Patent GB-745454-A (GB)
Title: Improvements in or relating to apparatus for determining the centre of gravity of an aircraft
IPC: G06G7/70
Filed: 1953-06-29
Abstract: 745,454. Electric analogue calculating systems. CONTINENTAL SILVER CO., Inc. June 29, 1953 [Aug. 8, 1952], No. 17988/53. Class 37. [Also in Group XXXVIII] General.-Equipment for determining the distribution of cargo of a given weight in an aircraft having main wheels and an additional wheel so as to obtain a desired centre of gravity for the loaded aircraft comprises a control circuit including a first variable electrical impedance unit and means for setting it to a value proportional to the weight of cargo yet to be loaded, a second variable electrical impedance unit and means for setting it to a value proportional to the moment of such cargo weight about a reference datum, and a third variable electrical impedance unit and means for setting it to value dependent on the ratio of the values of the first and second impedance units; together with a selector device controlled by the latter means which is set to a position determined by the present setting of the third impedance unit, and a multiplicity of grouped electric circuits corresponding to plural possible sequences of consecutive compartments among which the cargo is to be distributed, of which each group comprises plural circuits corresponding to the various numbers of compartments in the several possible loading sequences commencing with a given compartment; such selector device setting up for completion one circuit of at least one of the circuit groups, which circuit may be selectively completed to control, in conjunction with a device responsive to the cargo weight remaining unloaded, an indicating compartment loading director showing the next compartment to be loaded, in correspondence with the quotient of cargo weight and a constant representing the number of compartments in the selected loading sequence. Construction.-In Figs. 1, 2, an empty aircraft divided into plural compartments adapted to receive a predetermined cargo weight is positioned with its nose wheel on a weighing scale 41 and its main wheels on weighing scale 42 to respectively adjust linear resistances 44, 45 in proportion to the nose wheel weight and linear resistances 53, 54 together with logarithmic resistance 52 in proportion to the main wheel weight; linear resistances being shown in heavy line and logarithmic resistances in light throughout the Figures. An aircraft selector switch 58 manually operable by knob 61 in correspondence with the type of aircraft in use having ganged sections A, B and C inserts over section A a resistance in series with resistance 52 which is logarithmically proportional to the distance between the main and nose wheels, the combination being connected in one arm of a D.C. energized Wheatstone bridge circuit 71 determining the aircraft moment about the nose wheel completed by two fixed resistances and a variable annular logarithmic resistance 73 adjustable by a known rebalancing servo system 23, 36, normally disabled by the open contacts of a relay energisable over connection 305. Resistances 46, 53 are connected in series in a similar bridge circuit 87 determining the accumulated total weight of aircraft and cargo loaded completed by a linear rebalancing resistance 91 adjustable by a servo system normally disabled by the open contacts of a further relay energizable over connection 305. Logarithmic resistance 75 ganged for variation with resistance 73 and logarithmic resistance 86 ganged for variation with resistance 91 are respectively connected in series as one arm of a bridge 78 determining the aircraft centre of gravity as loading proceeds and as the opposite arm in series with logarithmic rebalancing resistance 82 adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connection 305. Resistances 47, 54 are connected in series over normally open contacts 103, 109 of a relay energizable over connection 325 in one arm of a bridge 113 determining the combined aircraft and accumulated cargo weight prior to loading a compartment, whose opposite arm includes a linear rebalancing resistance 121, connected in circuit over normally closed contacts 114, 116 of a relay energizable over connection 350, adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connection 325. Resistances 47, 54 are also connected in series over normally open contacts 104, 111 of a relay energizable over connection 306 in one arm of a bridge 127 determining the aircraft basic weight, whose opposite arm includes a linear rebalancing resistance 136 connected in circuit over normally closed contacts 129, 132 of a relay energizable over connection 320 and adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connection 306. Closure of contacts 132, 134 connects linear resistance 136 as one arm of bridge 142 determining the cargo