SNOWTAM Decoder

• How to use the SNOWTAM decoder?
• What is a SNOWTAM?
• Where does SNOWTAM data come from?
• What is the Global Reporting Format (GRF)?
• Runway Condition Codes (RWYCC)
• How RWYCC codes affect aircraft performance
• SNOWTAM validity
• What is the difference between a SNOWTAM and a FICON?
• How to read a SNOWTAM?
• SNOWTAM example
• SNOWTAM contaminant types
• Using SNOWTAMs for preflight briefing
• Common SNOWTAM interpretation mistakes
• Frequently asked questions about SNOWTAM decoding

How is runway condition data measured?

Runway condition assessment combines visual inspection and friction measurement equipment to determine surface performance. Friction and braking characteristics are measured using devices such as:

• •Continuous Friction Measuring Equipment (CFME) — vehicle-mounted devices that continuously measure friction across the runway length during a test run, producing a friction profile for each runway third
• •Decelerometers — instruments that measure the rate of deceleration of a braking vehicle or aircraft, used to derive a friction coefficient representative of the surface condition
• •Ground-based friction testers — dedicated test vehicles equipped with a measured braking wheel that assess surface friction at standardised speeds and loads

Each runway third (touchdown, mid-runway, rollout) is evaluated independently. The final RWYCC (Runway Condition Code) is assigned using ICAO GRF tables defined in ICAO Doc 9981, based on contaminant type, depth, and observed braking performance.

How is a SNOWTAM generated and distributed?

After the runway inspection is completed, the aerodrome operator submits the runway condition data to the national Aeronautical Information Service (AIS). The AIS encodes the report into the standardised GRF SNOWTAM format and distributes it through the ICAO NOTAM network. Once issued, SNOWTAMs become available within minutes via:

• •National AIS portals — the authoritative official source for each state, updated in near-real time upon issuance
• •Flight planning systems — commercial and operator dispatch systems that aggregate NOTAM data including SNOWTAMs into pre-flight briefing packages
• •Electronic flight bags (EFBs) — pilot-facing applications that retrieve, display, and decode SNOWTAMs alongside other preflight data

What triggers a SNOWTAM inspection?

A SNOWTAM inspection is triggered by any condition change that may affect runway braking performance, including:

• •Onset of precipitation — rain, snow, freezing rain, or any weather event that may deposit or alter surface contamination
• •Completion of runway treatment — snow clearing, sanding, or de-icing operations that change the reported surface condition
• •Observed change in surface contamination — any deterioration or improvement noted by aerodrome personnel or reported by arriving crews
• •Expiry of the required assessment interval — if conditions remain active, reassessment is required within the mandatory interval regardless of whether a change is observed

During active snow or rapidly changing conditions, reassessments may be required as frequently as every 30 minutes. At freezing onset or first contamination risk, a SNOWTAM must be issued before the next aircraft movement.

Each runway is inspected in both directions. SNOWTAMs are reported in landing direction order for each runway designator (e.g., 09L and 27R are reported separately with reversed runway thirds).

Where can pilots access SNOWTAM data?

SNOWTAMs are distributed through the standard ICAO NOTAM system and are accessed via the same channels as other NOTAMs. Primary sources include:

• •FAA NOTAM System (notams.faa.gov) — official source for all US domestic SNOWTAMs and FICON NOTAMs
• •NATS AIS — official AIS portal for the United Kingdom
• •Eurocontrol EAD — European AIS Database covering ICAO EUR/NAT region states
• •National AIS portals — the authoritative source for each ICAO member state, listed in each state’s AIP GEN section
• •Flight planning systems and EFB applications — third-party tools that aggregate NOTAM data including SNOWTAMs, useful for planning but not the authoritative source

Because SNOWTAMs are special series NOTAMs, they appear within standard preflight briefing packages (PIBs) alongside other NOTAMs affecting the aerodrome and route. During winter operations, SNOWTAMs should be specifically checked for:

• •Departure airport — to assess takeoff surface conditions and any contaminated runway performance requirements before engine start
• •Destination airport — to verify landing distance requirements and confirm conditions are within operator minima for the planned arrival
• •All alternate airports — to confirm alternates remain operationally suitable and that RWYCC values do not disqualify them from use

What was the purpose of the GRF?

The GRF was introduced to eliminate inconsistencies in runway condition reporting between states, airports, and operators. Before GRF implementation, runway condition descriptions such as “good,” “medium,” and “poor” were interpreted differently across jurisdictions, leading to inconsistent aircraft performance calculations and operational risk.

