Approaches without vertical guidance

Know what the approach actually provides

A nonprecision approach supplies lateral guidance without approved final vertical guidance. A LOC course is angular and becomes more sensitive near the antenna; a VOR course is also angular relative to its station. LNAV uses GPS/RNAV lateral guidance; LP uses WAAS lateral performance with angular final sensitivity. Both LNAV and LP have an MDA. LP does not provide an LPV glidepath, and an LPV-capable receiver is not automatically approved for every LP operation.

Read the chart, approved installation capability and actual navigator annunciation together. A displayed advisory descent cue, sometimes labeled with “+V” by a manufacturer, can help fly a continuous descent but does not change the selected LNAV/LP minimum to DA. An installation-specific label must be understood from its supplement. Lateral-only final stepdowns and the MDA remain binding.

A VOR final requires valid operational VOR navigation under the applicable rules; GPS situational information alone is not permission to replace required final guidance. Suitable RNAV substitution has specific limits: it is not a substitute for a localizer final. Review GPS/RNAV substitution and the current AIM before applying it to a conventional approach.

AIM 5-4-5: nonprecision types, LP/LNAV and advisory descent · AIM 1-1-17: GPS approach approval and guidance · AIM 1-1-18: WAAS LP and LPV capability · AIM 1-2-3: suitable RNAV substitution limitations · ACS VI.A.K1–K3, printed page 14

Build the brief and prove the source

Before the final segment, verify the correct current procedure and clearance, entry transition, final course, altitude sequence, FAF, stepdowns, applicable category/minima, VDP and MAP identification, full missed and any required climb gradient. Review weather, runway/lighting notices and alternate options while there is time to change the plan. If equipment or a clearance cannot be supported, advise ATC and obtain a usable alternative before entering that part of the procedure.

For a conventional approach, select the charted facility/frequency, identify the received signal and verify operational status. Confirm the correct receiver supplies the CDI/HSI and that the indication makes sense for position and course. A memorized frequency or database label can point to the wrong facility. Observe flags, signal anomalies and relevant NOTAMs. On an RNAV approach, retrieve the named procedure from the current appropriate database, compare fixes with the chart and confirm active leg, source, sensitivity, integrity and supported approach mode before final.

Set the usable MDA and visibility after applying category, authorized altimeter notes, NOTAMs, inoperative components and chart restrictions. If a stepdown fix cannot be identified, use a published higher-minima option only when the chart authorizes it; do not erase the fix or invent a substitute. An approach clearance does not waive these conditions.

AIM 5-4-5: equipment, minima and procedure notes · AIM 1-1-11: identifier removal and out-of-service facilities · AIM 1-1-17: database procedure and approach checks · 14 CFR §91.175(b), (i), (j): minima, entry altitude and course reversals

Plan the descent between protected floors

Draw or read the altitude sequence before choosing a descent rate. Crossing the FAF permits only the descent allowed on that segment. Remain at or above each stepdown altitude until its fix is positively identified. A map distance to a different waypoint or DME from a different facility is not that fix. Do not start descent from an unpublished vector merely because the runway is closer.

Invented cockpit calculation: cross the FAF at 2,400 feet; a stepdown 2 NM later requires at least 1,800 feet. At 90 knots groundspeed, travel is 1.5 NM/min and the leg takes about 1.33 minutes. Losing the full 600 feet in that time requires 450 ft/min. A planned 400 ft/min descent loses about 533 feet and reaches the fix near 1,867 feet, above the restriction. A 700 ft/min descent would lose about 933 feet and violate it. These values illustrate the arithmetic; they are not aircraft settings.

Once the fix is crossed, reassess the next restriction and the actual groundspeed. A wind change changes the descent rate needed for the same path. A constant angle must satisfy every crossing restriction, not just connect the FAF and runway. If a chart’s VDA is published only after a stepdown, it cannot be extended backward through a higher preceding floor.

