Patent GB-776524-A (GB)
Title: Navigation-aid apparatus for aircraft
IPC: G05D1/06
Filed: 1955-11-18
Abstract: 776,524. Aircraft navigation instruments. SPERRY RAND CORPORATION. Nov. 18, 1955 [Dec. 6, 1954], No. 33037/55. Class 4. [Also in Group XXXV] - Apparatus for aircraft equipped with high lift devices extensible at will, comprises a device for measuring the deviation in pitch of the aircraft from a reference pitch, and means for automatically adjusting the reference pitch simultaneously with adjustments made to the high lift devices, whereby if the aircraft is controlled so as to maintain the pitch deviation zero, lift transients due to operation of the high lift devices are avoided. The invention is applied to a system as described in Specification 690,985, wherein a vertical deviation signal from a glide path receiver or an altitude responsive device is added to a signal representing the deviation in pitch of the aircraft from a desired reference pitch, and the resulting signal is fed to an indicator which the pilot must keep in the null position, or is fed to the elevator servomechanism, whereby the aircraft approaches the desired flight path asymptotically. Figs. 5 and 6 show embodiments in which operation of high lift devices, requiring a change in the angle of attack to maintain the flight path or approach thereto, causes an appropriate change in the reference pitch angle. In Fig. 6, flaps 26 and a flap angle indicator 27 are operated by a motor 25 and a forward/off/reverse switch 28. The motor drive also operates a wiper 66, which contacts a segment 67 as soon as the flaps begin to extend. A bellows 62 responsive to the difference between total and static pressures operates the wiper arm 61 of a potentiometer 60 wound so that the wiper derives a voltage K 1/q, where K<SP>1</SP> is a constant and q the dynamic pressure, when the flaps are extended, and this signal is fed to one end of a potentiometer 37, contoured so that the wiper 38 driven by the flaps motor 25 picks off a signal f(F), being an appropriate function of the flap extension F, whereby the wiper 38 is at a potential to ground of Kq<SP>1</SP> + f(F). This signal is in series with a pitch signal derived from the gyro vertical 4, and the sum signal on lead 2 is mixed with the vertical deviation signal from the glide path receiver or altitude responsive device, and fed to the indicator or elevator servomechanism. In aircraft in which no significant change in airspeed occurs during landing approach, the signal K 1/q may be omitted. In Fig. 3 (not shown), the potentiometer 37 is linearly wound, but is driven through a non- linear transmission. In aircraft in which the change in airspeed during and after flap extension is laid down by operational procedure the signal K 1/q is omitted, and appropriate synthetic signals produced as in Fig. 5. Here the motor 25 drives the flaps 26 and indicator 27 as before, and also a cam 39 which, when the flap extension reaches 20 degrees, closes a contact 40 energizing a relay 42, which then holds itself on by contact 43 and closes contact 44, letting in an electromagnetic clutch 45, which drives the wiper 38 through the input 46 of a differential 47, the second input 48 being held by gear friction. When the flaps are. fully extended, a cam 50 makes a contact 51 energizing a relay 52 which holds itself on by contact 54 and makes a contact 55 energizing a motor 56 which drives the wiper 38 through the differential 47 to modify the pitch deviation signal to account for the changes in airspeed which should occur following flap extension according to operational procedure. When the motor has run for a predetermined number of revolutions, the cam 50 breaks a contact 53 de-energizing relay 52 to stop the motor. On retraction of the flaps, a contact 43<SP>1</SP> is broken by cam 39 at a flap extension of, say, 15 degrees, to de-energize relay 42. Specification 691,017 [Group XL(c)] also is referred to.