Precision Approach


Gain the skills associated with performing precision approach procedures solely by reference to instruments.


This is the required reading for this lesson. Numbers in [brackets] indicate the starting and ending page in the referenced reading material. Read all the pages and sections referenced.


The notes below highlight the important parts in the referenced material. Reading the notes without having read the actual referenced material is generally not sufficient to pass the written exam!

A precision approach is an instrument approach based on a navigation system which provides both course deviation information and glidepath deviation information.

IFH - Chapter 9

  • The most common precision approaches are
    • Instrument Landing Systems (ILS)
    • Precision Approach Radar (PAR)
    • Ground Based Augmentation System (GBAS) Landing System (GLS)
  • ILS Components
    • VHF Localizer
      • Provides horizontal guidance
      • 108.10 to 111.95 MHz
    • UHF Glideslope Transmitter
      • Provides vertical guidance
      • 329.3 to 335.0 MHz
      • Standard glideslope angle is 3 degrees


    Speed (knots) Angle
    2.5° 2.75°
    90 400 440 475
    110 485 535 585
    130 575 639 690
    150 665 730 795
    160 707 778 849

    Rate of Descent Chart (feet per minute)
  • The localizer course is very narrow, normally 5°. This results in high needle sensitivity.
    • A full-scale deflection shows when the aircraft is 2.5° to either side of the centerline.
    • With no more than one- quarter scale deflection maintained, the aircraft will be aligned with the runway.
  • The glidepath is normally 1.4° thick.
    • At 10 NM from the point of touchdown, this represents a vertical distance of approximately 1,500 feet, narrowing to a few feet at touchdown.
  • The localizer needle indicates, by deflection, whether the aircraft is right or left of the localizer centerline, regardless of the position or heading of the aircraft.
    • Rotating the OBS has no effect on the operation of the localizer needle, although it is useful to rotate the OBS to put the LOC inbound course under the course index.

IFH - Chapter 10

  • Approaches can be flown as
    • A full approach - Pilots conduct their own navigation using the routes and altitudes depicted on the instrument approach chart.
    • Radar vectors - ATC provides guidance in the form of headings and altitudes, which position the aircraft to intercept the final approach
  • Pilots may not operate an aircraft at any airport below the authorized MDA or continue an approach below the authorized DA/DH unless:
    • The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal descent rate using normal maneuvers
    • The flight visibility is not less than that prescribed for the approach procedure being used; and
    • At least one of the following visual references for the intended runway is visible and identifiable to the pilot:
      • Approach light system
      • Threshold
      • Threshold markings
      • Threshold lights
      • Runway end identifier lights (REIL)
      • Visual approach slope indicator (VASI)
      • Touchdown zone or touchdown zone markings
      • Touchdown zone lights
      • Runway or runway markings
      • Runway lights

Tomas Hansson (This email address is being protected from spambots. You need JavaScript enabled to view it.)
Chief Flight Instructor, VATSTAR
DISCLAIMER: all information contained herein is for flight simulation purposes only.
March 2021

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