Precision Approaches, IFR Departures & GPS Approaches

Precision Approach Defined

A precision approach is a standard instrument approach procedure that provides an electronic glide slope for vertical guidance. The two types are the Instrument Landing System (ILS) and the Precision Approach Radar (PAR). Descent minimums on a precision approach are expressed as Decision Altitude (DA) — the altitude at which you must decide to land or execute the missed approach.

The GBAS Landing System (GLS) is a newer alternative to the ILS. GLS uses GPS augmented by a ground-based augmentation system (GBAS) to provide precision lateral and vertical guidance equivalent to a Category I ILS. GLS approaches are charted similarly to ILS approaches and use DA for minimums.

ILS Components

The ILS provides three types of guidance to bring the aircraft from the approach environment to the runway (AIM 1-1-9):

1. Localizer (lateral guidance): Provides left/right course deviation. The localizer transmitter is located at the far end of the runway and broadcasts on frequencies 108.10 to 111.95 MHz (odd tenths only). The localizer course width is adjusted so that full-scale CDI deflection equals 2.5° from centerline — approximately 4 times more sensitive than a VOR.
2. Glideslope (vertical guidance): Provides an electronic descent path, typically at 3°. The glideslope transmitter is located beside the runway, offset from the centerline near the touchdown zone. It is automatically paired with the localizer frequency.
3. Marker beacons (position): Identify specific points along the approach path. The Outer Marker (OM) identifies the approximate glideslope intercept point. The Middle Marker (MM) is near decision altitude. Many marker beacon facilities have been decommissioned and replaced by GPS-based fixes or DME.

Final Approach Fix (FAF) & Glideslope Intercept Altitude (GSIA)

The Final Approach Fix is the fix from which the final approach segment begins. On approach charts:

• Maltese Cross symbol = FAF for non-precision approaches
• Lightning bolt symbol = FAF for precision approaches (glideslope intercept point)

The Glideslope Intercept Altitude (GSIA) is the published minimum and maximum altitude at which the glideslope should be intercepted. Statistically, 98% of glideslopes are intercepted from below at the GSIA — this is the correct and safe technique.

False Glideslopes

The glideslope transmitter produces side lobes at multiples of the primary 3° beam. These false glideslopes will provide erroneous guidance:

The 9° false glideslope is especially dangerous because its CDI commands behave normally — the pilot may not realize they are on a false signal until the descent rate becomes absurdly steep.

Prevention: Always intercept the glideslope from below at the published GSIA. If the glideslope needle is already centered or coming down from above when you have not yet reached the intercept point, you are likely on a false glideslope.

Landing Under IFR — 14 CFR 91.175

No pilot may operate an aircraft below the DA/DH or MDA unless all three conditions are met simultaneously:

1. The aircraft is continuously in a position to land at a normal rate of descent using normal maneuvers
2. The flight visibility is not less than the visibility prescribed for the approach being used
3. At least one of the following visual references is distinctly visible and identifiable:

Precision-Like Approaches (APV)

Approach Procedures with Vertical guidance (APV) are not required to meet ICAO precision approach standards, but they provide both course and glidepath deviation information. Types include:

• Baro-VNAV: Uses barometric altitude for vertical guidance. Temperature-sensitive — cold weather reduces accuracy.
• LDA with glidepath: A localizer-type directional aid with added vertical guidance.
• LNAV/VNAV: GPS lateral with barometric or WAAS vertical guidance. Uses DA (not MDA) for minimums.
• LPV (Localizer Performance with Vertical guidance): WAAS-based approach that provides precision-like guidance. Can have minimums as low as 200 ft DA — comparable to a Category I ILS. Requires WAAS-capable GPS.

APV approaches use Decision Altitude (DA) rather than MDA because vertical guidance is provided. However, they are technically classified separately from precision approaches (ILS/PAR).

