Runway Contamination and GRF

Why braking is just the beginning

If there's one winter challenge that keeps pilots, dispatchers and airport ops awake at night, it’s this: contaminated runways. Operations on contaminated runways means reduced friction, possibly associated with reduced visibility, increased stopping distances and the potential for a quick reduction in safety margins in case of errors or omissions.

Contaminated Runway Operations requires a good understanding of aircraft systems (such as autobrakes, use of reversers, anti-skid) and the effect of the contaminant on aircraft performance. That’s where the Global Reporting Format (GRF) comes in.

Let’s break it down.

Understanding the Global Reporting Format (GRF)

Introduced in November 2021, the GRF is now the ICAO standard for assessing and reporting runway surface conditions in winter and is designed to:

• Provide uniformity across the world’s airports.

• Improve pilot decision-making.

• Reduce misinterpretation of runway conditions.

The core concept? The Runway Condition Assessment Matrix (RCAM) is used to assess and report runway surface conditions, assigning Runway Condition Codes (RWYCCs) from 0 to 6 based on contaminant type and depth. This matrix helps pilots and operators determine the actual braking performance of an aircraft on contaminated runways, using data like rain, snow, ice, or slush, to enhance safety during take-offs and landings.

🔢 The Runway Condition Code (RWYCC)

Each third of the runway (i.e. TDZ, mid, end) is assigned a numerical code based on the observed surface conditions from 6 (dry) to 0 (nil braking). 

The RWYCC essentially represents the slipperiness of a specific third of a runway and provides a standardized “shorthand” for reporting this information. A RWYCC of 0 corresponds to an extremely slippery runway and 6 corresponds to a dry runway. RWYCCs serve to enhance all pilots’ situational awareness of where the slipperiest runway conditions and contaminants are located on a runway, and they can be used by pilots to make a time of arrival landing performance assessment.

The RWYCC usually aligns with the type/depth of contaminant as displayed in the below illustrated Runway Condition Assessment Matrix (RCAM), however, the GRF methodology requires the runway assessment to take into account local measurements, observations and expertise in order to provide the most accurate information to the flight crew. Therefore, the RWYCC can be downgraded (and upgraded under certain criteria) when compared to the normal type/depth allocation. The lowest RWYCC is always used as reference for performance calculations, regardless of the runway third from which it is recorded. 

For example, a runway where the first third has slush, the middle third compacted snow and the final third wet ice, the RWYCC would be promulgated as “3/2/1”.

Airports’ Reports

Airports’ reports will include the following elements:

• The RWYCC for each third of the runway.

• Type, depth and coverage of the contaminant for each third of the runway.

• Temperature.

✈️ What Pilots Receive (and Must Act On)

Via the Runway Condition Report (RCR), pilots get:

• RWYCC (6-0).

• Contaminant type, coverage, and depth.

• Braking action reports (if available).

• Time of the last assessment.

Before take-off or landing, flight crews must:

• Appropriately use the RWYCC and/or contaminant type/ depth to calculate applicable performance data. Be aware of how to use the GRF to calculate landing dispatch, in flight landing and take-off performance calculations.

• Accurately review and discuss the impact that increased required distances have on used flap settings, autobrake settings, reverse thrust use and V speeds.

• Be aware of crosswind limitations, which are affected by the RWYCC.

Risk Areas in Contaminated Runway Ops

❄️ Landing Distances

What may feel like a safe touchdown and adequate braking action in the initial part of the runway may rapidly change in the next third. Remain vigilant until safely parked on stand as a false sense of security in combination with varying runway condition states can quickly escalate to runway and/or taxiway excursions.

🌀 Crosswind Limits

Most aircraft have specific crosswind limits tied to RWYCCs. A Code 2 surface may drop the allowable crosswind by over 50%.

🔁 Runway Thirds Can Differ

You might land on a "3", then roll through a "1", plan accordingly.

⚠️ Surface Condition Changes Fast

Snowfalls vary in intensity. GRF gives a snapshot, but runway conditions can degrade rapidly. Keep ATC updated if you encounter worse than reported conditions.

People & Procedures: the Human Side of Snow

For Flight Crews:

• Know how to use the GRF in calculating aircraft performance for take-off and (dispatch) landing performance.

