Abstract: A system for providing a voice warning to the pilot of a fighter/attack aircraft when the aircraft is landing with the landing gear up monitors the radio altitude, airspeed and engine power of the aircraft and provides a predetermined voice warning if the landing gear is not down when the airspeed is less than a predetermined speed, for example, approximately 200 knots, the radio altitude is less than a predetermined altitude, for example, approximately 100 feet, and the engine is not developing take-off power.

Abstract: A ground proximity warning system is disclosed which can recognize when an aircraft is on a final approach to an airport without utilizing a landing flap signal input. Airports together with the surrounding terrain topography are modeled by a simple geometric shape, such as, an inverted truncated cone, and stored on-board the aircraft. The system uses navigational data to determine the distance of the aircraft from the geometric model. Once the aircraft is determined to be within the area defined by the geometric model, the system provides an enabling envelope indicative that the aircraft is on a final approach for enabling various ground proximity warning systems. Also disclosed is a system for altering the enabling envelope as a function of the aircraft's alignment with a particular runway.

Abstract: A vibrating beam force transducer that can be realized in a silicon micromachined device such as a micromachined accelerometer. The transducer includes a beam having a longitudinal axis, and a drive circuit electrically coupled to the beam for causing the beam to oscillate at a resonant frequency that is a function of a force applied along the longitudinal beam axis. The drive circuit provides an electrical current to the beam, and the beam, or a conductive portion thereof, conducts the current along a path that includes an axial component parallel to the longitudinal axis. A magnetic field is created intersecting the axial component, such that the electric current interacts with the magnetic field to produce a force that causes the beam to oscillate at the resonant frequency. In a preferred embodiment, the transducer has a double ended tuning fork configuration, and the current path extends along one beam and back along the other beam.

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 acceleration 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 dual vibrating beam force transducer having an electrostatic drive system. The transducer comprises a body having first and second generally parallel beams, coupled together at their ends. First and second electrodes are positioned adjacent to but not in contact with the respective beams. A drive circuit causes an oscillating voltage to be applied to the electrodes. The beams are thus subjected to electrostatic forces that cause the beams to oscillate in a vibration plane containing both beams. The mechanical resonance of the beams controls the oscillation frequency, such that the frequency is a function of a force exerted along the beams. An embodiment is also described in which the drive means is coupled directly to one of the beams.

Abstract: Apparatus and method for increasing the resolution of angular rate of rotation and linear acceleration of a body with respect to three orthogonal axes. Three pairs of accelerometers (10, 12; 14, 16; and 18, 20) are arranged with their sensitive axes antiparallel to each other, and each pair is vibrated back and forth along one of the orthogonal axes. The signals output from the accelerometers are processed to determine S.sub.rate and S.sub.vel for each of the rate axes as a function of the sum and differences of the signals produced by each of the accelerometers. The value of S.sub.vel for each axis is used by a microprocessor (82) to produce a signal equal to an incremental change in velocity for each axis. The incremental change in velocity is then used in conjunction with errors estimated from previous fractional portions of the dither period for each pair of accelerometers to calculate the rate of rotation of the body about each of the axes as a function fo the values for S.sub.rate.

Abstract: Prior steady-state accelerometers are subject to errors caused by differential thermal expansion between the force transducers and other accelerometer components. This problem is overcome by the present accelerometer that comprises a housing (32), a proof mass (30), a support (34,36) for mounting the proof mass with respect to the housing, and first and second force sensing elements (38,40). The force sensing elements have DC frequency responses, and are connected between the proof mass and the housing such that differential thermal expansion or contraction between the force sensing elements and the proof mass, support and housing results in rotation of the proof mass about a compensation axis (CA) normal to the sensitive axis (SA).

Abstract: A wind shear detection system compares air-speed with a composite signal derived from signals representative of longitudinal acceleration, normal acceleration, angle of attack and flight path angle to generate a shear signal. An enhanced version of the system is also compensated for roll angle, radio altitude and flap position. In a modified system, the accelerations are calculated along the velocity vector of the aircraft rather than along the horizontal axis to compensate for inaccuracies that could occur under extreme flight conditions such as high bank angle turns and dynamic maneuvers.

