Inspection

The Flybar and Rotor Head Assembly consists of the 2 Paddles, Flybar, Paddle Control Frame, 2 Flybar Weight Collars, 2 Retaining Collars, Rotor Head Set and Pitch Control Links.

This mechanism receives input from the Swashplate through the Paddle Control Frame Pushrods. This input varies the pitch in the paddles conversely (as one paddle pitches up the other pitches down an equal amount). This causes the "paddle disc" to tip which in-turn cycles the pitch in the main rotor blades through the Pitch Control Links. In essence, this mechanism must work correctly to provide smooth and accurate input to the main rotor blades so check it carefully.

The most frequent problems to be found in this assembly are either a bent Flybar or a paddle that has rotated out of position on the Flybar. If the Flybar is installed in the aircraft check it visually for straightness. Ideally the Flybar would be removed and rolled on a known flat surface to check for bends. To check for proper blade angle on the paddles simply eye down the length of the Flybar Assembly and compare the angle of the paddle to the angle of the Paddle Control frame - they should be parallel. Figure 1. The paddle blade angle is important. Check it often and keep the paddles properly adjusted.

Using a 1.5 mm hex wrench, make sure the Flybar Weights and Retaining Collars are secured. Also check the Paddle clamp screws for security. These should be tight. But remember what you're working with here. Don't torque the screws off.

Check the Paddle Control Frame for evidence of cracks or other obvious damage. Figure 2.

Check the Rotor Head Set for obvious damage. Make sure that it "flaps" freely and that the Rotor Head Frame retaining screws are secure.

Ensure that the Center Hub Cap retaining screw is secure. Careful here as the screw threads into the top of the Rotor Head which is made of composite.

If you have the Rotor Head removed and disassembled, check the Rotor Head Pivot Bearings for excessive play and for proper fit on the Rotor Head Pivot Pins.

Check the Pitch Control Links for bends. Ensure that the ball-and-socket joints are secure and pivoting freely.

Removal

If you have modified the pitch angle on the Flybar Paddles ensure that you are able to return the pitch angle to its current setting prior to removal. Use a pitch gauge to determine the current angle.

All parts should be marked in a manner that guarantees reinstallation to its original mating components. A small dot of fingernail polish is effective.

Remove the Center Hub Cap retaining screw using a #2 phillips screwdriver. While twisting, pull off the Center Hub Cap (030).

Disconnect the Pitch Control links from the Main Rotor Blade Grips.

Disconnect the Paddle Control Frame Pushrods from the Paddle Control frame. Figure 3.

Loosen or remove one of the Paddle clamp screws and unthread the Paddle from the Flybar. Loosen the set-screw on the Flybar weight Collar on the same side from which the Paddle was removed. Loosen the set-screws on BOTH Flybar Retaining Collars. Now pull the Flybar out of the Paddle Frame and Rotor Head by grasping the remaining Paddle and gently twisting as you pull. Figure 4. Pull the Rotor Head off of the Center Hub.

Removal is complete. If you suspect that the Flybar may be bent, or are troubleshooting main rotor problems, remove the other Paddle and Weight. Then roll the Flybar on a known flat surface to check for bends.

Disassembly

Disassembly will involve removal of the remaining Paddle (001) and Weight Collar (069) from the Flybar (003). Now is a good time to roll the Flybar (003) on a flat surface to check for bends.

To completely disassemble the Rotor Head (034) remove the 2 Cap Screws (032) from the Rotor Head Frame halves (005) (033). Figure 5. Separate the frame halves, guiding the bearings (014) from the pins on the Rotor Head (034). Figure 6.

Disconnect the Pitch Control Links (006) (007) from the Rotor Head Frame halves (005) (033).

Repair

Repair in this delicate and highly critical area is limited to replacing components. The one exception might be the Flybar (003) which can be straightened by hand in some instances.

As previously stated you must match repairs to the type of flying you do and the people and property around you. Don't practice advanced flight techniques with repaired components when people may be injured or property may be damaged. If you're hovering in your basement, make the repairs and hover away (until the new parts arrive).

