Precision Approach (ILS)
A precision approach provides both lateral (localizer) and vertical (glideslope) guidance to a decision altitude (DA). On an ILS you track the localizer and fly the glideslope with small, smooth corrections, run the approach checklist and configuration, and either land or execute the missed approach at DA.
Step by step
- 1Brief the approach: frequencies, final approach course, glideslope intercept altitude, DA, minimums, and the missed approach.
- 2Configure and slow the airplane to the approach/final speed before the final approach fix; complete the approach checklist.
- 3Intercept the localizer first, tracking it with small heading (wind-correction) changes to keep the needle centered.
- 4At glideslope intercept, reduce power/lower the nose to begin the descent and keep the glideslope needle centered.
- 5Make small, frequent corrections — a precision approach is flown with tiny inputs (keep both needles within ½ scale).
- 6Continuously cross-check altitude/airspeed/rate; identify the runway environment approaching DA.
- 7At DA, if you have the required visual references, land; if not, immediately execute the published missed approach.
Tips & common errors
- Pitch (and power) flies the glideslope; small heading changes fly the localizer — keep corrections tiny near the ground.
- A stabilized, properly configured approach before the FAF makes the whole thing easy; chasing configuration on final does not.
- Common error: getting behind the airplane, large needle deflections, or descending below DA without the required visual references.
- Decide at DA — go visual and land, or go missed. Do not "duck under."
ACS completion standards
The commonly-tested tolerances for this maneuver. Always confirm the current ACS for your certificate.
- Track the localizer and glideslope within ¾-scale deflection (ideally much less).
- Maintain airspeed ±10 knots; do not descend below DA without the required visual references and conditions of 14 CFR 91.175.
- Execute a timely landing or missed approach at DA.
FAA source
FAA-S-ACS-8 (Instrument Rating ACS), Task: Precision Approach; Instrument Flying Handbook FAA-H-8083-15, Chapter 11; 14 CFR 91.175.
This is an original, plain-English study summary grounded in the public-domain FAA Airman Certification Standards and FAA handbooks cited above. It is a study aid, not flight instruction, and not a substitute for the official ACS, the handbooks, your aircraft’s POH/AFM, or a certificated flight instructor.
Related maneuvers
- Attitude Instrument Flying & the Instrument ScanAttitude instrument flying is the foundation of all instrument flight: you control the airplane by interpreting the instruments instead of looking outside. You set an attitude on the attitude indicator (control), verify the result on the other instruments (performance), and trim. A disciplined cross-check (scan) prevents fixation and keeps every parameter in tolerance.
- Constant-Airspeed Climbs & DescentsOn instruments you frequently change altitude at a constant airspeed. You set a pitch and power for the desired airspeed, hold it with the scan, and lead the level-off so you roll out exactly on the new altitude and back at cruise airspeed.
- Rate Climbs & Descents (Constant Vertical Speed)Sometimes you must hold a specific vertical speed (for example to meet a crossing restriction or to fly a constant descent rate on an approach). You adjust pitch and power to pin the VSI to a target rate while still controlling airspeed, then lead the level-off.
- Steep Turns (Instrument)On instruments, a steep turn (typically a sustained 45° bank) tests your cross-check and control as the higher bank increases the back-pressure and power needed to hold altitude. With no outside horizon, you must control everything by the attitude indicator and supporting instruments.
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