Missed Approach Configuration

When decision altitude is reached without adequate visual reference, execute the missed approach immediately. The sequence:

1. Disconnect autopilot — take manual control
2. Mixture, prop, throttle forward — maximum power configuration
3. TO/GA — engage takeoff/go-around mode on the flight director
4. Pitch 7.5° to 10° nose up — establish a positive climb
5. Flaps 10° — reduce drag while maintaining lift
6. Positive rate — gear up — confirm climb before retracting gear
7. 200 ft AGL — flaps up — clean configuration
8. 400 ft AGL — verify missed approach altitude — confirm the published altitude and begin the missed approach routing
9. Notify ATC — "Missed approach" with intentions

Stabilized Approach Criteria

A stabilized approach is one of the most important safety concepts in instrument flying. The approach is considered stabilized when all of the following are met:

1. The aircraft is at the proper airspeed (V_REF or target approach speed)
2. The aircraft is on the correct flight path (localizer and glideslope centered)
3. The aircraft is in the correct landing configuration (gear down, flaps as required)
4. Appropriate power is set for the approach
5. The descent angle and rate are normal (approximately groundspeed x 5 FPM)
6. Only minor corrections are required to maintain the approach path
7. Normal bracketing — CDI deviations within ±5°

If the approach is not stabilized by 1,000 feet AGL in IMC (or 500 feet in VMC), execute a go-around. An unstabilized approach is one of the leading causes of approach-and-landing accidents.

Segment 1 — SID Departure Practice at KTEB

Start cold and dark at Teterboro Airport (KTEB). Load and brief the TEB SID (Standard Instrument Departure).

Departure Exercise

1. Brief the SID: Review the TEB departure for each runway — identify initial heading, top altitude, transition routes, and altitude restrictions
2. Practice departure from every runway to the published top altitude
3. Identify threats for each runway: Terrain, traffic conflicts, noise abatement turns, altitude restrictions before fixes
4. Use flight director through the entire climb — track heading bugs, verify altitude captures, and confirm course sequencing on the G1000

ATC Communications — KTEB Departure

Listen to each audio clip and practice your readback. Focus on extracting the clearance limit, route, altitude, departure frequency, and squawk code (CRAFT).

Segment 2 — Full Procedure LOC Approach at KPRB

Reposition to Paso Robles Municipal Airport (KPRB). Execute the LOC 11 approach as a full procedure.

1. Brief the approach: Identify the IAF (PRB), final approach course, FAF, MDA, missed approach point, and missed approach procedure. State the full briefing aloud.
2. Join the LOC 11 at PRB IAF: Begin the full procedure — course reversal or hold-in-lieu as published
3. Track the localizer inbound: Intercept and maintain the final approach course. Manage descent to MDA using stepdown fixes or dive and drive as appropriate.
4. Execute missed approach: At the MAP without visual reference, execute the full missed approach procedure:
   • "Missed approach" — announce
   • Max power, pitch 7.5-10° nose up
   • Flaps 10, positive rate gear up
   • 200 ft flaps up, 400 ft verify missed altitude
   • Fly the published missed approach routing
   • Contact ATC with intentions

Segment 3 — ILS Precision Approach at KSBP

Reposition for the ILS 11 at San Luis Obispo (KSBP). This is your primary precision approach practice.

1. Brief the ILS 11: Localizer frequency, inbound course, glideslope intercept altitude, DA, missed approach procedure
2. Intercept the glideslope from below at the GSIA: Confirm you are at the published altitude and the glideslope needle is coming down to center — never chase it from above
3. Track GS and LOC using flight director/autopilot:
   • First attempt: Autopilot in APR mode — monitor the system, verify it tracks correctly
   • Second attempt: Hand-fly with flight director — follow the FD bars for pitch and bank
   • Third attempt: Raw data — CDI for localizer, glideslope indicator for vertical, no FD
4. At DA: If visual references are not acquired, immediately execute the missed approach

Focus Points

• Rate of descent: Use groundspeed x 5. At 90 kts GS, target 450 FPM
• Corrections: Small heading changes (2-3°) on localizer. Pitch adjustments in half-bar increments on glideslope
• Stabilized approach: Configured by glideslope intercept — gear down, flaps set, approach speed established
• Scan pattern: Attitude indicator primary, with regular crosschecks of CDI, glideslope, airspeed, and altitude

