The Work of an Approved Propeller Repair Agency

Hartzell propeller repair

An approved propeller repair agency has to be able to work in a number of materials. Hartzell Propeller, Inc., for example, designs, develops, tests, manufactures, and supports both aluminium and composite propellers for aircraft piston engines and turboprops worldwide. Historically wood, Hartzell today manufactures aircraft propellers and spinners from spun aluminium or aerospace composites.

Metal Propeller Repair should always be done in accordance with latest techniques and best industry practices as recommended by the manufacturer to their network of Hartzell agency technicians. This is due to the critical effects of surface injury and subsequent repair on the fatigue of propeller blades. There is in the UK, for example, only one company relly qualified to do this.

Aluminium propeller repairs.

Aluminium alloy propellers and blades with dents, scars, scratches, nicks or leading-edge pitting, may be repaired, provided the removal or treatment does not materially affect the strength, weight, or the performance of the blade.
More than one injury is not sufficient cause alone for rejection of a blade. A number of repairs can be carried out on a blade and not necessarily result in a dangerous condition. However, if the location of the repairs relative to each other forms a continuous line that materially weakens the blade, that is a different matter.

Suitable sandpaper or fine-cut files may be used for removing surplus metal. In each case, the area involved will be smoothly finished with sandpaper or crocus cloth, and each blade from which any appreciable amount of metal has been removed will be properly balanced before it is used. Suspected cracks and all repairs are etched. To avoid removal of an excessive amount of metal, etching is done locally and should be done at intervals during the process of removing cracks. Upon completion of the repair, the entire blade is then inspected by chemical etching or anodizing. The effects of the etching process are removed with fine emery paper. Coldworked blades require peening after repair.

Blades that have the leading edges pitted from normal wear in service may be reworked by removing sufficient material to eliminate the pitting. The contour is kept the same, so trailing edges of blades can be treated in the same way. Beyond the 90 percent blade radius point, the blade width and thickness may be modified as required.

Propeller Balancing.

Propeller balancing dictates that upon completion of repairs, horizontal and vertical balance need to be corrected to manufacturer spec. A coaxial hole is sometimes drilled in the end of blades for the addition of lead to obtain static horizontal balance. The size of this hole must not be increased by the Hartzell agency.

To effect vertical balance, Hartzell may have drilled a single eccentric hole not closer than 1 inch to the nearest external blade surface.

Steel hubs and parts welding and remachining is permissible only when covered by the manufacturers service bulletins.