TM 1-1520-238-T-7
11–10
11–2.
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS (cont)
11–2
c. Longitudinal (Cyclic) Flight Control System.
The longitudinal flight control system (fig. 11–3) consists
of the pilot and CPG cyclic sticks, two LVDTs, two SPADs, feel spring and magnetic brake assemblies, the
longitudinal mechanical control linkage, the longitudinal servocylinder, the mixer assembly, and the torque link.
(1) Pilot and CPG Cyclic Sticks.
The pilot and CPG cyclic sticks, mounted to the floor centerline in
each crew station, control the main rotor assembly for longitudinal and lateral flight of the helicopter. The cyclic
sticks control longitudinal flight by forward and aft movement. When mechanical control is lost, BUCS maintains
longitudinal and lateral control. The cyclic stick consists of the grip, tube, housing, and support assembly.
(a) The grip assembly, mounted at the upper end of the cyclic stick, is a handle used to control the
cyclic stick containing various switches and controls.
(b) The tube assembly is the controller for the cyclic control system and is mounted to a fitting
assembly, which is supported by the lock and base assemblies. The tube assembly has five welded pieces
consisting of a tube, a fitting, a cover, a guide and a support. The upper portion mounts to the grip assembly, while
the lower portion mounts to the fitting assembly. A cable assembly is mounted to the upper portion of the tube
assembly and releases the lock assembly in the retracted position. The fitting assembly is mounted to the lower
portion of the tube assembly to provide mounting for the tube assembly and attachment of the lock assembly. The
lock assembly is mounted between the fitting assembly and the base assembly to allow the cyclic stick assembly
to be locked in an extended or retracted position.
(c) The base assembly, located at the lower portion of the cyclic assembly, provides mounting of the
lock assembly and the lateral pivot point. Links and levers are located and mounted to the fitting, the lock
assembly, and the base assembly to provide interconnection between the finger lock release lever and cable
assembly, to activate the lock assembly.
(d) The housing assembly, mounted to the support assembly at the floor centerline in each crew station,
provides longitudinal and lateral control movement of the cyclic stick assembly.
(e) The support assembly, mounted to the floor centerline in each crew station, provides mounting and
support for the housing assembly and the longitudinal SPAD.
(2) LVDTs.
One lateral and one longitudinal LVDT is installed at the canted bulkhead and is attached to
the base of the cyclic stick assembly in each crew station. The LVDTs generate electrical signals that are
proportional at the amount of cyclic stick movement. The LVDT sends a signal to the DASEC proportional to its
movement.
(3) SPADs.
The lateral and longitudinal SPADs, attached to the cyclic output bellcrank assembly at each
crew station, activate the fly-by-wire BUCS system if the mechanical flight controls are jammed and the shear pin
is severed. The SPAD incorporates a mechanical cam lock, switch, and shear pin that fits into a slot on one of the
bellcranks and locks the input and output bellcranks together as a single unit.
(4) Feel Spring and Magnetic Brake Assemblies.
The feel spring and magnetic brake assemblies are
installed beneath the pilot’s cyclic housing assembly (one set provides trim for both stations) to provide
longitudinal and lateral flight trim.
(a) The feel spring assembly, a spring loaded device, overrides the magnetic brake when locked by
moving the cyclic stick against the spring.
