Chapter 12 - Operational Issues

12.1 Meteorological Conditions

This section of the document discusses the typical Canadian meteorological conditions encountered during Ground Icing Operations. Individual holdover time table cell values are capped at 2 hours for all precipitation conditions except freezing fog, which is capped at 4hours.

12.1.1 Freezing Rain Conditions

Aircraft anti-icing fluids Hold Over Times have not been evaluated under moderate and heavy freezing rain conditions.

Aircraft have not been certified to fly in freezing rain conditions. The ability of an aircraft to continue to fly safely in these conditions is questionable.

Operation of an aircraft during freezing rain conditions should be avoided whenever possible.

12.1.2 Ice Pellet Conditions

Ice pellet conditions most often occur in conjunction with freezing rain.

The holdover time performance of an anti-icing fluid in the presence of ice pellets has not been evaluated, but is expected to be extremely short.

If ice pellets fall after anti-icing fluid has been applied to the critical surfaces of an aircraft, the fluid should be considered as failed.

12.1.3 Snow Conditions

Snow Column Cells in the HOT Guidelines

  1. The capability of antiicing fluid to tolerate a heavy snowfall rate has not been evaluated; therefore holdover times for heavy snow conditions have not been generated.

  2. In continuous heavy snow, operations should be suspended; holdover times are extremely short and inspections of the surfaces cannot guarantee safety.

  3. Operations during occasional heavy snow conditions will require that an inspection be conducted immediately prior to take-off to ensure that contamination is not adhering to the critical surfaces. This inspection is required irrespective of the time that has elapsed since anti-icing occurred. Such an inspection can only be carried out when the applicable moderate snow holdover time is a minimum of 20 minutes. There must be at least 5 minutes of moderate snow holdover time remaining after the inspection has been accomplished. The take-off needs to be initiated within five minutes of completion of the inspection. Further delay after inspection should result in a return for deicing/anti-icing.

  4. Type I fluid is particularly vulnerable to sudden failure and therefore must not be used as an anti-icing fluid during heavy snow conditions.

  5. During variable snow conditions the most conservative HOT Table cell time should be utilized; that is, the lowest time.

12.1.4 Wind Effects

If an aircraft encounters conditions of high winds and blowing snow on the ground, it is possible that aerodynamically quiet areas may become contaminated with snow. It may be difficult using normal deicing/anti-icing inspection techniques to detect this condition. It is recommended that specific additional inspections be conducted under such circumstances. It may be necessary to extend the high lift devices to accomplish an inspection in this case.

12.1.5 Freezing Drizzle

The fluids provide greater protection for freezing drizzle than for freezing rain, but similar caution should be exercised.

High winds or high taxi speeds can increase the effective precipitation rate for freezing drizzle. Drizzle can also be very light such that it is almost imperceptible.

12.1.6 Cold Dry Snow Falling on a Cold Dry Wing

Conditions are encountered whereby cold dry snow is falling onto the cold wing of an aircraft. The wind often causes the snow to swirl and move across the surface of the wing and it is evident that the snow is not adhering to the wing surface. Under these circumstances the application of deicing/anti-icing fluid to the wing of the aircraft would result in the snow sticking to the fluid. Under such operational conditions it may not be prudent to apply fluids to the wing.

However, if snow has accumulated at any location on the wing surface it must be removed prior to take-off. It cannot be assumed that an accumulation of snow on a wing will "blow off" during the take-off.

12.1.7 Frost

CAR602.11(3) states: Notwithstanding subsection(2), a person may conduct a take-off in an aircraft that has frost adhering to the underside of its wings that is caused by cold-soaked fuel, if the take-off is conducted in accordance with the aircraft manufacturer's instructions for take-off under those conditions.

12.1.7.1 HOARFROST

Hoarfrost is a uniform thin white deposit of fine crystalline texture, which forms on exposed surfaces during below-freezing, calm, cloudless nights with the air at the surface close to saturation but with no precipitation. The deposit is thin enough for surface features underneath, such as paint lines, markings and lettering, to be distinguished.

12.1.7.2 FROST ON THE FUSELAGE

Despite the requirement to clean contamination from critical surfaces, it is acceptable for aircraft, including those with aft fuselage mounted engines, to take-off when hoarfrost is adhering to the upper surface of the fuselage if it is the only remaining contaminant, provided all vents and ports are clear.

Contact the aircraft manufacturer for further details.

