Instrument Rating ACS Question
 

Looking for help double checking something in the ACS for Instrument Rating. Probably a dumb question splitting hairs, but I just want to double check.

Nonprecision Approach:
Skills - 8. Maintain, "prior to beginning the final approach segment," altitude within +/- 100 feet, heading within +/- 10 degrees, and allows less than 3/4 scale deflection of the CDI, and maintain airspeed within +/- 10 knots.

Skills - 12. Maintain the MDA, when reached, within +100 feet, -0 feet to the MAP.

A step-down fix with an altitude (underlined) PRIOR to reaching the final approach fix still must adhere to Skill #12 of that "MDA" for the segment of +100 feet and -0 feet, rather than Skill #8 "prior to beginning the final approach segment, +/- 100 feet correct?

The Terminal Procedures Publication defines any underlined altitude as the "Minimum Altitude" which should obviously be one that you would not descend below, but in a gray area might be legally defined as something different than the published "MDA" that you'd maintain to the MAP (you're not 'maintaining' it if it's a stepdown).

Clearly it'd be smartest to stay above the step down minimum altitude regardless (for safety reasons as well as the ACS), but for pass/fail standards in the ACS what is the result if you drop 50 feet below a minimum altitude at a stepdown fix prior to the FAF?

For those curious, I didn't bust it. Just reviewing the ACS. Thanks in advance for any feedback.

Altitudes prior to the FAF are not MDA’s so I would say it’s +/- 100 until the FAF like any other altitude after the IAF (or prior). Then it would be +100/-0 after the FAF to the MAP. Better to stay on the +100 side anytime though.

Whether an at-or-above altitude on a step down fix is MDA is irrelevant.

An underlined altitude has nothing to do with practical test standards; it's a requirement of the approach. It doesn't matter if you're taking an instrument checkride or flying an instrument approach. The same requirement applies. Maintaining altitude in general has plus or minus tolerances, but hard altitudes on an approach do not offer those tolerances; you can be high, but not low.

Thanks, makes perfect sense.