The GRF replaces these subjective descriptors with a standard numerical scale (RWYCC 0–6) that maps directly to aircraft manufacturer performance tables.

How are runway conditions reported under the GRF?

Under the GRF, each runway is divided into three equal sections:

• •Touchdown zone — the first third in the landing direction, from the threshold to one third of the runway length
• •Mid-runway section — the middle third, typically the area of peak speed during the landing roll
• •Rollout zone — the final third, where deceleration is most critical and braking performance most operationally significant

Each section is assigned an independent RWYCC code (0–6) based on contaminant type, contaminant depth, surface coverage, and observed braking performance. This allows asymmetric runway conditions to be reported accurately (e.g., RWYCC 5/4/2 across runway thirds).

How does RWYCC connect to aircraft performance?

The RWYCC system is directly linked to aircraft performance data. Operators use RWYCC values to determine:

• •Landing distance requirements — correction factors applied to dry landing distances based on the limiting RWYCC across runway thirds
• •Takeoff performance corrections — adjustments to accelerate-stop distance and takeoff run based on reduced braking effectiveness during a rejected takeoff
• •Braking action assumptions — standardised friction values used in performance calculations, replacing inconsistent pilot-reported descriptors

These values are published in aircraft flight manuals (AFM) and performance calculation tools, creating a standardised link between runway condition reporting and operational decision-making.

What did the GRF replace?

The GRF replaced fragmented national runway condition reporting systems that were not globally consistent. Before GRF implementation:

• •The United States used the RCAM (Runway Condition Assessment Matrix) — a national matrix linking runway surface descriptions to braking action categories, not directly compatible with other states’ systems
• •Other states used descriptive or hybrid systems — applying terms such as “good,” “medium,” and “poor” with varying operational definitions
• •METAR Runway State Groups (RSG) — single-digit contamination codes embedded in METAR reports, removed from ICAO METAR format following GRF implementation

These systems were removed or harmonised under ICAO standardisation to create a single global method of reporting runway conditions.

How do pilot reports affect RWYCC values?

The GRF includes a feedback loop based on pilot braking action reports. If a pilot reports braking performance significantly worse than the published RWYCC:

• •A runway condition reassessment is required — the aerodrome authority must inspect the surface and verify the reported conditions
• •The RWYCC may be downgraded — if the inspection confirms that actual braking is worse than reported, the RWYCC is lowered accordingly
• •A new SNOWTAM may be issued — replacing the previous SNOWTAM with updated RWYCC values reflecting the reassessed conditions

This ensures that runway condition reporting remains aligned with real operational conditions.

What were the legacy runway condition systems before the GRF?

Before 4 November 2021, runway condition reporting used a combination of:

• •Single-digit contamination codes (0–9) — representing contamination type (e.g., 4 = dry snow, 6 = slush, 7 = ice) in a compact coded format
• •Descriptive braking action scales (91–95) — where 91 indicated poor braking and 95 indicated good braking, used in place of the current RWYCC 0–6 scale
• •METAR Runway State Groups (RSG) — a compact code group appended to METAR reports to convey runway contamination, depth, and braking action, now removed from the ICAO METAR format

These formats are no longer part of ICAO GRF and are incompatible with current SNOWTAM decoding systems. Legacy SNOWTAMs can be identified by their lettered field structure (A), B), C) etc.), non-RWYCC contamination coding, and non-standard braking action descriptors.

EASA regulatory variants (GRF SNOWTAM descriptors)

EASA-regulated states use two additional runway surface condition descriptors within SNOWTAM reporting that refine ICAO GRF terminology for specific winter operation scenarios.

These descriptors are used within the standard GRF framework and appear in SNOWTAMs issued by EASA member states (including most European countries).

EASA-specific runway condition descriptors

Operational interpretation (RWYCC application)

RWYCC values are reported independently for each runway third:

• •Touchdown zone
• •Mid-runway
• •Rollout zone

The most limiting RWYCC value determines operational performance planning:

• •For landing: the limiting third is typically the rollout zone
• •For takeoff: the limiting third is the takeoff roll direction segment

Operators must apply RWYCC-based performance corrections using the aircraft’s AFM (Aircraft Flight Manual) or approved performance data. The SNOWTAM does not replace aircraft-specific landing or takeoff calculations.

Key point

EASA-only descriptors refine ICAO GRF reporting by providing additional friction context for winter runway operations, but RWYCC (0–6) remains the controlling performance input for all aircraft calculations.