• Dedicate appropriate time to discuss current and potentially changing meteorological conditions and runway states using the RCR, NOTAMs, METARs and TAFs.

• Take time to discuss the threats associated with contaminated runway operations during the arrival/ departure briefing. Review the importance of using reverse thrust, optimum use of autobrake settings, effectiveness of anti-skid at low speeds and recovery actions for when things do not go to plan.

• If anything feels off, go around - don’t risk it.

For Ground Ops & ATC:

• Ensure snow clearance priorities match operational flow.

• Communicate clearly using standard GRF phraseology.

• Don’t delay assessments during changing weather.

✅ Example GRF Report Breakdown

📄 Runway 08/26

• RWYCC: 3/2/1.

• Contaminant: Wet snow (25%), compacted snow (50%), ice (25%).

• Depth: 3mm/6mm/patchy.

• Temp: -4°C.

• Last updated: 08:45 UTC

Your decisions:

• Depending on the type of performance calculation use RWYCC 2 and/or the type and depth of contaminant. 

• Review current and forecast weather conditions (is the depth likely to increase?).

• Review the likelihood for any arrival/ departure delays,

• Be ready for degraded braking on rollout.

• Ensure selection of a suitable take-off and/or destination alternate

Winter Runway Ops - Safety Summary

🧠 Mindset

Never assume a runway is "okay" just because it's open. Think dynamically: crew should anticipate realistic degradation or aggravating factors that could affect takeoff/ landing operations. Determining the threshold at which a safe landing can still be performed is a way to manage uncertainty and remove a potential element of surprise should conditions evolve before landing. 

For example, if it is snowing and the latest airport report states RWYCC – 5 (equivalent to less than 3 mm (⅛ inch) of snow), crew should consider if the contamination may exceed the critical depth of 3 mm (⅛ inch) by landing time as this will reduce the RWYCC. An assessment can then be made to determine if the landing will be safe if the RWYCC is reduced to 3 due to 4 mm of snow on the ground.

👥 People

Train for GRF interpretation. Not only pilots, but dispatchers, ATC and safety teams also need a shared understanding of the codes and what they mean.

⚙️ Equipment

Braking action depends on tyres, spoilers, autobrake settings and reverse thrust. Review suitability of operating to/from contaminated runways with any such declared inoperative item.

📋 Compliance

Be diligent in the use of operating procedures and don’t over rely on previous experiences. Conditions may change rapidly and minor errors/ lapses can rapidly lead to significant safety events. 

⚠️ Risks

• Runway excursions during landing rollout due to the perception that the aircraft brakes satisfactory and subsequent cancellation of REV MAX and autobrake (before entering a section of reduced braking action).

• Rejected take-offs on slippery surfaces.

• Overrun or sideload due to crosswind misjudgement.

• Taxiway excursions due to excessive speeds on rapid exit taxiways that are not cleared to the same extent as the runway (in combination with anti-skid possibly not being active at low speeds).

📚 Learning

After-action reports from winter events regularly show:

• Inadequate GRF interpretation.

• Miss selections based resulting from previous experiences (for example selecting REV IDLE instead of REV MAX).

• Missed crosswind/RWYCC interaction.

Occurrence Example: “We Landed on a 3 But Rolled Through a 1”

A Safewings A321 landed on Runway 26 during light snow with a reported RWYCC of 3/3/3. During rollout, braking felt weaker than expected and thrust reversers had to be deployed at full. A post-flight review showed that a late snow burst hit the last third of the runway and updated runway conditions were only received after the aircraft had passed the runway midpoint.

Findings:

• The crew did not review the latest RCR before final approach.

• The runway condition changed within 10 minutes.

• The braking report was not passed by ATC in time.

Lessons:

• Always request the most recent RCR, especially in changeable conditions. Calculating a limiting RWYCC prior to starting the approach allows for a prompt review of landing performance

• ATC and flight crew communication protocols need reinforcement during snow periods.

• Ops now require a final pre-landing RWYCC reconfirmation if the last update is >15 mins old.

Final Word

Snow-covered runways are part of winter aviation. Understanding the GRF, preparing your team and making timely, informed decisions are how we stay one step ahead of the cold.

GRF isn’t paperwork, it’s your grip on reality.

Historic References

3 September (Update to EASA SIB) - EASA SIB Published.