GB905922A - Improvements in or relating to aerodynes - Google Patents

Abstract

905,922. Controlling aircraft; variable pitch propellers. ATELIERS D'AVIATION LOUIS BREGUET S.A. DES. April 7, 1961 [May 10, 1960], No. 12621/61. Classes 4 and 114. An aircraft comprises an even number of propellers, greater than two, mechanically interconnected, and having their slipstream directed over a wing system fitted with high lift devices, e.g. flaps and the pitch of the outer propellers can be reduced to increase the drag, while maintaining the lift produced by the action of the slipstream on the wing system. The high lift devices are used during low speed take-off and landing, to maintain the lift, the drag increase being required during landing. Fig. 2 shows four propellers H 1 -H 4 driven by shafts A 1 -A 4 all connected to a common shaft A through gearing and a freewheel permitting isolation of a failed engine. Blade pitch control mechanisms E 1 -E 4 are controlled by linkages T 1 -T 4 from a mechanical control unit 12 receiving input signals from an automatic pitch control unit 13 governed by a pilot's control lever 15 and engine speed information through gears 18, and from a manual pitch control lever 17 through rod 16. Figs. 3 and 3a together show the linkwork within unit 12, parts peculiar to the outboard engines being in Fig. 3 only, and those peculiar to the inboard engines in Fig. 3a only. A lever 39 is pivoted at 39a, 39b, to links 36, 16 connected to the automatic pitch control unit and the manual pitch control respectively. The pivot 42 of lever 39 works in a slot 43 in the lever, and is on a lever 40 having a fixed pivot 41 and connected by a link 44 to an electric jack 47. In one jack position, as shown, pivot 42 is aligned with pivot 39b, rod 16 is locked, and the automatic control is operative through rod 36. In the other jack position, pivots 42 and 39a are aligned, the manual control is free, and the automatic control is locked. Link 44 operates a switch 150 to disable the automatic control in this position of the jack. Movement of the operative rod 36 or 16, rocks lever 39 in pivot 42 to move a member 48 along a slider 49. Member 48 is connected to a counter balance means 50b, and has transverse arms 48a having pivots 53 for four bell crank levers Li, L 4 (Fig. 3) and L 2 , L 3 (Fig. 3a). The bell crank levers are pivoted at 52, 75, to the corresponding pitch control linkages T 1 -T 4 . Levers L 1 , L 4 , are pivoted at 54 to links 55 which are pivoted at 56 to a normally fixed member 57. Levers L 2 , L 3 are pivoted at 76 to links 77 which are pivoted at 78 to a normally fixed member 79. Movement of member 48 along slider 49 thus displaces all four levers L 1 -L 4 , and all four linkages T 1 -T 4 to effect simultaneous equal pitch changes in all four propellers, the range of operation being between high and low pitch settings. To reduce the pitch of the outboard propellers compared with that of the inboard propellers, an electric jack 61, Fig. 3, is rotated through a quarter of a revolution, to displace member 57 through link 59. This displaces the bell crank levers L 1 and L 4 through links 55, and displaces linkages Ti and T4. The range of movement is sufficient to reduce the low pitch setting obtainable through normal automatic control, to zero pitch setting. The automatic pitch control unit may be a constant speed regulator, so that reduction in the pitch of the outboard propellers will result in a lesser automatic increase in the pitch of all the propellers, keeping the lift constant. To obtain reverse pitch for braking, jacks 61 and 83, Figs. 3 and 3a, are rotated through half a revolution, displacing members 57 and 79, to displace all the bell cranks and linkages T 1 -T 4 in the sense to reverse the blade pitches. To obtain differential pitch control between the two outboard propellers, to assist in roll control of the aircraft, a pilot's roll control transmission rod 67 is pivoted at 66 to a lever 65 having a slot 65a containing a pivot 68 on a lever 69 pivoted to fixed structure at 70. A link 63 is pivoted to member 57 at 62, and to lever 65 at 64. A link 72 extends between pivot 71 on lever 69, and an electric jack 74. With the jack in the position shown, pivots 64, 68 are aligned, and movement of the roll transmission rod merely pivots lever 65 about pivot 68, and member 57 is not moved, so that the propellers do not assist in roll control. If jack 74 is rotated through half a revolution, pivot 68 moves to the other end of slot 65a, and any movement of rod 67 rotates lever 65, which rocks member 57 about pivot 58 through link 63, so that equal and opposite pitch changes are imposed on the outboard propellers, through links 55 and levers L 1 , L 4 . Specification 689,218 is referred to.