Abstract: A rate detection system (10) uses a balanced resonant sensor (12) having first and second tines (14,16) interconnected with a mounting pad (20). A sensing circuit (50) including a tunnel effect displacement sensor (38) having a first probe (40) connected to the mounting pad (20) and a second probe (42) connected to a reference pad (32) detects an output signal having a Coriolis component. A feedback circuit provides a compensation signal to the balanced resonant sensor (12).

Abstract: Warning systems for aircraft that provide a warning to the pilot of an excessive altitude loss or an excessive descent rate after take-off as long as he is flying below a predetermined altitude have the problem that they require a valid radio altitude signal for proper operation, and tend to generate nuisance warnings when used in low flying aircraft. This problem is solved by comparing the accumulated altitude loss after take-off (12, 14, 62, 34) with the product of a barometrically derived altitude and the length of time the aircraft has been flying (12, 14, 30, 32, 34). A warning is generated if the altitude loss is excessive for the accumulated time-altitude product after take-off (38, 40). Thus, the system is more sensitive immediately after take-off and becomes less sensitive as flight time is accumulated to permit low level maneuvering without generating false or nuisance warnings, and does not require a valid radio altitude signal to generate a warning.

Abstract: A pitch guidance system for an aircraft utilizes inertially derived pitch information to provide the pilot with information defining the optimum pitch angle for maximum climb during a wind shear condition. The system utilizes a pitch reference modulator that receives a stall warning discrete from a stall warning system to reduce the commanded pitch angle upon the occurrence of a stall warning to reduce the possibility of stalling the aircraft during degraded performance conditions such as tail winds and engine-out conditions. The system utilizes inertially derived pitch information rather than air mass derived angle of attack information to avoid transients in the angle of attack vane signal, and the commanded pitch angle is biased as a function of altitude and vertical speed to optimize the pitch angle for different altitudes and descent rates.

Abstract: A vibrating crystal transducer for measuring temperature including a bonding area from which three or more tines extend. The tines have a torsional mode resonant frequency that is a function of temperature. Electrodes on the transducer excite the tines into vibration so that the torsional moments of the adjacent edges of the adjacent tines are reverse symmetric. When the tines are vibrated, the reverse symmetrical vibrational moments of the individual tines cancel so that there is no torsional moment, or twisting, within the area between the points where the tines intersect, which is the area defined by the bonding area. Since the bonding area does not serve as a sink for torsional energy, torsional energy is not lost through the bonding area so that the transducer has a relatively high quality factor and torsional vibration of the transducer cannot cause the transducer to eventually work loose of a mounting pad to which it is attached.

Abstract: A drive system for providing different excitation voltages to the separate beams of a multiple beam vibrating transducer is disclosed. In one embodiment of the invention an amplified voltage at the resonant frequency of a master beam is amplified and applied to a secondary beam, to force the secondary beam to vibrate at the resonant frequency and amplitude of the master beam to force the transducer to resonate at the frequency of the master beam. Since the transducer vibrates at the resonant frequency of one of the beams, the transducer energy losses to the adjacent mounting structure are reduced. This results in a higher transducer quality factor so that frequency shifts in the resonant frequency can be readily measured as changes in the parameter that the transducer is intended to monitor.

Abstract: A mounting system for mounting a transducer to a case, such that the transducer position is fixed and stable, and such that stresses on the transducer due to thermal expansion are minimized. The mounting system comprises a band, lower arms extending in a first axial direction from the band, and upper arms extending in a second, opposite axial direction from the band. The transducer arms are connected to the lower, and the upper arms to the case. In response to differential thermal expansion, the arms S bend in a radial direction.

Abstract: Apparatus and method for counting frequency of a signal with improved resolution. Frequency counters (10, 60, and 100) accumulate clock cycles from a reference oscillator (20) during a sample interval. In the simplest form of the frequency counter, the reference clock signal is inverted and both the noninverted and inverted clock cycles are accumulated in separate counters (40 and 44). The accumulated counts are totaled in a summing circuit (48) and divided by two to determine their average, thereby doubling the resolution of the frequency counter. A more complex embodiment of the invention corrects a raw count of cycles of an input signal (12) that are accumulated during an extended sample interval defined by successive rising edges of a sample signal (114).

