This guide provides essential information and procedures for conducting safe and efficient flight operations during winter conditions for Boeing 737-800 and 737 MAX series aircraft. It is crucial to understand that this document serves as a supplementary resource and does not replace the information contained in the official Boeing Flight Crew Operations Manuals (FCOM), Flight Crew Training Manuals (FCTM), or airline-specific operations manuals. In case of any discrepancies, the official publications take precedence.
Winter operations present unique challenges due to the presence of ice, snow, slush, and freezing temperatures. This guide aims to enhance flight crew awareness and provide practical guidance on:
If in doubt, apply de-icing procedures — safety takes precedence.
Understanding ice conditions and associated risks.
Performing thorough pre-flight inspections in winter environments, with a focus on critical areas.
Executing proper de-icing and anti-icing procedures, including fluid types and application techniques.
Recognizing and mitigating the effects of contamination on aircraft performance, emphasizing the importance of clean surfaces.
Understanding holdover times and making informed decisions based on current weather conditions and fluid type.
Adherence to these guidelines, in conjunction with official documentation and sound judgment, is paramount for maintaining the highest levels of safety during winter operations. This guide also highlights the importance of effective communication among all parties involved in winter operations.
2. De-icing and Anti-icing Procedures
De-icing and anti-icing are critical procedures to ensure that the aircraft's critical surfaces are free from contamination before takeoff. These procedures involve removing existing contamination (de-icing) and applying fluids to prevent further accumulation (anti-icing).
2.1 De-icing/Anti-icing Fluids
Understanding the different types of de-icing/anti-icing fluids is essential for effective application:
Type I Fluid: Primarily used for de-icing due to its low viscosity, which allows for efficient removal of existing contamination. It offers limited holdover time protection and is typically heated before application.
Type II Fluid: A pseudoplastic fluid used for both de-icing and anti-icing. It thickens on the aircraft surface, providing longer holdover times than Type I. Application requires careful adherence to concentration and temperature guidelines.
Type III Fluid: Similar to Type II but with shorter holdover times. Its use is less common in contemporary operations.
Type IV Fluid: Primarily used for anti-icing, offering the longest holdover time protection. Its high viscosity ensures it remains on aircraft surfaces for an extended period.
Refer to Holdover Time (HOT) tables, published by recognized authorities, for specific guidance on fluid effectiveness based on prevailing weather conditions and fluid type. It is crucial to consult the latest and most accurate HOT tables before each de-icing/anti-icing event.
2.2 The De-icing/Anti-icing Process
A systematic approach to de-icing and anti-icing is vital to ensure its effectiveness:
Pre-Treatment Inspection: Conduct a thorough inspection of the aircraft to determine the type and extent of contamination present. This will inform the choice of fluid and application method.
Communication and Coordination: Establish clear communication with the de-icing crew. Provide specific instructions regarding fluid type, application sequence (single-stage or two-stage), and critical areas requiring treatment.
De-icing Application: If contamination is present, apply the appropriate de-icing fluid, ensuring complete removal from all critical surfaces. Pay attention to areas where contamination tends to accumulate.
Anti-icing Application (if required): If weather conditions warrant anti-icing, apply the chosen anti-icing fluid immediately after de-icing. Ensure uniform coverage, particularly on leading edges and upper surfaces.
Post-Treatment Verification: Perform a detailed post-treatment inspection to confirm that all critical surfaces are clean and adequately protected by the anti-icing fluid. Document the fluid type, application start time, and expected holdover time.
2.3 Single-Stage vs. Two-Stage Procedures
The choice between single-stage and two-stage procedures depends on the prevailing conditions and the type of contamination:
Single-Stage Procedure: Involves a single application of a fluid, typically Type II or IV, designed to both de-ice and provide anti-icing protection. This method is suitable for light to moderate contamination and when holdover time is a significant consideration.
Two-Stage Procedure: Utilizes a separate de-icing fluid (usually Type I) to remove existing contamination, followed immediately by an application of anti-icing fluid (Type II or IV). This method is often preferred when dealing with heavy contamination or when a longer holdover time is required.
2.4 External De-icing Application Guidelines
Adhere to standard operating procedures outlined in manufacturer documentation and the airline's operations manual, with particular attention to:
Ensuring all doors, hatches, and vents are properly closed and sealed to prevent fluid ingress.
Implementing necessary protections for engine inlets, APU inlet, and other sensitive areas as specified in the aircraft manufacturer's documentation.
