Precision Approaches: ILS and LPV
Key facts on ILS localizer/glideslope geometry, LPV glidepaths, and stabilized approach technique.
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Questions Covered in This Set
11 cards to master
Localizer full-scale deflection
2.5° each side (about 700 ft wide at threshold) — roughly 4x more sensitive than a VOR's 10° per side.
Glideslope full-scale deflection and typical angle
0.7° above and below a path normally 3.00°; one dot low ≈ 50 ft at the outer marker, ~8 ft at 200 AGL.
Localizer vs. glideslope frequencies
Localizer: VHF 108.10–111.95 MHz (odd tenths with hundredths); glideslope: UHF, automatically paired with the localizer.
What does LPV stand for, and how is vertical guidance produced?
Localizer Performance with Vertical guidance — a WAAS GPS approach whose glidepath is computed from the published Glidepath Angle and TCH in the database, not a radiated beam.
LPV lateral sensitivity progression
±1.0 NM en route, ±0.3 NM in the terminal, then at the FAF it splays to a localizer-like angular scale keyed to the runway threshold.
Is LPV a precision approach?
No — the FAA classes it as APV (approach with vertical guidance) even though DA can be as low as 200 ft; fly it like a precision approach anyway.
What happens if WAAS vertical integrity or database currency is lost?
You're downgraded to LNAV — go around or re-brief to the higher nonprecision minimums.
Descent rate rule of thumb for a 3° path
About 5 × groundspeed in fpm: 90 kt → 450 fpm; 120 kt → 600 fpm (changes with wind).
Control technique once established on the glideslope
Pitch for glideslope, power for airspeed, in small doses: half-bar pitch, 2° heading, 50 RPM changes; trim ruthlessly.
Glideslope false courses
False lobes exist above the true path (a strong one near 9°) with reversed sensing — avoid intercepting the glideslope from above while high and fast.
Bank-angle rule for localizer corrections
Use bank no greater than the degrees you're off course, and never more than about 5° near the runway; hold a wind-correction heading rather than chasing the needle.
