Abstract:
An accelerometer comprising a support (52) and a proof mass (40) mounted to the support by a flexure (50) or the like, such that the proof mass can rotate about a hinge axis (HA) perpendicular to sensitive axis (SA). An isolator (42) is also mounted to the support by an isolator suspension system (60, 62) that is relatively compliant for isolator movement parallel to a transducer axis (TA) normal to the hinge axis, and relatively noncompliant for isolator rotation about the hinge axis. Force transducers (80, 82) are connected between the isolator and the proof mass. The force transducers are parallel to the transducer axis, and positioned on opposite sides of the hinge axis from one another, such that rotation of the proof mass about the hinge axis puts one force transducer in tension and the other force transducer in compression. The isolator suspension system reduces the magnitude of common mode inputs, such as those caused by differential thermal expansion of the crystals with respect to other accelerometer components.
Abstract:
Disclosed is a combined flight data recorder data aquisition circuitry (10) and airborne integrated data circuitry (12) that can be variously packaged to supplement and update existing aircraft systems or serve as a standalone flight data recording and/or airborne integrated data system. The flight data recorder system circuitry (10) and airborne integrated data system circuitry (12) are separately programmed microprocessor based systems that are capable of processing aircraft parametric signals provided by a variety of aircraft signal sources. In the disclosed arrangement, the airborne integrated data system circuitry (12) is arranged and programmed to automatically monitor engine start and shutdown procedures, aircraft takeoff and cruise and to provide a landing report that indicates fuel consumption and landing weight. To minimize memory storage requirements and provide readily available engine condition information, the automatic monitoring consists of a single set of signals for each monitored condition and the information is converted to standard engineering units. Monitoring of selected parametric signals to detect excessive levels also is provided. Stored data is periodically retrieved by means of a ground readout unit (30).
Abstract:
A circuit (62, 64) for receiving a periodic input signal at frequency f, and for producing a pseudosinusoidal staircase output signal at a fundamental frequency f from which predetermined harmonics of the fundamental frequency are absent. Also provided are an oscillator in which such a circuit forms the drive circuit for a piezoelectric crystal, and an accelerometer in which such an oscillator is used as the force sensing means. In the accelerometer, the reaction force of a proof mass (40) is sensed by a resonator that comprises a drive circuit (44) for producing a drive signal and a piezoelectric crystal (42) connected between the proof mass and support (46). In response to the drive signal, the crystal undergoes mechanical vibration at a frequency f that varies with the force applied to the crystal. A resonator signal corresponding to the mechanical vibration is produced and input to drive circuit. The drive circuit responds by producing the drive signal in the form of a periodic, pseudosinusoidal staircase function. The staircase function has fundamental frequency f, and has N steps of M discrete nonzero amplitude levels per period. N and M are integers greater than one, with M being less than N. The drive circuit produces the M amplitude levels such that predetermined harmonics of the fundamental frequency f are not present in the drive signal, thereby reducing the possibility of activity dips in the accelerometer output.
Abstract:
A wind shear detection and alerting system (30) compares inertially derived accelerations with air speed rate to provide a wind shear warning signal. Inertially derived accelerations are used instead of purely inertial accelerations because purely inertial systems generally require a vertical gyro. By utilizing angle of attack (.alpha.) and flight path angle (.gamma.) instead of pitch angle (.theta.) in the calculation, no vertical gyro signal is required and the system will be responsive to vertical as well as horizontal shear conditions. An enhanced version of the system is also compensated for roll angle (.phi.), with the roll angle being derived from the rate of change of heading (.PSI.) to avoid the need for a vertical gyro. The alerting system is capable of providing visual and aural warnings for a variety of wind shear conditions, such as, head shear, tail shear, head shear followed by tail shear and wind shear trend. The waring system is also capable of providing a wind shear warning which is a function of the radio altitude of the aircraft.
