The concept of “clean aircraft” provides for the need to completely clean its surface from ice, snow and any other contaminants. This is due to the extreme sensitivity of the aerodynamic properties of the aircraft even to minor changes in the geometric parameters of the fuselage and wing. In addition, icing can cause complete or partial blocking of the steering surfaces. All this is fraught with extremely undesirable consequences. To prevent these phenomena, the relevant rules provide for the aircraft to be treated with anti-icing fluid before departure.
The reasons for the formation of ice
At a temperature close to negative values, crystallization of water in the atmosphere occurs. This may occur in the form of frost or ice crystals settling on the surface of the aircraft. Sometimes this is a consequence of precipitation, the most unpleasant of which are the so-called ice rains. Often moisture gets to the surface of the machine during taxiing at the airport. To combat this natural phenomenon, anti-icing fluids or mechanical cleaning of the aircraft are used, which is a rather laborious and lengthy process. However, in military aviation, it is still the main way and is the responsibility of the crew.
What are the fluids
There are four types of anti-icing fluid. Typically, their type is indicated by Roman numerals from the first to the fourth. The following is a brief description of these fluids:
- Type I does not contain thickeners (unlike other types), does not have a protective effect, it is used only in hot form and serves only for cleaning from snow, dirt and ice. The color is red-orange.
- Type II contains thickeners and at least 50% ethylene glycol, but is able to provide protection against re-icing only for a short period of time. It has shades of yellow.
- Type III is similar to type II, but there is even less thickener. This type is used for processing low-speed aircraft. Colorless.
- Type IV contains a high concentration of thickener and provides long-term protection against re-icing. It has an emerald green color.
All liquids are used in the form diluted with water, the norms of the water content in the liquid for each type are strictly regulated and depend on weather conditions. The freezing temperature of the liquid should be at least 10 degrees lower than the ambient temperature. It is strictly forbidden to mix anti-icing fluids of different types with each other. It is also forbidden to mix liquids of the same type, but from different manufacturers. At civilian aerodromes, the main type is type IV fluid.
Regulation
In Russia, GOST R54264-2010 is in force, which describes the methods and procedures for using anti-icing fluid for aircraft. The provisions of this GOST are unified with the international standards ISO 11075 and ISO 11078. Current world practice provides for mandatory testing of all anti-icing fluids in special laboratories and the publication of lists of fluids approved for use. Such publications are publicly available. In Russia, the Federal Air Transport Agency is involved in this. The following liquids are allowed for use for the current autumn-winter period: type I - “Arctic DG”, Safewing EG I 1996 (88), “AVIAFLO EG” (AVIAFLO EG), OCTAFLO EG, Oktaflo Lyod, “DEFROST EG 88.1”. Only one fluid is allowed for type II: Safewing MP II FLIGHT. Type III is not used at Russian airports, since this type is not in the list of the Federal Air Transport Agency. For type IV, you can use Safewing MP IV LAUCH, Max Flight Sneg, Max Flight 04, Max Flight AVIA and Safewing EG IV NORT.
Processing types
There are two main types of preflight processing aircraft. Under favorable conditions, they are limited to cleaning the aircraft in one step. Usually this is done before the aircraft is delivered for boarding passengers. Snow and other deposits are simply removed from the aircraft with Type I anti-icing fluid. In cases where there is an increased risk of icing on the surfaces, the treatment is carried out in two stages. First, by the method already described, and then, immediately before takeoff, they are treated with type II, III or IV anti-icing fluid. The decision to carry out the processing is taken jointly by the aircraft commander and the airport controller. Moreover, if one of them is for, and the other is against, processing is still performed.
Manufacturers
Formally, anti-icing fluids for aircraft do not differ in too complicated chemical composition and do not require special high-tech production facilities, but the entrance ticket to this market has a rather high price. The need for accreditation, passing multi-stage tests, surrounded by strong competitors with many years of experience and reputation - all this greatly complicates the entry of new manufacturers into the market.
Currently, the main brands are American and Canadian Killfrost, Safewing, Octaflo, Maxflight. Recently noticeable products of the German company Clarion. From domestic brands can be called type I liquid "Arctic". As can be seen from the above list of liquids allowed for use, the domestic manufacturer is allowed to produce only anti-icing liquids of type 1. At the same time, Russian enterprises operate on the territory of the country, which produce products of Western brands under license and obtained technologies. In particular, this is Moscow-based Oktafluid CJSC, working together with the Americans, as well as the Nizhnekamsk firm Arcton. The volume of fluid consumption of all types only at Moscow airports is estimated at 12 thousand tons per year. Therefore, the stock of anti-icing fluids at the airport should be quite large.
Processing equipment
For aircraft processing, special machines are used on the truck platform. They are equipped with telescopic rods with swiveling nozzles for spraying anti-icing fluid. The operator’s cabin is equipped with a heating device, and the machine itself is equipped with sensors and signal lights, allowing you to get as close to the aircraft as possible without touching it. To handle hard-to-reach areas, such as the bottom of the aircraft, separate hoses with spray guns are provided.
Processing the aircraft with anti-icing fluid serves solely to protect the machine on the ground, until take-off, when the remainder of this fluid is blown away by the oncoming air stream. In the future, directly in flight, each aircraft uses its own standard anti-icing systems.
Air crashes
Despite the fact that the phenomenon of icing of the aircraft body has long been well studied, disasters continue to occur due to neglect of aviation safety rules. Some of them are the crash of the Belavia CRJ plane in Yerevan in 2008, the crash in Sochi in December 2016 and the very recent crash of the An-148 plane this year. Therefore, passenger discontent caused by delayed departure due to the need for anti-icing treatment, to put it mildly, is not justified.