From the early days of aviation, icing has been one of the most frightening of atmospheric phenomena. We must keep in mind that adverse weather conditions play significant causal roles in nearly one third of all aircraft accidents, including general aviation. Among them, more than 20% are directly related to icing.
1. COMPANY POLICY
1.1 Clean aircraft concept:
The aircraft performance is certified based upon a clean structure. If the clean aircraft concept were not applied, ice, snow or frost accumulations would disturb the airflow, affect lift and drag, increase weight and result in deterioration.
The U.S federal aviation administration FAA prohibit T/Off when frost, ice or snow adheres to airplane wings, propellers, or control surfaces.
1.2 Responsibility:
The person technically releasing the aircraft is responsible for the performance and verification of the results of the de/anti-icing treatment.
The Commander is directly responsible for accepting the performed treatment, and the transfer of responsibility takes place at the moment the aircraft starts moving under its own power.
1.3 Environment and health:
Besides water, de-icing/anti-icing fluids contain glycols and different additives as main ingredients. Type II and IV fluids also contain a thickener system.
1.3.1 Biological degradation:
Glycols are entirely biodegradable (Biodegradable means that a conversion is achieved by aerobe bacteria changing glycol to water and carbon dioxide by the aid of oxygen).
The best way to handle waste fluids is to drain them into local waste water treatment plants.
Thickener system of Type II and IV fluids, approximately 1% of volume of the fluid, is totally neutral to the environment. It will not be biodegraded but has no negative effects on the environment.
Additives and inhibitors can have an effect on the overall biodegradability.
In any case, the fluids have to meet local regulations concerning biodegradability and toxicity.
1.3.2 Toxicity:
Although biodegradable, glycol should be considered as harmful if swallowed. The principal toxic effects of ethylene glycol are kidney damage, in most cases with fatal results.
The Standard precautions taken when handling chemicals should be adopted when handling glycols.
2. EFFECTS OF CONTAMINATION
Icing conditions can cause the following;
Additional uncontrolled weight.
Reduction in Maximum lift that can be produced by wing surfaces.
More drag.
Significant increase in stalling speed.
Loosing Controllability (it may become extremely difficult or impossible).
Engine efficiency is affected by contamination.
Pitot heads, static ports and angle of attack sensors contamination cause unrealistic flight parameters being supplied to systems and displayed to flight crew.
The consequences of operating an aircraft under these conditions can be grave.
3. WEATHER CONDITIONS REQUIRING DE/ANTI-ICING
3.1 What is icing:
Icing is defined by any deposit or coating of ice on an object caused by the impact of liquid hydrometeors usually supercooled.
Anticyclonic conditions in winter, with clear night skies and little wind, can cause a sharp drop in ground temperature, which leads to formation of hoar frost on an aircraft parked outside overnight. Moreover, the contact of humid air with cold aircraft structure can cause cold soaking. As whole airframe surfaces may be affected, the aircraft has to be cleaned prior to take-off.
The operator must develop procedures for cold weather servicing by developing and implementing cold weather preventive procedures that will improve the safe operating level of their aircraft in adverse climatic conditions.
3.2 Formation:
Icing conditions on ground can be expected when air temperatures approach or fall below freezing and when moisture or ice occurs in the form of either precipitation or condensation. However, ice accretion can also occur when humid air at temperatures above freezing comes in contact with cold structure, this phenomenon is known as cold-soaking.
3.3 Definitions:
Freezing conditions are conditions in which the outside air temperature is below +3°C and visible moisture in any form (such as fog with visibility below 1.5 km, rain, snow, sleet or ice crystals) or standing water, slush, ice or snow is present on the runway.
Freezing fog (Metar code: FZFG) is a suspension of numerous tiny supercooled water droplets which freeze upon impact with ground or other exposed objects, generally reducing the horizontal visibility at the earth's surface to less than 1 km.
Freezing drizzle (Metar code: FZDZ) is a fairly uniform precipitation composed exclusively of fine drops - diameter less than 0.5 mm - very close together which freeze upon impact with the ground or other objects.