12.1.8 Rain

12.1.8.1 RAIN ON A COLD SOAKED WING

Cold soaking derives largely from fuel stored in a wing for an extended period of time at high altitude; which often results in the aircraft arriving at an airport with the wings at a below freezing temperature. When rain or warm humid conditions are present at the destination airport ice tends to form on the wing upper surface. There may also be an accumulation of ice at the wing's cold corner. In addition, there may also be substantial frost or ice forming under the wing. Under such conditions careful checks should be made because this type of ice is often difficult to identify; the wing may only appear to be wet.

12.2 Cleaning Aircraft Components Other than "Critical Surfaces"

12.2.1 Cabin Windows

Whenever practicable, cabin windows should be free of frozen contaminants. The cabin windows are an important part of the safe operation of an aircraft. The flight crew may be required to look at the wings from a vantage point within the aircraft cabin to determine if the wings are free of frozen contaminants and that the aircraft is safe for take-off.

In the event of an "on ground" emergency requiring rapid passenger evacuation, cabin safety personnel will be required to look out of the cabin windows to assess the situation to determine if it is safe for the passengers to exit from one side or the other of the aircraft. In either of these cases, it is important that the cabin windows be clear.

Therefore, it is considered prudent to ensure that the cabin windows, especially those required for flight crew and cabin safety personnel duties, are free of frozen contaminants.

12.2.2 Emergency Exits

During periods of freezing drizzle and freezing rain in particular, an aircraft on the ground may accumulate a significant thickness of ice on the fuselage. One of the potential effects of a sheet of ice over the entire fuselage of the aircraft is that the ice may prevent normal operation of the emergency exits.

Operators should consider this situation during ground deicing operations, particularly when freezing drizzle or freezing rain has occurred at the airport while the aircraft has been sitting for an extended period of time on the ground.

12.3 Configuration During Deicing Procedures

It is important for operators to consider the configuration of their aircraft during deicing.

Manufacturers may indicate that their aircraft need to be in a specific configuration during the deicing and anti-icing process. However, if an aircraft is in a clean configuration, that is with all high lift devices retracted, during deicing, the air operator needs to consider what untreated areas of the wing are subsequently exposed to freezing precipitation once the devices are extended/deployed, during periods of active precipitation.

The areas under a leading edge flap or slat, if not protected by anti-icing fluids, have the potential of becoming a contaminated critical surface prior to take-off.

Air operators need to consider this scenario and may need to develop additional procedures to ensure that the aircraft is taking off in an uncontaminated condition.

Two possible options are: delaying slat/flap deployment until just prior to take-off; or deploying the devices prior to deicing/antiicing so that the surfaces under these devices are treated.

Training and checklist changes may be required.

12.4 APU Lessons Learned

During the 2000/2001 winter operating season, an F28 was being de-iced/anti-iced in strong, gusty wind conditions with engines and APU running. Despite all precautions taken by the crew applying the fluids, some fluid entered the APU inlet. The fluid passed through the compressor and entered the combustion chamber as hot, compressed additional fuel that had not been processed by the APU's Fuel Control Unit. The APU reacted to the extra fuel as it was designed to do - more fuel, more fire, and faster rotation - by auto-accelerating, the design limits were exceeded and a rotor burst occurred.

Air operators and service providers should ensure that all personnel involved in the application of deicing/anti-icing fluids are aware of this incident. Additional precautions must be taken when strong winds make control of fluid application difficult, and consideration should be given to asking the flight crew to shut down the APU if there is any doubt that fluid cannot be prevented from entering the APU inlet.

12.5 Extreme Operational Conditions

Extreme operational conditions often require specific solutions. Winter operations in the Canadian North pose their own problems due to the extremes in both weather and temperature. It has been noted that a number of Air Operators carry TypeI fluids with them in the aircraft from station to station so that it is available. The containers in which the fluid is kept resemble the common garden insecticide sprayer. The fluid in this circumstance would appear to be kept at a room temperature. Application of this fluid at ambient temperature with such an applicator will result in limited effectiveness of the fluid, depending upon the conditions. Contact the fluid manufacturer for further details.

12.6 Pilot Issues

The Pilot-in-Command of an aircraft holds the ultimate responsibility for ensuring that the aircraft takes off in a safe manner; and in the case of ground icing conditions, the Pilot-in-Command must ensure that his aircraft's critical surfaces are free of frozen contaminants. It is important therefore that the Service Provider understand what specific requirements a pilot has in the pursuit of his duties during ground icing conditions.

