Freezing Rain. Water condensed from atmospheric vapor falling to earth in supercooled drops, forming ice on objects.
(6) Rain or High Humidity (on Cold-Soaked Wing).
Water forming ice or frost on the wing suriace when the temperature of the aircraft wing surface is at or below 0°C (32°F). This ice or frost may freeze over the entire wing surface and on the wing leading edge. Some aircraft may be susceptible to the formation of frost or ice on wing surfaces when the wing surfaces are cold-soaked and the aircraft is exposed to conditions of high humidity, rain, drizzle, or fog at ambient temperatures above freezing.
(7) Underwing Frost. Takeoff with frost under the wing in the area of the fuel tanks (caused by cold-soaked fuel) within limits established by the aircraft manufacturer, authorized by FAA aircraft certification offices, and stated in aircraft maintenance and flight manuals may be permitted.
b. Effects of Frost, Ice, Snow, and Slush on Aircraft Performance, Stability, and Control. The certificate holder should obtain this information from the manufacturer of each type of aircraft it uses in its operations and should ensure that its pilots are trained in the following effects of contamination on aircraft performance.
(1) Increased drag/weight.
(2) Tendency for rapid pitch-up during rotation or wing roll off.
(3) Loss of lift.
(4) Stall occurs at lower-than-normal angle of attack.
(5) Buffet or stall occurs before activation of stall warning.
(6) Decreased effectiveness of flight controls.
15. TYPES AND CHARACTERISTICS OF DEICING/ANTI-ICING FLUIDS.
a . Certificate holders should refer to the SAE and ISO publications in paragraphs 3(f) and 3(g) for additional information on specific deicing and anti-icing methods and procedures and on fluid characteristics and capabilities.
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b. If the certificate holder intends to use deicing/ anti-icing fluids for ground deicing, the types and characteristics of deicing/anti-icing fluids should be included in the certificate holder's training program and operations manual. Deicing and anti-icing fluids with differing characteristics and capabilities exist; they may undergo improvements, and new types of fluids may be developed.
Certificate holders should ensure that their pilots are knowledgeable about the characteristics of each type of fluid used.
C. Certificate holders should ensure that the following subjects are discussed, as applicable:
(1) Deicing Fluids.
(i) Heated water.
(ii) Heated mixtures of water and SAE/ISO Type I fluid.
(iii) Heated mixtures of water and SAE/ISO Type II fluid.
Note: Deicing fluid should be applied heated to assure maximum efficiency.
(2) Anti-Icing Fluids.
(i) Mixtures of water and SAE/ISO Type I fluid.
(ii) SAE/ISO Type II fluid.
(iii) Mixtures of water and SAE/ISO Type II fluid.
Note: SAE/ISO Type II anti-icing fluid is normally applied cold on clean aircraft surfaces, but may be applied heated. Cold SAE/ISO Type II fluid normally provides longer anti-icing protection. SAE/ISO Type I anti-icing fluid should be applied heated and diluted.
(3) Unapproved Fluids and Antifreeze. Use freezing point depressant (FPD) fluids approved for use by the aircraft manufacturer. Some fluids may not be compatible with aircraft materials and finishes and some may have characteristics that impair aircraft performance and flight characteristics or cause control surface instabilities. Use of automotive antifreeze for deicing is not approved. Its holdover time and its effects on aircraft aerodynamic performance are generally unknown.
14 Par 15
Par 15 field length. attitude. takeoff. length. the use of the different deicing/anti-icing fluids. manufacturer may also provide performance information regarding following handling/performance factors. The aircraft flows off the wing during takeoff determines the effects of the Implications. fluid to progressively flow off the wing during takeoff. gel-like consistency) on wing. of Type I fluids. C. 12/12/94 15 (vi) Increased drag during climb. (v) Increased drag during acceleration/increased (iv) Lift loss at climbout/increased pitch (iii) Increased stall speeds/reduced stall margins. (ii) Increased control (elevator) pressures on (i) Increased rotation speeds/increased field The type fluid used and how completely the fluid (3) Deicing/Anti-Icing Fluids Handling/Performance Windflow over the wing (shear) causes the (iv) Application results in a thick liquid film (a (iii) (ii) Longer holdover times in comparison to those (i) Thickened. (2) Type II Fluids: (iii) When applied, forms thin liquid film on wing. (ii) Limited holdover time. (i) Unthickened. (1) Type I Fluids. AC 135-16
16. COLD WEATHER PREFLIGHT INSPECTION PROCEDURES.
Pilot Preflight Inspection/Cold Weather Preflight Inspection Procedures. This is the normal walk-around preflight inspection conducted by a pilot. This inspection should be used to note any aircraft surface contamination and initiate any required deicing/anti-icing operations.
b. A thorough preflight inspection is more important in temperature extremes because those temperature extremes may affect the aircraft or its performance. At extremely low temperatures, the urge to hurry the preflight of the aircraft is natural, particularly when the aircraft is outside and adverse weather conditions exist, which make the preflight physically uncomfortable for the pilots. This is the very time to perform the most thorough preflight inspection.
Aircraft areas that require special attention during a preflight inspection during cold weather operations depend on the aircraft design and should be identified in the certificate holder's training program. The preflight should include all items recommended by the aircraft manufacturer. A preflight should include items appropriate to the specific aircraft type.
Generally, those items may include:
(1) Wing leading edges, upper and lower surfaces.
(2) Vertical and horizontal stabilizing devices, leading edges, upper surfaces, lower surfaces, and side panels.
(3) Lift\drag devices such as trailing edge flaps.
(4) Spoilers and speed brakes.
(5) All control surfaces and control balance bays.
(6) Propellers.
(7) Engine inlets, particle separators, screens, and pressure probes.
(8) Windshields and other windows necessary for visibility.
(9) Antennas.
(10) Fuselage.
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Par 16 17 (2) Random snow accumulation. (1) Progressive surface freezing or snow accumulation. include: deicing/anti-icing fluid or contamination on aircraft surfaces Some indications for loss of effectiveness of indications of loss of effectiveness of fluids. applicable) to recognize contamination on aircraft surfaces and techniques for the use of their pilots (and other personnel, if Certificate holders should have aircraft-specific 17. TECHNIQUES FOR RECOGNIZING CONTAMINATION ON THE AIRPLANE. (6) Fuel vents. (5) Elevator and rudder controls. (4) Engine air intakes and carburetor intakes. (3) Heater intakes. (2) Wheel wells. (1) Pitot tubes and static system sensing ports. ice before flight: operations. The following openings should be free of snow and aircraft where snow can enter, freeze, and obstruct normal snow, special attention should be given to openings in the Blowing Snow. If an aircraft is exposed to blowing (14) Landing gear. intakes, and exhausts. (13) Cooling and auxiliary power unit (APU) air (12) Fuel tank and fuel cap vents. ports. angle-of-attack vanes, pitot-static pressure probes, and static (11) Exposed instrumentation devices such as 12/12/94 AC 135-16
(3) Dulling of surface reflectivity (loss of gloss) caused by the gradual deterioration of the fluid to slush.
(4) Fluid characteristics and indications that the fluid is losing its effectiveness obtained from the deicing/anti-icing fluid manufacturers.
Milina y Milite William J. White Deputy Director, Flight Standards Service 18 Par 17
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