Theory of Operation

TM 11-6625-646-15

c. .. Width........................................ 20.75 inches

b. During open loop testing, the channel output is

d. .. Weight ..................................... 63.25 pounds

routed directly through a meter multiplier resistor and

relay contacts to the metering circuit output of the

1-12. Theory of Operation

actuator-simulator card at pins 20 and 23 of receptacle

J64.

1-13. The test set consists of essentially independent

c. During closed loop testing, the channel output is

circuits which simulate signals normally produced by the

converted to a positive or negative dc voltage, chopped,

extensible links, the pitot-static system, and the yaw

converted to a nominal sine wave, amplified, and fed

(sideslip) ports in the helicopter. The test set includes

back to the SAS amplifier as a simulated feedback

circuits to check the output of each channel of the SAS

signal (para 1-18 through 1-25).

This simulated

amplifier, the demodulator-modulator card, the amplifier

feedback signal is also rectified on the actuator-

card, the metering circuits, and the half-gain mode

simulator card and connected through relay contacts to

circuit. An ASE mode test circuit is not used for CH-47

the metering circuit output at pins 20 and 23 of

SAS amplifiers. Each channel test circuit includes an

receptacle J64.

actuator simulator card. The demodulator-modulator

card test circuit includes an amplifier card. The test set

d. The open or closed loop metering circuit output

also contains ac and dc power supplies and a pneumatic

of the actuator-simulator card from receptacle J64 pins

system. The power supplies enable operation of the test

20 and 23 is routed to ROLL AXIS meter M3 through

set and the SAS amplifier circuits. The pneumatic

adapter switch S5.

system enables testing of airspeed and sideslip circuits.

e. The feedback signal output of the actuator-

Refer to figure 1-2 for the schematic diagram of the

simulator card from receptacle J64 pin 25 is routed to

actuator-simulator card. Refer to figure 1-3 for the

jumpered pins U and W of receptacle J60. From this

schematic diagram of the amplifier card. Refer to figure

point, the signal is routed to the SAS amplifier feedback

1-4 for the schematic diagram of the function meter

(cancellation) circuits.

circuits. Refer to figure 1-5 for the overall schematic

diagram of the test set. Refer to figure 1-6 for the

f. The 2.5-volt ac feedback resistor excitation

pneumatic system schematic. Refer to figure 1-7 for the

voltage from the SAS amplifier channel is connected to

adapter schematic.

pins V and X of receptacle J60. From pins V and X the

excitation voltage is connected to the reference voltage

1-14. Channel Test Circuits

input of the actuator-simulator card at pins 8 and 9 of

receptacle J64. On the actuator-simulator card, the

1-15. Roll Channel

excitation voltage is used to phase-relate the operation

(figs. 1-5 and 1-7)

of a chopper stage to the operation of the SAS amplifier

The roll channel test circuit measures the open and

channel (para 1-22). The excitation voltage is also

closed loop channel output of a SAS amplifier under

connected to the ac metering circuits through the ROLL

test.

(or PITCH) FEEDBACK POT. EXCITATION position of

a. The channel output signal is connected to pins

FUNCTION switch S7 (para 132).

R, S, and T of receptacle J60. From here the signal is

g. From pins p of SAS amplifier receptacle J1 and

connected through pins 2, 3 (dc common), and 5 of

adapter receptacle J101, 26 volts ac is connected to the

receptacle J64 to the phase inverter stage of the

primary of adapter transformer T101. A primary tap

actuator-simulator card. The differential output of the

supplies approximately 13-volt ac to SAS amplifier roll

SAS amplifier channel at pins 2 and 5 is also connected

signal demodulator Q302. The secondary of T101 is

by jumper wires to pins 21 and 24 of receptacle J64.

connected through dropping resistors R101

Only one of these simulator card input circuits is active,

depending on the mode of test set operation selected by

AXES METERS READ switch S4.