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4. Place a solid object (e.g., a heavy wooden block that is at least a couple of inches higher off the ground than the distance between the propeller tip and the ground) next to the propeller tip so that it just touches or attaches a pointer/indicator to the cowling itself. [Figure 7-34] 

5. Rotate the propeller slowly to determine if the next blade tracks through the same point (touches the block/ pointer). Each blade track should be within 1 ⁄ 16 inch (plus or minus) from the opposite blade’s track. 

6. An out-of-track propeller, may be due to one or more propeller blades being bent, a bent propeller flange, or propeller mounting bolts that are either over- or undertorqued. An out-of-track propeller causes vibration and stress to the airframe and engine and may cause premature propeller failure. 

## Checking and Adjusting Propeller Blade Angles 

When you find an improper blade angle setting during installation or is indicated by engine performance, follow basic maintenance guidelines. From the applicable manufacturer’s instructions, obtain the blade angle setting and the station at which the blade angle is checked. Do not use metal scribes or other sharply pointed instruments to mark the location of blade stations or to make reference lines on propeller blades, since such surface scratches can eventually result in blade failure. Use a bench-top protractor if the propeller is removed from the aircraft. [Figure 7-35] Use a handheld protractor (a digital protractor provides an easy measurement) to check blade angle if the propeller is installed on the aircraft or is placed on the knife-edge balancing stand. [Figure 7-36] 

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## Universal Propeller Protractor 

The universal propeller protractor can be used to check propeller blade angles when the propeller is on a balancing stand or installed on the aircraft engine. Figure 7-37  shows the parts and adjustments of a universal propeller protractor. The following instructions for using the protractor apply to a propeller installed on the engine: 

Turn the propeller until the first blade to be checked is horizontal with the leading edge up. Place the corner spirit level at right angles to the face of the protractor. Align degree and vernier scales by turning the disk adjuster before the disk is locked to the ring. The locking device is a pin that is held in the engaged position by a spring. The pin can be released by pulling it outward and turning it 90°. 

Release the ring-to-frame lock (a right-hand screw with thumb nut) and turn the ring until both ring and disk zeros are at the top of the protractor. 

