7
Understand the Concept
Before doing anything on the flaps system
pull out drawings No. 12 and No. 14. They will
give you a good familiarity of how the different
parts relate to one another and how they work.
Also, study the photos in this section. They will
clarify any questions.
The flap system is quite simple in that it is
nothing but a torque tube coming in from the root
with an actuating arm at each end. At the root it is
attached to a cable and at the other end a push rod
is attached to the middle flap hinge and pushes the
flap out. The flaps are held in the up position by the
long springs included in the later kits or available
from AviPro for the older kits.
The procedures we’ll use to install the sys-
tem include:
1. Install torque tube
2. temporarily slide actuating arms into
position on the torque tube
3. Position and drill outboard actuating arm.
4. Install inboard actuating arm, but don’t
drill.
5. Install springs
Install Torque Tube
The torque tube slides through
the steel stand-off bushng at the root and
through a similar bearing stand-off at the
mid-wing cross member. Before sliding
the outboard end into the bearing note
that one of the outboard arms has to be
slid in place first (see photo).
Because both the torque tube and
the bearings have been painted, it’s a
good idea to remove the paint from both
the inside of the bearings and the area on
the torque tube where the bearings will
ride. This not only makes it much easier
to slide the tube into position but greas-
ing the metal-to-metal contact makes for
much smoother operation.
Drilling the Actuating Arms
Each torque tube has three actu-
ating arms, one at the root and two that
perform as one and clamp the push rod
between them (see pictures). A hole needs to be
drilled through the base of the arms and through the
torque tube to accept AN3 (3/16” bolt) to stop the
arms from rotating on the torque tube..
It is best if these bolts have a snug fit, so
rather than drilling with a 3/16 bit, drill with an
11/64” and ream to size to eliminate any possibili-
ty of slop in the holes.
On the outboard arms, first bolt the short
The actuating pushrod is trapped by two actuating arms, both of which have
a spring (not shown) going forward and holding the flaps up.The torque tube
(going to the left) must be drilled to hold the arms
Wings: Installing the Flap Actuation System
Paint must be removed from inside the arms and off the torque
tube to ease getting the actuating arms on the tube. Note how
the pushrod is sandwiched between two actuating arms.
Summary of Contents for Bearhawk N33RB
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