Applying fluids in the recommended sequence, typically starting with the wings, followed by the fuselage, and then the tail surfaces, to prevent recontamination.
Avoiding direct spraying of fluids onto critical sensors, probes, and static ports to prevent damage or malfunction.
Maintaining continuous communication with the de-icing crew throughout the process, confirming fluid application and addressing any concerns.
Specific operational bulletins may provide further guidance on procedures such as flap/slat contamination removal and stabilizer trim settings, which are crucial for safe takeoff following de-icing. Always refer to the latest airline-specific documentation.
3. Contamination Awareness
A thorough understanding of the various types of contamination and their potential impact on aircraft performance is fundamental for safe winter operations.
3.1 Types of Contamination
Frost: A thin, crystalline layer of ice that forms on cold surfaces when the air temperature is at or below freezing and the surface is below the dew point. Even a seemingly insignificant layer of frost can disrupt airflow and negatively affect lift.
Snow: Frozen precipitation composed of ice crystals. Its density and accumulation rate can vary significantly, affecting visibility and aircraft weight.
Slush: Snow that has partially melted and refrozen, creating a semi-liquid mixture. Slush can adhere to aircraft surfaces and refreeze, posing a significant hazard.
Ice: Can form from various sources, including freezing rain, freezing drizzle, or the refreezing of melted snow. Adhered ice is particularly dangerous as it is difficult to detect and remove completely.
Freezing Rain/Drizzle: Liquid precipitation that freezes upon contact with surfaces that are at or below freezing. This type of ice can accumulate rapidly and is a serious threat to flight safety.
3.2 Impact of Contamination on Aircraft Performance
Any form of contamination on the aircraft's critical surfaces (wings, horizontal stabilizer, vertical stabilizer, control surfaces) can severely degrade aerodynamic performance:
Substantially reducing lift, increasing stall speed, and compromising takeoff performance.
Adversely affecting stall characteristics, potentially leading to unpredictable aircraft behavior.
Impairing the effectiveness of control surfaces, making the aircraft less responsive to pilot inputs.
It is unequivocally prohibited to attempt takeoff with any contamination present on the aircraft's critical surfaces.
4. Pre-flight Inspection in Winter Conditions
A meticulous pre-flight inspection is of paramount importance during winter operations to ensure that the aircraft is free from contamination and that all systems are functioning correctly in cold weather conditions.
4.1 Detailed External Inspection
Pay close attention to the following critical areas:
Wings (upper and lower surfaces, leading and trailing edges): Examine closely for any signs of ice, snow, frost, or fluid residue. Ensure that de-icing boots (if equipped) are functioning correctly.
Control Surfaces (ailerons, elevators, rudder): Verify that they are completely free from any contamination and that they move freely and without obstruction throughout their full range of motion.
Horizontal and Vertical Stabilizers: Inspect thoroughly for any accumulation of ice or snow, especially in areas where it may be less visible.
Engine Inlets and Fan Blades: Check for ice or snow buildup inside the inlets and on the fan blades. Ensure that the fan rotates freely by hand, as per manufacturer documentation procedures.
Landing Gear: Inspect landing gear struts, wheels, and brakes for any ice or snow that could impede retraction or extension, or affect braking performance.
Probes and Sensors (e.g., Pitot tubes, static ports, temperature probes): Ensure they are clear of ice and snow to prevent erroneous readings.
Fuselage: Check for any significant accumulation of snow or ice, particularly around doors, vents, and access panels, which could cause operational problems.
Operational bulletins may emphasize the need for additional checks for contamination, especially following anticipated de-icing procedures where residual fluid or melted contamination might refreeze.
4.2 Enhanced Cockpit Checks
In addition to standard pre-flight cockpit checks, pay particular attention to:
Verifying the operational status and proper configuration of all anti-ice and de-ice systems (engine anti-ice, wing anti-ice, windshield heat, etc.).
Confirming the correct stabilizer trim setting, especially if de-icing was performed prior to engine start, as specific procedures may dictate an initial trim setting.
Thoroughly reviewing the latest weather reports, METARs, TAFs, and NOTAMs for any reports or forecasts of icing conditions along the route and at the destination.
Checking the operation of the aircraft's ice detection systems, if equipped.
5. Post-Treatment Checks
Following de-icing and/or anti-icing procedures, a thorough post-treatment check is essential to definitively confirm the effectiveness of the treatment and the aircraft's suitability for flight.
