Abstract: In order to improve the accuracy of borehole survey systems utilizing probes with inertial components including inclinometers, two ring laser gyro units are included to provide rotation information to the system. When the probe is moving in a borehole, inclinometer iformation is used to produce a synthetic rotation signal to take the piece of a third gyro and the earth's rotation is used for a similar purpose in combination with signals from the two ring laser gyros when the probe is stopped. Wire line velocity is used in combination with the inclinometer and gyro information to provide signals representing the probe velocity and position. Coordinate transformations are provided in the probe to transform the inertial signals and wire line velocity signals into earth reference coordinate system. Kalman filtering incorporates noninertial velocity data to reduce the effect of errors inherent in the generation of various input signals to the system.

Abstract: An apparatus and method for counting the number of cycles of a sensor signal and of a reference signal that occur during respective time intervals associated with a sampling interval defined by a sample signal. Sensor and reference gate signals are produced and respectively define sensor and reference intervals. The sensor interval begins and ends synchronously with respect to the sensor signal, and the reference interval begins and ends synchronously with respect to the reference signal. The sensor, reference and sampling intervals are approximately coextensive with one another. Cycles of the sensor and reference signals are counted during the sensor and reference intervals, respectively. The process may be repeated for a plurality of successive sampling intervals.

Abstract: In a structure utilizing a pair of accelerometers vibrating in a direction normal to their force sensing axes, a circuit utilizing voltage-to-frequency converters is utilized to convert the analog output signals from the accelerometers to digital signals representing the translational motion and the angular rate rotation of the structure.

Abstract: An accelerometer includes a hinged proof mass constrained from movement by a beam resonator force transducer. To afford greater movement of the proof mass and greater latitude in positioning mechanical stops, one end of the force transducer is connected with the accelerometer base through a compliant mount. The other end of the force transducer is connected with the proof mass at the center of percussion of the proof mass. Adjacent surfaces of the proof mass and base provide squeeze film viscous gas damping. A pair of proof mass-force transducer systems are mounted on a carrier in opposite positions with the sensitive axes of the proof masses aligned and the proof mass hinge axes parallel and opposed to each other.

Abstract: An apparatus for inertially determining the rate of angular rotation and translational motion of a structure is provided which utilizes a pair of vibrating accelerometers vibrating along a single axis with their force sensing axis located normal to the axis of vibration and rotated 90.degree. from each other. Signals from the vibrating accelerometers can be processed to provide indications of angular rotation about two axes and translation motion about two axes. Two of the sets of vibrating accelerometers can be combined to provide a three axis inertial reference system.

Abstract: In an inertial system for sensing the angular rotation and translational motion of a structure utilizing a pair of accelerometers in a back-to-back arrangement vibrating substantially linearly along an axis normal to their force sensing axes, a mechanism utilizing a parallelogram structure is used to impart the vibratory motion to the accelerometers.

Abstract: A weight and balance system which automatically compensates for loading errors while the aircraft is stationary. A weight signal is generated from the outputs of a pair of inclinometers mounted on adjacent opposite ends of a landing gear member which bends in response to aircraft weight. The weight signal generated just after no movement of the aircraft is detected is held in a latch. The held weight signal and a subsequently generated weight signal are combined to provide a signal representative of the difference therebetween. The difference signal is scaled by an error correction coefficient to provide a loading error compensation signal which is combined with the subsequently generated weight signal to provide a corrected weight signal. The system further includes means for performing reasonableness tests in response to the restoration of power to the system after power has been down.

Abstract: A static low tire pressure detection system for detecting the presence of a low tire mounted on a structural member of an aircraft, such as a bogie beam or nose axle, includes a pair of inclinometers mounted on the structural member and adapted to sense the bend therein. The signals from the inclinometers are stored in a memory once the aircraft is at rest on the ground to provide reference signals indicating the angle of the structural member with respect to an inertial reference and the weight carried thereby. The reference signals are compared against later-developed signals representing instantaneous angle and weight on the structural member to develop difference signals. The difference signals are used to generate an indication of tire pressurization, which is then checked to determine whether the tire pressurization is within acceptable limits.

Abstract: In order to provide for accurate setting of a preload force on an accelerometer force responsive pendulum and to provide for rigid support for the pendulum, a pendulum support assembly is constructed with a flexure member that is attached at one end to the accelerometer frame. The flexure receives the preload force from a preload pin at the other end and has one pendulum axle bearing attached to it between the attachment point and the preload pin. In addition, the flexure includes a hinge portion located next to the attachment point that serves to make the flexure a statically determinate beam so that the preload force on the bearing can be accurately determined.

Abstract: A method of determining the alignment of a first transducer mounting surface relative to a second transducer mounting surface includes utilizing a laser in conjunction with first and second precision ground fixtures secured to the first and second transducer mounting surfaces, respectively. An optically flat mirror is carried by each of the fixtures, with the mirror of the first fixture being partially light-transmissive. The incident light beam from the laser is directed at the partially light-transmissive mirror which, in turn, reflects part of the incident beam to form a first reflected beam. The remaining portion of the incident beam is transmitted and is reflected by the other mirror to form a second reflected beam. The two beams reflected by the mirrors are projected upon a screen disposed in front of the laser, such screen having an aperture through which the incident beam passes.

