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:

Airport infrastructure, including runway markings, weather reporting, navigation facility monitoring, and lighting, directly dictates the type, usability, and minimums of instrument approach procedures.
Basic runway markings can restrict a perfectly aligned approach with a normal descent angle to circling-only minimums, as demonstrated by the Chatham, MA example.
The availability and type of weather reporting, along with the monitoring status of navigation facilities, significantly impact an approach's eligibility for commercial operations, alternate planning, and altimeter setting requirements.
Pilots should understand these critical links, as infrastructure status and outages (often communicated via NOTAMs) can profoundly affect available approach capabilities and published minimums.

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.