12-33-01
ALL ú ú 01 Page 306 ú May 28/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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A
757 MAINTENANCE MANUAL
2) The temperature is 34°F or higher, and stable or on the increase.
CAUTION:_______ DO NOT POINT A SOLID FLOW OF FLUID DIRECTLY AT THE
SURFACE. APPLY THE FLUID AT A LOW ANGLE TO PREVENT DAMAGE
TO THE AIRPLANE SURFACES. DO NOT USE A HIGH PRESSURE
SPRAY TO BLOW THE ICE AND SNOW OFF THE AIRPLANE SURFACES.
(d)
For the best results in the ice or snow removal, you must increase the temperature of the deicing fluid and hot water to 180-200°F, at the tank. A fine to medium spray is recommended to apply the fluid across a large area of ice or snow. This will cause the ice or snow to melt the fastest. A solid flow of fluid is recommended to flush the ice or snow from the airplane surfaces. Make sure the maximum force of the solid flow of fluid on the surfaces is not more than 10 psi on an area of 25 square inches. This will prevent damage to the surfaces.
(e)
To find the quantity of deicing/anti-icing fluid to use in the deicing mixture at a given temperature, refer to the airline procedure or the manufacturer's specifications for the fluid you use. For Type I fluids use Fig. 302 in this document. For Type II and Type IV fluids, also use Fig. 302. The lower of the ambient temperature or the temperature of the airplane surface is the temperature to use for the Table. See if the mixture of melted ice or snow and deicing/anti-icing fluid freezes again on the airplane as it flows off. If it does, a larger quantity of deicing/anti-icing fluid in the mixture is necessary.
(f)
A layer of anti-icing fluid will give protection from ice, snow, and frost if you apply the fluid to a dry wing. A mixture of anti-icing fluid and water (the ambient temperature will have an effect on when to use a mixture with water) will also give protection if you apply it to a dry wing. The fluid must be applied before the conditions start. Use the conditions that follow to make a decision to apply anti-icing fluid to a cold-soaked airplane: 804 1) There is precipitation 804 2) The air temperature is above freezing. Since the temperature of the external surfaces of the airplane can be below freezing, ice can occur and attach to the surface. There can be clear ice below the layer of snow or slush, which is not easy to find. Make sure that all the ice is removed after you do the ice removal or ice removal/anti-icing procedure. Possibly it will be necessary to feel the surface to do the inspection.
(g)
When the precipitation is continuous, the two-step ice removal/anti-icing procedure is usually recommended. Use one of the items that follow to find the quantity of fluid to use in the mixture: 1) The airline experience
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12-33-01
ALL ú ú 01 Page 307 ú May 28/00
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
757
MAINTENANCE MANUAL
GUIDELINE SUMMARY FOR APPLICATION OF TYPE I FLUID MIXTURES (MINIMUM CONCENTRATIONS) AS A FUNCTION OF OAT
TEMPERATURE OUTSIDE AIR OAT ONE-STEP PROCEDURE TWO-STEP PROCEDURE
DEICING/ANTI-ICING 1ST STEP: DEICING 2ND STEP: ANTI-ICING 1
AND ABOVE -3`C (27`F) 10`C (18`F) BELOW OAT FP OF HEATED FLUID MIXTURE SHALL BE AT LEAST SHALL BE NOT MORE THAN FP OF HEATED FLUID MIXTURE FLUID AND WATER. TANK, OR A HEATED MIX OF (180`F) MINIMUM AT THE WATER TREATED TO 82`C 3`C (5`F) ABOVE ACTUAL OAT. FP OF FLUID MIXTURE SHALL BE AT LEAST 10`C (18F) BELOW ACTUAL OAT
-3`C (27`F) BELOW
TYPE I FLUIDS
FP OAT `F `C FREEZING POINT OUTSIDE AIR TEMPERATURE DEGREES FAHRENHEIT DEGREES CELSIUS
_______WING SKIN TEMPERATURES MAY DIFFER AND IN SOME CASES MAY BE LOWER THAN OAT.CAUTION: A STRONGER MIX (MORE GLYCOL) CAN BE USED UNDER THE LATTER CONDITIONS.
____FOR HEATED FLUIDS, A FLUID TEMPERATURE NOT LESS THAN 82`C (180`F) AT THE TANK
NOTE: IS DESIRABLE. UPPER TEMPERATURE LIMIT SHALL NOT EXCEED FLUID AND AIRPLANE MANUFACTURER'S RECOMMENDATIONS.
1 TO BE APPLIED BEFORE FIRST STEP FLUID FREEZES, TYPICALLY WITHIN 3 MINUTES
Fluid Mixture Guidelines for Deicing
Figure 302 (Sheet 1)
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