FK1153
SA
malfunction occurs, the SAS/FPS computer will shut off the trim actuator(s) driving the affected axis, and the TRIM FAIL and FLT PATH STAB caution legend will illumi-nate. If the malfunction is of an intermittent nature, the indication may be cleared by simultaneously pressing both POWER ON RESET switches. In addition to the trim release switch, a four-way trim switch on each cyclic stick establishes a trim position without releasing trim. With trim engaged, the trim position is moved in the direction of switch movement. The cyclic is moved by the trim switch in one direction at a time. When FPS is engaged, the TRIM switch changes the pitch and roll attitude reference instead of the cyclic stick position reference. The trim system release feature permits the pilot or copilot to .y the heli-copter with light stick forces. The push-on/push-off TRIM switch on the AUTO FLT CONT panel or the TRIM REL switches on the pilot/copilot cyclic grips may be used to release trim. When the switch is ON, the trim system pro-vides gradient and detent holding force for pitch, roll, and yaw. When turned off, the trim system is released and light cyclic control forces are present.
2.33.3 Flight Path Stabilization (FPS).
a. Proper FPS operation requires that the BOOST, TRIM and SAS 1 and/or SAS 2 functions have been selected on the AUTO FLT CONT panel. Although not required for proper operation, the FPS performance will be improved by the proper operation of the stabilator in the automatic mode. To use the FPS features, the pilot .rst assures that BOOST, SAS and TRIM are on and operat-ing, and then turns the FPS switch ON. The desired pitch and roll attitude of the helicopter may be established in one of these ways:
(1)
Pressing the STICK TRIM switch to slew the reference attitude to the desired attitude.
(2)
Pressing the TRIM REL switch on the pilot/ copilot cyclic grip, manually .ying the helicop-ter to the desired trim condition, and releasing the TRIM REL switch.
(3)
Overriding the stick trim forces to establish the desired trim condition, and then neutralizing stick forces by means of the trim switch.
b.
The trim attitude, once established, will be automati-cally held until changed by the pilot. At airspeeds greater than 60 knots, the pitch axis seeks to maintain the airspeed at which the trim is established, by variation of pitch atti-tude. When pitch attitude is changed by means of the STICK TRIM switch, there is a delay from the time that the STICK TRIM switch input is removed until the new reference airspeed is acquired. This is to allow time for the helicopter to accelerate or decelerate to the new trim speed. The yaw axis of the FPS provides heading hold at airspeeds less than 60 knots and heading hold or turn coordination at airspeeds greater than 60 knots. For heading hold operation at airspeeds less than 60 knots, the helicopter is maneu-vered to the desired heading with feet on pedals. When trimmed at the desired heading, the pilot may remove feet from pedals, at which time the existing heading becomes the reference, which is automatically held. To change head-ing, the pilot may activate one or both pedal switches, trim up on the desired heading and remove feet from pedals. At airspeeds greater than 60 knots, heading hold will be auto-matically disengaged, and coordinated turn engaged under these conditions:
(1)
STICK TRIM switch is actuated in the lateral direction.
(2)
TRIM REL switch is pressed and roll attitude is greater than prescribed limits.
(3)
About 1/2 inch cyclic displacement and a roll attitude of about 1.5°. Heading hold is auto-matically reengaged and turn coordination dis-engaged upon recovery from the turn when the
lateral stick force, roll attitude, and yaw rate are within prescribed limits.
c. To make a coordinated turn, the pilot enters a turn in one of these ways:
(1)
Changing reference roll attitude by pressing the STICK TRIM switch in the desired lateral di-rection.
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