12.6.1 Sufficient Lead Time

An efficient and reliable method of communication, appropriate to the site, allows pilots to communicate their intentions to the Service Provider at the earliest possible time. This may include details on: aircraft type, the estimated time of arrival (ETA) at the de-icing pad (if off gate deicing operations are in effect), the possible requirement for a ground power unit (GPU), the possible requirement for engine shutdown and treatment of the propellers (if so equipped), the pertinent type of treatment required, the type of any fluid(s) which may be required, or any anomalies specific to the impending operation.

This early exchange of information allows the flight crew to adapt to problems that may come to light as a result of feedback received through early communication with the Service Provider. For example, if a specific fluid type were found to be unavailable, the pilot would be in a better position to review options and proceed with alternate arrangements if necessary and thereby reduce confusion and delay during ground deicing operations. This scenario will always be preferable to a situation where an aircraft arrives at the deicing location and then, due to a problem unknown to the pilot, is unable to undergo deicing with the likely result that the aircraft will need to return to the gate. This causes a delay and will inconvenience everyone involved, including the passengers and crews of other aircraft waiting in turn to enter the deicing facility or to use the deicing equipment.

If a flight crew receives an early warning of problems such as other aircraft experiencing unusually long delays, the aircraft Pilot-in-Command might elect to change plans. The change of plans may include adjusting fuel uplift, and making additional communications. From an airport perspective this pre-planning can reduce congestion and improve on time departure success rates and contribute to safe ground operations.

In summary, communication between the pilot and the Service Provider, as soon as possible in advance of the aircraft arriving at the deicing location, ensures that the deicing operation will be accomplished in the safest and most efficient manner, for both the flight crew and the ground crew.

12.6.2 Taxi Communication

Once an aircraft has received permission to proceed to the deicing location and has begun taxiing, it is important that flight crews be able to receive prompt notification of any changes to the deicing operation, or of problems that arise. This may include notification from the Service Provider of unserviceable equipment, delays entering the deicing location, unusually slippery conditions at the deicing location operation. The sooner that pilots receive this type of feedback, the earlier they can adjust to the changing situation.

When radio frequency changes are required enroute to the deicing location, the pilot must clearly understand when and where to change frequency, so that confusion is averted. Erosion of the communication link between the pilot and the Service Provider could result in an aircraft proceeding to the wrong deicing location, to entering the pad incorrectly or in an unsafe manner. This could jeopardize both the efficiency and the safety of the entire operation, as well as compromising the safety of the deicing personnel working at the deicing location.

One way to ensure that the communication process used for deicing operations is clearly understood by the pilots involved, is to outline the process in the appropriate publication(s). Procedures must be in place to alert pilots to any change in published procedures. In this way, pilots will know what to expect and what is expected of them during normal deicing operations. By maintaining the communication link and providing pilots with reliable frequency handoffs when required, any last minute changes or problems that arise will be less likely to jeopardize operational efficiency and safety.

12.6.3 Procedures for Entry into Deicing Locations

The procedures used by the Service Provider for entry of aircraft into a deicing location must be made clear to the flight crews. Pilots of aircraft entering the pad must have a clear set of instructions concerning: the point of entry, the required ground track, the required hold short points the meaning of visual signals, the required stop points, the propeller feathering procedure, the engine handling, and other safety oriented instructions. Some of this information will be general and will apply to procedures common to all or most deicing location operations. Other information will be site-specific and will apply to procedures that are applicable to a particular deicing location, at a particular airport. These directives should be included in the pertinent operational literature and made readily available to the flight crews.

Where visual signals, such as, in-ground lighting, message boards, hand signals, are used, the signals should be standardized. Pilots need a clear indication regarding how and when to enter the deicing location, and the deicing crews need to know the standard configurations at the facility. The safety of the operation is dependent upon clear directions.

An aircraft entering the pad incorrectly could result in injury to personnel, in damage to the aircraft, in damage to ground equipment, in loss of separation between the aircraft and the ground crews, and in possible damage to other aircraft parked or manoeuvring on the pad. When procedures are not clearly defined and confusion exists, combined with inclement weather, slippery conditions and poor visibility, which often accompany deicing operations, there is an increased potential for an accident.

A direct communication link between the aircraft's Pilot-in-Command and the Service Provider can help reduce the possibility of errors and maintain an efficient aircraft throughput.

12.6.4 Establishing the Pilot/Deicing Coordinator Communication Link

Once an aircraft is parked on the deicing location and preparing to receive a deicing/anti-icing treatment, it is imperative that the Pilot-in-Command of the aircraft establish a communication link with the Deicing Operator coordinator that is responsible for the operation. This link may be established by means of standardized hand signals at airports where hard wire (head set) or radio communications are not available, or by hard wire or radios where these are the standard means of communication. No deicing vehicles should approach the aircraft to begin the deicing process until this communication link has been established.