Landing performance and RWYCC

For landing, RWYCC determines the landing distance correction factor applied to the dry runway landing distance from the AFM.

The most limiting RWYCC value across the runway thirds governs landing performance, because it represents the worst braking condition encountered during rollout.

Typical landing distance increase vs dry runway

The table below shows indicative landing distance correction factors for each RWYCC value compared to a dry runway baseline.

These values are indicative ranges. Exact corrections must be taken from the aircraft-specific AFM or approved performance data.

Takeoff performance and RWYCC

For takeoff, RWYCC affects both:

• •Takeoff run (acceleration performance)
• •Accelerate-stop distance (rejected takeoff stopping performance)

The governing RWYCC for takeoff performance is the lowest code along the usable takeoff roll and rejected takeoff path, since braking performance is required if the takeoff is aborted.

Low RWYCC values significantly increase accelerate-stop distance. In some configurations, especially in turboprops and transport-category jets, RWYCC 2 or lower may cause the required accelerate-stop distance to exceed available runway length at certain weights, making the takeoff unsafe or infeasible without weight reduction.

Slush and wet snow performance effects

Slush and wet snow introduce additional aerodynamic and rolling resistance drag during the takeoff roll that is separate from RWYCC-based braking corrections.

This results in:

• •reduced acceleration
• •longer takeoff roll
• •increased rotation distance requirements

ICAO and manufacturer performance data apply slush corrections based on depth increments (commonly 6 mm intervals). Slush depths greater than approximately 15 mm are associated with severe performance penalties and may prevent safe takeoff within available runway length.

When slush is reported, both of the following must be applied:

• •RWYCC-based braking correction
• •contaminant-specific drag correction from AFM data

Using RWYCC alone will underestimate total performance impact in slush conditions.

Operator minima and limitations

Operators often define minimum RWYCC thresholds in their operations manuals.

Typical constraints include:

• •RWYCC 1: often minimum allowed for commercial jet operations
• •RWYCC 0: generally considered nil braking and prohibited for operations

RWYCC 0 indicates effectively no usable braking action and is operationally treated as a non-operable surface by most operators.

All contaminated runway decisions must comply with operator-specific performance minima in addition to RWYCC interpretation.

Validity period (B-field and C-field)

A SNOWTAM is valid from the time of the runway surface observation (B-field) until the expiry time (C-field).

The maximum validity period is 8 hours from the B-field time. If no C-field is provided, the SNOWTAM is assumed to expire 8 hours after the B-field timestamp.

Operators must verify that the SNOWTAM validity window covers the planned operation time. If the SNOWTAM expires before the estimated time of arrival or departure, it is no longer operationally valid and an updated SNOWTAM must be obtained.

Supersession rule (latest SNOWTAM applies)

A newly issued SNOWTAM for the same aerodrome immediately replaces all previous SNOWTAMs, regardless of remaining validity time.

When multiple SNOWTAMs exist for the same airport, only the most recently issued SNOWTAM is operationally valid. The issuance time must always be checked to confirm currency.

Cancellation and NIL condition reports

A SNOWTAM may be cancelled when runway conditions return to dry and no contamination exists.

In some cases, a nil-condition SNOWTAM is issued, indicating that the runway surface is reported as dry and no contamination is present.

The absence of a SNOWTAM does not automatically confirm dry conditions. It may also indicate that no recent inspection has been performed or that the report has not yet been distributed.

During active precipitation or winter operations, SNOWTAM currency must always be verified before flight.

Key operational rule

For operational use, only two conditions are valid:

• •The SNOWTAM is within its 8-hour validity window
• •It is the most recently issued SNOWTAM for that aerodrome

If either condition is not met, the SNOWTAM must not be used for performance or operational decision-making.

1. SWXX header

The SWXX header identifies the SNOWTAM and provides tracking and observation time information.

Format: SWXXnnnn CCCC DDHHmm

• •SWXX = SNOWTAM identifier and region code
• •nnnn = serial number
• •CCCC = ICAO aerodrome code
• •DDHHmm = UTC observation time

2. NOTAM wrapper (if present)

Many SNOWTAMs are distributed inside a standard NOTAM container.

This includes:

• •NOTAM number (e.g. B0045/23 NOTAMN)
• •Q-line qualifiers
• •Lettered fields (A, B, C)

The NOTAM wrapper is for distribution only.

The runway condition data is contained in the SNOWTAM body (E-line equivalent).

