Figure 2-4. Damaged Tip Repair

TM-1-1500-204-23-5 General Aircraft Maintenance Manual
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TM 1-1500-204-23-5 Figure 2-4. Damaged Tip Repair (e) Check three-bladed propeller assembly with each blade placed in a downward vertical position, as shown in figure 2-8. (2) Suspension method. In the suspension method, the propeller or part is hung by a cord, any unbalance is determined by noting the eccentricity between a disk firmly attached to the cord and a cylinder attached to the assembly or part being tested. The suspension method is used less frequently than the simpler and more accurate knife-edge method. b. Aerodynamic Balancing. Aerodynamic unbalance results when the thrust (or pull) of the blades is unequal. This type of unbalance can be largely eliminated by checking blade contour and blade angle setting. c. Dynamic Balancing. Dynamic unbalance results when the center of gravity of similar propeller elements, such as blades on counterweights, does not follow in the same plane of rotation. Since the length of the propeller assembly along the engine crankshaft is short in comparison to its diameter, and since the blades are secured to the hub so they lie in the same plane perpendicular to the running axis, the dynamic unbalance resulting from improper mass distribution is negligible, provided the track tolerance requirements are met. d. Blade Tracking. Blade tracking is the process of determining the positions of the tips of the propeller blades relative to each other. The blades should all track one another as closely as possible. The difference in track at like points must not exceed the tolerance specified by the propeller manufacturer. Use the following procedures to check blade tracking: (1) Mount indicator, which may be a slender point strip of wood or metal, on a stand, as shown in figure 2-9. Point of indicator should just touch nearest part of the blade. (2) Rotate propeller until next blade is in same position as No. 1 blade was prior to rotation. (3) When No. 2 blade does not touch point of indicator, measure distance from point to point nearest point of blade. When No. 2 blade is nearer the stand than No. 1 blade was, move indicator back until it just touches No. 2 blade. (4) Rotate propeller again until No.1 blade is down and measure distance from pointer to blade. With pointer set to touch nearest blade, the distance to other blade or blades must not exceed maximum allowable in overhaul instructions manual for applicable propeller; otherwise, propeller must be removed for overhaul. When propeller track is within repairable limits, make correcting adjustments in accordance with applicable aircraft or propeller maintenance manual. 2-12. Propeller Installation. Propellers shall be installed using the applicable maintenance manual. Preparation for installation is explained by the following procedures: a. Depreserve serviceable propellers received from stock following procedure outlined in applicable maintenance manual. 2-12

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