Abstract: A compact, low g range accelerometer comprising a support (22), a proof mass (20), flexures (24, 26) for mounting the proof mass to the support, and a force sensing element (40). The proof mass has a single rotational degree of freedom about a hinge axis (H) perpendicular to the accelerometer's sensitive axis (S). The force sensing element is positioned along a line that is normal to the hinge axis and that lies in a plane that is normal to the hinge axis and that passes through the center of gravity (46) of the proof mass. The perpendicular distance between the hinge axis and the force sensing element is less than the distance between the hinge axis and the center of the proof mass. The force sensing element may be parallel to the pendulous axis, to produce an extremely compact accelerometer, or may be oriented at an acute angle with respect to the pendulous axis, such that the line along which the force sensing element is positioned passes through the center of percussion of the proof mass.

Abstract: A push-pull force transducer comprising a unitary body formed from a crystalline substrate. The body comprises first and second mounting elements for mounting the force transducer to first and second structures, and first and second force sensing elements connected to the mounting elements. Each force sensing element has first and second ends, a line extending from the second to the first end defining a force sensing axis for the force sensing elements. The force sensing elements are oriented with their force sensing axes parallel to and aligned with one another. The first force sensing element has its first end connected to the second mounting element and its second end connected to the first mounting element. The second force sensing element has its first end connected to the first mounting element and its second end connected to the second mounting element. Also described are embodiments utilizing strain relief flexures and an embodiment featuring a leveraged design.

Abstract: An accelerometer comprising a body (10, 16, 12), a proof mass (18, 30, 32), a mounting strucutre comprising flexures (20, 22) for mounting the proof mass to the body, and force sensing elements (34, 38). The flexures permit translational motion of the proof mass with respect to the body along a sensitive axis SA and rotation of the proof mass with respect to the body about a hinge axis HA that is perpendicular to the sensitive axis. Acceleration of the accelerometer along the sensitive axis results in translational motion of the proof mass along the sensitive axis. The force sensing elements reacts to such translational motion by producing a signal indicative of acceleration along the sensitive axis.

Abstract: A matched pair of vibrating beam force transducers for use in an instrument such as an accelerometer, to provide enhanced linearity and common mode tracking, while decreasing the possibility of lock in or cross-talk between the transducers. In a preferred embodiment, first and second transducers are provided, the transducers producing respective first and second output signals having respective first and second frequencies. The transducers are connected in an arrangement in which for a given acceleration, one frequency increases and the other frequency decreases. The first transducer comprises a pair of first beams, and the second transducer comprises a pair of second beams.

Abstract: Disclosed is a method and apparatus for processing signals supplied by accelerometer assemblies in which one or more accelerometers are cyclically displaced in a predetermined manner so that signals representing the specific force experienced by the accelerometers and the angular rate experienced by the accelerometers are produced. The signal processor separately estimates the signal components of the signal being processed and provides an error signal by subtracting the estimated signal components from the signal being processed. The error signal is fed back through circuitry that controls the magnitude of the estimated signal components so that the value of each estimated signal component rapidly converges to the value of the signal components of the signal being processed.

Abstract: A system for landing an aircraft is described, using a ground installation and an airborne installation which are synchronized together using GPS system time. Specifically, the ground installation includes a ground transmitter which radiates the sequence of signals which provide precision guidance information to the aircraft, an aircraft installation which includes a radio receiver and a processor to receive and process the transmitted guidance signals and to provide indications to aid the pilot in landing the aircraft, a GPS receiver in the air and on the ground for producing signals representative of GPS system time, and a channel selector in the aircraft for actuating the processor to synchronize its operation with the ground installation transmitter. Range information is provided by measuring the time interval between the transmission of a reference at the ground and its receipt in the air.

