Document ID: chunk:federal_register_of_legislation:F2007L04873:body:0:p4
Version: federal_register_of_legislation:F2007L04873
Segment Type: other
Provision Reference: 
Character Range: 7569–10316

from draughts.

       (3)After being allowed to dry for at least 12 hours, the fabric covering must be given 1 coat of undercoating varnish complying with a specification approved by the Director.

9 Metal sheathing

       9.1The metal sheathing, if specified, must be fitted in accordance with the instructions on the approved drawing.

       9.2Localised reduction of the thickness of sheath segments, e.g. by filing, is prohibited and the segments must, therefore, be worked in such a way as to make this unnecessary.

       9.3Sheaths must be attached by approved countersunk wood screws (suitably plated or dipped), except where the blade is less than 10 mm thick, in which region 14 SWG tinned copper rivets must be used. The position and spacing of screws and rivets must be as indicated on the approved drawing.

       9.4To prevent any movement of sheath segments relative to the blades, the edges of the screw and rivet holes in the segments must be punched or spun into the timber to form a countersink for the screw or rivet head which, when in place, must be slightly below the surface of the sheath. Care must be taken to prevent bulging or buckling of the sheath and/or damage to the covering and timber when the punching or spinning is done.

       9.5Slots in screw heads must be thoroughly cleaned before the screws are inserted. After insertion, screw and rivet heads must be flooded over with soft solder.

       9.6The application of solder to the whole or to any segment of a sheath for the purpose of securing balance is prohibited.

       9.7Drainage of the propeller blades must be provided for by filing slots in the tip segments after they have been lapped over and secured.

       9.8Care must be taken to avoid damage to the blade surface or protective covering when forming the edges of the sheaths.

10 Balance

       10.1The propeller must be tested for balance at the following stages:

(a) after final shaping has been completed;

(b) after sheaths have been fitted;

(c) when it is in the finished state (except for any small alteration necessary to secure balance);

(d) after any alterations shown to be necessary by the preceding tests.

       10.2The balance tests must be made on an approved type of balancing stand.

       10.3During the tests specified in paragraph 10.1 of this subsection, and making allowance for the known error for the balancing apparatus as ascertained by testing it with the propeller in position, any lack of balance detected in the propeller must not exceed the following limit whatever the position of the propeller in the plane of rotation:

 1 500 mm-gms for propellers of up to 2 m diameter, increasing by 750 mm‑gms for each 1 m, or part thereof, for propellers