Patent GB-958096-A (GB)
Title: Position indicating device, more particularly for monitoring the position of landinggear and landing gear doors of aircraft
IPC: B64C25/28
Filed: 1962-06-27
Abstract: 958,096. Warning indicators on aircraft. K. DIEHL. June 27, 1962 [June 27, 1961], No. 24586/62. Heading B7W. An indicating device for indicating the positions of elements of undercarriage gear and doors on aircraft comprises a first signal lamp for each element for indicating one limit position thereof and also comprises a second signal lamp for each element for indicating the other limit position thereof while a circuit is provided for each of said lamps and includes means operable by the respective element at the corresponding limit of its travel for illuminating said lamp, means being provided which are operable during movement of each of said elements between the limit positions thereof for effecting periodic illumination of one of said lamps pertaining thereto. The visible face of the instrument comprises a frame 5, 6 surrounding a signalling area 7 formed with windows 8, 9 representing a nose-wheel and door therefor respectively; and other windows 10-15 representing port and starboard main wheels and doors. A panel of lamps (Fig. 3, not shown) is arranged behind the area 7 so that two lamps, one red and one green, illuminate each window, light screening devices being arranged between the various groups of lamps. A cancelling button 16 is provided. The circuit shown in Fig. 5 is for eight only out of a total of sixteen signalling circuits for lamps L1-L8, all of one colour, each lamp being connected by a respective limit switch S1-S8 and a common conductor 50 to a voltage source and also through a common conductor 49 to an electronic switch V10 which is adapted to be operated intermittently by a bi-stable electronic switch S12. Switches S1-S8 are arranged in parallel with circuits D1-D8 and amplifier and reversing circuit means V1-V8 respectively, the conductors 59 connecting these to the lamps being connected to earth through resistors R1-R8. The conductors 59 are connected also through coupling condensers C1-C8 respectively connected to a conductor 41 in turn connected through a diode 42 to switch S12. An impulse generator MV controls an amplifier V9, the output of which passes over conductor 51 to the inlet of all circuits D1-D8 and a reversible switch FS connected with the operating member of the landing gear is connected through lead FWA to uneven numbered circuits D1, D3 &c. and lead FWE to even numbered circuits D2, D4 &c., the leads being connected through resistors R12 and R13 to a source of current. The circuit is completed by switches S9, S10 and S11 respectively coupled to landing gear doors, engine throttle linkage and landing gear control member, and a further switch LT for turning off the signalling installation after it has properly indicated the nominal position of the elements. With the appropriate limit switches closed the coloured lamp will be illuminated to indicate that the undercarriage element is locked in its up or down position and between these positions the amplifying reversing switches V1-V8 cause the appropriate lamp to be illuminated intermittently to give a blinking signal.