Abstract: A lightweight, substantially corrosion-proof, conductive wire and terminal assembly (10) comprising a wire (12) laid on and welded to a terminal pad (18) at or near the end (16) of the wire. The wire (12) has an electrically conductive core (24) having a cylindrical surface. The cylindrical surface is substantially completely enveloped in a sheath of noble metal plating (26, 28). The terminal pad (18) has a noble metal surface where it is welded to the cylindrical surface of the wire (12), so the joint (22) formed by the weld is substantially sheathed in a noble metal, and thus is substantially as corrosion-proof as the noble metal sheath (26, 28) and terminal pad (18). The wire (12) is preferably covered with insulation (30) except at its end (16), which may be stripped.

Abstract: A dual-edge frequency counter and method for minimizing the effects of duty cycle modulation. In its simplest form, a dual-edge counter (50) includes a first counter (52) that accumulates reference clock pulses between successive rising edges of an input signal. An input signal is also applied to an inverter (54), which inverts the square wave signal prior to applying it to a second counter (56) that also accumulates reference clock cycles between successive rising edges of the inverted sensor signal. A summation junction (60) totals the accumulated counts from the first and second counters so that they can be averaged by a divider (62), which divides the total count by two. The technique is also employed in connection with a frequency counter that includes an integer counter (72) for totaling the number of cycles of the sensor signal occurring during a sample time defined by successive gate signals.

Abstract: A technique for reducing the effects of aliasing in a frequency output sensor system. The system includes a sensor for producing a sensor output signal at a frequency that varies within a modulation range as a function of an input parameter. The system also includes a processor for measuring the frequency of the sensor output signal at a sequence of sample times. The invention provides an analog filter for filtering the sensor output signal. In a first embodiment, the filter has an increasing phase lag versus frequency characteristic within the modulation range. In a second embodiment, the filter comprises a phase lock loop having frequency dividers in the input signal path and in the feedback path.

Abstract: In the signal acquisition system disclosed herein, frequency, phase and time uncertainties are resolved essentially simultaneously by including a preselected code group in the transmitted signal and by applying the received signal to a differential detector and then to a passive differential matched filter, the parameters of which are selected in correspondence with a code group, thereby to generate a corresponding series of complex match values. The absolute magnitude of the complex sum of the match values is maximized when the received signal is modulated by the preselected code group. When the presence of the code group in the received signal is detected, the phasing of the complex sum is detected thereby to determine carrier frequency offset. A directly detected version of the received signal is applied to a corresponding masking filter and the phase of a resultant sum signal is detected to determine carrier phase offset.

Abstract: An improved preload system for an accelerometer in which an acceleration sensitive structure is clamped between first and second clamping members. The acceleration sensitive structure includes a paddle supported such that the paddle has a degree of freedom along a sensing axis. The accelerometer further includes a case within which the acceleration sensitive structure and clamping members are mounted. The preload system comprises an internal mounting surface in the case that faces in a first direction along the sensing axis, and that contacts the second clamping member and prevents it from moving in a second direction opposite to the first direction. The preload system also includes a spring washer extending between the first clamping member and the case, such that the spring washer exerts a force on the first clamping member in the second direction. A positioning ring may also be provided between the first clamping member and spring washer, to laterally locate the first clamping member within the case.

Abstract: A mounting/coupling structure for use in an accelerometer to mount the electronics assembly with respect to the case, and to electrically couple the electronics assembly to the acceleration sensitive structure. The mounting/coupling structure may be positioned such that it provides gas damping for the paddle, and may also include means for holding the acceleration sensitive structure in a fixed position with respect to the case.

