Precision Approaches

From the FAF to DA/DH: no more than ¼-scale deflection of either the vertical or lateral guidance indications, and airspeed ±5 knots of the desired value, on a stabilized final (AA.VI.E.S12). Before the final approach segment: altitude ±100 feet, selected heading ±5°, airspeed ±10 knots (S9). The ACS defines ¼ scale as the needle displaced ¼ of its total available deflection (ACS Appendix 3). The instrument-rating standard was ¾ scale and ±10 knots — the ATP corridor is a third the width, at transport final-approach speeds.

At least two precision approaches in simulated or actual IMC, flown to the DA using aircraft navigation equipment for centerline and vertical guidance:

• At least one without the autopilot, with the manually flown segment beginning no later than the FAF — raw data or flight director, at the evaluator's discretion
• One should be flown with backup or partial panel instrumentation or navigation display representing a realistic failure mode
• One may be flown via the autopilot, if equipped — provided the DA/DH does not violate the authorized minimum altitude for autopilot operation

The evaluator decides whether each ends in a landing or a missed approach (ACS Appendix 3).

Every autopilot has a minimum engagement/use height for approach — a certification and OpSpecs limit that varies by installation, which is why the ACS states the coupled-approach option only works provided the DA/DH does not violate the authorized minimum altitude for autopilot operation (ACS Appendix 3). The number itself is type-specific: it lives in your AFM and, for an operator, the OpSpecs. Expect the oral question in exactly that form: "Can you stay coupled to this DA?" — and answer from your airplane's limitation, not a generic figure.

Roughly groundspeed × 5 in fpm for a 3° path — 120 knots means 600 fpm (IPH ch. 3's descent rule of thumb). Compute it before the FAF so it's already established at the point where vertical guidance begins: the ACS calls for a predetermined rate of descent that approximates what's needed to follow the vertical guidance. Capturing the glideslope with the power and pitch already trending toward that rate is what makes the ¼-scale standard flyable; capturing it level at approach power and then chasing produces the classic porpoise the evaluator is watching for.

With all required ground and airborne components operative:

• CAT I — DH 200 feet, RVR 2,400 (RVR 1,800 with touchdown zone and centerline lighting)
• CAT II — DH 100 feet, RVR 1,200
• CAT IIIa — no DH or DH below 100 feet, RVR not less than 700
• CAT IIIb — no DH or DH below 50 feet, RVR less than 700 but not less than 150
• CAT IIIc — no DH and no RVR limitation — and to date, no U.S. operator has OpSpecs approval for IIIc

CAT II and III require special certification for operators, pilots, aircraft, and airborne/ground equipment; the authorizations and minimum RVRs live in OpSpecs Part C (IPH ch. 4).

Touchdown zone RVR is required, must be used, and is controlling for all CAT II ILS operations — and unlike CAT I (which permits substituting mid-field RVR when touchdown-zone RVR is unavailable), CAT II permits no substitutions for TDZ RVR (IPH ch. 4). Under part 121 the broader gate applies to every approach: you may not continue past the FAF unless the latest weather report puts visibility at or equal to or more than the procedure's minimums (121.651(b)).

Yes — this is the part 121 "look-see" provision. Having begun the final approach segment in compliance with 121.651(b), a later below-minimums report lets you continue to DA/DH or MDA. Below that, you may continue only if:

• The airplane is continuously in a position to land within the touchdown zone, using normal maneuvers and rate of descent
• Flight visibility is not less than prescribed
• A required visual reference is distinctly visible and identifiable

This is the same three-part logic as 91.175(c), with the TDZ-touchdown clause added for parts 121/135 (121.651(c)). And no landing when flight visibility is below the prescribed minimum (91.175(d)).

Depending on the autoflight systems, some aircraft require a DH to ensure landing in the touchdown zone, and some use an Alert Height as a final cross-check of the autoflight system's performance. Both are based on radio altitude, and the values come from the specific aircraft's AFM (IPH ch. 4). Conceptually: a DH is a decision about seeing; an alert height is a decision about the machine — below it, a fail-operational system continues the autoland unless a failure is announced. Which philosophy your airplane uses is a type question; answer it from the AFM.

No — as long as the descent doesn't continue. The ACS is explicit that continuing below DA/DH without the runway environment in sight is unsatisfactory, but most airplanes briefly descend below DA/DH from momentum when the miss is initiated at the DA — and that momentary descent does not constitute unsatisfactory performance as long as it does not continue (ACS Appendix 3, Task I discussion). The decision must be made at DA: immediately initiate the miss if the references aren't distinctly visible and identifiable (AA.VI.E.S13). What's graded is the promptness of the decision, not the physics after it.

Smaller and sooner. The needles' angular sensitivity increases all the way down, and at transport groundspeeds the same heading error builds displacement roughly twice as fast as it did in a trainer. The working method:

• Fly the flight director when authorized — but cross-check raw data; the manual approach may be raw-data at the evaluator's discretion (ACS Appendix 3)
• Heading changes of a degree or two; hold each correction and watch the trend rather than re-correcting on every needle twitch
• Pitch changes measured in tens of feet per minute against the precomputed rate (AA.VI.E.S11)
• Trim and thrust stable: on-speed ±5 knots (S12) is thrust discipline — configuration and airspeed established before the FAF for the conditions (S8), then leave it alone

Deviations you can't promptly stop are the cue to go around, not to work harder at salvage (AA.VI.E.R5).

Recognize, announce, act. On a precision final, the response is rarely creative: losing the vertical guidance below the point where another line of minima can be briefed means a missed approach; a disagreement between displays means reverting to the surviving source per your type's procedure and deciding whether the approach is still authorized. The skills behind this: select, tune, identify, and confirm the operational status of navigation equipment before the approach (S3), and recognize if any flight instrumentation is inaccurate or inoperative, and take appropriate action (S5). The oral version asks for your airplane's annunciations — flags, miscompare monitors, autoland status — from the AFM (K2).

Adjust the published DA/DH and visibility for NOTAMs, inoperative airplane or navigation equipment, or inoperative visual aids (S10). Mechanics: consult the TPP's Inoperative Components Table — the IFH's example raises visibility ¼ mile for a malfunctioning MALSR — and honor chart notes that exempt specific components (IFH ch. 1). Losing a required component of the guidance itself is different from losing a light: lights raise the visibility; a dead glideslope changes the approach into a localizer-only procedure flown to an MDA under the non-precision task's rules. Under 121, remember the OpSpecs may authorize different (including lower) minimums than the chart — the OpSpecs govern (121.651(a); IPH ch. 1).

Because the corridor is real: airports run simultaneous dependent, simultaneous independent, and simultaneous independent close parallel approaches, with diagonal separation as tight as 1 NM for dependent pairs (IPH ch. 4). Chart notes may impose flight director or autopilot requirements for simultaneous operations (IPH ch. 4). A localizer excursion on a close parallel isn't just a tolerance bust — it's an incursion into someone else's protected airspace. The ¼-scale ATP standard and the airline environment are the same requirement wearing two hats.