AIM 5-4-5: charted restrictions and advisory VDA · AC 120-108A §3.5, printed 3-7–3-8: controlling stepdown fixes · AC 120-108A §3.4, printed 3-3–3-4: descent gradient/rate calculation

Use CDFA without changing the legal minimum

A continuous descent final approach (CDFA) is a technique for a stabilized descent on a nonprecision final, rather than rushing down and flying an extended low level segment. FAA AC 120-108A recommends it where practical. Plan the angle or descent rate, crossing restrictions and visual transition before final; establish appropriate configuration and speed in time. A published VDA is advisory and is not required for CDFA, but any computed path still needs to respect the whole procedure.

MDA remains a hard floor when landing conditions are absent. Unlike a DA operation, the aircraft must not descend through MDA during the transition to a missed. The AC therefore calls for initiating the go-around sufficiently above MDA to avoid a dip below it; it describes this higher decision point as a derived DA (DDA). Select the margin through aircraft-specific training and procedures. There is no universal 50-foot addition that this course can prescribe, and a DDA does not convert the published MDA into an approved DA.

If visual conditions permit, continue a normal visual descent while seeing and avoiding obstacles. If they do not, initiate the planned missed/climb while remaining at or above MDA and preserve the final lateral path to the published MAP before the missed turn, unless ATC directs otherwise. Observe any maximum altitude restriction. If using a planned level segment instead, capture MDA without undershoot and remain above it; never create a last-second dive to save the landing.

AC 120-108A Chapter 2, printed 2-1–2-2: stabilized CDFA technique · AC 120-108A §§3.7–3.8, printed 3-9–3-10: DDA, MDA and decision · AIM 5-4-21: early missed and MAP path · AIM 5-5-5: altitude restrictions during early missed

Arrive at final ready to descend

Use the actual AFM/POH and checklists to select approach speed, power, configuration and limitations for weight, wind, icing and other conditions. Complete the relevant approach/landing checklist with enough time to verify its result. Do not copy a generic gear/flap schedule or pitch/power number from a different airplane. Plan the go-around configuration sequence as well as the landing configuration.

A stable approach has a manageable flightpath, appropriate speed/configuration, small corrections, a suitable descent rate and enough power/control margin. Use the operator/instructor’s aircraft-specific stabilized criteria and decision gates. FAA CDFA guidance describes 1,000 feet above TDZE in IMC and 500 feet in VMC as recommended stabilization windows; those are guidance, not universal Part 91 legal landing limits. A high, fast or large-deviation approach may require a missed before minimums.

Anticipate final sensitivity. Correct track with small deliberate changes and monitor trend, rather than chasing each needle motion. Cross-check attitude, airspeed, altitude, course, rate and remaining distance; use an installed MFD to understand position and wind drift without fixating on it. Large descent rates or configuration changes near MDA can exhaust the time needed to level or go around. Do not trade altitude-floor protection for needle centering.

AC 120-108A §2.2, printed 2-1: energy and stabilization windows · IPH Chapter 4, printed 4-37: stabilized approach and descent planning · ACS VI.A.K4, R4–R5 and S7–S9/S11–S12, printed 14–15

Make the visual or missed decision in time

For ordinary natural-vision descent below MDA, all three §91.175 conditions must exist: a continuous position for a normal descent with normal maneuvers, flight visibility at least the published value, and a listed runway reference distinctly visible and identifiable. Ground reports inform planning but do not replace flight visibility. Seeing an airport beacon, town lights or the wrong runway does not satisfy the listed-reference requirement.

A published VDP helps identify where a normal visual descent from MDA can begin. The AIM advises against descent before it. Neither VDP nor advisory guidance supplies permission below MDA. The visual segment may contain obstacles. If the runway appears after the VDP and a normal landing is no longer possible, go missed even though the lateral MAP has not yet arrived. Approach lights alone retain the 100-feet-above-TDZE limit unless the specified red terminating or side-row bars are also identifiable.

Identify the MAP by the charted fix, facility, DME, waypoint or timing method. If timing is prescribed, start at the specified FAF and use the appropriate published groundspeed time; approach speed/configuration changes can invalidate the estimate. Use the installation’s proper sequencing procedure for an RNAV MAP. At the MAP without landing conditions, miss promptly. If conditions are lost after starting visual descent, the below-minimums go-around requires the special care described in Missed approaches.

