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Servo arms:
Your new Extra 330SC has provision for 2 servo s per aileron,
we recommend the use of two high quality high torque
servo s. We used JR NX8921 (30+kgs) on all surfaces. We
also used 1.5 Alloy servo arms on the ailerons and elevators.
For the rudder there is a Phenolic arm supplied, this arm
needs to be attached to an alloy servo disc, DO NOT USE
THE STANDARD NYLON SERVO DISCS! The nylon servo
arm/disc supplied with your servos are unsuitable, and should
not be used, they may strip under heavy loads resulting in
surface flutter. If you wish to use an alloy servo arm on the
rudder, a 4 to 4.5 offset arm is suitable.
Please consider the use of a good quality throttle servo, preci-
sion is required to maintain good throttle trim and consistent
idle control. A poor quality servo will result in an inconsistent
idle, and poor throttle transition. A 1 throttle servo arm is all
that is required, try and keep the servo end points as close to
100% as possible. Setting up a good mechanical linkage is
critical for obtaining a good throttle transition and consistent
idle.
Engine Choices:
There is a multitude of engines available for you to use in your Sukhoi SU-31. The airframe is suited to today s current
crop of 120cc engines. We used a DA120 in the process of producing this manual, the performance is excellent with
an abundance of power, as well as being very light.
Sukhoi SU 31—2.75m/2.6m
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