Maintaining unobstructed approach corridors is essential to ensuring the efficiency and safety of instrument approach procedures to thousands of airports. When obstacles penetrate a zone known as the visual surface area, also commonly referred to as the 20:1 slope along the runway’s extended centerline, approach minimums may have to be raised—or worse, a notice to airmen may inform pilots that the approach is not authorized at night.
The complications don’t end there.
“Next, each airport is now given 30 days to validate the obstruction and to determine how they will deal with those that are verified, normally by removing or lowering the obstruction,” said Rune Duke, AOPA senior director of airspace, air traffic, and aviation security.
The impact of a procedure not being available at night can be significant.
“In one case, a lifeguard operator lost access to its home airport at night, which had a significant impact on their ability to operate. It is important for airport sponsors to take their responsibility for maintaining safe approach paths to their runways seriously,” Duke said.
If the task facing an obstructed airport seems daunting, the FAA provides support for airport management engaged in the risk-mitigation process.
A major component of that support is a 20:1 Surface Analysis and Visualization (SAV) Tool that 796 airports had used as of May 2018 to quantify their obstruction hazards.
Now the FAA Office of Airports is updating the SAV tool to bring it into compliance with policy that took effect in March 2016. This fall those changes will result in the removal of the existing high, medium, and low categories from risk assessments that were established under an interim policy that was in effect from 2014 to 2016. Speeding up the tool’s interface, refining the obstruction database, and removing analysis surfaces other than the 20:1 slope are also in the works. A separate tool to analyze other surfaces, such as the 30:1 slope, is under consideration by the obstruction evaluation office.
“The tool is helpful for airport managers to be proactive and to deal with 20:1 obstructions quickly,” Duke said, noting that although there are “thousands of 20:1 penetrations” to be dealt with at the nation’s airports, “the good news is the FAA over the last few years has dramatically decreased the number.”
Current policy calls for a formal review of an airport’s obstruction-mitigation plan by the FAA Flight Standards Procedure Review Board (PRB), a group that meets weekly on airport obstructions, and includes representatives from the Flight Standards Service, Operations Support Group Flight Procedures Teams, Airport Standards Division, and Mission Support Services. The PRB and the background of the FAA’s evolving 20:1 slope protection policies are discussed in the AOPA fact sheet, "20 to 1 Airport Obstructions."
As the fact sheet notes, during the two years the interim policy was in effect, 3,002 airports were studied, and all 16,518 instrument approach procedures (about 32,000 lines of minima) in the United States were reviewed. During the period, more than 900 airports and about 2,000 procedures were constrained by the presence of a 20:1 surface obstacle.
Of the approximately 900 airports affected, 565 eventually removed or mitigated the obstruction, thereby eliminating the constraints on their approaches, Duke said.