Abstract: Automatic flight control apparatus, preferably for use in a helicopter, comprises a parallel connected servosystem which allows the apparatus to discern manual input forces and to respond naturally to them. The manual forces are sensed internal the parallel servosystem by monitoring the corrective error drive signal to the parallel servomotor. A signal indicative of excess manual force is used to develop other signals, one of which aids in temporarily defeating the command signal generated by the autopilot in trying to do its job, and another of which temporarily contributes positive feedback within the parallel servosystem so as to cause the servomotor to aid the pilot's manual input force. Another preferred embodiment includes a series connected servosystem.

Abstract: Digital apparatus receives digital data and outputs a ramp-like analog waveform. The digital apparatus comprises a reference digital word source, a variable digital word source, a testing circuit, and a D/A converter. The reference word and the variable word are tested for a predetermined relationship and the variable word changes until the predetermined relationship or condition is satisfied. The D/A converter receives the variable word and converts changes in same into either positive or negative slope ramps. The D/A converter output is constant during intervals where the variable word is not changing.

Abstract: A flight control system increases the automatic control authority over, preferably, a helicopter yaw axis. A limited authority series servo is complemented with a full authority parallel servo. The parallel servo is driven by a combination of a trim command signal and a signal representing the excess of the yaw command signal over the amplitude limited drive signal to the series servo.

Abstract: An indicator instrument for aircraft may be operated in either of two modes. In an HSI mode, first indicia reflect heading, second indicia reflect selected course, and third indicia reflect course deviation. In a CDI mode, the first indicia reflect selected course, the second indicia assume a fixed position, and the third indicia reflect course deviation. A compass validity signal automatically triggers the changeover from HSI mode to CDI mode.

Abstract: A measuring system includes a plurality of resistors and circuitry connected thereto which generates first and second signals each containing different information about one or more of the resistors. Each information is possibly contaminated by error but only by substantially the same error contaminating the other information. Subtraction of two such informations thus gives error-free information because the like errors cancel.

Abstract: A non-light-emitting (passive) display such as a dichroic LCD is frontally illuminated with polarized light incident obliquely upon the display, the incident light having followed multiple paths to arrive at the display from multiple directions. Relative to a typical display viewing axis, some light arrives from one side of such axis and some light arrives from the other side of such axis. An appropriately positioned light emitter, preferably comprising a reflective cavity, lamp, and polarizer, casts some light directly on the display, and casts other light, which is also substantially collimated, on an appropriately positioned reflector which re-directs incident light to the display.

Abstract: A variable inductor includes a coil, a moveable contactor, and moveable magnetic material caused to move proximate the coil and simultaneously with the contactor. The contactor establishes first and second portions of the coil and, relative to the condition using no magnetic material, the inductance of the first portion is increased while the inductance of the second portion is substantially unchanged. Thus, over substantially all the tuning range, the first portion inductance is maintained greater than the second portion inductance.

Abstract: Sensor structure integrates multiple piezoelectric bender elements into a single piezoelectric unit. A single base member comprising a plurality of plates of piezoelectric material includes three or more electrodes for forming two or more bender elements. Preferred embodiments include one or more of the following: (i) electrodes for forming inactive regions near structure center and/or ends, (ii) aspects of structural symmetry aiding to establish preferred signal phase and amplitude relationships (iii) base member fashioned according to a three layer laminated structure (iv) circular base member (v) uniform plate polarization (vi) two or four substantially matched bender elements.

Abstract: An aircraft attitude indicator employing a gyro driven tape display. The tape takes the form of a closed loop stretched about a carrier mechanism, and includes a viewable horizon indication. The tape further includes a set of perforations which, preferably, are engaged and driven by sprocket teeth borne on a sprocket wheel member attached to the pitch gimbal of the gyro. The tape travels in response to tilt of the gyro spin axis relative to the aircraft, and in a direction so that reversed pitch sensing is accomplished.

Abstract: A variable inductance includes a coil and a moveable contactor which maintains continuous contact with the coil. An electrical connection, which is moveable along with the moveable contactor and away from a first end of the coil, connects the moveable contactor with further contact means positioned remote from the first end of the coil.

Abstract: As part of a moveable carriage assembly, a plurality of trolley wheels are capable of being driven, in worm-gear fashion, along a coil which is rotatable about its axis. One end of the coil is conductive and the other end of the coil is preferably non-conductive. A further part of the traveling carriage assembly electrically interconnects a conductive trolley wheel with an electrical contact situated remote from one end of the coil. Multiple conductive wheels are electrically interconnected.

Abstract: A plurality of moveable contactors may travel along a rotating coil, one end of which is conductive and the other end of which is non-conductive. Two or more electrically interconnected moveable contactors effect a shorting across unused electrical turns and thereby affect unused coil portion resonance. For tuning conditions where very little of the coil is unused, the non-conductive coil portion serves as a sidetrack onto which one or more contactors can move and acts as a mechanical storage or memory for preserving relative positions between contactors.

Abstract: A receiver with squelch capability includes squelch gate control circuitry which operates the squelch gate on the basis of substantially pure noise even in environments such as offset carrier networks which cause or create substantial interference energy in the receiver.

Abstract: A simplified digital NRZ data phase detector is provided with a minimum number of components and with an expanded measuring interval to enable the use of slower speed components. In a phase locked loop application, a first input gate, such as a flip-flop, responds to NRZ data, and a second input gate responds to clock pulses and the output of the first gate. Variable and fixed width correction signals are derived directly from the outputs of the first and second gates, respectively, within a measuring interval initiated by a data transition and terminated by a clock transition. The difference in duration between the directly derived variable and fixed pulses provides phase indication.

Abstract: Pulsed RF operation of a class C biased BJT is enhanced using a three element system to control the BJT emitter current. The three element system includes a transformer having a secondary connected in the emitter current path. Connected to the transformer primary are the other two elements, namely, an impedance and a pulse source. The three elements cooperate to cause the emitter current to substantially conform to a desired or predetermined pulse waveform.