In summary, as is the case in most aspects of an aircraft's flight operations, whether on the ground or in the air, communication which is clear and concise is vital to a safe airline operation. The communication link which is established between a pilot preparing for deicing, and the Deicing Operator coordinator is an important part of safe operations.

12.6.5 Central Deicing Facilities Operations

In most cases, pilots will want to talk directly to the Deicing Operator responsible for the operation; however, in large centralized deicing facilities a single controller may be required. This arrangement at a CDF will be the safest means of communication since there is a reduced risk of misunderstanding between the pilot and those providing the service. Direct radio communication allows for a flow of operational information, and allows that information to be exchanged more quickly. This factor becomes very important when an emergency arises. For example, a pilot experiencing an engine fire during the deicing procedure can immediately notify the deicing crew and they can quickly take the necessary action in such a time critical situation. One difficulty with relaying this information by means of hand signals or through a third party should be readily apparent. It is possible that the Deicing Operator would not be alerted to the problem, which could jeopardize the safety of the deicing team and the aircraft. The efficiency of a possible passenger evacuation may also be compromised in this scenario.

Once an aircraft is parked on the deicing location and preparing to receive a deicing/anti-icing treatment, it is imperative that the Pilot-in-Command of the aircraft establish a communication link with the Deicing Coordinator that is responsible for the operation. This link may be established by means of standardized hand signals, hard wire (head set), or radios where these are the standard means of communication. No deicing vehicles should approach the aircraft to begin the deicing process until this communication link has been established.

Once an aircraft has reached the entry point to the facility control MUST be transferred from Air Traffic Services (ATS), Apron control to Pad Control. A communication link between the Pilot-in-Command and Pad Control must be established prior to the aircraft entering a deicing bay.

12.6.6 Exchange of Vital Information Prior to the Deicing/Anti-Icing Fluid Application

Prior to commencement of the deicing/anti-icing operation, certain vital information will need to be shared and acknowledged to ensure that the aircraft is treated correctly, in a safe manner, and with a safe result.

In order to ensure that these basic criteria are met, the following items, should be accomplished prior to commencing the operation:

12.6.6.1 REMOTE LOCATIONS:

Between the Deicing Coordinator and the Pilot-in-Command:

  1. Confirmation that brakes are set and aircraft correctly configured for the type of deicing being accomplished (e.g. engines at idle, propellers feathered, bleed systems correct, etc.);
  2. Confirmation of the deicing/anti-icing methodology being used;
  3. Communication of any last minute cautionary or advisory information deemed pertinent to the impending deicing/anti-icing operation;
  4. Confirmation of type of fluid(s) to be applied to aircraft;
  5. Confirmation of fluid mixture ratio, if applicable;
  6. Communication of any last minute cautionary or advisory information deemed pertinent to the impending deicing/anti-icing operation;
  7. Confirmation from the Deicing Operator to the Pilot-in-Command that deicing/anti-icing operations are about to commence; and
  8. Time noted at the start of anti-icing fluid application. This is required by the Pilot-in-Command for the commencement of HOT timing. The Service Provider should note the time and advise the Pilot-in-Command.

12.6.6.2 CDF FACILITIES:

Between Pad Control and the Pilot-in-Command:

  1. Confirmation that brakes are set and aircraft correctly configured for the type of deicing being accomplished (e.g.: engines at idle, propellers feathered, bleed systems correct, etc.);
  2. Confirmation of the deicing/anti-icing methodology being used;
  3. Communication of any last: minute cautionary or advisory information deemed pertinent to the impending deicing/anti-icing operation; and
  4. Confirmation that deicing/anti-icing operations are about to commence.
  5. Confirmation of fluid mixture ratio, if applicable;
  6. Communication of any last minute cautionary or advisory information deemed pertinent to the impending deicing/anti-icing operation;
  7. Confirmation from the Deicing Operator to the Pilot-in-Command that deicing/anti-icing operations are about to commence; and
  8. Time noted at the start of anti-icing fluid application. This is required by the Pilot-in-Command for the commencement of HOT timing. The Service Provider should note the time and advise the Pilot-in-Command.

12.6.7 Recommended "Clean Aircraft Concept" practices

The following list, while not exhaustive, is intended to indicate the kinds of things that flight crew can do, or should consider, to improve upon the safety of the operation of their aircraft during ground icing operation conditions.

