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Chapter 3 - Turret Environmental Protection
Pressure Equalization and Airflow Pathway
When the aircraft descends in altitude, air goes into the turret through the desiccant drying agent material. Moisture
or salt in the air is filtered out by the desiccant material. The desiccant humidity indicator, found on the cartridge,
measures the water saturation level of the desiccant material. If the upper quadrants 30 & 40 of the humidity
indicator are lavender (pink), replace the desiccant material or the desiccant assembly.
Do not confuse the desiccant humidity indicator with the humidity indicator of the turret. Although the turret is a
sealed unit, with the protection of the desiccant assembly, moisture levels can increase in the turret. When the
upper quadrants 30 & 40 of the turret humidity indicator are lavender (pink), use nitrogen to purge the turret. You
can find the purge valve on the rear door.
There is no regular or scheduled interval for these maintenance actions. The replacement of the desiccant
assembly and purging of the turret is dependent on operational and environmental use factors:
•
The relative humidity of the environment during flight.
•
The relative humidity of the environment when stopped.
•
The period of time between flights.
•
The number of times the aircraft ascends and descends.
Air Pathway
October 2007
64
t
o n
F r
Turret
Humidity Indicator
Desiccant
Assembly
Desiccant
Humidity Indicator
Turret
Purge Valve
Figure 3-3 Turret Desiccant Breather Assembly
Desiccant
Breather Valve
Figure 3-4 Pressure Equalization and Airflow Pathways
1.0 psi
TM00358 Rev. A
t
o n
F r
Desiccant
Assembly
L-3 WESCAM
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