09/11/2018
RANS S-21 OUTBOUND
TEXT MANUAL
148
HORIZONTAL STABILIZER
NOTE:
Ensure the 2nd hole for the aft attach of the horizontal stabilizer to
S-11 has been drilled and both bolts are secured. This is in the Horizontal
Stabilizer Attachment section.
Due to the various engine options which change the CG and therefore the ideal
horizontal stabilizer incidence, incidence adjusters are used to set the incidence of the
horizontal stabilizer and minimize drag. The goal is to adjust the incidence such that the
elevator is flat with the horizontal when cruising at the desired cruise speed at the most
common expected weight and CG.
INCIDENCE ADJUSTMENT
1.
Remove the horizontal stabilizer fairing, tailcone closeout, and large inspection
panel on the bottom of the tailcone.
2.
Loosen the bolts on the front of the horizontal stabilizer/S-10 bulkhead so that the
bolts can slide freely in the slots of the incidence adjuster.
3.
Loosen the top 4 cap screws
4.
Use the bottom 2 cap screws to set the desired incidence. Press down on the
front of the horizontal stabilizer to ensure the bushings are against the bottom
cap screws.
5.
Check the horizontal stabilizer for twist compared to the fuselage and adjust the
incidence of each side using the cap screws as needed.
6.
Apply the appropriate thread lock to the 4 top screws and tighten them down onto
the bushings.
7.
Remove the bottom 2 cap screws and apply thread lock. Tighten them back up.
TUNING
1.
Set the incidence to initial height depending on engine installation.
NOTE:
This should have been completed during the assembly of the
horizontal stabilizer to the tailcone.
a. Titan X-340
i. 1/8" from the bottom of the slot
b. Rotax 912ULS
i. 1/8" from the top of the slot
NOTE:
Fine tuning can only be completed once the airplane is flying. Fine
tuning of the incidence is optional, but will yield a small reduction in drag.
2.
Fly the airplane at the weight and CG expected to be used most in cruise. At
cruise speed in straight and level flight in smooth air, note the orientation of the
balance weights of the elevator.