TERPS 101

Since we trust our lives to procedures designed to TERPS standards whenever were in the soup, lets pull back the curtain just a little bit to see whats going on behind the scenes of our approach charts. Note that collectively the TERPS standards easily run over 1000 pages and often involve quite a bit of math, so this is intended to be an overview and is by no means exhaustive. We will be looking at basic concepts and how they apply to approach procedures in this article; in a future article well discuss standards for other phases of flight.

IFR Staff

Monday, October 28, 2019 at 12:00 AM ET

Verified

Key Takeaways:

TERPS (U.S. Standard for Terminal Instrument Procedures) is the fundamental standard for designing instrument flight procedures, primarily ensuring aircraft safety through the application of Required Obstacle Clearance (ROC) within defined Obstacle Evaluation Areas (OEA).
The standards rigorously account for various real-world uncertainties, including navigation system errors, altimeter inaccuracies, and obstacle data limitations, often increasing ROC to maintain an acceptable level of safety.
TERPS criteria directly dictate the minimum altitudes (MDA/DA), climb gradients, and visibility requirements published on approach charts, providing the essential basis for pilot trust in instrument flight.

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Successfully flying instruments requires several ingredients. There are the skills, knowledge, and reflexes developed during training. Varying amounts of technology must be in working order. However, the most fundamental requirement for the existence of IFR flying is literally blind trust. We trust (and hopefully verify whenever possible) ATC to keep us clear of traffic, and we trust our instrument procedures to keep us safe while navigating (it’s a bit harder to verify that one).

Putting this trust into human controllers and procedure designers who are just as fallible as anyone else is no small task, but it is mitigated by the existence of required standardized operating procedures. This doesn’t mean they are always done perfectly, but they statistically provide an acceptable level of safety.