Abstract: An apparatus for producing signals indicative of both a Coriolis rate and an acceleration along a preferred axis while decoupling extraneous vibration and motion that would introduce errors into the signals, and a driving mechanism for vibrating the apparatus at a dither frequency. The apparatus includes a parallelogram frame (50) including two accelerometer support surfaces (24, 26) on which are mounted two accelerometers (20 and 22) having their sensitive axes in parallel alignment. A driving mechanism (64) is connected to the parallelogram frame and is operative to drive the accelerometers at a desired frequency, causing them to vibrate back and forth in a direction substantially transverse to their sensitive axes. The driving mechanism includes a mounting plate (72) and a coil frame (66) on which are mounted two electromagnetic coils (70) having a "C" shaped core (80).

Abstract: An aircraft ground proximity warning system having an excessive descent rate warning mode which generates a warning signal when the descent rate of the aircraft exceeds a predetermined limit for the particular altitude of the aircraft above ground. The warning system provides for three separate warnings. A SINK RATE advisory warning is generated for combinations of lesser descent rates and greater altitudes. A PULL UP warning is generated for higher descent rates at lower radio altitudes. After a predetermined time after the SINK RATE warning is generated a TERRAIN warning is provided to indicate to the pilot of the aircraft that an excessive sink rate condition exists and the aircraft is flying over undulating or mountainous terrain. Also disclosed is logic circuitry for detecting that the aircraft is flying over undulating terrain.

Abstract: An apparatus for producing signals indicative of both a Coriolis rate and an acceleration along a preferred axis while decoupling extraneous vibration and motion that would introduce errors into the signals, and a driving mechanism for vibrating the apparatus at a dither frequency. The apparatus includes a parallelogram frame (50) including two accelerometer support surfaces (24, 26) on which are mounted two accelerometers (20 and 22) having their sensitive axes in parallel alignment. The accelerometer support surfaces are connected to opposite ends of a flex member (52), which includes six flexures (32, 34, 36, 38, 40, 42) having parallel bending axes. Two of the flexures (34, 38) are disposed at opposite ends of one side of each flexure member, and have a "long" axis that is substantially parallel to the sensitive axes of the accelerometers and aligned with a line connecting their centers of percussion.

Abstract: An aircraft ground proximity warning system is disclosed having an inadequate terrain clearance warning mode, wherein the criteria required to generate the warning is modified when the aircraft is flying over undulating or mountainous terrain. The system is responsive to signals representative of the radio altitude, the barometric altitude, the speed of the aircraft, the flap position and the landing gear position to provide warnings when the aircraft is operating below a predetermined altitude with either or both of the landing gear of the flaps not in a landing configuration. The warning system also provides a warning when the aircraft is traveling above a predetermined speed and below a predetermined altitude irrespective of the configuration of the landing gear or the flaps. Also disclosed is logic circuitry for detecting that the aircraft is flying over undulating or mountainous terrain and modifying the warning envelope during such condition to provide longer warning times.

Abstract: A method and apparatus is disclosed for passively determining altitude above the ground of an aircraft by use of an active emitter carried on a second higher altitude aircraft. Specifically, the altitude of the aircraft is determined by measuring the time difference between direct path radiation and reflected path radiation, taking into account the distance between an upper antenna which receives the direct path radiation and a lower antenna which receives the reflected path radiation and the angles of travel relative to the vertical between the direct path radiation and the reflected path radiation.

Abstract: A magnetometer sensor is described for a borehole survey. The magnetometer features a bobbin made from a metal alloy such as copper-nickel, which has a very low magnetic permeability, on the order of 1.0001, which can be joined to a magnetic metal alloy, such as Permalloy, by welding, which can be treated by annealing at a temperature of 1500 degrees Fahrenheit and which has a thermal coefficient of expansion generally on the order of the magnetic alloy. In one particular embodiment, the magnetometer sensor comprises a strip of magnetic metal alloy wrapped around the aforesaid bobbin to define a magnetic core, one excitation winding wrapped around the core, a plastic frame for carrying the magnetic core and excitation winding and at least one sense winding wrapped around the frame, the core and the excitation winding.