Patent GB-313416-A (GB)
Title: Improvements in or relating to means for the trimming of aircraft in flight
IPC: B64C13/00
Filed: 1927-12-10
Abstract: 313,416. Randall, C. R. J. Dec. 10, 1927. Steering and balancing.-For preserving the longitudinal trim of those aircraft wherein the thrust of the airscrew acts above or below the centre of gravity of the machine, both during engine on and engine off conditions at different speeds of flight, a main stabilizing tail plane is placed in the slip stream from the propeller and an auxiliary tail plane is placed outside the slipstream, the angle of incidence of one or each of the tail planes being adjustable so that the change of effective incidence of one of them relative to its airstream differs from the change of effective incidence of the other. Fig. 1 shows a flyng boat with its line of propeller thrust above the centre of gravity, a main stabilizing plane 20 being arranged in this slipstream at a negative angle of incidence and an auxiliary plane 21 being arranged above the slip stream. Independent means may be provided for adjusting the planes 20, 21 or alternatively for adjusting elevator flaps 23, 24 onthe planes. Fig. 3 shows a modification in which the plane 20 is pivoted at 28 and the plane 21 at 29, a link 27 connecting the plares as shown. An extension 32 is movable vertically to tilt the planes in opposite senses by a worm 35 and nut 31 turned by gear 30 moved by a cable 33 from the pilot's position. Alternatively the shaft 32 may be extended and have two similarly handed worms engaging nuts on the planer, or the shaft may have right and left screws engaging corresponding edges of the planes instead of opposite edges as shown. In a further modification, elevator flaps are connected by cables passing over pulleys on levers on the usual transverse rock shaft of a control lever and around two pulleys on the lever. Normal fore and aft movement of the control lever moves both elevators together for balancing purposes, but rotation of the pulleys moves the elevators in opposite directions. Fig. 8 shows the two pulleys 38, 39 mounted on a common spindle 40 passing through a fitting on the control lever 36. A disc 54 mounted on ball bearings 55 and against a bracket 52 has a handle 60 the shaft of which carries a pinion 59 meshing with two internally toothed rings 56, 57 on the pulley 39 and bracket 52 respectively. The rings 56, 57 differ bv one tooth so that rotation of the disc 54 eftects a fine adjustment of the pulleys 38, 39. A hinged fork 61 engages the handle 60 to hold the pulleys in adjusted position. According to the Provisional Specification the two elevators are connected to independently movable pulleys which can be locked together and to the control lever. This subject-matter does not appear in the complete Specification. Instead of mounting the auxiliary plane above the slip stream, lateral extensions of the main stabilizing plane may be arranged outside the slip stream, or in the case of twin engined machines, a central portion of a laterally extended plane may act as the auxiliary plane. In some cases it may be necessary to vary the position of the engine axis to ensure the same speed during engine on and engine off conditions. For this purpose the engine bearer 71, Fig. 11, is supported by members 72, 73 of which the member 73 is pivoted to the rear spar of a main plane and the member 72 is connected to a strap on an eccentric 76 moved by worm gear 80. Adjustable struts between main and auxiliary tail planes may enable an initial setting to be made to suit the load.