IFR Airport Basics

Recently, a reader asked about a puzzling approach at Chatham, MA (KCQX). The RNAV (GPS)-B is perfectly aligned with Runway 24 and the descent angle is a routine 3.05 degrees, yet it has only circling minimums. Approaches most often just have circling minimums if the alignment to the runway exceeds 30 degrees (for most procedure types) or the descent angle is greater than 3.77 degrees (for Category C and below). So, whats up at Chatham?

Editorial Staff

Friday, January 08, 2016 at 12:00 AM ET

Verified

Key Takeaways:

The type of runway markings significantly determines the availability of straight-in instrument approach minimums, as seen at Chatham, and impacts the potential for lower precision minimums.
Airport weather reporting is vital for commercial operations and alternate airport planning, while altimeter setting sources (local or remote) can affect approach minimums.
Navigation facility monitoring and airport lighting systems also directly influence instrument procedure usability, affecting alternate eligibility, visibility minimums, night operations, and requiring pilots to be vigilant for relevant NOTAMs.

See a mistake? Contact us.

This procedure has only circling minimums because of the runway markings, of all things. The runway has basic, visual markings; straight-in minimums require at least non-precision instrument runway markings. This little detail isn’t found on the chart or in the Airport/Facility Directory, but can be found in online sources, such as Airnav.com, which are based on FAA airport survey data.