Abstract:
A dual sensor, frequency output accelerometer that does not require either high sampling rates or mechanical matching of the sensors to achieve high levels of accuracy. In one embodiment, the accelerometer comprises a first sensor (12, 14, 16) that produces an output signal S.sub.1 having a frequency f.sub.1 related to acceleration along the sensitive axis, and a second sensor (18, 20, 22) that produces a second signal S.sub.2 having a frequency f.sub.2 related to acceleration along the sensitive axis, the sensors being arranged such that a given acceleration causes the frequency of one output signal to increase and the frequency of the other output signal to decrease. Velocity change .DELTA.V during time interval T is determined according to:.DELTA.V=A[.DELTA..phi.+FT+B.SIGMA..phi.]where A, F and B are constants, .DELTA..phi.is the difference between the phase changes of the output signals over time interval T, and .SIGMA..phi. is the sum of the phase changes of the output signals over time interval T. Higher order correction terms are also described for very high precision applications. Also disclosed is an accelerometer or measuring velocity change during a time interval that includes a subinterval during which electrical power is unavailable.
Abstract translation:双传感器,频率输出加速度计,不需要高采样率或传感器的机械匹配来实现高水平的精度。 在一个实施例中,加速度计包括产生具有与沿着敏感轴的加速度相关的频率f1的输出信号S1的第一传感器(12,14,16)和产生第二传感器的第二传感器(18,20,22) 具有与沿着敏感轴的加速度相关的频率f2的信号S2,传感器被布置成使得给定的加速度使得一个输出信号的频率增加,另一个输出信号的频率降低。 时间间隔T内的速度变化DELTA V根据以下方式确定:DELTA V = A [DELTA phi + FT + B SIGMA phi]其中A,F和B是常数,DELTA phi是输出信号的相位变化之间的差异 时间间隔T,SIGMA phi是时间间隔T上的输出信号的相位变化的总和。对于非常高精度的应用,还描述了高阶校正项。 还公开了一种加速度计或在包括电力不可用的子间隔的时间间隔期间测量速度变化。
Abstract:
Prior mounting systems for tuning fork temperature sensors have resulted in unpredictable activity dips within the sensor operating ranges. This problem is eliminated by the mounting and isolation system (32) of the present invention that is adapted to mount temperature sensitive tuning fork (20) to a support structure. The mounting system comprises a mounting member (34) adapted for rigid connection to the support structure, and support means (36) connecting the tuning fork base to the mounting member such that the tuning fork is supported solely by the support means. The support means comprises a low pass mechanical filter that transmits only vibration frequencies that are less than the operating range of frequencies of the tuning fork.
Abstract:
An aircraft ground proximity warning system having an excessive terrain closure warning mode and a below glide slope warning mode monitors the glide slope signal and modifies the terrain closure warning envelope to accept a lesser terrain clearance when the aircraft is within the glide slope beam.
Abstract:
In a single-frequency precision guidance landing system, the use of a DME interrogator in the aircraft and a DME receiver at the ground installation, each tuned to the same DME channel frequency, to uniquely interrogate a selected ground station and hence identify it by virtue of its replies being synchronous in the aircraft with the interrogations, the interrogations and the replies also being used to obtain range to the ground installation. This technique uses airborne already-installed DME interrogators for selective interrogation of a desired landing installation, thereby to eliminate any need to add additional special purpose equipment to the aircraft to accomplish the desired uniqueness of interrogation and ground installation identification achieved by this invention.
Abstract:
In order to provide timely aircraft performance data from an aircraft flight data recorder in a useful format, a flight data display system is provided: with a data storage unit; an interface circuit for reformatting flight data from the flight data recorder; a central processor for converting selected portions of the reformatted data into engineering units and storing the converted data into the storage unit; and a video display unit including a keyboard for selecting the desired portions of the reformatted flight data for display on the video display unit. The video display unit provides for the multicolor display of flight data in either graphical form or in a cockpit instrument form on a cathode ray tube.
Abstract:
A warning system for providing an aural warning to the pilot of a rotary wing aircraft monitors the altitude above ground and barometric descent rate of the aircraft and generates the warning if the descent rate of the aircraft is excessive for the altitude at which the aircraft is flying. The system provides two distinct warnings, one being an early warning advising the pilot of a hazardous condition, and the other being a warning alerting the pilot of imminent danger. The system also includes tactical and non-tactical modes of operation, wherein the warning criteria are adjusted to meet tactical and non-tactical flight conditions.