Freezing rain (Metar code: FZRA) is a precipitation of liquid water particles which freezes upon impact with the ground or other exposed objects, either in the form of drops of more than 0.5 mm diameter or smaller drops which, in contrast to drizzle, are widely separated.
Frost is a deposit of ice crystals that form from ice-saturated air at temperatures below 0°C by direct sublimation on the ground or other exposed objects.
Hoar frost is a rough white deposit of crystalline appearance formed at temperatures below freezing point, usually occurs on exposed surfaces on a cold and cloudless night. It frequently melts after sunrise; if it does not, an approved de-icing fluid should be applied in sufficient quantities to remove the deposit. Generally, hoar frost cannot be cleared by brushing alone.
Thin hoar frost is a uniform white deposit of fine crystalline texture, which is thin enough to distinguish surface features underneath, such as paint lines, markings, or lettering.
Glaze ice or rain ice is a smooth coating of clear ice formed when the temperature is below freezing and freezing rain contacts a solid surface. It can only be removed by de-icing fluid; hard or sharp tools should not be used to scrape or chip the ice off as this can result in damage to the aircraft.
Hail (Metar code: GR) is a precipitation of small balls or pieces of ice, with a diameter ranging from 5 to 50 mm, falling either separately or agglomerated.
Light freezing rain is a precipitation of liquid water particles which freezes upon impact with exposed objects, in the form of drops of more than 0.5 mm which, in contrast to drizzle, are widely separated. Measured intensity of liquid water particles are up to 2.5mm/hour or 25 grams/dm2/hour with a maximum of 2.5 mm in 6 minutes.
Rain (Metar code: RA) is a precipitation of liquid water particles either in the form of drops of more than 0.5 mm diameter or of smaller widely scattered drops.
Rime (a rough white covering of ice deposited from fog at temperature below freezing). As the fog usually consists of supercooled water drops, which only solidify on contact with a solid object, rime may form only on the windward side or edges and not on the surfaces. It can generally be removed by brushing, but when surfaces, as well as edges, are covered it will be necessary to use an approved de-icing fluid.
Sleet is a precipitation in the form of a mixture of rain and snow. For operation in light sleet treat as light freezing rain.
Slush is water saturated with snow, which spatters when stepping firmly on it. It is encountered at temperature around 5° C.
Snow (Metar code SN): Precipitation of ice crystals, most of which are branched, starshaped, or mixed with unbranched crystals. At temperatures higher than about -5°C, the crystals are generally agglomerated into snowflakes.
Dry snow: Snow which can be blown if loose or, if compacted by hand, will fall apart upon release. Dry snow is normally experienced when temperature is below freezing and can be brushed off easily from the aircraft.
Wet snow: Snow which, if compacted by hand, will stick together and tend to or form a snowball. Wet snow is normally experienced when temperature is above freezing and is more difficult to remove from the aircraft structure than dry snow being sufficiently wet to adhere.
Compacted snow: Snow which has been compressed into a solid mass that resists further compression and will hold together or break up into chunks if picked up.
Snow grains (Metar code: SG) is a precipitation of very small white and opaque grains of ice. These grains are fairly flat or elongated. Their diameter is less than 1 mm. When the grains hit hard ground, they do not bounce or shatter.
Snow pellets (Metar code: GS) is a precipitation of white and opaque grains of ice.
These grains are spherical or sometimes conical. Their diameter is about 2 to 5 mm. Grains are brittle, easily crushed; they bounce and break on hard ground.
Supercooled water droplets is a condition where water remains liquid at negative Celsius temperature. Supercooled drops and droplets are unstable and freeze upon impact.
Visible moisture: Fog, rain, snow, sleet, high humidity (condensation on surfaces), ice crystals or when taxiways and/or runways are contaminated by water, slush or snow.
4. FLUIDS CHARACTERISTICS ANS APPLICATION TECHNIQUES
4.1 Fluid selection:
Different types of fluids are available (Type I, II, and IV). They differ by their chemical compounds, their viscosity (capacity to adhere to the aircraft skin) and their thickness (capacity to absorb higher quantities of contaminants) thus providing variable holdover times.
