Required Visual Reference: The 10 Legal Cues & Landing Minima
Continuing descent below Decision Altitude (DA) or Minimum Descent Altitude (MDA) is prohibited unless the required visual reference is established and maintained. Here is the operational breakdown of all 10 statutory visual cues, the advisory nature of published landing visibility, and the missed approach boundary.
What is the "Required Visual Reference"?
In respect of an aircraft on an approach to a runway, required visual reference means:
"That section of the approach area of the runway or those visual aids that, when viewed by the pilot of the aircraft, enables the pilot to make an assessment of the aircraft position and the rate of change of position relative to the nominal flight path."
Notice the two vital prongs of this definition: you must not only see an approved ground reference, but it must be distinct enough to judge where you are and where you are going relative to the runway glide path and centreline.
DA vs. MDA: How the Decision Differs
Decision Altitude (Precision / APV)
An altitude specified on a precision approach (ILS, PAR) or an approach with vertical guidance (LPV, LNAV/VNAV) referenced to mean sea level.
Minimum Descent Altitude (Non-Precision)
A specified altitude referenced to sea level for non-precision approaches (LOC, VOR, NDB, LNAV) below which descent must not be made until visual reference is established.
The 10 Approved Visual References
At least one of these must be distinctly visible and identifiable to continue descent below DA/MDA:
Runway Visual Environment & Approach Aids
The Runway or Runway Markings
The physical asphalt or concrete surface, painted runway centerline stripes, or runway designation numerals.
Runway Threshold or Threshold Markings
The beginning of that portion of the runway usable for landing, including threshold bar, piano keys, or displaced threshold arrows.
Touchdown Zone (TDZ) or TDZ Markings
The first 3,000 feet (or first third of runway, whichever is less). Marked by symmetrical rectangular bar pairs along the centerline.
The Approach Lights
High or medium intensity approach systems (e.g., ODALS, SSALR, ALSF-2, MALS). Provides immediate roll guidance and centerline lineup.
Approach Slope Indicator System
PAPI (Precision Approach Path Indicator) or VASIS light bars providing red and white vertical glidepath alignment.
Runway Identification Lights (RILS)
Unidirectional flashing strobes positioned on each side of the runway threshold to provide rapid identification in poor visibility.
Threshold and Runway End Lights
Green threshold lights marking arrival end and red lights marking the departure rollout end of the usable runway.
Touchdown Zone Lights (TDZL)
Two rows of transverse white light bars flush in the pavement extending into the first 3,000 feet of the landing runway.
Parallel Runway Edge Lights
White elevated or flush runway edge lights outlining the lateral physical perimeter of the landing surface.
Runway Centreline Lights
Flush lights along the exact physical runway axis (white transitioning to alternating red/white for the last 3,000 ft, then all red for the last 1,000 ft).
Why Published Landing Visibilities are "Advisory"
Look at the minima box on an instrument approach chart: you will see an advisory visibility printed next to the DA/MDA (for instance, 1/2 SM or RVR 26).
Published landing visibilities associated with all instrument approach procedures are advisory. They are not limiting for the touchdown itself. Their purpose is twofold:
• Probability Indicator: They indicate the meteorological visibility that, if prevailing, should result in the required visual reference being established and maintained to a landing.
• Pilot Judgement Metric: Pilots use the advisory value to judge the likelihood of a successful approach compared against available weather reports.
While landing visibility is advisory for touchdown at the runway, the Approach Ban legally restricts aircraft from continuing past the Final Approach Fix (FAF) inbound. If reported RVR or ground visibility is below the applicable approach ban limit when crossing the FAF, the approach cannot be continued.
Missed Approaches Initiated Beyond the MAP
When the required visual reference is not established or maintained, a missed approach must be initiated. A critical safety boundary applies to non-precision procedures:
On non-precision approaches, the protected obstacle clearance surface for missed approach procedures is designed assuming the climb begins at or before the Missed Approach Point (MAP). Continuing past the MAP at MDA hoping to spot the runway before going around places the aircraft into unassessed obstacle airspace.
Landing Minima & Visual Reference Quiz
Ace Your INRAT & ATPL Written Examinations
Approach ban rules, landing minima definitions, and visual reference criteria form the bedrock of Transport Canada flight examinations. PilotD'Mello provides structured ground school courses to ensure operational mastery.