3. A-line — Aerodrome

The A-line identifies the aerodrome ICAO code.

All runway condition data applies only to this aerodrome.

4. B-line — Valid from (observation time)

The B-line defines when the runway was inspected and when the SNOWTAM becomes valid.

Format: YYMMDDHHmm (UTC)

This is the start of operational validity, not the issue time.

5. C-line — Valid until (expiry time)

The C-line defines when the SNOWTAM expires.

Format: YYMMDDHHmm (UTC)

• •Maximum validity: 8 hours from B-line
• •Always verify that C-line covers your planned operation window
• •If your arrival is after C-line → SNOWTAM is not valid

6. Runway designator

Each runway block starts with the runway identifier (e.g. RWY 09L).

All subsequent fields apply only to that runway.

Data is always reported in landing direction order:

• •First third = touchdown zone
• •Second third = mid-runway
• •Third = rollout zone

7. RWYCC — Runway Condition Codes (per third)

RWYCC is reported as: RWYCC X/X/X

Each value represents:

• •Touchdown zone
• •Mid-runway
• •Rollout zone

Scale:

• •6 = dry runway
• •0 = nil braking

The lowest RWYCC typically governs landing performance and braking assessment.

8. Contamination coverage

Coverage describes how much of each runway third is contaminated.

Values:

• •NR = <10% or not reported
• •25 = 10–25%
• •50 = 26–50%
• •75 = 51–75%
• •100 = 76–100%

High coverage (75–100) combined with low RWYCC indicates significant performance impact.

9. Contaminant depth (Item F)

Depth is reported in millimetres for specific contaminants only:

• •Standing water (≥4 mm)
• •Slush (≥3 mm)
• •Wet snow (≥3 mm)
• •Dry snow (≥3 mm)

For other contaminants (ice, frost, compacted snow):
→ depth is not applicable (NR)

Important rule:

• •NR does NOT always mean no contamination
• •It may indicate “not measurable”

Slush > 15 mm is operationally significant due to drag effects.

10. Contaminant type

Defines the surface material for each runway third.

Common values:

• •DRY SNOW
• •WET SNOW
• •COMPACTED SNOW
• •SLUSH
• •ICE
• •WET ICE
• •FROST

Each runway third is reported separately.

This field provides context for RWYCC interpretation and performance planning.

11. Cleared runway width (Item H)

Reports usable runway width in metres when reduced.

• •Only shown if less than published width
• •If missing → full runway width applies

Reduced width affects:

• •crosswind handling
• •rollout safety margins
• •directional control

12. Snowbank information

Reports snow accumulation near runway surfaces.

Codes:

• •NR = not reported
• •NO = no snowbanks
• •ON = on runway
• •BRD = runway edge
• •LFT / RGT = left or right side

Snowbanks reduce usable surface margin and may affect safety clearance.

Section 2 — Situational awareness (Items I–T)

These items appear only when relevant and always follow runway data.

13. Reduced runway length (Item I)

Reports reduced available runway distance.

Always verify against declared distances (TORA/TODA/ASDA/LDA).

14. Drifting snow (Item J)

Reports wind-driven snow affecting surfaces.

Applies to:

• •full movement area, or
• •specific runway if stated

15. Loose sand (Item K)

Indicates runway friction enhancement treatment.

16. Chemical treatment (Item L)

Indicates anti-icing or de-icing application.

May influence RWYCC stability.

17. Snowbanks on runway (Item M)

Reports snowbanks encroaching on runway surface.

Includes:

• •side (L / R / LR)
• •distance from centreline

18. Snowbanks on taxiway (Item N)

Reports snow accumulation affecting taxiways.

19. Snowbanks adjacent to runway (Item O)

Reports snowbanks near runway obstacle clearance areas.

May affect:

• •wingspan clearance
• •engine clearance
• •runway edge safety margin

20. Taxiway conditions (Item P)

Reports poor taxiway surface conditions.

21. Apron conditions (Item R)

Reports apron surface condition degradation.

Affects:

• •pushback
• •de-icing
• •ground handling

22. Friction measurement (Item S)

Optional measured friction values per runway third.

Important:

• •Supplementary only
• •RWYCC remains primary performance reference
• •Not used in EASA systems (NR shown instead)

23. Plain language remarks (Item T)

Final section containing operational notes not covered elsewhere.

Examples:

• •ongoing treatment
• •partial closures
• •reinspection notes
• •operational warnings

Always read fully — this is often the most operationally important free-text section.