4.2 Fluid characteristics:
Fluids can be principally divided into two classes, Type I and Type II/IV fluids.
4.2.1 Type I fluid:
No thickener system.
Minimum 80% glycol content; the rest comprises water, inhibitors and wetting agents. The inhibitors act to restrict corrosion, to increase the flash point or to comply with other requirements regarding materials compatibility and handling. The wetting agents allow the fluid to form a uniform film over the aircraft's surfaces.
Newtonian fluid (without thickener): viscosity depends on temperature.
Relatively short holdover time.
Orange Colour.
Type I fluids are normally diluted with water of the same volume. This 50/50 mixture has a lower freezing point than the concentrated fluid and, due to the lower viscosity, it flows off the wing much better. The freezing point is in the range of - 10°C.
4.2.2 Type II/IV fluid:
With thickener system.
Minimum 50 percent glycol- plus different inhibitors; wetting agents and a thickener system giving the fluid a high viscosity. The rest is water.
Pseudo-plastic or non Newtonian fluid (with thickener): Viscosity depends on temperature and shear forces to which the fluid is exposed.
Relatively long holdover time.
Translucent Colour for type II.
Green Colour for type IV.
The glycol in the fluid reduces the freezing point to negative ambient temperatures.
The wetting agent allows the fluid to form a uniform film over the aircraft's surfaces.
The thickening agent in Type II and IV fluids enables the film to remain on the aircraft's surfaces for longer periods.
The freezing point is in the range of -7°C.
4.3 De-icing: (Curative action)
The operation of removing all frost, ice, snow or slush from aircraft, in order to have clean surfaces at engine start. De-icing can be accomplished by use of fluids, mechanical means or by heating the aircraft. To minimize heat loss, fluids shall be applied close to the aircraft surfaces.
In order to effectively remove snow and ice, the following guidelines are recommended:
Wings/horizontal stabilizers: Spray from the tip towards the root, from the highest point of the surface camber to the lowest.
Vertical surfaces: Start at the top and work downward.
Fuselage: Spray along the top centreline and then outboard; avoid spraying directly onto windows.
Landing gear and wheel bays: Keep application of de-icing fluid in this area to a minimum.
Engines: Deposits of snow should be mechanically removed (for example using a broom or brush) from engine intakes prior to departure. Any frozen deposits, that may have bonded to either the lower surface of the intake or the fan blades, may be removed by hot air or other means recommended by the engine manufacturer.
4.4 Anti-icing: (Preventive action)
The operation of protecting the aircraft against formation of frost or ice and accumulation of snow, for a limited period of time (holdover time), in order to have clean surfaces at lift off.
The anti-icing fluid application process should be as continuous and as short as possible. Anti-icing should be carried out as near to the departure time as is operationally possible, in order to maintain holdover time.
Most effective results are obtained by commencing on the highest part of the wing section and covering from there towards the leading and trailing edges. On vertical surfaces, start at the top and work down.
The following surfaces should be protected by anti-icing:
Wing upper surface,
Horizontal stabilizer upper surface,
Vertical stabilizer and rudder,
Fuselage depending upon amount and type of precipitation.
Caution: Under no circumstances can an aircraft that has been anti-iced receive a further coating of anti-icing fluid directly on top of the existing film.
All reasonable precautions must be taken to minimize fluid entry into engines, other intakes / outlets and control surface cavities.
Engines are usually not running or are at idle during treatment. Air conditioning should be selected OFF. The APU may be run for electrical supply but the bleed air valve should be closed.
Do not spray de-icing / anti-icing fluids directly onto exhausts or thrust reversers.
De-icing / anti-icing fluid should not be directed into the orifices of pitot heads, static vents or directly onto angle-of-attack sensors.
Do not direct fluids onto flight deck or cabin windows because this can cause cracking of acrylics or penetration of the window sealing.
