Airspace® and TERPS® September 2019 Updates

Recently, at an Airspace Obstacle Evaluation Conference for the FAA only, Technical Operations made a presentation on new VGSI (Visual Glide Slope Indicator) and ALS (Approach Light System) criteria. The VGSI discussed the implementation of VGSI Obstacle Clearance Surface (OCS) and its Light Signal Clearance Surface (LSCS). We provided information on this change in our November 2017 News Letter. The new surface doubles the older OCS distance from the runway from 4 nm to 8 nm and is wider. The tools for VGSI analysis can be found in your TERPS software program under the MAP menu item, sub-menu Runway. The new requirement for the ALS is in software design. We wish to analyze of both types of equipment automatic to our users from within Airspace.

It is known which runways in the NAS, have operational VGSI equipment. However, their exact location (Latitude/Longitude/AMSL) for all equipment is not known either by us or the FAA. We currently have about 650 VGSI locations in our development data-base but the NAS contains thousands. We are working on completing this data. Concerning the ALS equipment the controlled area is significantly smaller and located directly in front of the runway. The start point of the ALS analysis is the runway threshold.


Updates related to:

  • Airspace® and TERPS® software
  • FAA updates to relevant Orders, Advisory Circulars, Engineering Briefs, etc.
  • Industry related topics

If you have any questions or concerns, please give our office a call at (321) 777-1266, or send us an email,, we would be happy to assist you.