Patent GB-1232601-A (GB)
IPC: G06G7/78
Filed: 1968-05-02
Abstract: 1,232,601. Flight path computers. THOMSON-CSF. 2 May, 1968 [3 May, 1967], No. 20975/68. Heading C4G. In a system enabling an aircraft pilot to determine the deviation between an actual flight path and a selected descent or climb path whose angle to the horizontal is indicated in the aircraft, the latter A (Fig. 1) at altitude H on path AS of slope #, wherein C = ES, the ground distance between D.M.E. transmitter E and the ground intersection S of the flight path; the parameters C and # are set on board the aircraft and H # (C + D)0, where D is the slope distance from aircraft to D.M.E. transmitter. At A<SP>1</SP> the aircraft follows a programmed flight path A<SP>1</SP> A<SP>11</SP> (parameters C<SP>1</SP>, #<SP>1</SP>) and then A<SP>1</SP> A<SP>111</SP> (parameters C<SP>11</SP>, #<SP>11</SP>) and then ILS flight path A<SP>111</SP> # to the runway. For each flight path to lie above the prolongation of the succeeding one, with parameter C fixed, where C<SP>1</SP> 1  and C<SP>11</SP> 1  are the distances between ground intersections of AA<SP>1</SP> and A<SP>1</SP> A<SP>11</SP> and of A A<SP>1</SP> and A<SP>11</SP> A<SP>111</SP> respectively. In Fig. 2, manually set potentiometer 2 supplies analogue voltage representing # to transformer 3 energizing manually set potentiometer 4 to supply analogue voltage representing C#, while potentiometer 5 set by D.M.E. receiver 6 supplies analogue voltage representing D#, all to adding analogue computer 7 to apply voltage representing H = (C + D)0 to indicator 10, also receiving true altitude signal Hr from altimeter 11 to produce an error voltage. A contactor 33 linked to the # preset control supplies voltage over one of e.g. three terminals 300 respectively corresponding to three sets of values of #<SP>1</SP> and #<SP>11</SP>, lower than three predetermined values of #, to the logic circuitry 30, so that output 305 selectively develops voltages, zero for #, and subsequently analogous to C<SP>1</SP> 1 # and C<SP>11</SP> 1 #<SP>11</SP>, in accordance with the preprogrammed flight path slope parameter, which are applied to computer 7. If the initial slope may be chosen arbitrarily by manual control (Fig. 2) analogue computer 35 receives chosen slope # input, and programmed values of 01 and H<SP>1</SP>c from output 307 of 30, to compute values of C<SP>1</SP> 1 , #<SP>1</SP>, C<SP>11</SP> 1  #<SP>11</SP> &c. from the relation C<SP>1</SP> 1 # = H<SP>1</SP>c (1 - #<SP>1</SP>/#) for application to input 301, while for discrete selection of slope #, the computer is not used and the successive values of C 1 <SP>1</SP>, C 1 <SP>11</SP> &c. are programmed and stored. Output 306 supplies voltage analogues of the programmed altitudes H<SP>1</SP>c, H<SP>11</SP>c at which changes of flight path occur to comparator 32 also receiving voltage analogues of H (or Hr) to supply a control pulse at equality to the input 302 of logic 30 (Fig. 3) which comprises a memory 310 storing predetermined values of H<SP>1</SP>c, #<SP>1</SP>; H<SP>11</SP>c, #<SP>11</SP>. Address selector 311 controlled by pulses from 302 (Fig. 2) extracts the appropriate values to outputs 303, 307, 306. The selector is also controlled over gate circuits from the selected terminal 300 to inhibit selection of certain addresses as described, while input 301 receiving values C<SP>1</SP>, #<SP>1</SP> &c. is gated to output 305 over 313 controlled by pulses from 302. In operation, value # is initially selected by the pilot so that height value H is derived at 7 and the aircraft follows path AA<SP>1</SP> with switch 31 as shown in Fig. 2. Contactor 33 then applies to address selector 311 of logic 30 a voltage inhibiting selection of a programmed slope >#, and selects from memory 310 the first programmed value of #<SP>1</SP> corresponding to flight path A<SP>1</SP> A<SP>11</SP> and height H<SP>1</SP>c. At point A, when computed H = H<SP>1</SP>c the comparator 32 pulses 302 to develop at 303 and 307 the first preselected #<SP>1</SP> and H<SP>1</SP>c signals, and at 306 the substitution of H<SP>11</SP>c signal for H<SP>1</SP>c signal, while changing over switch 31 to substitute a # signal for the # signal at transformer 3 and potentiometer 5, and opening gate 313 to develop product signal C 1 <SP>1</SP> # at output 305; calculated by 35 from values #, #<SP>1</SP>, H<SP>1</SP>c according to C 1 <SP>1</SP> #<SP>1</SP> = H<SP>1</SP>c(1- #<SP>1</SP>/#). Hence the relation: H = D#<SP>1</SP> + C#<SP>1</SP> + C<SP>1</SP> 1 #<SP>1</SP> = D#<SP>1</SP> + C<SP>1</SP>#<SP>1</SP> for flight path A<SP>1</SP>A<SP>11</SP> is calculated, and at pointA<SP>11</SP>, H = H<SP>11</SP>c) whereat the comparator supplies a further pulse signal replacing #<SP>1</SP> by #<SP>11</SP>, C1 1 #<SP>1</SP> by C<SP>11</SP> 1 #<SP>11</SP>,H<SP>11</SP>c by H<SP>111</SP>c, and so on until the aircraft joins the ILS path. An example of a three-programmed section flight path is given (Fig. 4, not shown). Alternatively a servomechanism controlled as a function of altitude may produce variable voltage analogues of #<SP>1</SP> and C<SP>1</SP> 1  #<SP>1</SP> and the instant of commencement of the servo-controlled flight path is controlled by a set value of # for selected slope. The law of variation of the variable analogue voltages may be arbitrarily determined in accordance with tne required flight path. Specification 1,225,691 is referred to.