All doors and windows must be closed to prevent:
Galley floor areas being contaminated with slippery de-icing/anti-icing fluids
Upholstery becoming soiled.
Any forward area from which fluid may blow back onto windscreens during taxi or subsequent takeoff should be free of fluid residues prior to departure.
If Type II or IV fluids are used, all traces of the fluid on flight deck windows should be removed prior to departure, with particular attention being paid to windows fitted with wipers (De-icing/anti-icing fluid can be removed by rinsing with clear water and wiping with a soft cloth. Do not use the windscreen wipers for this purpose. This will cause smearing and loss of transparency).
Landing gear and wheel bays must be kept free from build-up of slush, ice or accumulations of blown snow (Do not spray de-icing fluid directly onto hot wheels or brakes).
When removing ice, snow or slush from aircraft surfaces, care must be taken to prevent it entering and accumulating in auxiliary intakes or control surface hinge areas (remove snow from wings and stabilizer surfaces forward towards the leading edge and remove from ailerons and elevators back towards the trailing edge).
4.5 De-icing/Anti-icing process:
De-icing and Anti-icing may be performed as a one-step or two-step process, depending on predetermined practices, weather conditions, concentration of FPD (Freezing Point Depressant) used, and available de-icing equipment and facilities. However, a two-steps procedure is recommended when a large holdover time is needed.
4.5.1 One-step process:
In this process a heated or in some cases an unheated FPD mixture is used, the residual FPD fluid film provides a very limited anti-icing protection.
4.5.2 Two-step process:
This process involves both de-icing and anti-icing procedures. First step "de-icing" is accomplished with hot water or a hot mixture of FPD fluid and water. The second step "anti-icing" involves application of type II or type IV fluid and water to the critical surfaces of the aircraft.
4.6 Equipment and material used:
4.6.1 Products:
De-icing and anti-icing procedures use the following products:
Hot air.
Heated water.
Type I de-icing fluid.
Type II or type IV anti-icing fluid.
4.6.2 Equipments/Trucks:
With a chassis on which the fluid tanks, pumps, heating and lifting components are installed.
Although centrifugal pumps are installed in older equipment, more modern equipment is fitted with cavity pumps or diaphragm pumps showing very low degradation of Type II and IV fluids.
Most of the trucks have an open basket from which the operator de/anti-ices the aircraft.
Closed cabins are also available, offering more comfort to the operator in a severe environment.
4.6.3 Stationary equipment:
Stationary de/anti-icing facilities, currently available at a limited number of airports, consist of a gantry with spraying nozzles moving over the aircraft, similar in concept to a car wash.
The advantage of such a system is a fast and thorough treatment of the surface of the aircraft. As these systems can be operated by computers, working errors are practically excluded and consistent quality can be ensured.
The disadvantage, however, is the operational bottleneck. If only one system is available and de/anti-icing is necessary, the takeoff capacity of the respective runway will be limited by the productivity of the gantry.
4.7 Fluid handling:
During fluid handling, avoid any unnecessary spillage; comply with local environmental and health laws and the manufacturer's safety data sheet.
Mixing of products from different suppliers is generally not allowed and needs extra qualification testing.
The holdover time is gained essentially by viscosity which can be adversely affected by overheating, mechanical shearing and contamination by corroded tanks, in such a manner that the expected and required holdover times cannot be achieved. Therefore trucks, storage tanks and dressing plants have to be adequately conceived and maintained to comply with these requirements.
4.8 Storage:
Tanks dedicated to the storage of the de-icing/anti-icing fluid should be made of a construction material compatible with the fluid, as specified by the fluid manufacturer. They should be conspicuously labelled to avoid contamination.
Tanks should be inspected annually for corrosion and/or contamination. If corrosion or contamination is evident, they should be maintained to standard or replaced.
The stored fluid shall be routinely checked to ensure that no degradation or contamination has taken place.
To prevent corrosion at the liquid/vapour interface and in the vapour space, a high liquid level in the tanks is recommended.
The storage temperature limits must comply with the manufacturer's guidelines.
