(5) TEST Button TEST button checks
indicator R/T unit and flag operation.
c. Normal Operation.
(1) Setting Decision Height Altitude. The
radio altimeter also provides altitude and decision
height information to the GCAS. Set the decision
height altitude using the decision height set knob.
Setting the radio altimeter decision height marker to a
decision height altitude will cause the GCAS to
announce the "Minimums, Minimums" aural warning
when the aircraft transitions through the selected DH
(2) Testing. Operating the TEST button
causes the flag to come into view and altitude pointer
to indicate approximately 100 feet. Release of button
causes pointer to return to existing altitude and flag to
3C-29. VERTICAL SPEED INDICATORS.
The vertical speed indicators are mounted on
both sides of the instrument panel. The face is
placarded VERTICAL SPEED, UP, and DOWN. The
range of the instrument is from 0 to 4000 feet per
minute, with the first 2000 feet graduated in 100-foot
per minute increments and the remainder in 250-foot
per minute increments.
3C-30. TURN AND SLIP INDICATOR.
Refer to Chapter 2, Paragraph 2-77 for detailed
3C-31. GYRO MAGNETIC COMPASS SYSTEM.
systems provide accurate directional information for
the aircraft at all latitudes of the earth. For heading
directional gyro (FREE) mode, or slaved (SLAVE)
In areas where magnetic
references are reliable, the system is operated in the
SLAVE mode. In this mode, the directional gyro is
slaved to the magnetic flux valve that supplies
magnetic reference for correction of the apparent drift
of the gyro. In FREE mode, the system is operated as
a free gyro. In this mode, latitude corrections are
DECREASE switches located outboard of each HSI.
The slave/free mode is selected as desired using the
SLAVE / FREE switches also located outboard of
each HSI. Both compass systems (No. 1 and No. 2)
are ac power dependent and are powered by the
Gyro compass 1 provides heading information
for the pilot's HSI and copilot's RMI. Gyro compass 2
serves the copilots HSI and the pilot's RMI.
c. Compass Synchronization Annunciator.
Consists of the symbol 2 or X (dot or cross) displayed
in a window. When the compass system is in the
slaved mode, the display will oscillate between the 2
and X, indicating the heading dial is synchronized with
gyro stabilized magnetic heading.
3C-32. VERTICAL GYRO SYSTEM.
The pilot's and copilot's vertical gyro systems are
independent and powered by the ac power bus located
in the nose avionics compartment. The purpose of the
vertical gyro systems is to provide the pilots with visual
indications of aircraft pitch and roll attitudes on the
flight director indicators. The gyroscope develops
through synchros, pitch, and roll signals representative
established by two gravity sensitive switches, which
control a torque motor for each gyro axis. High or low
erection rate of the gyro is accomplished by applying
high or low voltage to the respective torque motor.
Panel mounted switches, placarded NO. 1 (pilot) and
NO. 2 (copilot) V GYRO FAST ERECT, provide the
means for fast erection of the gyros. Pressing the
FAST ERECT switch will erect the gyro to within 1.0
of pitch and roll within 60 seconds of power
application, and erect to within 0.5 within 2 minutes.
a. Description. The combined Total Airspeed,
Static Air Temperature indicator provides a digital
display of both TAS and SAT or TAT as generated by
the air data computer.
b. Display. The input signals are displayed as
follows. Refer to Figure 3C-21.
(1) TAS Displays TAS.
(2) SAT Displays SAT in two digits and the
± sign from -99° to + 50° C.