Gear 1 meshes with and drives gears 2 and 3. When clutch 4 is engaged by means of shifter 6, rotation of gear 2 is transmitted through worm 9, worm wheel 10 and, if clutch members a are engaged, further through gears 13 and 14 to worm 15. The pitch of the propeller (not shown) is either increased or decreased, depending upon the direction of rotation of worm 15. When clutch 5 is engaged by means of another shifter 6, rotation of gear 3 is transmitted through bevel gears 7 and 8, worm 9, worm wheel 10 and further through gears 13 and 14 to worm 15 which now rotates in the reverse direction. Worm 9 and worm wheel 10 have a high transmission ratio and serve for slowly varying the pitch of the propeller. If the pitch is to be rapidly changed, clutch members a are disengaged and members b are engaged by means of shifter lever 16. Then rotation is transmitted through gears 11, 12, 13 and 14. In this case, if clutch 5 is engaged, rotation is transmitted from gear 3 through bevel gears 7, gears 11 and 12, and further through gears 13 and 14 to worm 15. If clutch 4 is engaged, rotation is transmitted from gear 2 through bevel gears 8, gears 11, 12, 13 and 14 to worm 15 which then rotates in the reverse direction.
$2977$CxG,FD$