Abstract: A system for warning the pilot of a tactical aircraft in a tactical maneuver such as a dive of the point at which recovery must be immediately initiated to prevent the aircraft from descending below a minimum desired altitude monitors and the altitude, descent rate and pitch angle of the aircraft, and issues a voice warning when recovery must be initiated. The system also provides warnings of dangerous flight conditions during non-tactical or common route segments of a flight such as the take-off, landing and cruise segments of a flight. Circuitry responsive to the arming of the weapons of the aircraft enables the tactical warning portion of the system and disables certain functions of the non-tactical portion of the sysem that may cause false warnings to be genrated during tactical manuevers.

Abstract: A transformer and method for sensing displacement, A linear variable displacement transformer (LVDT) 50, 100, 150, 200, and 250) is disclosed with respect to several embodiment,s each including a core (52, 102, 152, 202, and 252) having a primary leg (56, 104, 154, 204, and 254), and two secondary legs (58 and 60, 106 and 108, 158 and 160, 206 and 208, and 258 and 260). A primary coil (54, 110, 156, 210, and 264) is disposed on the primary leg, and secondary coils (62 and 64, 112 and 114, 162 and 164, 212 and 214, and 266 and 268) are disposed on the secondary legs. Pole pieces (70 and 72, 120 and 122, 170 and 172, 222 and 224, and 274 and 276) are disposed in gaps between the primary leg and each secondary leg, so that they control the reluctance to a magnetic flux produced by an electric current flowing thorugh the primary coil.

Abstract: An instrument (10) is disclosed for an aircraft having a windshear warning system to vary the threshold alarm setting as a function of a thermodynamic property of the air and as a function of local geographic and seasonal conditions. Specifically, a function generator 16 and other circuitry is disclosed. The output from the function generator 16 and other circuitry is then added to a fixed threshold acceleraton signal to produce a threshold alarm signal which has a value that is a function of the temperature of the air, in a basic embodiment.

Abstract: A limit sensing device for permanently indicating when a predetermined temperature limit has been reached in a fluid conduit, includes a housing mounted on the conduit in heat transmitting relation with the fluid and an indicator movable in the housing between a retracted position and an activated, non-resettable, extended position to provide a visual indication that the predetermined temperature limit has been reached. The indicator is biased outwardly towards the activated position and a retainer in the form of a separate and discrete annulus formed of fusible material normally secures the indicator in the retracted position within the housing against the force of a biasing spring until the predetermined temperature has been reached causing the retainer to melt or fuse and thereby release the indicator to move outwardly to the extended position providing a visual indication signaling that an overtemperature condition has been reached in the fluid conduit.

Abstract: A thermal actuator utilizes a bimetallic snap action member such as a disc to actuate a member such as the armature of a switch to effect opening and closing of the switch. A resilient biasing member, such as an elongated curved spring member or a compressible member, engages the bimetallic member on a side opposite that of the actuated member to oppose the force exerted by the actuated member during the operation of the actuator.

Abstract: Warning systems that monitor the altitude above ground and descent rate of an aircraft and generate a warning if the descent rate of the aircraft is excessive for the altitude in which the aircraft is flying are well suited to aircraft whose flight and operational characteristics are readily predictable but not as suitable for aircraft, such as tactical aircraft whose operating conditions are not so predictable. To overcome this problem, the criteria for providing the warnings are altered (30, 32) as a function of flight configuration (16, 18) to optimize the warnings for different flight conditions.

Abstract: A fiber optic transducer utilizes a single optical fiber having one end surface, disposed adjacent a sensor element, cut at an angle to result in frustrated total internal reflection. The end surface of the optical fiber is spaced away from the sensor element. As the sensor element is displaced with respect to the end surface of the optical fiber, the amount of light reflected from the sensor element varies. Light injected into the optical fiber is reflected back toward the light source until the element comes into relatively close proximity with the angled end of the optical fiber. When this occurs, a portion of the light is transmitted across the gap and absorbed by the sensor element. The ratio of the light reflected from the reflective surface to the total light input into the optical fiber produces a signal representative of the displacement of the sensor element. This signal can then be converted to a corresponding temperature or pressure signal and displayed at a remote location.