  1. Perform a pre-take-off inspection just prior to take-off.
  2. Be knowledgeable of ground deicing and anti-icing procedures and practices that are appropriate for your aircraft type; these procedures shall be followed by the Service Provider.
  3. Do not allow deicing or anti-icing procedures to be performed on the aircraft unless the deicing practices and safety precautions in place are satisfactory.
  4. Be aware that the HOT Guidelines are not exact values and that as conditions and circumstances change, during ground icing operations, the applicable HOT values will change. Continued vigilance is required at all times during ground icing conditions.
  5. The general rule for ground icing procedures is that the deicing and anti-icing processes must be done symmetrically. That is, whatever treatment is administered on one wing must be applied to the other wing for aerodynamic symmetry reasons.
  6. Deice and anti-ice the aircraft as close to the take-off point and the take-off time as possible to maximize the chances of safely completing the take-off before expiration of the HOT time.
  7. If the aircraft has leading edge devices that must be retracted during the deicing and anti-icing process, the area under the leading edge devices will remain untreated. Under these circumstances the deployment of the leading edge devices will expose the untreated leading edge to contamination. This factor must be taken into account and may require an amendment or revision to the pre-take-off checklist. The aircraft manufacturer should be consulted on this matter.
  8. Ground icing operations in conditions of blowing snow, slush, and in close proximity to other operating aircraft can cause the critical surface of the aircraft to become contaminated much more quickly than may be expected, due to the deposition of contaminates from the ground onto the surfaces. The Pilot-in-Command must remain vigilant.
  9. Do not attempt a take-off, under any circumstances, if, for any reason, there is doubt as to the condition of the critical surfaces.

12.6.8 Aerodynamic Effects of Contamination

The following information, while not exhaustive, should serve to remind Pilot-in-Command of some of the aerodynamic concerns and/or consequences of ground icing operations and critical surface contamination.

Research has indicated that small amounts of contamination on an aircraft's critical surfaces can have a very large effect on the aircraft's performance and handling qualities. This is particularly true during the take-off phase of flight.

Very slight surface roughness, caused by frozen contaminants, can have extremely significant effects on an aircraft's stalling speed, stalling characteristics, handling qualities and power required due to drag increases. Wing contamination, especially near the leading edge, can cause the wing stalling angle to be reached prior to any indication by the stall warning or stall pusher systems, especially during periods of high angles of attack, such as during the take-off rotation. The pilot will have little or no warning under these conditions. Leading edge roughness, especially during periods of high angles of attack such as during the take-off rotation, has particularly pronounced negative effects on aerofoil performance. Contamination of the leading edge of a wing is therefore of particular concern.

Controllability, especially in the rolling axis , may become extremely difficult or impossible. This lateral control difficulty can occur when the wing is contaminated ahead of the ailerons, thus disrupting the airflow over the aileron and reducing the effectiveness of the aileron. This condition may be exaggerated if the wings are asymmetrically contaminated, that is, if one wing is more contaminated that the other. The consequences of operating an aircraft under these conditions can be grave.

Thickened fluids, such as TypesII & IV, are aerodynamically designed for "high take-off speed" aircraft. The pilot should ensure that the fluid being used is suitable for the aircraft.

If the aircraft has leading edge devices, which must be retracted during the deicing and anti-icing process, the area under the leading edge devices will remain untreated. Under these circumstances the deployment of the leading edge devices will expose the untreated leading edge to contamination. This factor must be taken into account and may require an amendment or revision to the pre-take-off checklist. The aircraft manufacturer should be consulted on this matter.

Propeller efficiency and balance are affected by contamination and they are therefore considered critical surfaces and must be cleaned before take-off.

12.6.9 Passenger Pre De/anti-icing Briefing

CAR602.11(7) states: "before an aircraft is de-iced or anti-iced, the pilot-in-command of the aircraft shall ensure that the crewmembers and passengers are informed of the decision to do so".

Therefore, prior to commencing deicing activities the Pilot-in-Command must advise the passengers.

12.6.10 Final Anti-icing Fluid Application Start Time

The start time of the final application of anti-icing fluid to the aircraft must be relayed to the Pilot-in-Command. The Pilot-in-Command will use this time to establish the beginning of the holdover time (HOT). The start time will be given to the Pilot-in-Command, by the Service Provider, in a clear and concise manner. If the pilot needs to know which wing was sprayed first in a one truck de/anti-icing operation the pilot should request this information.

12.6.11 Communicating the Existence of Problems to the Pilot

anti-icing fluid application start time, the type of fluid used, and information on the contamination status of the critical surface (i.e. clean or contaminated).

