INDICATORS
Cabin Altitude and Differential
Pressure Indicator
Cabin altitude and differential pressure are
indicated on a single indicator incorporating
two scales and two pointers (Figure 12-7).
The cabin altitude is indicated by a single
pointer and circular scale on the outer edge with
CABIN ALT markings from 0 to 50,000 feet.
The cabin differential pressure is indicated
by a circular scale on the inner portion of the
indicator and a single pointer. The scale rep-
resents differential from 0 to 10 psi. It has a
green band from 0 to 8.9 psi on SNs prior to
24-350 and 25-227, and from 0 to 9.4 psi on
later SNs. It has an amber band from 8.9 to 9.2
psi on early aircraft and 9.4 to 9.7 psi on cur-
rent aircraft. A red band appears above 9.2 psi
on early aircraft and above 9.7 on current air-
craft. Cabin altitude should always be equal
to or less than the aircraft altitude.
Cabin Vertical Speed Indicator
The cabin vertical speed indicator is positioned
to the right of the cabin altimeter. It provides
an indication of cabin climb or descent rates
of between 0 and 6,000 feet per minute.
12-8
FOR TRAINING PURPOSES ONLY
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