For example, runway protection zones are trapezoid-shaped areas drawn around airports and confirmed to be clear of obstructions that could pose a safety hazard. In addition, obstruction-free zones (OFZs) ensure aircraft have obstacle-free paths to transition to and from the terminal area safely. The dimensions of the OFZ depend on the airport and type of aircraft that operate there. Remember that not all approaches are created equal. Each runway has a defined approach path with a particular slope.  Approaches to visual runways have a 20:1 slope (20 feet of horizontal travel for every 1 foot of vertical rise) while nonprecision instrument runways have a shallower and more protective 34:1 slope. Even shallower slopes protect precision instrument runways.

In both precision and nonprecision instrument approaches, obstacle clearances (including a safety margin) define the minimum altitude at each point along a given approach. As long as the pilot follows the published procedure accurately, obstacle clearance is guaranteed. For runways equipped with a visual approach slope indicator, or VASI, obstacle clearance is ensured 10 degrees left and right of centerline, out to 4 nautical miles. Staying on course is the key to a safe approach.

Routine preflight preparation should include reviewing the chart supplement to determine if any obstacles exist at the applicable airport(s), what they are, and where. There may also be temporary obstructions near an airport, such as construction cranes. The temporary nature of some obstructions means they won’t be charted, yet they can be found in the notams—another of many reasons to ensure your preflight routine includes a notam check.

Knowledge of instrument departure procedures can also be helpful to pilots flying under visual flight rules. Obstacle departure procedures, for example, can be used for obstacle clearance on departure. These can be found on instrument charts or can be accessed through your electronic flight bag.

If you know where obstructions are, you can be on the lookout for them. To aid pilots in seeing and avoiding, obstructions will be illuminated, red or white.

There’s more to learn on this topic in the Pilot’s Handbook of Aeronautical Knowledge and the Aeronautical Information Manual.

Also, the FAA’s Advisory Circular AC 150/5300-13B focuses on Airport Design, AC 70/7460-1M describes the FAA’s standards for marking and lighting structures, and FAR Part 77 covers the protection of navigable airspace.