In addition to routine communications, the following are examples of other times when information of a critical nature needs to be relayed to the pilot. The ground icing training program needs to address circumstances such as these and describe the correct response. Following are examples:

  1. Damage or potential damage to the aircraft

    The Pilot-in-Command must be informed when any structural piece of equipment used in the deicing operation comes into contact with the aircraft, whether there is apparent damage to the aircraft or not. Fuel tanks, communication and navigation antennas, aircraft control and lifting surfaces, windows and windscreens, static wicks, pitot tubes, angle of attack and stall vanes, radomes, and various other aircraft structures are particularly susceptible to damage, which may not be visible to the naked eye. Contact between the Service Provider's equipment and any portion of the aircraft will require an inspection in order to assess the damage. In some cases the damage may be obvious. In other cases the damage may be so subtle that there will be no indication of damage apparent to the deicing crew. The Pilot-in-Command must always be advised of the occurrence.
  2. The inadvertent spraying of sensitive aircraft parts.

    When the Deicing Operator becomes aware that the spray nozzle has been inadvertently directed at an area of the aircraft which should not receive fluid spray, the Pilot-in-Command of the aircraft must be informed of this fact. On some aircraft, when the stream of the deicing spray is directed at door or hatch seals, for example, fluid can enter at that point and result in fluid pooling inside the body of the aircraft. This may not require any action or it may require a "mop up" of the affected area. On some aircraft, this same incident may have an effect that is operationally more consequential.

    Deicing fluids should never be directed into engine or APU intakes or exhaust ports. In some cases this may result in a strong and unpleasant smell inside the aircraft, as engine or APU bleed systems carry the odors to the passengers and crew. Deicing spray directed into the inlets of reciprocating engines can cause thermal shock and damage to engine cylinders and turbo chargers. Spray directed into turbo-jet or turbo-propeller engines may cause flameout or other problems, depending upon the volume of fluid ingested.

    Deicing fluids aimed directly at the flight deck or the cabin windows can cause cracking and de-lamination of acrylic layers and penetration damage to the fitting seal; which can further lead to a pressurization incident. Care should be taken to avoid this situation, but when inadvertent spraying of these windows occurs, the deicing operator must inform the Pilot-in-Command.

    If windows need to be deiced, direct a spray of fluid on the fuselage above so that the fluid will flow down over the windows.

    Deicing crews will not spray fluid directly onto hot brakes, wheels or landing gear, unless cleared to do so. Damage to the brakes and wheel assemblies can occur when deicing fluid comes in contact with hot brakes, due to thermal shock of the brake components. If spraying this area of the aircraft is not authorized, the flight crew must be informed when an inadvertent spray occurs. This is important since braking efficiency while taxiing or during a rejected take-off could be greatly reduced.
  3. Notice of risk or injury to the deicing operator personnel.

    The ground deicing personnel may be in the best position to assess potential risks that develop during the deicing operation. By being able to immediately contact the Pilot-in-Command potential incidents and accidents may be averted. Communication to the pilot may involve an urgent request to power down engines in order to reduce propeller or jet blast, or to stop an aircraft that has begun to slide forward on a slippery surface, for example.

    The pilot may be requested to shut down an engine or engines when there is risk of injury to Deicing Operator members.

    It is important that the Deicing Operator be able to relay instructions to the aircraft Pilot-in-Command quickly and clearly.

12.6.12 General Items Pertinent to the Deicing Operation

The Pilot-in-Command should consider the following when receiving de/anti-icing treatment.

  1. Aircraft alignment during deicing

    Most pilots will prefer to align their aircraft into the prevailing wind when preparing for a de/anti-icing operation, in order to reduce or prevent any fluid(s) being used from blowing back onto the flight deck windows.
  2. De/anti-icing fluid on the cockpit windscreen

    Deicing Service Providers need to be made aware that even small amounts of deicing fluid covering flight deck windows can cause pilots to lose visual contact with the operation, which is taking place around the aircraft.

    The fact that deicing spray can significantly reduce visibility from the cockpit, makes a compelling argument for the use of a hard wire or radio communication link between the Deicing Operator and the aircraft Pilot-in-Command.
  3. Adequate nighttime flood lighting

    Deicing an aircraft in a dimly lit, low visibility environment can be both difficult and unsafe. The lighting should be sufficiently bright to allow for "day like" operations to take place. Nighttime lighting should be shielded to prevent glare for pilots of aircraft taxiing, landing or taking off in close proximity to the deicing facility.