4.9 Pumping:
De-icing/anti-icing fluids may show degradation caused by excessive mechanical shearing. Therefore, only compatible pumps as well as compatible spraying nozzles should be used in accordance with the fluid manufacturer's recommendations.
4.10 Transfer lines:
Dedicated transfer lines must be conspicuously labelled to prevent contamination and must be compatible with the de-icing/anti-icing fluids to be transferred. An in-line filter, constructed according to the fluid manufacturer's recommendations, is recommended to remove any solid contaminant.
4.11 Heating:
De-icing/anti-icing fluids must be heated according to the fluid manufacturer's guidelines. The integrity of the fluid following heating in storage should be checked periodically, by again referring to the fluid manufacturer's guidelines. Such checks should involve at least checking the refractive index and viscosity.
4.12 Application:
Application equipment shall be cleaned thoroughly before the first fill with de-icing/anti-icing fluid, in order to prevent fluid contamination. Fluid in trucks should not be heated in confined or poorly ventilated areas such as hangars. The integrity (viscosity) of the Type II and IV fluids at the spray nozzle should be checked annually, preferably at the beginning of the winter season.
5. HOLDOVER TIME (HOT)
5.1 Definition and guidance:
It is a period of time in which the anti-icing fluid remains on and ensures protection of aircraft surfaces.
Published tables should be used as guidance only, as many parameters may influence their efficiency - like severe weather conditions, high wind velocity, jet blast...- and considerably shorten the protection time.
The tables below are examples of the Holdover times for SAE Type I, II and IV fluids mixtures.
Approximate holdover times(hours: minutes): SAE Type I fluid mixture
OAT (°C)
Weather condition
Frost
Freezing Fog
Snow
Freezing Drizzle
Light Freezing Rain
Rain on cold Soaked Wing
Others
Above 0
00:45
00:12 - 00:30
00:06 - 00:15
00:05 - 00:08
00:02 - 00:05
00:02 - 00:05
CAUTION:
No Holdover time guidelines exist
0 to -10
00:45
00:06 - 00:15
00:06 - 00:15
00:05 - 00:08
00:02 - 00:05
CAUTION:
Clear ice may require touch for confirmation
Below -10
00:45
00:06 - 00:15
00:06 - 00:15
Approximate holdover times (hours: minutes): SAE Type II fluid mixture
OAT (°C)
Fluid concentration Neat-fluid/water (Vol % / Vol %)
Weather condition
Frost
Freezing Fog
Snow
Freezing Drizzle
Light Freezing Rain
Rain on cold Soaked Wing
Others
Above 0
100/0
12:00
1:05 - 02:15
0:20 - 01:00
0:30 - 1:00
0:15 - 0:30
0:05 - 0:40
CAUTION:
No Holdover time guidelines exist
75/25
6:00
0:50 - 1:45
0:15 - 0:40
0:20 - 0:45
0:10 - 0:25
0:05 - 0:25
50/50
4:00
0:15-0:35
0:05-0:15
0:05-0:20
0:05-0:10
CAUTION:
Clear ice may require touch for confirmation
0 to -3
100/0
8:00
0:35-1:30
0:20-0:45
0:30-1:00
0:15-0:30
75/25
5:00
0:25-1:00
0:15-0:30
0:20-0:45
0:10-0:25
50/50
3:00
0:15-0:35
0:05-0:15
0:05-0:20
0:05-0:10
Below -3 to -14
100/0
8:00
0:30-1:05
0:15-0:35
0:15-0:45
0:10-0:30
75/25
5:00
0:20-0:55
0:15-0:25
0:15-0:30
0:10-0:20
Below -14 to -25
100/0
8:00
0:15-0:20
0:15-0:30
Below -25
100/0
May be used below -25°C provided the freezing point of the fluid is at least 7°C below the OAT and the aerodynamic acceptance criteria are met.
Consider use of SAE Type I when SAE Type II fluid cannot be used.
