Diamond DA 42 NG, Maintenance Manual

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AIRCRAFT
DA 42 NG AMM Flight Controls
Doc # 7.02.15
Rev. 4
27-21-00
Page 3
15 Mar 2018
2. Description
The mechanical rudder trim system has three main parts:
)
A handwheel assembly with trim indicator.
)
A long flexible cable which connects the handwheel to the trim tab operating mechanism.
)
The trim tab actuator assembly.
A. Rudder Trim Handwheel Assembly
A handwheel assembly at the top of the center console controls the rudder system. The handwheel
attaches to a rectangular drive on the top of a long spindle. The rectangular drive at the top of the
spindle also drives the trim indicator. The trim indicator system is a mechanical device and attaches
to the lower surface of the center console cover plate.
The long spindle is supported at the top by the center console cover plate and at the bottom by a
bearing located on a bracket bolted to the structure of the center console.
The lower section of the spindle has an external thread. A spindle block with an internal thread is
positioned on the threaded portion of the spindle. The spindle block has spigots which engage with
slots on a bellcrank assembly. The bellcrank has two input arms with slots that engage with the
spindle block spigots and an operating lever that connects to a long flexible cable.
The two input arms of the bellcrank have a hole drilled through both arms that will align with a hole
drilled through the structure of the center console. When the holes are aligned the handwheel
assembly is in the neutral position. You can insert a rigging pin through the holes when you will
adjust the rudder trim control system.
B. Flexible Cable
A long flexible cable connects the trim handwheel assembly to the trim tab actuator assembly. The
cable goes through holes in all the fuselage bulkheads and through the bottom of vertical stabilizer.
From the rear of the vertical stabilizer the cable goes into the rudder lower mounting bracket where
it connects to the rudder trim tab actuator assembly.
The cable has an inner core with threaded end fittings. Fork end fittings attach to the threaded end-
fittings of the inner core. The fork end fittings attach to the operating lever of the handwheel
assembly at one end and to the trim tab operating rods at the other end.
The outer sleeve of the flexible cable has threaded sections at each end. These threaded sections
screw into fixings at the handwheel assembly and the trim actuator assembly. Locknuts are used
on the threaded ends to secure the flexible cable in position.