    Good flood lighting, whether permanently fixed, portable or vehicle mounted, should be installed in consideration of the following points:

    1. Adequate nighttime lighting at the deicing facility will allow pilots to see clearly and therefore follow the hand signals of the deicing Service Provider.
    2. Deicing crews will require sufficient nighttime flood lighting to enable them to provide the best possible deicing/anti-icing treatment.
    3. Pilots will also need a well-lit environment within which to conduct a pre-take-off contamination inspection.

12.6.13 Post de/anti-icing considerations

12.6.13.1 CONFIRMATION THAT THE CRITICAL SURFACE INSPECTION HAS BEEN COMPLETED

Once the deicing/anti-icing treatment is complete, the Pilot-in-Command must be advised that the deicing crew has completed the Critical Surface Inspection, and that aircraft critical surfaces are free of contamination.

The "clean aircraft concept" is facilitated, in part, by the Critical Surface Inspection, which is a pre-flight external inspection of critical surfaces conducted by a qualified person, to determine if they are contaminated by frost, ice or snow. Under ground icing conditions, this inspection is mandatory. This inspection must be accomplished upon completion of the deicing/anti-icing operation. A report shall be made to the Pilot-in-Command of the aircraft. The AGIP must describe how this inspection will be accomplished, including the lighting conditions required to conduct the inspection.

12.6.13.2 DEPARTURE NOTIFICATION FOR THE FLIGHT CREW

Following a deicing/anti-icing treatment of the aircraft and confirmation that the Critical Surface Inspection has been completed, and that the aircraft is free of frozen contaminants, the Pilot-in-Command will need the following information from the deicing crew:

  1. Confirmation that all staff and equipment are safely away from the aircraft.
  2. Authorization to start engines (if applicable).
  3. Authorization to unfeather propellers (if applicable).
  4. Notification to switch to hand signals (if applicable).
  5. The Pilot-in-Command must be notified when it is time to depart the deicing facility.

12.7 Rotorcraft Specific Issues

Rotorcrafts are unique aircraft and the differences between them and fixed wing aircraft go beyond mere appearances.

Many of the principles expressed throughout this document are applicable to a rotorcraft. However, many fixed wing techniques for coping with ground deicing conditions do not suit a rotorcraft, and in fact may cause damage to a rotorcraft.

This section of the document is intended to indicate some of the operational similarities, operational differences, operational experiences, and limitations associated with the operation of rotorcraft in Ground Icing Conditions.

12.7.1 Regulatory

The Operational Regulations that govern aircraft operations during ground icing conditions apply to both fixed wing and rotorcraft. In particular, the "clean aircraft concept" applies to both categories of aircraft.

Canadian Aviation Regulations (CARs) 602.11 states: "No person shall conduct or attempt to conduct a take-off in an aircraft that has frost, ice or snow adhering to any of its critical surfaces"; and the associated Commercial Air Service Standard (GOFR) 622.11, outlines the requirements of a ground icing program.

12.7.2 Aerodynamics

The principles of aerodynamics apply to both fixed and rotary winged aircraft. Contamination of an aerofoil section will result in reduced lift and an increase in drag. The manner in which these effects manifest themselves in fixed wing aircraft as compared to a rotary winged aircraft do, however, differ considerably.

It can be appreciated that small amounts of frozen contamination on a critical surface of a fixed wing aircraft can result in a significant increase in stall speed, a large increase in drag and produce serious handling difficulties. All of these effects can result in a loss of aircraft control.

Likewise, for a rotorcraft, small amounts of frozen contamination on a critical surface can result in serious performance degradation. There will be a decrease in main and tail rotor thrust, there will be an increase in main and tail rotor drag. The combinations of these effects will result in a demand for increased engine torque. There are quite likely to be handling and control issues that can result in the loss of rotorcraft control. The performance and handling effects for the same amount of contamination will likely be more serious in the rotorcraft case than in the fixed wing case; this is a qualitative notion only.

It cannot be denied frozen contaminants on any of the thrust generating surfaces will probably have dramatic negative consequences.

12.7.3 Operational environment

Rotorcraft parked in outside suffer from icing of aerodynamic surfaces, engine inlets and windscreens caused by frost, snow, freezing drizzle and freezing rain. Unless removed, snow and ice may linger after the precipitation ends, grounding the rotorcraft for hours or days, depending upon temperature.

12.7.4 Fluids

Accumulations of frozen precipitation are typically removed from fixed-wing aircraft using heated glycol deicing solutions. Glycol is expensive, and potentially damaging to rotorcraft rotor head components. Composite rotorcraft blades and fuselage components are susceptible to damage from deicing operations because physical impact, scraping, high temperatures, and rapid thermal cycling may cause de-lamination.