Abstract: An accelerometer has two proof masses each constrained from movement by a beam resonant force transducer. The proof mass-force transducer systems are mounted with the sensitive axes of the proof masses aligned and the force transducers arranged so that their resonant frequencies f.sub.1 and f.sub.2 vary oppositely with a change in acceleration. The acceleration is determined in accordance with the relationa=A.sub.1 f.sub.1 -A.sub.2 f.sub.3 +A.sub.0ora=A.sub.1 f.sub.1.sup.2 -A.sub.2 f.sub.2.sup.2 +A.sub.0where a is the acceleration and A.sub.1, A.sub.2 and A.sub.0 are calibration coefficients.

Abstract: A head moving mechanism for a tape deck provides for accurate shifting of a magnetic head from one set of tracks to another by securing the magnetic head to a head carriage member which in turn is attached to the tape deck by two flexures. A solenoid secured to the head carriage member serves to move the magnetic head by means of a linkage mechanism attached to the tape deck.

Abstract: A transducer for sensing the angular position or rate of change of displacement of a housing of a borehole survey instrument with respect to a reference position includes a rotor magnetically suspended within a stator which is in turn secured to the housing. The rotor is constrained by the magnetic suspension to rotate about a single axis relative to the stator. A frame of reference is established for the transducer, against which subsequent measurements are compared. Optical sensing means are included for sensing the movement of the rotor about the axis of motion to develop an indication of the angular position or rate of change of position of the housing.

Abstract: In order to provide for substantially reduced costs in acceptance testing of aircraft computers, the acceptance test system described herein includes: a group of input circuits for receiving the computer output data signals; an input circuit adapted to receive signals from the aircraft computer representing the computer input data signals; and a transmitter for transmitting the computer input data to the computer. In this automatic acceptance test system, the computer under test generates both serial and parallel input data signals for itself which are then retransmitted to the computer under test by the automatic test system.

Abstract: A flexure in a transducer such as an inertial guidance accelerometer for suspending a force sensitive element to a mounting base includes a reduced thickness central portion and a pair of relatively thick ribs disposed on opposite sides of the central portion. An electrically conductive coating is disposed on at least one face of the central portion to provide electrical connections to components located on the element. The reduced thickness of the central portion minimizes errors caused by stresses in the interface between the conductive coating and the element and the relatively thick ribs provide a desired strength and spring rate for the element suspension.

Abstract: A borehole survey instrument has a probe with a polarized light system for transmitting a signal representing the angular orientation of the probe to the surface. Light from a source in the probe is directed through a polarizing filter with an axis of polarization orthogonal to the longitudinal axis of the probe. The polarized light beam is transmitted to the surface through an optical fiber light conduit. The angle of polarization is detected with a rotating polarizing filter and provides a measure of the probe orientation. In surveying a borehole, azimuth is determined from inclinometer measurements. The probe orientation in vertical sections of the borehole is measured by the polarized light system. Two measures of borehole azimuth are combined, providing an improved measure of azimuth in boreholes near vertical and near horizontal.

Abstract: To increase the effectivity of warnings and to decrease nuisance warnings in a ground proximity warning system having several modes of operation, the switching from one mode to another is done as a function of radio altitude and time. In addition, in a ground proximity warning system where a warning signal is generated in accordance with a predetermined relationship between flight parameters, one or more of these parameters can be varied as a function of radio altitude and time in order to, for example, increase the altitude above ground as a function of radio altitude and time from take-off that a terrain clearance warning is generated or to decrease as a function of radio altitude and time, the radio altitude below which a negative climb after take-off warning is generated.

Abstract: Gain peaking and attenuation of audio signals above the peak gain frequency are provided in an audio frequency equalization preamplifier that includes an operational amplifier having a feedback network including first and second resistors and a feedback capacitor connected between the output and the second feedback resistor. Two or three low pass RC filter sections are connected between the audio signal source and the noninverting input of the operational amplifier with a circuit connecting a capacitor of the second RC section from the noninverting input to a node between the second feedback resistor and the feedback capacitor.

Abstract: Automatic selection of a directional antenna providing the best television reception is provided for in an antenna control circuit that includes a circuit for automatically sampling the video output for each directional antenna and connecting the directional antenna that produces the strongest video signal to the receiver. The antenna control circuit includes a timer circuit that responds to the horizontal and vertical synchronizing pulses of the receiver to control the duration and timing of the sampling.

Abstract: An improved mounting between a cylindrical package, containing a sensitive instrument, and a protective cylindrical housing disposed thereabout. Plugs at opposite ends of the housing each have a conical recess opening toward the other plug and between which the package is confined. O-rings at each end of the package engage the tapered wall of the adjacent recess and absorb longitudinal and radial shock and center the package within the housing. To restrain relative rotational movement between the housing and instrument package, a plurality of coil springs are disposed within aligned bores in an end of the package and the adjacent plug.