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Runway Surface Conditions: The Global Reporting Format

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Category: Runway Excursion Runway Excursion
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Global Reporting Format

GRF

Introduction

A runway excursion is generally defined as a “veer-off or overrun of the runway surface”, where "veer-off" is associated with departing the side of the runway and "overrun" implies leaving the runway at the end. Both events most often occur during takeoff or landing. One of the main contributing factors to runway excursion involves adverse weather that results in the runway surface being contaminated by snow, ice, slush or water. These contaminants all result in a decrease in runway surface friction which in turn can have a negative impact on an aircraft’s braking, acceleration or controllability.

In the past, there have been numerous ad hoc initiatives developed by individual states, research institutions and both regional and international organisations to develop various means to measure and report runway conditions. On an international basis, these inconsistent measuring and reporting protocols have lead to instances of operator misinterpretation of actual runway condition. This, on occasion, has been a contributing factor in an excursion event.

To help mitigate the risk of excursion due to such misinterpretation, ICAO has developed a harmonised methodology for the assessment and reporting of runway surface conditions. This methodology, known as the Global Reporting Format (GRF), will be globally applicable as of November 2020.

Global Reporting Format

The Global Reporting Format (GRF) provides a means for airport operators to consistently, rapidly and, most critically, correctly, assess runway surface conditions. The format is intended, and is able, to cover conditions found in all climates, from wet surfaces to frozen contaminants such as snow, slush, ice or frost. The GRF is tailored to include the ability to report rapidly changing conditions, such as those that might be found during a winter blizzard or a tropical thunderstorm. The GRF methodology involves three steps:

  • Evaluation of the runway
  • Assignment of a Runway Condition Code to each third of the runway
  • Production of a Runway Condition Report

Runway Evaluation

The runway surface is evaluated by a trained runway assessor who will determine the condition type, the percentage coverage, and if applicable, the depth of the contaminate for each third of the runway. Depth of the contaminate is measured in millimetres (mm) and coverage will not be reported for a given runway third if less than 10% of the surface is affected. The following is an alphabetical listing of all of the possible condition types that can be reported using the Global Reporting Format:

  • COMPACTED SNOW
  • DRY
  • DRY SNOW
  • DRY SNOW ON TOP OF COMPACTED SNOW
  • DRY SNOW ON TOP OF ICE
  • FROST
  • ICE
  • SLUSH
  • STANDING WATER
  • WATER ON TOP OF COMPACTED SNOW
  • WET
  • WET ICE
  • WET SNOW
  • WET SNOW ON TOP OF COMPACTED SNOW
  • WET SNOW ON TOP OF ICE

Runway Condition Code

Using the ICAO standardised Runway Condition Assessment Matrix depicted below, the assessor will assign a Runway Condition Code (RWYCC) for each third of the runway. The code is based on the effect that the runway conditions would have on aircraft braking performance. With this information, the flight crew can derive, from the performance information provided by the aeroplane manufacturer, the required stopping distance for an aircraft on approach under the prevailing conditions. The RWYCC is presented as a numerical value from 0 to 6 with 6 representing a bare, dry runway and 0 a runway that is covered with wet ice or similar. The code is amplified by a description of the contaminate and the containate depth for each third of the runway.

Runway-Condition-Assesment-Matrix.png

Runway Condition Report

The data obtained from the runway evaluation and the assigned Runway Condition Code are used to complete a standard format report known as the Runway Condition Report (RCR). This report will then be forwarded to air traffic services and the aeronautical information services for dissemination to pilots. The Report format consists of two sections, an Aeroplane Performance Calculation section and a Situational Awareness section. Note that not all information will be included on every report. The reportable items are as listed below. Where indicated, (M) refers to a mandatory entry, (C) a conditional item, and (O) an optional item.

  • Aeroplane Performance Calculation section:
    • aerodrome location indicator (M)
    • date and time of assessment (M)
    • runway designation number (M)
    • RWYCC for each runway third (M)
    • per cent coverage contaminant for each runway third (C)
    • depth of loose contaminant for each runway third (C)
    • condition description for each runway third (M)
    • width of runway to which the RWYCCs apply if less than published width (C)

Using the above criteria, the report for runway 24R in Toronto taken on 15 January at 0225z and having 50% coverage of slush with a depth of 6mm in the first third of the runway and wet snow on the remaining two thirds (75% and 100% coverage respectively at a depth of 12mm) might be coded:

CYYZ 01150225 24R 2/3/3 50/75/100 06/12/12 SLUSH/WET SNOW/WET SNOW
  • Situational Awareness section:
    • reduced runway length (O)
    • drifting snow on the runway (O)
    • loose sand on the runway (O)
    • chemical treatment on the runway (O)
    • snowbanks on the runway (O)
    • snowbanks on the taxiway (O)
    • snowbanks adjacent to the runway (O)
    • taxiway conditions (O)
    • apron conditions (O)
    • State-approved, and published use of, measured friction coefficient (O)
    • plain language remarks (O)

The Situational Awareness section for Toronto runway 24R, with a snowbank on the left side of the runway, 30 metres from the centreline, and degraded taxiway and apron conditions, might read as follows

RWY 24R SNOWBANK L30 FM CL. ALL TWY POOR. T1 APRON MEDIUM TO POOR. T3 APRON POOR. CRFI 0.27.

For complete decoding information, refer to ICAO Doc 9981 under Further Reading.

Related Articles

Further Reading

ICAO



[[Category:Veer Off] [[Category:Overrun on Take Off] [[Category:Overrun on Landing] [[Category: Runway Excursion]