Approximate holdover times (hours: minutes): SAE Type IV fluid mixture
OAT (°C)
Fluid concentration Neat-fluid/water (Vol % / Vol %)
Weather condition
Frost
Freezing Fog
Snow
Freezing Drizzle
Light Freezing Rain
Rain on cold Soaked Wing
Others
Above 0
100/0
18:00
1:05 - 02:15
0:35 - 01:05
0:40 - 1:00
0:25 - 0:40
0:10 - 0:50
CAUTION:
No Holdover time guidelines exist
75/25
6:00
1:05 - 1:45
0:20 - 0:40
0:30 - 1:00
0:15 - 0:30
0:05 - 0:35
50/50
4:00
0:20-0:35
0:05-0:20
0:10-0:20
0:05-0:10
CAUTION:
Clear ice may require touch for confirmation
0 to -3
100/0
12:00
1:05-2:15
0:30-0:55
0:40-1:00
0:25-0:40
75/25
5:00
1:05-1:45
0:20-0:35
0:30-1:00
0:15-0:30
50/50
3:00
0:20-0:35
0:05-0:15
0:10-0:20
0:05-0:10
Below -3 to -14
100/0
12:00
0:40-1:30
0:20-0:40
0:20-0:55
0:10-0:30
75/25
5:00
0:25-1:00
0:15-0:25
0:20-0:55
0:10-0:30
Below -14 to -25
100/0
12:00
0:20-0:40
0:15-0:30
Below -25
100/0
May be used below -25°C provided the freezing point of the fluid is at least 7°C below the OAT and the aerodynamic acceptance criteria are met.
Consider use of SAE Type I when SAE Type IV fluid cannot be used.
With a one-step de/anti-icing operation, holdover begins at the start of the operation. With a two-step operation, holdover begins at the start of the second (anti-icing) step.
Holdover time will have effectively run out, when frozen deposits start to form/accumulate on aircraft surfaces.
Type I fluid forms a thin liquid-wetting film (no thickener), which gives a rather limited holdover time.
Type II and Type IV fluids contain a thickener which enables the fluid to form a thicker liquid-wetting film on external surfaces. This film provides a longer holdover time.
The lower limit of the published time span is used to indicate the estimated time of protection during heavy precipitation, and the upper limit the estimated time of protection during light precipitation.
5.2 Communication:
No aircraft should be dispatched for departure after a de-icing / anti-icing operation unless the flight crew has been notified of the type of de-icing / anti-icing operation performed.
5.3 Anti-icing codes:
It is essential that the flight crew receive clear information from ground personnel concerning the treatment applied to the aircraft.
The AEA (Association of European Airlines) recommendations and the SAE (Society of Automotive Engineers) and ISO (International Standard Organization) specifications promote the standardized use of a four-element code. This gives flight crew the minimum details to assess holdover times. This information must be recorded and communicated to the flight crew by referring to the last step of the procedure.
Examples of anti-icing codes:
AEA Type II/75/16.43 local GVA / 19 Dec 99
AEA Type II
:
Type of fluid used
75
:
Percentage of fluid/water mixtures by volume 75% fluid / 25% water
16.43 local
:
Local time of start of last application
19 Dec 99
:
Date
ISO Type I/50:50/06.30 UTC/ 19 Dec 99
ISO Type I
:
Type of fluid used
50:50
:
Percentage of fluid/water mixtures by volume 50% fluid / 50% water
06.30 UTC
:
UTC time of start of last application
19 Dec 99
:
Date
6. INSPECTION AND CONTAMINATION RECOGNITION
A visual inspection must cover all critical parts of the aircraft. In particular, these parts include:
Wing surfaces including leading edges,
Horizontal stabilizer upper and lower surface,
Vertical stabilizer and rudder,
Fuselage,
Air data probes,
Static vents,
Angle-of-attack sensors,
Control surface cavities,
Engines,
Generally intakes and outlets,
Landing gear and wheel bays.
During checks on ground, electrical or mechanical ice detectors should only be used as a back-up advisory (They are not a primary system and are not intended to replace physical checks).
