TM 1-1520-238-T-5
8–25
8–7.
SYSTEM DESCRIPTION (cont)
8–7
(e) The pilot SAI (fig. 8–18) is a self contained gyroscope (gyro) which indicates pitch and roll motion of
the helicopter. The pilot SAI operates on 28 VDC input or 24 VDC emergency power. An internal static converter
converts VDC input to 26 VAC, 400 Hz. The 26 VAC runs the motor which spins the gyro. The spinning gyro
provides visual roll and pitch information. The word CLIMB appears on the gyrosphere when the helicopter
upward pitch reaches 35. The word DIVE appears on the gyrosphere when the helicopter downward pitch
reaches –35. The pitch trim control knob adjusts the pitch of the gyrosphere horizon to the fixed aircraft symbol.
An OFF flag is displayed if the gyro is caged or power is lost.
STATIC
INVERTER
MOTOR
GYROSCOPE
PILOT SAI
ELAPSED
TIME
INDICATOR
OFF
FLAG
EMERGENCY
DC BUS 28 VDC
OR BATTERY
24 VDC
ROLL
PITCH
PILOT
EXT LT/
INTR LT
PANEL
0 - 5 VDC PANEL
EDGE - LIGHTING
CAGE
PITCH TRIM
AND CAGE
KNOB
M68-129
Figure 8–18.
Pilot SAI Functional Block Diagram