Conduct a visual inspection of all critical surfaces from multiple vantage points to ensure they are completely clean and free of any residual contamination. Pay close attention to leading edges, upper surfaces, and control surfaces.
Verify that the anti-icing fluid, if applied, has been distributed uniformly over the treated surfaces and provides adequate coverage, without any runs or untreated areas.
Closely monitor the Holdover Time (HOT) and ensure that takeoff occurs within the established protection window. Note the time of anti-icing application start, as this is crucial for calculating the remaining HOT.
If the HOT is exceeded, or if there is any doubt about the integrity of the anti-icing fluid due to changing weather conditions (e.g., increased precipitation, temperature changes), a re-inspection and potentially a re-treatment are mandatory.
Document the type of fluid used, the application time, and the HOT expiration time in the appropriate logs and reports.
Ensure that all personnel involved in the de-icing/anti-icing process communicate effectively to confirm that the treatment was completed according to the established procedures.
Approach and Landing in Winter
Review braking action reports and RWYCC codes from SNOWTAMs.
Configure autobrake appropriately for contaminated surfaces.
Consider crosswind and tailwind limitations with wet/icy runways.
Initiate reverse thrust early but with caution to avoid spray ingestion.
Use full runway length when landing distance is marginal.
Landing distance may vary significantly based on surface condition. Always crosscheck LDR calculations using the latest SNOWTAM/NOTAM updates.
Depth: Reported in mm per each runway third (e.g., 5/8/10).
Example: RWY 28 - 5/3/2 - Wet snow - 6/10/12 mm.
Holdover Time Table (Example)
Fluid Type
Precipitation Type
OAT (°C)
HOT Range
Type I
Light Snow
-1 to 0°C
6–12 min
Type II
Snow Showers
-5°C
15–30 min
Type IV
Freezing Drizzle
-4°C
25–40 min
Always refer to the official FAA or EASA HOT tables before departure.
6. Responsibilities - De-icing/Anti-icing
Effective de-icing and anti-icing operations require a clear delineation and understanding of responsibilities among all personnel involved to ensure safety and efficiency.
Flight Crew: Holds the ultimate responsibility for initiating the de-icing/anti-icing request, providing all necessary information to the ground crew, meticulously performing pre-treatment and post-treatment checks, and making the final decision regarding the aircraft's readiness for safe takeoff.
Ground Crew/De-icing Personnel: Responsible for the accurate and safe application of de-icing and anti-icing fluids in strict accordance with established procedures and flight crew instructions. They must also communicate any issues or concerns to the flight crew.
Airport Operations: Responsible for designating and maintaining safe and accessible de-icing areas, ensuring that adequate equipment and trained personnel are available, and facilitating clear communication and coordination between flight crews and ground personnel.
Airline Operators: Develop and provide clear, comprehensive winter operations procedures and training programs, ensuring that all personnel are proficient in their respective roles and responsibilities.
7. Winter Operations Checklists
Adherence to specific winter operations checklists, provided by the airline and referenced in the Flight Crew Operation Manual, is essential. These checklists offer a structured and systematic approach to ensure that all critical steps and considerations for winter operations are addressed.
Airline-specific winter operations manuals will contain detailed checklists tailored to the airline's procedures and the aircraft type. Always refer to the most recent, operator-approved procedures and updates.
Key Items Typically Included in Winter Operations Checklists:
Detailed procedures for conducting pre-flight inspections in potential or actual icing conditions.
Step-by-step guidance for initiating and managing de-icing and anti-icing procedures.
Specific checks to be performed during post-treatment inspections to verify cleanliness and fluid coverage.
Procedures for calculating and monitoring Holdover Times, including decision-making procedures when the HOT is approaching or exceeded.
Guidance on the proper use of engine anti-ice and wing anti-ice systems during various phases of flight in winter conditions.
Procedures for engine start in cold weather, including cold soak considerations.
Runway condition assessment and takeoff/landing performance calculations for contaminated runways.
8. Regulatory References
EASA GM1 CAT.OP.MPA.250: Clean Aircraft Concept – No takeoff allowed unless surfaces are clear of contamination, unless specifically approved in the AFM.
FAA Holdover Time Guidelines (2023–2024): Provides official HOT charts for all fluid types and precipitation categories.
ICAO Doc 9640: Standardized practices for aircraft operation in adverse (winter) conditions.