Diamond DA 42 NG, Maintenance Manual

Page: 846 / 2339

AIRCRAFT
Flight Controls
DA 42 NG AMM
Page 4
15 Mar 2018
27-21-00
Doc # 7.02.15
Rev. 4
C. Trim Tab Actuator Assembly
The trim tab is a GFRP molding. The trim tab has a control horn with two integral levers. Two trim
tab operating rods connect the integral levers to the flexible cable fork end fitting. The operating
rods have spherical end fittings screwed into each end of the rods. The spherical end fittings are
bolted to the integral levers and the fork end fitting.
The end of the flexible cable outer sleeve screws into a friction block assembly. The friction block
assembly has a hole with an internal thread. The flexible cable outer sleeve screws into this
threaded hole.
The top section of the friction block has a hole drilled in it for the friction rod. The friction rod passes
through the upper section of the friction block and attaches to the fork end fitting. A friction shoe
in the top section of the friction block is held in contact with the friction rod by springs. This
clamping action on the friction rod dampens the movement of the trim tab actuator should the trim
tab control system fail.
3. Operation
If the pilots rotates the trim control knob clockwise during flight then these events occur:
)
The trim control spindle rotates clockwise. The trim indicator moves to the right to show the position
of the spindle.
)
The spindle-block moves up the threaded portion of the trim control spindle.
)
The moving spindle block rotates the bellcrank and the bellcrank lever arm moves forward.
)
The bellcrank lever arm pulls the inner core of the flexible cable forward.
)
The flexible cable fork end fitting moves forward and the trim tab control rods move forward.
)
The trim tab moves to the left and the dynamic forces acting on the rudder trim tab move the rudder
to the right.
If the pilot rotates the trim control knob counterclockwise during flight the system operates in the
reverse direction.