It is important to note that the rate of ice formation is considerably increased by the presence of an initial depth of ice. Therefore, if icing conditions are expected to occur along the taxi and takeoff path, it is necessary to ensure that all ice and frost is removed before flight.
7. SAFETY
7.1 Protective clothes:
Precautions include preventive skin protection by wearing thick protective clothing, as well as waterproof gloves.
Protective glasses and masks in order to cover eye and face, Protective headwear and headsets, footwear (boots) and fall protection systems (harness, lanyards), and reflective safety vests, should all be worn.
Soaked clothes should be changed and, after each de-icing / anti-icing activity, the face and hands should be washed with water.
Further details are available from the fluid manufacturers and the material data sheets for their products.
All Safety materials, equipment, devices and clothing used to protect the health and safety of the employee must be approved.
7.2 Procedures and work environment
JETBLAST: Even when an aircraft engine is running at low thrust or idle equipment, operators must maintain safe distances from the aircraft.
ENGINE INLET: Personnel and Foreign objects when in close proximity to operating engines are capable of being ingested and causing fatal loss in human lives and aircraft engines.
SAFETY ZONES: are used for manoeuvring deicing equipment.
SLIPPERY APRONS: if accumulation of fluid deposits occurs on aprons areas, over-sprayed fluid must be picked up before starting any task.
VISIBILITY/WIND/WEATHER: de/anti-icing operations may need to be slowed or ceased under poor visibility. And operating equipment restrictions, under extreme weather conditions, must be known.
AIRCRAFT AND VEHICLE MOVEMENT: Established procedures and patterns for vehicle movement must be adhered to.
AIRCRAFT POSITIONING: Caution should be examined when positioning light aircraft behind heavy aircraft with operating engines. This situation should be avoided as much as possible.
ADHERENCE TO PROCEDURES: Strict adherence to procedures is required. And the employee is responsible for reporting any problem with procedure or process application to his/her immediate supervisor.
Summary:
Aircraft contamination endangers T/Off safety and must be avoided. The aircraft must be cleaned.
To ensure that takeoff is performed with a clean aircraft, an external inspection has to be carried-out, bearing in mind that such phenomenon as clear-ice cannot be visually detected. Strict procedures and checks apply. In addition, responsibilities in accepting the aircraft status are clearly defined.
If the aircraft is not clean prior to T/off it has to be de-iced. De-icing procedures ensure that all the contaminants are removed from aircraft surfaces.
If the outside conditions may lead to an accumulation of precipitation before T/Off, the aircraft must be anti-iced. Anti-icing procedures provide protection against the accumulation of contaminants during a limited timeframe, referred to as holdover time.
The most important aspect of anti-icing procedures is the associated holdover time. This describes the protected time period. The holdover time depends on the weather conditions (precipitation and OAT) and the type of fluids used to anti-ice the aircraft.
Different types of fluids are available (Type I, II, and IV). They differ by their chemical compounds, their viscosity (capacity to adhere to the aircraft skin) and their thickness (capacity to absorb higher quantities of contaminants) thus providing variable holdover times.
Published tables should be used as guidance only, as many parameters may influence their efficiency - like severe weather conditions, high wind velocity, jet blast...- and considerably shorten the protection time.
NAME & SURENAME
........................................
SCORE
/ 100
DATE
........................................
Under icing conditions or when icing is expected, take off is only allowed if;
The aircraft is clean.
The aircraft's anti-icing system is operative and cannot affect the required takeoff performance.
The aircraft skin is warm enough in order to not allow any ice accumulation during takeoff.
The PIC was dealing with a delay, and he couldn't have a confirmation if his aircraft was clean, what should he do?
He considers the aircraft as clean and proceeds to takeoff, since he considers ground staff are completely aware of the situation, and "no feedback means no problem".
He can proceed to takeoff if he judges the weather conditions as not completely severe or dangerous.
His decision depends on the holdover time, "let's see how much holdover time we do have".
No action is allowed until he gets a formal confirmation that the aircraft is clean.
Who may inspect an aircraft, immediately prior to takeoff, for contamination?
The PIC.
