CS 22.925  Propeller clearance

CAA ORS9 Decision No. 1

If an unshrouded propeller is to be installed, propeller clearances with the powered sailplane at maximum weight, with the most adverse c.g. and with the propeller in the most adverse pitch position, may not be less than the following: 

(a) Ground clearance. There must be a clearance of at least 180 mm (for a powered sailplane with a nose-wheel landing gear) or 230 mm (for a powered sailplane with a tail-wheel landing gear) between the propeller and the ground, with the landing gear statically deflected and in the level attitude, normal take-off attitude or taxying attitude, whichever is most critical. In addition, there must be positive clearance between the propeller and the ground in the level take-off attitude, with: 

(1) the critical tyre completely deflated and the corresponding landing gear strut statically deflected; and 

(2) the critical landing gear strut bottomed and the corresponding tyre statically deflected. 

(b) Structural clearance. There must be: 

(1) At least 25 mm radial clearance between the blade tips and the sailplane structure, plus any additional radial clearance necessary to prevent harmful vibration; 

(2) At least 13 mm longitudinal clearance between the propeller blades or cuffs and stationary parts of the sailplane; and 

(3) Positive clearance between other rotating parts of the propeller or spinner and stationary parts of the sailplane.