Patent GB-741748-A (GB)
Title: Improvements relating to aircraft control means
Inventor: CHAPLIN HERBERT EUGENE
IPC: B64C13/00
Filed: 1953-04-16
Abstract: 741,748. Aircraft controls. FAIREY AVIATION CO., Ltd. April 13, 1954 [April 16, 1953], No. 10467/53. Class 4. [Also in Group XXIV] Aircraft control means includes a control surface and operating member, means interconnecting them including a variable ratio gear whereby the movement of the control surface for a given movement of the operating member can be varied, means arranged to vary the gear ratio automatically in response to changes in a function of the equivalent airspeed, and means arranged to vary automatically, in response to changes in altitude, the available range of gear ratio by decreasing or increasing the maximum available gear ratio with increase or decrease of altitude. As shown, an operating member 10, e.g. a control column, is arranged to operate a surface 11, e.g. an elevator through rods 12, 13 and a variable gear unit 14. A rudder bar 15 operates a rudder 16 through rods 17, 18 and a variable gear unit 19 similar to the unit 18, and connected thereto by gears 27, so as to vary the gear ratios equally together. Rods 12, 13 are pivoted to cranks 28, 29 keyed to shafts 31, 32, attached inside the unit (Fig. 2) to cranks 33, 34. A lever 35 is slidable on rollers 41 with respect to a plate 39 pivoted at 43 to a member 44 slidable on rollers 45 with respect to the casing 46 of the unit, and lever 35 is pivoted at one end 100 to the end of crank 33, and the other end is slidable on rollers 37 with respect to a plate 36 pivoted at 101 to crank 34. When shaft 31 rotates crank 33, plate 39 is rotated about pivot 43 by lever 35, which also slides a little relatively to plate 39. Plate 36 is displaced by the lever 35, relative sliding again taking place, and crank 34 is thereby rotated to operate the elevator. Links 48, 49, the former keyed to a shaft 51 and the latter pivoted at 50 to member 44, are adapted on rotation of shaft 51 to move member 44, hence pivot 43, and so to alter the effective leverage of lever 35 and alter the ratio of angular movement of cranks 33, 34. The unit 21 (Fig. 1) contains a capsule subject inside to the total head and outside to the static pressure, both being obtained from a pitot tube. The capsule is adapted to rock lever on change of relative pressures to operate one of two microswitches to energize in one sense or another an electric ram 22, which by links 23, 24, 25, 26 rotates shaft 51. Links 76, 75 also rotate shaft 74 to move the microswitches, and provide a follow-up action. A second capsule inside'unit 21 contains air at sea level pressure, and its expansion with altitude positions a stop to limit the range of variation in ratio in a manner depending on altitude, so that the ratio is fixed above a speed of about Mach 0.9. A servomotor may be disposed between the operating member and variable ratio gear, or between the latter and the control surface. In a further embodiment, a link connected to the surface is pivoted to the plunger of a ram and to an intermediate point of a floating lever, one end of which is controlled by the operating member, and the other pivoted to a link controlling the ram control unit, providing follow-up action. The latter pivot is of the pin-and-slot type, the position of the pin in the slot being adjustable by a bellows unit such as that described above, providing a variable gear. The connections of the control surface link and the ram plunger to the floating lever may be at separated points to impose a fractional load on the operating member to provide " feel " In a further embodiment according to the Provisional Specification, a capsule unit is arranged to operate the plunger of a hydraulic ram, mounted on a control arm adapted to be rotated about a control axis by the operating member. At the free end of the control arm is pivoted a lateral arm, the free end of which is moved by the ram to be nearer to or further from the control axis. The free end operates a servomotor controlling the aircraft surface. Another arrangement is described in the Provisional Specification, wherein two parallel levers have adjacent ends connected by a rigid link, the other end of one being connected to the operating member, and of the other to the control surface servomotor. Pivots for the two levers are provided by two pins movable in slots in the levers, the pins being mounted at the ends of a rockable lever, which when rocked moves the lever pivots so that the velocity ratios of the two levers are increased or decreased together.