Key Takeaways

1. DA vs. MDA — know the difference. Decision Altitude (DA) is used for precision and APV approaches — you decide to land or go around at DA. Minimum Descent Altitude (MDA) is for non-precision approaches — you level off and look for the runway. DA requires an immediate decision; MDA allows continued flight at that altitude to the MAP.
2. ILS = localizer + glideslope + markers. The localizer provides lateral guidance (2.5° full-scale), the glideslope provides a 3° descent path, and marker beacons (or GPS fixes) identify positions along the approach. Localizer frequencies are 108.10-111.95 MHz, odd tenths only.
3. False glideslopes exist at 6° and 9°. The 6° false glideslope has reversed CDI commands. The 9° false glideslope has normal-appearing commands but an impossibly steep descent. Always intercept from below at the published GSIA to avoid both.
4. 91.175 requires three conditions to descend below DA. You must be in position to land normally, flight visibility must meet minimums, and at least one of 10 visual references must be distinctly visible. Know all 10 references — this is a checkride favorite.
5. Groundspeed x 5 = required rate of descent. For a standard 3° glideslope: 90 kts GS = 450 FPM, 120 kts GS = 600 FPM. If your descent rate is significantly higher, suspect a false glideslope or configuration problem.
6. Missed approach is a specific sequence. Disconnect AP, max power, TO/GA, pitch 7.5-10°, flaps 10, positive rate gear up, 200 ft flaps up, 400 ft verify missed altitude, notify ATC. Practice this flow until it is automatic.
7. GPS approaches offer multiple minimums. LNAV (lateral only, uses MDA), LNAV/VNAV (lateral + baro vertical, uses DA), LPV (WAAS precision-like, uses DA — can be as low as 200 ft). LPV requires WAAS-capable GPS. The same chart may show all three lines of minimums.

Oral Exam Self-Test

1. Define a precision approach. What two types qualify as precision approaches?
2. What are the three components of an ILS? Describe the function of each.
3. What is the localizer frequency range? How do you distinguish localizer frequencies from VOR frequencies in the same range?
4. What is CDI full-scale deflection on a localizer? How does this compare to a VOR?
5. Explain false glideslopes. At what angles do they occur, and how do the CDI commands differ for each?
6. How do you prevent capturing a false glideslope?
7. What three conditions must be met to descend below DA/DH under 14 CFR 91.175?
8. Name all 10 visual references that satisfy 91.175.
9. What is the 100-foot rule regarding approach lights?
10. What is Decision Altitude (DA) and how does it differ from Minimum Descent Altitude (MDA)?
11. What is the Glideslope Intercept Altitude (GSIA) and why is it important?
12. What does the lightning bolt symbol indicate on an approach chart? The Maltese Cross?
13. Describe the missed approach configuration sequence from DA.
14. What is an LPV approach? What equipment is required? How low can LPV minimums go?
15. What are the stabilized approach criteria? At what altitude should you go around if not stabilized?

Pilot Preparation for Lesson 6

Lesson 6 covers LOC and VOR approaches without vectors and deepens your GPS approach mastery.

Reading

1. Everything Explained: LOC Approach section (review), VOR Approach procedures, GPS Approaches (complete)
2. Instrument Procedures Handbook: Full procedure approaches, procedure turns, hold-in-lieu-of-PT
3. Instrument Flying Handbook: Non-precision approach techniques, timing and descent planning

Key Topics to Preview

• Full procedure approaches without ATC vectors — navigating to the IAF independently
• Procedure turn types: 45/180, 80/260, hold-in-lieu-of-PT
• VOR approach step-down fixes and MDA management
• GPS approach sequencing on the G1000: terminal mode, approach mode, scaling changes
• RAIM requirements and GPS NOTAM checks
• Timing for non-precision approaches — groundspeed-based timing tables

Resources

• Instrument Rating Files — ILS approach plates, GPS approach plates, SID charts for KTEB/KMMU
• Instrument Flying Handbook (FAA-H-8083-15B)
• Instrument Procedures Handbook (FAA-H-8083-16B)