Patent GB-1108780-A (GB)
Title: Aircraft vertical path computer
Inventor: HATTENDORF EDWIN RALPH
IPC: G06G7/78
Filed: 1966-08-04
Abstract: 1,108,780. Aircraft navigation computers. COLLINS RADIO CO. 4 Aug., ,1966, No. 35015/66. Heading G4G. In a computer for aircraft navigation in a vertical plane, input parameters of slant range to a way point (S) ground distance to a way point (D) offset between waypoint and aimpoint (D 0 ) corrected barometric altitude (h b ) reference altitude (h o ) true airspeed (TAS) altitude rate h and selected vertical path angle (# s ,) are inset, and the vertical path deviation (##) from the selected angle, the actual flight path angle y, the corrected ground distance to the waypoint, and the time-to-go to the waypoint are calculated. It is shown (Fig. 1) that A slant range selsyn signal from a distance measuring equipment output 10 (Fig. 3) is applied over switch 11 as shown to longitudinal distance mechanism 12 (Fig. 8, not shown) to energize the stator of a synchro whose rotor output energizes a velocity feedback motor generator adjusting the rotor and that of a linear synchro transformer whose stator is A.C. energized to produce a signal proportional to the input, which excites resolver 13 also receiving over switch 11 a differential altitude signal #hh b  - h 0  from mixer 15 receiving reference altitude signal h o  set in at 17 and a corrected altitude signal hb from mixer 16 energized by signals from altitude source 19 and barometric correction setting 18. The resolver unit (Fig. 9, not shown) receives slant range signals to energize buffer amplifier 60 and rotor 62 of resolver 61 with feedback to the amplifier input; the stator windings 64, 65 developing signals proportional to the input multiplied by sin 0, cos #, where 0 is angular deflection between rotor and stator; the sine signal energizing a servoamplifier and velocity feedback motor generator together with #h at an angular deflection such that S sin # t  = # t  = (h b  -h o ) and D=S S cos # t  derived from winding 65. When input is desired as a direct ground distance signal from a doppler or navigational computer source 48, # t  is disconnected and the resultant altitude signal at the resolver is zero, so that as before the ground distance signal D is derived from winding 65. A selsyn signal representing time airspeed from source 28 is applied to a longitudinal speed mechanism 29 (Fig. 10, not shown), wherein a synchro energizes follow up velocity feedback servomotor generator to adjust a linear synchro transformer to produce at null a true airspeed signal applied to a mixer 30, whose input is applied to a flight path angle and ground speed resolver 26 also receiving an altitude rate signal h from source 31, e.g. of the kind described in Specification 1,101,219. The unfiltered distance signal D is applied to a mixer 45 receiving also the output of a distance integrator 21 to develop a difference signal AD, and in the synchronizing mode of logic operated switch 24, 25 for cross-country flight, the integrator (Fig. 14, not shown) comprising a velocity feedback servo amplifier motor generator and linear synchro transformer, operates as a follow-up servo, and the difference #D is applied to the integrator input. The wind integrator 23 has its output connected to its input for zeroization in synchronizing mode. In the tracking mode of switches 24, 25 when the apparatus is responsive to a localizer or doppler beam, the output of mixer 45 energizes wind integrator 23 and mixer 27, while the direct feedback loop round the integrator is removed and completed through mixer 27. A complementary ground speed signal 33 compensating for the filtering lag of the integrator is derived from wind integrator 23 and combined in mixer 30 with TAS signal 46 and applied to resolver 26 together with altitude rate signal h at 47. The wind integrator (Fig. 13, not shown) comprises a rate servo system with an amplifier receiving difference signal AD to energize a velocity feedback motor generator driving the rotor of a linear synchro transformer to derive in the stator winding an integral signal of the input representing longitudinal wind; the #D input being disconnected and the input and output interconnected during the synchronizing mode. The ground speed D modified by #D is integrated to a signal representing distance D, and the wind integrator adds a compensating signal to TAS to derive an output proportional to longitudinal wind. The resolver 26 (Fig. 12, not shown) comprises an amplifier receiving a signal representing TAS + wind to energize a rotor of a feedback compensated resolver, which has stators developing outputs representing (TAS + wind) sin Y and (TAS + wind) cos y = ground speed D. The former signal energizes a servo amplifier together with altitude rate signal h to energize a velocity feedback motor generator driving the resolver rotor and that of a selsyn to develop a selsyn signal output representing flight path angle y at null. The derived ground speed signal is applied to mixer 27. In memory mode of switches 24, 25, operative if slant range or ground distance signals are lost, #D is disconnected from input of wind integrator 23, so that its output is held to represent memorized wind. The #D input integrator 21 is also disconnected, so that it computes ground distance from TAS and memorized wind signals. The ground speed signal is thus computed from ground distance over the long term and TAS over the short term. A computed filtered distance signal 22 (D) is utilized to compute actual vertical path angle # a  by application to a mixer 35 also receiving an offset distance signal D o  set into source 34 to derive a ground distance to aim point signal (D - D o ) applied together with a differential altitude signal (h b  - h o ) to vertical path angle resolver 39 (Fig. 11, not shown), wherein D, D o  are amplified as D - D o  to a stator winding of a resolver while the signal (h b  - h 0 ) is amplified and applied to a further quadrature stator winding; feedback rotor windings being provided. A rotor winding develops a signal amplified to energize a feedback servomotor generator driving the rotor winding to null and also a selsyn developing at null a signal representing which is combinable with a similar signal from a vertical path angle selection source 41 to produce a signal 42 representing ##, the error between actual and required vertical paths. A ground speed signal 33 (D) from resolver 26 is applied to a dividing computer 43 with the ground distance to aimpoint signal (D - D o ) at 37 to determine time to go to the aimpoint. A mathematical analysis of the transient filtering applied to the distance signals is given.