SWXX identifies this as a SNOWTAM. Serial number 0123 — used to reference and supersede this report. EGLL = London Heathrow Airport. 221430 = observed on the 22nd of the month at 1430 UTC. SNOWTAM serial numbers reset to 0001 at 0000 UTC on 1 January each year.

This SNOWTAM is distributed inside a standard NOTAM container (B0045/23) for distribution through the AFTN/AIS network. NOTAMN indicates a new notice — no previous SNOWTAM is superseded by this wrapper reference.

A) EGLL — this SNOWTAM applies to London Heathrow Airport. B) 2301221430 — valid from 22 January 2023 at 1430 UTC (the runway inspection time). C) 2301222230 — valid until 2230 UTC on the same day, an 8-hour validity window. Any planned arrival between 1430 and 2230 UTC on 22 January 2023 must use this SNOWTAM for performance assessment.

All data below applies to Runway 09L in the landing direction from the 09L threshold. The first third is the touchdown zone at the 09L threshold, the second third is the mid-runway, and the third is the rollout zone at the 27R end. A pilot landing on 27R must reverse the third order.

The governing code for landing distance correction is RWYCC 1 — the lowest code, present in the rollout zone where deceleration is most critical. This is a poor braking condition (ice) and requires a large landing distance correction factor from the AFM.

100% coverage across all three thirds. The entire runway is covered by contamination — no dry patches are present. Full RWYCC corrections apply across the complete runway length.

Depth increases from 15 mm in the touchdown zone to 25 mm in the rollout zone. All depths exceed the critical 15 mm slush threshold for takeoff performance. The increasing depth toward the rollout end — where aircraft speed is lowest and deceleration is most critical — compounds the RWYCC 1 ice condition. Note that the contaminant type is compacted snow and ice, not slush, so drag penalties are less severe than slush at the same depth.

Touchdown zone and mid-runway: compacted snow (RWYCC 3 and 2 respectively — compacted snow has been compressed further toward the rollout end, or is in the process of freezing). Rollout zone: ice — the compacted snow has frozen to an ice surface at the 27R end, consistent with the RWYCC 1 condition. The transition from compacted snow to ice explains the deteriorating RWYCC codes toward the rollout zone.

75% of the declared runway width has been cleared at the touchdown zone and mid-runway thirds. The rollout zone has been cleared to 100%. The reduced cleared width at the first two thirds means that only three quarters of the declared width is available for landing. This must be considered in crosswind assessments and landing technique.

Snowbanks of 10 cm height at the touchdown zone and mid-runway thirds, adjacent to the cleared surface. Not reported (NR) at the rollout zone. The 10 cm snowbanks at the first two thirds reduce the effective operating width and present a hazard if an aircraft departs the cleared surface area.

Anti-icing treatment is in progress at the time of the inspection. This is operationally significant — conditions may improve after treatment is completed, and a new SNOWTAM may be issued before the current 8-hour validity expires. Monitor for an updated SNOWTAM, particularly if the expected arrival time is several hours after this report.

Operational summary: This is a challenging winter runway. The governing landing distance code is RWYCC 1 (poor — ice in rollout zone), requiring a large landing distance correction from the AFM. 75% cleared width at the touchdown zone and mid-runway reduces effective runway width. Anti-icing is in progress — a newer SNOWTAM may be available before your arrival showing improved conditions. Verify available landing distance, confirm compliance with operator RWYCC minima, and check for a superseding SNOWTAM before arrival.

1. Verify SNOWTAM validity against your arrival time

A SNOWTAM is only operationally valid if your planned operation occurs within its B-field and C-field time window.

• •B-field = observation time (start of validity)
• •C-field = expiry time (end of validity)

If your planned arrival or departure occurs after the C-field time, the SNOWTAM is not valid for operational use. In rapidly changing conditions, a newer SNOWTAM may replace the one in your briefing, so always confirm the most recent issue before departure.

2. Use the most limiting RWYCC for performance planning

RWYCC must be evaluated per runway third (touchdown, mid, rollout), but performance planning uses the most limiting value.

• •The lowest RWYCC governs landing distance calculation
• •The rollout zone is often the critical segment for landing safety
• •This value determines the required AFM landing distance correction

A single low RWYCC (e.g. ice in rollout zone) can override otherwise acceptable runway conditions.

3. Evaluate cleared runway width

Cleared width defines the usable runway surface when it is less than published width.

