TM 1-1520-238-T-7
11–28
Change 4
11–2.
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont)
11–2
(4) Stabilator Actuator Assembly.
The stabilator actuator assembly attaches to the tail boom and the
stabilator at left butt line 3.5 and positions the stabilator in response to commands from the SCUs. The stabilator
actuator assembly consists of two tandem linear actuators mounted back-to-back. Linear actuator 2 comprises the
upper half of the actuator assembly when mounted. Linear actuator 1 comprises the bottom half of the actuator
assembly. Each linear actuator contains a reversible dc motor, a potentiometer, and internal retract and extend
limit switches.
(5) SCUs.
SCU 1 and 2, located in the left side of the aft equipment bay, control the position of the
stabilator in the automatic mode of operation. The SCU is a solid state LRU with four electrical connectors and a
handle on the front.
(a) Engagement of the SCU is automatic when electrical power is applied to the helicopter if the ac
power monitor and the SCU program monitor are both satisfied, and if 26 VAC demodulator reference is present.
(b) The SCU program monitor checks the feedback position of the two motor actuators at 80 and 110
knots. If the feedback position at 80 knots is more than 30 (8.39 0.4 VDC), the engage logic is commanded to a
fail condition within 1.25 seconds. If the feedback position at 110 knots is more than 20 (1.68 0.4 VDC), the
engage logic is commanded to a fail condition within 150 milliseconds.
(6) Stabilator Position Transducer.
The stabilator position transducer, centrally mounted between the
stabilator and the fuselage at the pivot point of the stabilator, is a cylindrical synchro transmitter which monitors
stabilator position and provides a signal to the pilot and CPG STAB POS indicators.
(7) STAB POS Indicators.
STAB POS indicators, located in the upper right side of each crew station,
provide a visual indication of stabilator trailing edge position as commanded by the stabilator position transducer.
(8) Stabilator Relay Box.
The stabilator relay box, mounted in the left side of the aft equipment bay,
provides mounting for the SCS relays and contains the following SCS relays:
AUTO/MAN (auto/manual) relay (K1-1/2).
Manual select relay (K1-3/4).
Manual control relay (K1-5).
Auto reset relay (K1-6).
Approach relay 1 (K1-7).