Assembly

To assemble the Rotor Head place both Bearings (014) into the Rotor Head Frame Halves (005)(033). Make sure that the bearings are properly seated in the frame halves. Place a small drop of lubricant on each Rotor Head pin. Install the Frame Halves onto the Rotor Head pins.

It is possible to install the larger frame halve upside-down. Temporarily slide the Rotor Head onto the Center Hub. Rotate the Blade Grips to their normal operating position (nut-capture side down). See if the Pitch Control Link ball-and-socket attachments are aligned as shown in Figure 7. If they are aligned, you're good to go. If not, flip the large frame halve over and recheck alignment.

The frame halves should fit snugly, yet slide on smoothly. Don't cock the bearings as they are slid onto the pins to prevent binding. Once the two frame halves have been installed to the point where they contact one another, pinch them firmly together with your fingers. Figure 8. Check that the Frame Assembly pivots freely on the bearings. If they do not pivot freely, disassemble and reassemble - the bearings were cocked and binding. Install the 2 Frame Halve retaining screws (032). You should not use the screws to draw together the frame halves. The need to do so would indicate bearing misalignment. Tighten the screws snugly, but do not over tighten or the female threads in the large frame halve (005) will be damaged. Ensure that the Frame Assembly pivots freely on the bearings.

Reattach the Pitch Control Links (006)(007) to the Rotor Head (005).

Installation

Prior to installation of the Flybar and Rotor Head Assembly make sure that the Rotor Head (034) inner sleeve is clean. Use a Q-tip. Again, using a clean Q-tip, apply a light film of lubricant to the Rotor Head inner sleeve. Also apply a very light film of lubricant to the Center Hub (008) where it will contact the Rotor Head. Figure 9.

Slide the Rotor Head Assembly onto the Center Hub (008) checking for proper fit. There should be no binding. Any binding must be remedied prior to continuing.

Position the Paddle Control Frame (031) as shown in Figure 10 and insert the Flybar (003) through the Paddle Control frame (031), Rotor Head (034) and Center Hub (008). Continue to push the Flybar (003) through until it is centered in the Rotor Head Assembly. Use your favorite measuring device to ensure that it is centered. Figure 11. While maintaining the centered position, install both Retaining Collars (004). Don't confuse the Flybar weight Collars (069) with the Retaining Collars (004). The Retaining Collars needed in this step have the larger inner diameter. Set screws should face up and should engage the previous indentation on the Paddle Control Frame (031). Using a 1.5 mm hex wrench, tighten the Collars (004) to prevent movement of the Flybar (003). Do not over tighten. Rotate the Paddle Control Frame (031) and Flybar (003) as a unit. It should not bind on the Rotor Head. If you notice binding, loosen one of the Retaining Collars (004) and gently pull the Paddle Control Frame (031) away from the Rotor Head Assembly. Then retighten the Retaining Collar (004). This binding is usually caused by pushing the Retaining Collar (004) against the Paddle Control Frame while tightening the Retaining Collars.

Install a Flybar weight Collar (069) precisely 0.6 inches in from the ends of the Flybar as shown in Figure 12. Align the setscrews in the Weight Collars with the setscrews in the Retaining Collars (004). Now thread one of the paddles onto an end of the Flybar until it makes contact with the Flybar weight Collar (069). The Paddle (001) must end up with its leading edge on the same side of the Flybar as the Pitch Control Link ball connection. Figure 13. And the Paddle must be installed at 0 degrees. Use a pitch gauge if you have one. Otherwise just eye down the length of the assembly and compare the angle of the Paddle to the angle of the Paddle Control Frame (031). They must be parallel (0 degrees) as shown in Figure 1.

Ideally, the Paddle (001) will contact the Weight Collar exactly as it rotates into the 0 degree position but probably will not. The smallest increment of adjustment here is one turn of the Paddle (001). So, if the Paddle is contacting the Weight Collar (069) and cannot be brought to 0 degrees, unthread it until it is. When you have the Paddle angles correctly adjusted tighten the Paddle Clamp screws (041).