internal process uses to create the charts as there is no workflow to ensure everything corresponds ending with multiple back and forths between all the requests that may come. What if you got two points very close to each other with same elevations? or What if two points are exactly on the same spot with different elevations?
3. Creating obstacle charts like the Aerodrome Obstacle Type A and B takes a lot of time and resources! So much invested when it can be easily done through the provision of
   • Terrain dataset
   • Obstacle dataset

Whatever data you provide can easily be seen in a CAD or GIS software and style according to whatever needs the user has. A pilot while flying IFR will not be using the obstacle charts he assumes the procedure designs are correctly calculated for their operations. You can add the relevant obstacles he needs to avoid or be aware visually in the final and missed approach but has no use for the Type A or Type B ones, the performance engineers would gladly have the data instead.

Besides the actual provision problems the updating and the frequency of this update on the data is critical, in many parts of the world this isn’t really done in a correct way and it definitely will have an effect on the procedure design part and by extension on safety.

What are some of the challenges you have with the provision of Obstacle Data? Would you rather just publish a data file?

I invite you to run a risk assessment which you should under SMS to see what are the hazards and probabilities of those hazards due to your lack of provision of updated obstacle data or of not using the best delivery method no matter if its an ICAO SARPs. You can go beyond the minimum requirements and with the introduction of datasets you are given a powerful tool to go digital do not waste it.