(g)
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.
(h)
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 2) The instructions of the fluid manufacturer 3) The air temperature
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A
747-400 MAINTENANCE MANUAL
GUIDELINE SUMMARY FOR APPLICATION OF TYPE I FLUID MIXTURES (MINIMUM CONCENTRATIONS) AS A FUNCTION OF OAT
OUTSIDE AIR ONE-STEP PROCEDURE TWO-STEP PROCEDURE
OAT TEMPERATURE DEICING/ANTI-ICING 1ST STEP: DEICING 2ND STEP: ANTI-ICING 1
-3`C (27`F) AND ABOVE MIXTURE SHALL BE AT LEAST FP OF HEATED FLUID 10`C (18`F) BELOW OAT 3`C (5`F) ABOVE ACTUAL OAT. WATER TREATED TO 82`C (180`F) MINIMUM AT THE TANK, OR A HEATED MIX OF FLUID AND WATER. FP OF HEATED FLUID MIXTURE SHALL BE NOT MORE THAN BELOW ACTUAL OAT BE AT LEAST 10`C (18F) FP OF FLUID MIXTURE SHALL
BELOW -3`C (27`F)
TYPE I FLUIDS
`F `C FP OAT DEGREES FAHRENHEIT DEGREES CELSIUS FREEZING POINT OUTSIDE AIR TEMPERATURE
CAUTION: WING SKIN TEMPERATURES MAY DIFFER AND IN SOME CASES MAY BE LOWER THAN OAT. A STRONGER MIX (MORE GLYCOL) CAN BE USED UNDER THE LATTER CONDITIONS.
NOTE: FOR HEATED FLUIDS, A FLUID TEMPERATURE NOT LESS THAN 82`C (180`F) AT THE TANK 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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G34365
A
747-400 MAINTENANCE MANUAL
GUIDELINE SUMMARY FOR APPLICATION OF TYPE II/TYPE IV FLUID MIXTURES (MINIMUM CONCENTRATIONS) AS A FUNCTION OF OAT
CONCENTRATION (PERCENTAGE BY VOLUME)
ANTI-ICING FLUID/WATER
OAT OUTSIDE AIR TEMPERATURE ONE-STEP PROCEDURE 2 TWO-STEP PROCEDURE 2
DEICING/ANTI-ICING 1ST STEP: DEICING 2ND STEP: ANTI-ICING 1
-3`C (27`F) AND ABOVE HEATED TYPE II/IV 50/50 WATER TREATED TO 82`C OR A HEATED MIX OF TYPE I, (180`F) MINIMUM AT THE TANK TYPE II OR TYPE IV FLUID AND WATER. TYPE II/IV 50/50
-3`C (27`F) BELOW TO -14`C (7`F) HEATED TYPE II/IV 75/25 HEATED SUITABLE MIX OF TYPE I, TYPE II OR TYPE IV TYPE II/IV 75/25
BELOW -14`C (7`F) TO -25`C (-13`F) 100/0 HEATED TYPE II/IV 3`C (5`F) ABOVE ACTUAL OAT. WITH FP NOT MORE THAN 100/0 TYPE II/IV
BELOW -25`C (-13`F) CONSIDER USE OF TYPE I FLUID WHEN TYPE II/TYPE IV FLUID CANNOT BE USED. CONFORM TO THE LOWEST OPERATIONAL USE TEMPERATURE/AERODYNAMICS ACCEPTANCE LIMITATION. 7`C (13`F) BUFFER BETWEEN THE FP OF THE NEAT FLUID AND OAT, AND THE FLUID SHALL USE OF TYPE II/TYPE IV FLUID FOR ANTI-ICING BELOW -25`C (-13`F) SHALL MAINTAIN
TYPE II AND TYPE IV FLUIDS
CAUTION: WING SKIN TEMPERATURES MAY DIFFER AND IN SOME CASES MAY BE LOWER THAN OAT. A STRONGER MIX (MORE GLYCOL) CAN BE USED UNDER THE LATTER CONDITIONS.
NOTE: FOR HEATED FLUIDS, A FLUID TEMPERATURE NOT LESS THAN 82`C (180`F) AT THE TANK IS DESIRABLE. UPPER TEMPERATURE LIMIT SHALL NOT EXCEED FLUID AND AIRPLANE MANUFACTURER'S RECOMMENDATIONS.
TO BE APPLIED BEFORE FIRST STEP FLUID FREEZES, TYPICALLY WITHIN 3 MINUTES
REFER TO PARAGRAPH 1.C. FOR DEFINITIONS FOR ONE-STEP, TWO-STEP AND ANTI-ICING PROCEDURES.
Fluid Mixture Guidelines for Deicing
Figure 302 (Sheet 2)
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