Patent GB-217304-A (GB)
Title: Improvements in or relating to dual control systems for aircraft
IPC: G09B19/16
Filed: 1923-03-12
Abstract: 217,304. Harrison, H. G. March 12, 1923. Steering and balancing.-In dual control apparatus for aeroplanes comprising two control sticks one or each of which has a ball-and-socket joint at its lower end normally held rigid by a spring-pressed bolt adapted to be released by hand-operated means, or in which one or each of two rudder bars is connected to a supplementary bar by a spring-pressed bolt, the bolts are withdrawn by hydraulic motors supplied with pressure fluid through flexible piping from an accumulator or generator to render one or either control stick or rudder bar inoperative. Means also are provided for positively ensuring the re-engagement of the bolts when required. Fig. 1 shows an apparatus in which the front control stick 2 has a ball-and-socket joint 4, 5, and the rear control stick 1 is removable and normally held in a socket 36 by a clip 37. A front rudder bar 16 is connected by cables 54 to a bar 14 mounted coaxially with the rear rudder bar 13 to which the rudder cables are connected. The stick 2 is normally held in alignment with its socket by a plunger 38, Fig. 5, pressed down by a spring 39, but is released when it is desired to cut out the front control by admitting pressure fluid beneath a piston 43 through a flexible pipe 34. The bars 13, 14 are normally locked together by a similar bolt pressed down by a spring in a cylinder 52 containing a piston adapted to be raised by pressure fluid. A plate on the lower bar prevents the bolt from fouling the edges of the bar. A spindle 56 in the control stick 2 and a similar spindle in the cylinder 52 extend to the outsides of the stick and cylinder respectively to enable the plungers to be moved positively into their locked positions by hand or foot pressure if necessary. The flexible pipes 34 lead to the outlet 33 of an oil reservoir 19 shown in section in Fig. 3, the oil being subjected to the pressure of a spring 21 through a piston 20. A stop valve 22, normally pressed down against a port 24 by a spring 23, is raised by a spindle 26 when a bell-crank lever 28, 47 is moved by a Bowden cable 30 connected to a lever 31 on the rear control stick 1. and simultaneously a spring-pressed valve 46 closes an outlet 45. When the cable 30 is released, a spring 32 returns the bell-crank lever, the arm 47 of which opens the valve 46 to permit the return of pressure fluid through the outlet 45 and a by-pass tube to the upper side of the piston 20. A handle 50 on a piston rod 51 enables the spring 21 to be recompressed, the oil in the upper part of the cylinder passing through a non-return valve 49 in the piston. A groove 52 in the rod 51 is adapted to be engaged by a fork to hold the piston in its upper position when the cylinder is being filled. When both control sticks have ball joints, a twoway cock may be provided on the outlet of the reservoir 19 to direct the pressure fluid to one or the other control. This cock may be accessible to both pilots and a lever 31 may be provided on both control sticks. Alternatively, a simple T-joint may be employed, the control stick required for use having its locking bolt held in engagement by hand through its spindle 55. When it is required also to disconnect either rudder bar, each is connected by a bolt to a lower bar similar to the bar 14, the two lower bars being connected together and to the rudder.