• •If Item H is absent → full runway width applies
• •If reduced → only the cleared portion is usable

Operational impact includes:

• •reduced lateral margin for landing and rollout
• •crosswind limitation changes
• •increased risk of runway excursion

Cleared width must be considered alongside RWYCC, not separately.

4. Assess slush depth for takeoff performance

Slush creates additional drag that is not fully represented by RWYCC alone.

Key thresholds:

• •≥3 mm = reportable slush
• •15 mm = significant performance degradation

Slush affects:

• •acceleration during takeoff roll
• •required takeoff distance
• •rejected takeoff stopping distance

Always apply AFM slush-specific corrections when slush is present.

5. Apply operator RWYCC minima

Each operator defines minimum acceptable RWYCC values for operations.

Typical limits:

• •RWYCC 1 = minimum for many jet operations
• •RWYCC 0 = operationally prohibitive for most operators

Regulatory or company minima always override general guidance. If RWYCC is below operator limits, the runway is not operationally usable regardless of other factors.

6. Read SNOWTAM remarks in full

The remarks field contains unstructured operational information not included in coded fields.

Common content includes:

• •runway treatment status (de-icing, sanding, anti-icing)
• •ongoing maintenance activity
• •partial closures or restrictions
• •pending condition updates

Remarks can modify or clarify RWYCC interpretation and must always be reviewed.

7. Check SNOWTAMs for all alternate airports

Alternates must meet the same performance standards as the destination.

A SNOWTAM may render an alternate unsuitable if:

• •RWYCC is below operator minima
• •runway width is reduced below aircraft requirements
• •performance limits cannot be met

Alternate SNOWTAMs must be current at the time of dispatch, not just at initial planning.

8. Verify ETOPS en-route alternate suitability

For ETOPS operations, SNOWTAMs at en-route alternates directly affect dispatch validity.

An alternate becomes unsuitable if:

• •runway contamination exceeds aircraft performance capability
• •RWYCC requires landing distance greater than available runway
• •conditions invalidate safe diversion assumptions

ETOPS planning must assume SNOWTAM validity may change during flight, so time-based validity at diversion time is critical.

9. Obtain the most recent SNOWTAM before departure

SNOWTAMs can change rapidly during active precipitation or winter operations.

A briefing obtained during planning may be outdated by departure time.

Best practice:

• •always perform a final SNOWTAM check immediately before engine start or pushback
• •treat preflight briefing and departure briefing as separate validation steps
• •prioritize the latest issuance time over earlier planning data

1. Using an expired or superseded SNOWTAM

A SNOWTAM becomes invalid when it is outside its B-field to C-field validity window or when it is replaced by a newer SNOWTAM for the same aerodrome.

Key failure modes:

• •Using a SNOWTAM after the C-field expiry time
• •Using an older SNOWTAM when a newer one has been issued
• •Assuming multiple SNOWTAMs for the same airport are all valid

A superseding SNOWTAM immediately replaces all previous versions, regardless of remaining validity time.

2. Applying RWYCC data to the wrong runway direction

RWYCC values are reported in landing direction order for a specific runway designator.

This creates a common error when using the reciprocal runway:

• •RWY 09L data is not directly usable for RWY 27R
• •The runway thirds reverse when the landing direction changes

Misinterpreting runway direction leads to incorrect assignment of touchdown, mid, and rollout conditions.

3. Using average RWYCC instead of the limiting value

RWYCC values vary across the three runway thirds and must not be averaged for performance planning.

Example: RWYCC 5/3/1

• •5 = touchdown zone
• •3 = mid-runway
• •1 = rollout zone (critical)

Using an average overestimates runway performance capability and may result in unsafe landing distance calculations.

4. Ignoring slush depth in takeoff calculations

Slush introduces aerodynamic and mechanical drag that is not fully represented by RWYCC values alone.

Key characteristics:

• •RWYCC reflects friction, not drag
• •Slush depth directly affects acceleration and takeoff distance
• •Depth becomes critical above 15 mm

A runway with identical RWYCC values may produce significantly different takeoff performance depending on slush depth.

• •RWYCC-based performance correction
• •AFM slush-depth takeoff corrections

RWYCC alone is not sufficient for slush conditions.

5. Ignoring the remarks field

The remarks field contains operational information that is not encoded in structured GRF fields.

Common critical information includes:

• •runway treatment activity (sanding, de-icing, anti-icing)
• •ongoing or incomplete surface operations
• •temporary restrictions or partial closures
• •uncertainty or pending condition updates

These factors may change runway performance conditions without immediately changing RWYCC values.