Inspection

Stock flat-bottom blades and symmetrical wooden blades:

To properly inspect the Main Rotor Blades (042) they should be removed from the aircraft.

The stock Main Rotor Blades (042) are covered with a thin plastic film. Check this film for tears. A torn film can rise up during rotation and spoil the airflow causing disturbed lift on that blade. Many times you will hear increased rotor noise as the torn "flap" of plastic rises due to drag. When the blades are not turning the torn flap may lie back down and go undetected without careful inspection. Visually inspect the blade film for tears. These usually appear as hair-line cracks. Figure 1

Check the Main Rotor Blades for damaged tips due to blade strikes. It is recommended that damaged rotor blades be replaced immediately. Flying with damaged rotor blades is unsafe. This is especially true for advanced high-speed and 3D flight. Also check the entire blade surface for dents, cracks and obvious damage resulting from blade strikes. A blade strike can also cause the trailing edge of the main rotor blade to contact the Blade Grip (037) resulting in a sharp dent at the point of contact. Figure 2. If you notice this condition check the blade and blade grip for damage.

To check for blade damage hidden under the plastic film, gently twist the rotor blade while holding each end. Listen and feel for damaged wood fibers.

Check the blade attachment fittings for general condition and security.

Carbon fiber blades:

The carbon fiber blades have no film coating and are therefore easier to inspect. Check for dents, cracks and abrasions which may result from blade strikes. Eye down the leading and trailing edges of the blades to check for straightness. Replace damaged blades.

Removal

Use a 1.5 mm hex wrench to remove the Main Rotor Blade Retaining Screws (036). Figure 3.

Catch the nut from the bottom of the blade grip. Completely remove the blade retaining screw from the blade and blade grip. Then gently separate the main rotor blade from the grip by pulling outward on the blade.

Repair

Repairing the wooden blades with film covering is not recommended for safety reasons. That said, here's how to do it.

Rips in the plastic film can be repaired with Scotch tape. Assuming that you are interested in maintaining a well-balanced main rotor assembly always cut 2 identical pieces of tape. Use one for the repair and place the other on the opposite blade at precisely the same location as the repaired blade.

I must admit that my first set of blades was literally shattered from frequent furniture-related blade strikes. I was able to use wood glue to repair the blades after removing the plastic film from the damaged areas. I then applied tape to the heavy blade to achieve balance. At one point, just prior to replacing my first set of blades, the blade tips were missing about 3/8 inch of wood, but it just kept on flying.

Now you would never do any REAL flying with damaged or repaired blades, but realistically, if you're new to helis and just working on hovering go ahead and use the repaired blades as long as you can.

Repairing the carbon fiber blades is limited to sanding or filing out minor "dings". The assumption is that if you're using CF blades you're probably beyond just hovering in your basement. And as mentioned with the wood blades; if you're doing any serious flying don't skimp on the blades - use CF blades that are in good condition only.

Installation

Ensure that the correct blade is installed on the appropriate grip to maintain balance. Check for correct blade orientation by matching that of the fly bar. Flat bottom blades are to be installed with the flat side down. If the Main Blade Grips were removed and reinstalled ensure that the grips are installed correctly by observing the location of the nut-capturing indent on the blade grips. Figure 4. These indents must face down.

Insert the Main Rotor Blade (042) into the Blade Grip (037). You may have to pinch the Blade Hold-Down Plates (010, 012) against the blade prior to insertion. Align the blade retaining screw holes on the blade and grip. Insert the blade retaining nut into the nut-capture indent on the blade grip. If the nut does not stay in the capture hold it in place with your finger while inserting the screw.

Use a 1.5 mm hex wrench to secure the Blade Retaining Screw (036). The Blade Retaining Screw should be tightened only enough to prevent the blade from pivoting loosely on the blade retaining screw.

The manufacturer's manual says to tighten so that "moderate" pressure is required to pivot the blade. That's kind of vague. The correct way to do this would be to develop a standard that requires the use of a spring-scale attached perpendicular to the blade along the axis of rotation and at a precise distance out from the pivot point. Then it could be established that, for example, 2 ounces of pressure is required to cause the blade to move within its pivot. However I think this is maybe overkill. You don't want the blades so tight that they "chatter" when pivoted and you don't want them so loose that they "flop" when the aircraft is held on its side. The reason they are allowed to pivot in this manner is to reduce the force transferred to the rotor head and main shaft during a blade strike. Also this pivot allows the rotor to dynamically adjust lead/lag as the rotor spins. This aids in balancing the main rotor assembly.