Non Precision Approach


Gain the skills associated with performing non 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 non-precision approach is an instrument approach based on a navigation system which provides course deviation information, but no glidepath deviation information.

IFH - Chapter 9

  • The most common non-precision approaches are
    • VOR, VORTAC, VOR/DME - VHF Omidirectional Range
    • NDB - Non-directional Beacon
    • GPS/RNAV - Requires Receiver Autonomous Integrity Monitoring (RAIM)
    • LOC - Localizer
    • LDA - Localizer type Directional Aid
  • Marker Beacons
    • Outer - Localizer Front course, 4-7 miles from airport
      • Indicates a position at which an aircraft, at the appropriate altitude on the localizer course, will intercept the glidepath
    • Middle - Centerline of localizer, 3,500 feet from landing threshold
    • Inner - Located on the front course between the MM and the landing threshold
      • Indicates the point at which an aircraft is at the decision height on the glidepath during a Category II ILS approach

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

AIM - Para. 5-4-5

  • The navigation equipment required to join and fly an instrument approach procedure is indicated by the title of the procedure and notes on the chart
  • Approach minimums are based on the local altimeter setting for that airport, unless annotated otherwise
  • RNP units always include Vertical Navigation (VNAV) capabilities. For GPS units, some do, and some do not. Those that do are able to fly approaches with LPV -- Localizer Performance with Vertical Guidance; flying a GPS approach without vertical guidance is termed LP -- Localizer Performance without Vertical Guidance, or sometimes simply LNAV -- Lateral Navigation. Most GPS Approach plates list separate minimums depending on which of these modes you're employing.
  • Many airports have both GPS and RNP approaches to the same runway. These will usually be designated RNAV (GPS) Y and RNAV (RNP) Z approaches. The flightpaths for the two approaches are not the same, so when requesting and/or accepting an RNAV approach assignment from ATC, it is important to be clear about which one is being assigned, and whether you are able to accept it.
  • Unlike other approach types, ATC will typically not offer vectors onto course; they will simply clear you direct to the starting point for the approach and immediately also for the approach itself.

AIM - Para. 5-4-7

  • Aircraft approach category is based on VREF or 1.3 VS0 if VREF is not specified.
    • Category A: Speed less than 91 knots
    • Category B: Speed 91 knots or more but less than 121 knots
    • Category C: Speed 121 knots or more but less than 141 knots
    • Category D: Speed 141 knots or more but less than 166 knots
    • Category E: Speed 166 knots or more
  • When flying an RNP approach, or a GPS approach with LPV, the unit will provide vertical guidance to help the pilot find the proper glidepath for the final approach; and while it is not considered a precision approach, it's close, with minimums being nearly what you would see on an ILS. Most of the time there will be two sets of minimums, and the different numbers (0.15 DA or 0.30 DA) refer to how precisely the unit is capable of keeping its position calculation.

AIM - Para. 5-4-20

RVR Visibility (statute miles)
1600 1/4
2400 1/2
3200 5/8
4000 3/4
4500 7/8
5000 1
6000 1 1/4
  • Approach minimums are published for different aircraft categories and consist of a minimum altitude (DA, DH, MDA) and required visibility.
  • When a fix is incorporated in a non-precision final segment, two sets of minimums may be published: one for the pilot that is able to identify the fix, and a second for the pilot that cannot.
  • Two sets of minimums may also be published when a second altimeter source is used in the procedure.

Sim Pilot Notes

These notes highlight the differences between simulator and real-world flying. These differences are most often due to simulator limitations or specific VATSIM rules.

  • On VATSIM you can always assume that RNAV equipment is certified to highest available, as it is not enforced by anyone.

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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