Aircraft Deicing Guidance for the Removal of Frost, Snow, Slush, or Ice from Aircraft Surfaces before Anti-Icing Operations
Sofema Online (SOL) www.sofemaonline.com considers Aircraft Deicing best practices compliant with Aerospace Standard AS6285 REV.E
Strict adherence to these guidelines is crucial for safe aircraft operations.
>> All personnel involved in deicing and anti-icing must be familiar with these procedures and exercise caution during application and post-treatment inspections.
>> Safety and efficiency in operations are the primary objectives of these practices.
Introduction
This document provides guidelines for the removal of frost, snow, slush, or ice from aircraft surfaces before dispatch from the facility or before anti-icing operations.
It outlines procedures for deicing with fluids and infrared energy, and the responsibilities for ensuring aircraft are free from contaminants that could affect flight safety.
Pre-Dispatch Contaminant Removal
Before dispatch, the aircraft must be clear of frost, snow, slush, or ice. This is a mandatory step to ensure optimal aerodynamic performance and safety.
De-icing Procedures
Infrared Deicing
>> Infrared energy is utilized for deicing, which involves applying heat to break the bond of frozen contamination on the aircraft surfaces.
>> Continuation of infrared application may be necessary to melt and evaporate the contaminants.
Note - After infrared deicing, if surfaces are wet and outside air temperature (OAT) is at or below freezing point, heated deicing fluids must be applied to prevent refreezing.
Caution: Retreatment with fluids may be necessary if refreezing occurs, especially if fluids were applied before flight. Standard fluid deicing procedures should then be followed.
Post-de-icing Inspection
>> Perform a thorough check of the aircraft following deicing.
Infrared Anti-icing Requirements
>> Anti-icing must be carried out as per procedures adjusting infrared power levels to avoid re-accumulation of contamination.
Deicing with Fluids
>> Responsibilities
>> The deicing service provider is responsible for complete removal of frozen deposits using deicing fluids.
Note - Frost may remain under certain conditions
>> Following the deicing / anti-icing procedures and prior to takeoff, the critical aircraft surfaces shall be free of all frost, snow, slush, or ice accumulations in accordance with the following requirements.
>> Pitot Tubes, Static Ports, and All Other Air Data Sensing Devices
>> Pitot tubes, static ports, angle of attack sensors and other air data sensing devices shall be free of frost, snow, slush, ice, and fluid.
>> Wings, Tails, and Control Surfaces
>> Wings, tails, and control surfaces shall be free of frost, snow, slush, or ice unless the aircraft manufacturer and state regulatory authority permits that a coating of frost may be present on wing lower surfaces in areas cold-soaked by fuel between forward and aft spars; and/or on upper wing surfaces within defined areas, in accordance with the aircraft manufacturer’s published documentation.
Note: Except for frost due to cold-soaked fuel as mentioned above, and unless otherwise specified in the Aircraft Flight Manual or other aircraft manufacturer’s documentation, contamination is not acceptable on the upper or lower surfaces of the horizontal stabilizer and elevator/tab; strakes; inboard, outboard, upper, and lower surfaces of the wing and wing tip devices; and either side of the vertical stabilizer and rudder.
Caution: Refer to the aircraft maintenance manual for limitations regarding the application of glycol-based (AMS1424/1 and AMS1428/1) and non-glycol-based fluids (AMS1424/2 and AMS1428/2).
Techniques for Contaminant Removal
- Fluid Application
>> Apply fluids closely and at temperatures and pressures within specified limits to remove frost, light snow, slush, and ice effectively.
- Frost and Light Ice Removal
>> Use a solid cone spray nozzle for a large droplet pattern, applying hot fluid close to the surface with minimal fluid for effective melting.
- Snow Removal
>> Adjust nozzle for snow type and accumulation, prioritizing heavy flow for heavy deposits and considering pre-deicing for large accumulations.
- Ice Removal
>> Utilize heated fluid directed at the ice to break the bond by taking advantage of the high thermal conductivity of metal aircraft skins.
- Cold Dry Snow and Ice
>> Monitor for conditions where non-adhering cold dry snow may start to adhere due to temperature changes or other environmental factors.
Caution: Close monitoring of fluid's lowest operational use temperature (LOUT) is vital for safe operations.
Special Considerations
Fueling and Deicing Fluids
>> Refueling with warm fuel can cause non-adhering snow to stick to the wings.
>> Using heated deicing fluids can make cold dry snow adhere, potentially necessitating anti-icing treatment.
Equipment and Environmental Impact
>> Heat from ground equipment can create adherence conditions for non-adhering snow.
>> Aircraft parking location can affect snow accumulation.
Proximity Hazards
>> Nearby aircraft may cause contamination to blow onto critical components or melt and refreeze, impacting safety.
Caution: Aircraft with rear-mounted engines are particularly at risk of ingesting frozen contaminants, which may result in damage or engine failure. Adequate removal of contamination is essential.
Strict adherence to these guidelines is crucial for safe aircraft operations. All personnel involved in deicing and anti-icing must be familiar with these procedures and exercise caution during application and post-treatment inspections. Safety and efficiency in operations are the primary objectives of these practices.
Next Steps
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