12.7.4.1 FLUID EVALUATION

Generally, the work that has been accomplished in fluid research has been in consideration of fixed wing aircraft and not rotorcraft. The Methods and Procedures that have been developed under the tutelage of SAE G-12 committee have been in consideration of fixed wing operations. A comprehensive set of practices, principles, procedures, methods, fluids, training guidance, and equipment specifications are not known to have been developed for rotorcraft.

12.7.5 Experience

The obvious and most effective method used to maintain the clean helicopter concept is to place the helicopter in a hangar whenever possible. Where operators do not have this option, other measures must be taken. Ideally the person that teaches the subtleties of helicopter deicing and winter maintenance is someone with current practical operational experience on the type of rotorcraft to be used in remote locations.

  1. The preparation for flight in a harsh environment will be a longer process than normal to maintain operational safety. Caution must be used due to slippery upper decks, and due to slippery hand and foot holds. Inspection panels or cowlings should not be forced when fouled with ice or snow, as damage could result in damaged closure mechanisms. The delicate balance of rotor assemblies necessitates removal of all ice and snow from all rotor systems to maintain the symmetry of rotating components.
  2. Use waterproof material covers for the main and tail rotors and transmission deck. Ideally, covers will protect the windshield, the pitot static system and a good portion of the fuselage. As well, install inlet and exhaust plugs. Install covers and plugs at the end of each day or whenever the aircraft is not scheduled for use to ensure it is protected during periods of unexpected surface contamination conditions.
  3. The act of chipping may damage the component that you are removing ice from. Use a combustion heater with sufficient outlet hose to allow the application of heat to the transmission area, rotor components and engine compartment, and to assist in the removal of frozen covers. Thermal methods, including infrared heating and hot air, do not mechanically injure helicopter blade composites, however, they can overheat composites causing delamination and thus must be closely monitored. Consult the rotorcraft manufacturer for advice on the use of such devices.
  4. Remove the covers and then examine the fuselage for contamination to ensure ice or snow from the covers has not fallen onto the fuselage or into engine intakes. Pooled water a by product of preheating, has been known to cause control binding, electrical problems, drain line clogs, and many other minor problems when it reverts to the solid state during start up and flight. For this reason pooled water should be dealt with while in the liquid state.
  5. Remove any contamination adhering to the fuselage or tail boom by any of the procedures outlined by aircraft manufacturers' recommendations. Extreme caution must be exercised for areas such as rotor blade trim tabs, Outside Air Temperature indicators, antennas, and Plexiglas windows. Do not tap thinly covered honeycomb panels to remove ice, as the result may be an expensive repair or replacement.
  6. Free skids, wheels or any part of the landing gear that is frozen to the ground or snow cover.

12.8 Operational Control Considerationss

12.8.1 General

Depending upon the type of operation and the Regulation governing the operation, an operational control system may be required. The requirement for such a system is, in particular, relevant to CAR704 (Commuter Operations) and CAR705 (Airline Operations) operations.

"Operational Control" is defined as follows: Operational Control is the exercise of authority over the formulation, execution, and amendment of an operational flight plan in respect of a flight

CASS725.20(1) General (ii) states in part..."the flight dispatcher and the pilot-in-command share responsibility for Flight Watch and shall share pertinent and related flight information and any proposed changes to the Operational Flight Plan."

12.8.2 Regulations

CAR704.15 and CAR705.20, each state: "No Air Operator shall operate an aircraft unless the Air Operator has an operational control system that meets the Commercial Air Service Standards and is under the control of its operations manager.

12.8.3 Standards & Guidance

  1. CASS723.16 "Operational Control Systems" describes the requirements of a system to satisfy CAR703.16.
  2. CASS724.15 "Operational Control Systems" describes the requirements of a system to satisfy CAR704.15.
  3. CASS725.20 "Operational Control System" describes the requirements of a system to satisfy CAR705.20.
  4. Company Indoctrination Training: 724.115(6)(f) & 725.124(5)(f).

12.8.4 Aeroplane Surface Contamination Training

CASS725.124(23) "Training Program" outlines the training requirements for "Aeroplane Surface Contamination Training" for all operations personnel, including dispatchers.

12.8.5 References

The following Transport Canada publications have detailed information related to Operational Control and should be referenced:

  1. TP12513E "Study and Reference Guide - Flight Dispatchers".
  2. TP13498E "Generic Dispatchers Training Manual for Air Operators".
  3. TP13562E "Generic Operational Control Manual (Dispatcher Manual) for Air Operators".
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