Patent GB-1083103-A (GB)
Title: Improvements in installations for controlling the path with respect to the ground of aircraft
IPC: B64C29/00
Filed: 1965-04-23
Abstract: 1,083,103. Electric measuring systems. CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE. April 23, 1965 [April 24, 1964; March 2, 1965], No.17318/65. Heading G1N. An installation for determining the path of an aircraft along a runway comprises a plurality of detection elements, in the form of pneumatic tubes, placed across the runway at known distances apart and each adapted to produce at least one electric signal when a wheel of an aircraft passes thereover, and means responsive to the signals to indicate the characteristics of the path. The characteristics which may be calculated include the speed and acceleration of the aircraft, the alignment of the path relative to the runway, the position of the aircraft when the nose wheel leaves or touches the ground, and the point of take-off or landing. The signals may also be employed to rotate a camera pivoted on the control tower roof so that it is always directed at the aircraft. In a first embodiment, Fig.14 (not shown ), each pneumatic tube (29) is connected at one end to a pressure pick-up (31) comprising a diaphragm (36) carrying a coil (39) disposed in the field of a permanent magnet (40). When a wheel passes over the tube a pressure wave passes along the tube to the pick-up (31) and the coil (39) delivers a signal e to a signal shaping circuit (32) which gives a square wave output signal E independent of any parasitic pressure waves in the tube. The signals E from all the detection elements are fed by a common collector cable (4) Fig.4 (not shown) to a computer (5) which determines the distance travelled by the aircraft, its speed and acceleration, and whether the nose wheel is in contact with the runway. This information is displayed in the control tower and is also transmitted by radio to the aircraft. The computer (5) also supplies a control signal to a step-by-step motor (17) which rotates the camera (14). In a second embodiment, Figs.7 and 11, (not shown), each end of each tube (29) is connected to a respective pressure pick-up and signal shaping circuit and the output signals Fa, Fb from the signal shaping circuits are fed to an electronic comparator (35). If the aircraft is travelling along the axis (XX) of the runway the signals Fa, Fb are in phase and the comparator (35) delivers a zero signal, but if the path of the aircraft is displaced from the centre of the runway the pressure waves in the tube reach the pressure pick-ups at different times, the signals Fa, Fb are out of phase, and the comparator delivers a signal F the duration of which is proportional to the magnitude of the displacement and the sign of which indicates the direction of the displacement. The signals F from the comparators are fed by a common collector cable (26) to analyzing and indicating apparatus (27, 28). In a further embodiment, Fig.15 (not shown), which is capable of providing all the information supplied by the previous two embodiments, each tube is connected at each end to a pressure pickup and signal shaping circuit and the output signals from the signal shaping circuits on the two sides of the runway are fed by respective common collector cables (52a, 52b) to an analysis apparatus (53) which delivers a signal corresponding to the signal F. The cable (52a) carries signals E which are fed to a computer (105) as in the first embodiment. The tubes (29) are embedded in the runway at the expansion joints between the concrete units.