content_image/522881.jpg
take final blade measurements and record on each blade’s inspection record. Balance and match the propeller blades and anodize and paint them for long-term corrosion protection. 

## Prop Reassembly 

When both the hubs and the blades have completed the overhaul process, the propeller is ready for final assembly. Recheck part numbers with the manufacturer’s specifications. Lubricate and install the parts per each unit’s particular overhaul manual. After final assembly, check both high- and low-pitch blade angles on constant-speed propellers for proper operation and leaks by cycling the propeller with air pressure through its blade angle range. Then, check the assembled propeller for static balance. If necessary, place weights on the hub areas of each “light” blade socket to bring about its proper balance. These weights should be considered part of the basic hub assembly and should not be moved during subsequent dynamic balancing to the engine. As with most aircraft components, all of the hardware on the propeller assembly must be safety wired, unless secured by self-locking devices. Then, the final inspector fills out and signs maintenance release tags reflecting the work accomplished, applicable ADs, and all incorporated service documents. These documents certify that the major repairs and/or alterations that have been made meet established standards and that the propeller is approved for return to service. All minor repairs and minor alterations on propellers must be accomplished by a certified repair station, an airframe and powerplant technician (A&P), or a person working under the direct supervision of such a technician or an appropriately rated air carrier. Major repairs or alterations, including the overhaul of controllable pitch propellers, must be done by an appropriately rated repair station, manufacturer, or air carrier. 

## Troubleshooting Propellers 

Some brief examples of troubleshooting problems and possible causes are provided in the following subsections. Always refer to the correct manual for actual information on troubleshooting. 

## Hunting and Surging 

Hunting is characterized by a cyclic variation in engine speed above and below desired speed. Surging is characterized by a large increase/decrease in engine speed, followed by a return to set speed after one or two occurrences. If propeller is hunting, an appropriately licensed repair facility should check: 

1. Governor, 

2. Fuel control, and 

3. Synchrophaser or synchronizer. 

## Engine Speed Varies with Flight Attitude (Airspeed) 

Small variances in engine speed are normal and are no cause for concern. An increase in engine speed while descending or increasing airspeed with a nonfeathering propeller could be. 

A. The governor not increasing oil volume in the propeller. 

B. Engine transfer bearing leaking excessively. 

C. Excessive friction in blade bearings or pitch changing mechanism. 

## Failure to Feather or Feathers Slowly 

Failure to feather or slow feathering of the propeller requires the FAA-certificated A&P technician to: 

1. Refer to the air charge section in the maintenance manual if the air charge is lost or low. 

2. Check for proper function and rigging of propeller/ governor control linkage. 

3. Check the governor drain function. 

4. Check the propeller for misadjustment or internal corrosion (usually in blade bearings or pitch change mechanism) that results in excessive friction. This must be performed at an appropriately licensed propeller repair facility. 

## Turboprop Engines and Propeller Control Systems 

Turboprop engines are used for many single, twin, and commuter aircraft. [Figure 7-43]  Smaller turboprop engines, such as the PT-6, are used on single and twin engine designs; the power ranges from 500 to 2,000 shaft horsepower. [Figure 7-44] Large commuter aircraft use turboprop engines, such as the P&W 150 and AE2100 that can deliver up to 5,000 shaft horsepower to power mid-sized to large turboprop aircraft. [Figure 7-45] The turboprop propeller is operated by a gas turbine engine through a reduction-gear assembly. It has proved to be an extremely efficient power source. The combination of propeller, reduction-gear assembly, and turbine engine is referred to as a turboprop powerplant. 

<img src='content_image/522881.jpg'>