A flight crew member of the aircraft who is designated by the PIC.
A person designated by the operator of the aircraft who has received the required surface contamination training.
No inspection is needed.
All: (a) + (b) + (c).
Aircraft performance may be affected by frost, ice or snow on the wings and control surfaces because of;
Increase in aircraft weight.
Disruption of smooth airflow.
Possible loss of aircraft control.
Uncontrolled CG movement.
All: (a) + (b) + (c) + (d).
Frost, ice or snow on a wing will
Increase the stall speed but will not affect climb performance (rate of climb).
Increase the stall speed and reduce climb performance.
Decrease the stall speed but will not affect climb performance.
Decrease the stall speed and reduce climb performance.
Not affect the stall speed or climb performance.
Icing can occur if the aircraft skin's temperature is
Below freezing and the surrounding air is cool and humid.
Below freezing and the surrounding air is below freezing.
Cool and the surrounding air is below freezing.
All: (a) + (b) + (c).
Holdover time is defined as
A maximum fluid expiration time limit given by the manufacturer.
The estimated time to fluid shear from the aircraft surfaces.
The estimated time that a fluid application is effective in protecting the aircraft from contamination.
The estimated fluid application time.
Type II and Type IV anti icing fluids are applied
Directly on contaminated aircrafts.
Directly after de-icing the aircraft.
In both cases (a) and (b).
Which fluid Type(s) provide(s) a longer protection time?
Type I and Type II
Type I and Type IV
Type IV
Type II and Type IV
Type I fluid can be defined by its Colour which is
Grey
Green
Yellow
Orange
Type II fluid can be defined by its Colour which is
Grey
Green
Orange
Type II fluid has no Colour (translucent).
Type IV fluid can be defined by its Colour which is
Grey
Green
Orange
Type IV fluid has no Colour (translucent).
SAE Type I fluid Holdover time [refer to course notes ( C/Work ) page 12]
Freezing Drizzle is falling and the reported outside temperature is 3°C. SAE Type I fluid is used for de/anti-icing the aircraft, what is the expected minimum holdover time?
2 minutes.
5 minutes.
6 minutes.
12 minutes.
SAE Type II fluid Holdover time [refer to course notes ( C/Work ) page 12]
Snow is falling and the reported outside temperature is 1°C. Undiluted SAE Type II fluid is used for anti-icing the aircraft, what is the expected minimum holdover time?
5 minutes.
15 minutes.
20 minutes.
30 minutes.
40 minutes.
SAE Type IV fluid Holdover time [refer to course notes ( C/Work ) page 13]
Snow is falling and the reported outside temperature is 2°C. A 75/25 mixture of SAE Type IV fluid is used for anti-icing the aircraft, what is the expected minimum holdover time?
20 minutes.
40 minutes.
35 minutes.
5 minutes.
SAE Type IV fluid Holdover time [refer to course notes ( C/Work ) page 13]
Snow is falling and the reported outside temperature is -2°C. SAE Type IV fluid is used for anti-icing the aircraft and the advised holdover time is between 20 and 35 minutes, what fluid concentration is used?
100/0.
75/25.
50/50.
25/75.
When de-icing an aircraft, it is important to know
The kind of contamination.
The concentration is correct for the conditions.
The recommended holdover times.
All of the above (a) + (b) + (c).
When de-icing windows, it is recommended to
Use hot water.
Spray fluid directly to the windows.
Spray the fuselage above the windows and allow the fluid to flow down.
Spray directly on the top of the windows and allow the fluid to flow down.
De-icing windows is not necessary.
Holdover time is calculated from
The start of the operation for the one-step process and the start of the second step for the two-step process.
The start of the first step in both processes (one-step and two-step).
The end of the operation for the one-step process and the end of the second step for the two step process.
The end of the first step in both processes (one-step and two-step).
A Newtonian fluid is a fluid.....
Containing a thickener system (Type I fluid).
Without a thickener system (Type I fluid).
Containing a thickener system (Type II fluid).
Without a thickener system (Type II fluid).
