Aeronautics and Aviation

20:1 letter for airports

Google Earth has a free version that works on most smart phones, tablets, and iPads that allows the airport manager to walk to the location of the obstructions. The FAA developed a policy to address penetrations through validation. This process allows airport operators to dispute obstacle data which they feel is inaccurate in the FAA database before NOTAMs are issued restricting airport access. Sometimes the database contains old information and the obstacles have already been removed. If the airport manager determines that the data is invalid, the FAA will remove it from their database.
For those objects that are verified to be 20:1 visual area penetration, the next step for airport operators is to provide a compliance plan to the FAA. The compliance plan must be submitted no later than 30 days. Returning to the AGIS website the airport manager updates the obstacle information for their airport, reporting those objects that no longer penetrate the 20:1 surface and verifying the objects that do penetrate the 20:1 surface.
Compliance plans include a full range of options for obstacle mitigation including obstacle elimination/lowering, obstacle lighting, use of visual aids, and acceptance of procedural restrictions. Though Visual Glide Slope Indicators (VGSI) may exist at the airport, and they are listed as a means of compliance, our experience has been that getting acceptance for using VGSI to mitigate obstacles takes longer than the grace period. The Regional Airspace Procedures Team (RAPT) will monitor completion of the compliance plan put in place to ensure the penetrations are being mitigated.
Your airport consultant or MnDOT operations staff can assist you in responding to a 20:1 letter. Both can gain access to the AGIS site and help you to identify the objects and prepare your response.
The best way to deal with a 20:1 letter is to keep it from appearing. The FAA posts their schedule for IAP reviews and by working ahead, the airport can identify and mitigate obstacles before they are identified in the IAP review.