RV 7A/9A with GEAR WELDMENT COVERS, GUST BUSTER INSTALLATION
INSTRUCTIONS
The rudder control spar brackets mount using existing screw locations on the 7A and 9A.
1) Mount the spar Brackets as shown in the pictures.
2) Next pull the pins out of the stowed position on the rudder gust control tubes (Note there is some spring tension so hold the rudder pedal bracket when pulling the pin so it doesn't fly out).
3) Snap the rudder pedal brackets on to the rudder pedals, they go on the inboard sides of the inboard rudder pedals. Slip the rudder control brackets (on the end of the yellow tubes) into the previously mounted spar brackets from the bottom up then rotate the latch on the bottom of the spar bracket to lock them in place.
4) Now you can determine where you need to drill the holes in the yellow tubes for your particular rudder pedal location. With the rudder controls now installed, while sitting in the seat hold the rudder pedals evenly and full forward to take all the slack out of the cables, make a mark at the forward end of the yellow outer tubes on the inner tubes. These marks will be at the same location on both inner tubes if you held the rudder pedals even during marking. If they are not, repeat the process. Remove the rudder gust controls from the airplane.
5) Take one of the marked rudder controls apart, first remove the rudder pedal bracket from the inner tube then remove the rudder control bracket from the yellow outer tube. Then slide the spring and UHMW spacer and gray tube out of the yellow tube.
6) Next lay the gray tube next to the yellow tube with the mark on the gray tube at the same end of yellow tube as when you marked it in the airplane. Then move the gray tube so the mark is 7/8" away from the end of the yellow tube.
7) (Note the adjusting bolt on the end of the gray tube for future reference). Place the spring at the top of the adjusting bolt then the spacer on top of the spring as shown in the picture. Mark the yellow tube even with the top of the spacer. This is where you need to drill a 3/16" or #11 hole for the pin. This hole location will provide pre load on the springs for your particular rudder location.
A note on drilling the holes: Drill the holes in alignment with the stow holes. It is best to drill them on a drill press if possible; it helps you get a straighter hole through both sides of the tube. If you do not have a drill press drill as straight as you can by hand. Drill the other yellow tube in the same location. It is not necessary to take the 2nd rudder control apart before drilling but you must make certain that the springs and spacers are out of the way before drilling.
Do not over tighten the bolts when reassembling the rudder control; it will distort the aluminum tubes. Just snug them down good and a little into the nylok nuts.
The rudder gust control is now ready for use. Place the pins in the holes you just drilled (be sure the springs and spacers are below the pins) and reinstall in the airplane. We recommend installing the pilot side first then the passenger side. Pushing on the rudder pedal with your foot when installing the 2nd rudder control will help take the spring tension off during installation.
A note on using the Gust Buster on the inboard rudder pedals. For maximum performance the Gust Buster rudder control should be used on the same rudder pedals as the rudder cables are connected to. If you have installed Classic Aero Design upholstered gear weldment covers on your RV7A or 9A or if you are installing the Gust Buster on a RV6A the Gust Buster cannot be used on the out board rudder pedals due to interference with the weldment covers or the weldment itself in the case of the 6A. Due to the distance from the inboard rudder pedals to the rudder control cables (on the outboard sides of the outboard rudder pedals) “flex” or torsion occurs in the rudder pedal system. Therefore the Gust Buster cannot be adjusted to prevent the rudder from contacting the airplanes mechanical rudder stop as it can when using the pedals the cables are connected to. (The force of the contact of the rudder and rudder stop will be minimized by apx. 42lbs of spring pressure). Following these instructions will provide the most performance for the inboard pedal installation with minimum flexing of the rudder pedal system. The springs used for the inboard pedals are slightly different than the models utilizing the pedals the rudder cables are directly linked to. If you should decide to use the Gust Buster on the outboard pedals in the future you may want to purchase the slightly higher performance springs and make adjustments to prevent the rudder from contacting the mechanical stop.
Engineering information: During high energy wind events the Gust Buster allows the rudder to move to
or near the airplanes mechanical rudder stop (appx. 35 degrees). Engineering information provided by Bill Snapp, RV8A builder/owner, and engineer reveals that if the wind is 90 degrees to the rudder during the wind event and the rudder is allowed to move to or near the stop the wind load on the rudder will be reduced by at least 19%. A wind gust of 50 kts. produces 71lbs. of force on the RV7/9 rudder. With the rudder deflected 35 degrees the wind load is reduced to 58lbs of force. In addition the springs on the Gust Buster for the RV7A, 9A using the inboard pedals will absorb approximately 40lbs of force while the rudder is in motion. If the rudder is “locked” the structure itself would have to absorb the full force of the wind. Damage reports reveal that structural damage occurs during wind events at or near 50 kts. if the rudder is locked using current common methods.