Failure Mode. If the cooling air passages become clogged,
the bleed air temperature becomes too hot, and if the bleed
air passages become clogged, the bleed air flow and the
final distribution air flow decrease.
3.
Overtemperature Switch (fig. 1-10).
The overtemperature switch, located
in the bleed air outlet duct,
just downstream from the precooler,
senses the temperature of the
bleed air just after it leaves the
precooler.
This switch has a
vapor generator in a probe partially
filled with liquid and a three-
pin electrical connector.
Figure 1-10.
Overtemperature Switch Location.
Operation (fig. 1-11).
The overtemperature switch detects
an overtemperature condition at the precooler bleed air
outlet.
When the switch detects an overtemperature
condition (above 325,F ƒ10,F), it turns on the (SPONSON IN
OVER HEAT) warning light on the commander's control panel.
The switch works on pressure created in the liquid filled
probe.
The pressure created in the probe is directly
proportional to the temperature of the bleed air.
If the temperature reaches the control point (325,F
ƒ10,F), the pressure created in the probe moves a stainless
steel diaphragm to actuate the switch and close the
contacts.
The contacts of the switch remain closed until
the temperature of the bleed air drops to 300,F ƒ15,F, the
reset point.
12
OD1705
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