14 CFR §91.175(c)–(e): visual conditions and missed triggers · AIM 5-4-5: VDP and visual-segment limits · AIM 5-4-20: MAP and visibility · AC 120-108A §3.6–3.8, printed 3-9–3-10: timing and MDA decision

Treat guidance and mode changes as new decisions

An armed approach mode is not proof that the aircraft captured the correct source or leg. Verify active and armed modes, expected sensitivity, current leg and the actual aircraft response. Know the supplement’s procedures for manual flight, mode reversion, missed sequencing and any required source change. A GPS map may remain reassuring when the selected LOC receiver is flagged; a frozen CDI may look centered. Compare independent available information and flags instead of judging integrity from appearance.

If guidance, integrity, attitude or altitude information becomes unreliable, maintain control and use the approved failure procedure. Do not continue a final that now lacks required guidance or integrity. Promptly inform ATC when workload permits, state the capability you have and request a supported alternative. §91.187 reporting of IFR equipment malfunctions and the current AIM GNSS-reporting guidance apply; known NOTAMed GNSS testing has specific reporting treatment.

When a service downgrade happens before final, reassess the available line and complete a new usable brief only if equipment, procedure, altitude, visibility and workload permit. A late failure is not permission to improvise a switch to a lower line while descending. Disconnect or change automation according to the actual installation when its behavior is unreliable, and be ready to hand fly. Loading an approach or pressing Direct To must not bypass a required segment.

AIM 1-1-17: GPS integrity, approach mode and failure action · AIM 1-1-18: WAAS service annunciations · 14 CFR §91.187: IFR equipment-malfunction reporting · ACS VI.A.R3 and S5–S6, printed page 14

Protect the scan while managing the approach

Read back clearances and restrictions, use the correct communications frequency for each segment, and distinguish an approach clearance from a landing clearance. If a clearance is unclear or impossible because of equipment, performance or position, say “unable” with a concise reason and request an alternative. Avoid silent assumptions about a new direct routing or an early turn. Brief the intended communications change before a busy final.

Use single-pilot resource management: organize chart and checklist access, set reminders for floors/MAP, brief the missed, and postpone nonessential tasks. In a crew, assign who flies, monitors the source/altitudes and calls the decision. A qualified instructor or safety pilot may support training, but the flying pilot remains responsible for control. Do not let a tablet, checklist, radio call or runway search consume the instrument scan.

Weather changes can require a different operation before final or a missed at minimums. Recheck runway wind, visibility, lighting status and landing performance; decide whether repeating this approach has a reason to succeed. Do not use fuel pressure as a reason to descend lower. Plan holding/diversion options and tell ATC promptly when the current approach no longer fits.

AIM 5-4-6: clearance and procedure responsibilities · AIM 5-4-21: missed planning · ACS VI.A.R6 and S2/S4/S6/S15, printed 14–15

Explore the full approach before flight

Use a current chart and the actual aircraft supplement with an instructor. Trace the cleared entry to final and missed, identify each source, read every altitude restriction, choose/adjust MDA and visibility, and explain what would make the operation unusable. Calculate one descent leg, then change the wind or remove a required fix. State how you would preserve the altitude floors. Demonstrate the controls on the ground only as appropriate for the installation.

Rehearse a stable descent, MDA capture or CDFA decision, runway-reference assessment and missed. Add a source failure, a deteriorating report or an “unable” clearance call. Explain how the MFD helps identify position and drift while the primary instruments govern control. The scenario is preparation for a selected approach, not a completed flight demonstration.

These tolerances describe evaluation; they do not authorize violating a crossing altitude, chart restriction or MDA. Study questions cannot demonstrate these skills. Flight training must confirm checklist use, source selection, communications, configuration, control, navigation and resource management.

ACS VI.A.S1–S15, printed 14–15 · ACS Appendix 3, printed 33–34: nonprecision approach task definition

FLIGHT SCENARIO

What would change your plan?