weight accumulated in the aircraft, in series with a linear rebalancing resistance 143 adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connection 320; the bridge being completed by a linear resistance 146 ganged for adjustment by the rebalancing servo system of bridge 87, together with other ganged linear resistances 147, 148, 149. Resistance 147 is connected in one aim of bridge 163 determining the weight accumulated in each compartment, whose opposite arm comprises resistance 121 in series, over contacts 116, 118 when closed, with linear rebalancing resistance 174 adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connection 350, and resistance 148 is connected in series with a linear resistance 160 variable manually in proportion to the total cargo weight to be loaded as one arm of bridge 168 determining the gross weight of the aircraft, which is completed over normally closed contacts 179, 182 of a relay energizable over connection 326 by a linear rebalancing resistance 186 adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connection 326; while resistance 149 is connected in one arm of bridge 172 determining the remaining cargo weight in series with a linear rebalancing resistance 231 adjustable by a servo system normally disabled by the open contacts of an associated relay energizable over connection 326, the bridge being completed on closure of contacts 182, 184 by the variable resistance 186 of bridge 168. A logarithmic resistance 188 ganged for variation by the rebalancing servo system of bridge 168 is connected in series with a resistance corresponding to the aircraft type inserted by section B of aircraft selector switch 58 as one arm of bridge 202, determining the gross moment of the aircraft about the nose wheel, completed by a logarithmic rebalancing resistance 204 adjustable by a servo system normally disabled by open contacts of an associated relay energizable over connections 320; which is also ganged to adjust a linear variable resistance 206, forming one arm of bridge 212 determining the gross cargo moment about the nose wheel. The bridge is completed by linear resistance 222 ganged for adjustment by the rebalancing servo system of bridge 71, in series with a linear rebalancing resistance 215 adjustable by a servo system normally disabled, by open contacts of an associated relay energizable over connection 326, and a logarithmic variable resistance 217 ganged for adjustment by the servo system is connected over line 241 in series with the logarithmic rebalancing resistance, adjustable by a servo system normally disabled by open contacts of the associated relay energizable over connection 326, of bridge 239 (Fig. 3), which determines the ratio between the remaining cargo moment and remaining cargo weight and is completed over line 238 by the logarithmic resistance ganged for variation by the rebalancing servo system of remaining cargo weight bridge 172. The rebalancing servo system of bridge 239 is ganged to rotate a contact arm 248 of a compartment sequence selector switch 249 (which with its associated apparatus described below is multipled for differing aircraft types and selected for operation by section C of the aircraft selector switch 58 connecting positive battery to the appropriate contact arm 248) engaging plural concentric arcuate rows of insulated contacts, 263, 264, &c., the number of which rows correspond to the number of cargo compartments in the aircraft and the number of contacts in each row diminishing sequentially by one per row from maximum in the outer row to minimum in the inner. The contacts of the outer row 263 are designated C, C-D, C-E, C-F, C-G ... C-O and are connected to respective contacts 266 of each of 13 sections a to m of a multiway ganged compartment loading selector switch 267, the contacts of the next inner row 264 are designated D, D-E, D-F, D-G ... D-O and are connected to respective contacts 268 of the switch sections a to l, and so on sequentially; the number of contacts of each switch section diminishing progressively from 13 in section a to 1 in section m. Corresponding ganged contact arms 271 manually operated by knob 272 traverse the switch sections, and are respectively connected to the coil of an associated relay 273 a to m, each having normally closed contacts 275, 277 and normally open contacts 276, 278. The free end of each relay coil is connected to contact 275 of the succeeding relay; the opposite contacts 277 being connected in common to negative battery. Contacts 278 are respectively connected to linear annular concentric resistances 291 equal in number to the relays 273 and the contact rows 263, 264, &c., which are traversed by a common wiper arm 294 connected to positive battery and ganged for rotation by the rebalancing servo system of remaining cargo weight bridge 172, while the opposite contacts 276 are connected in common