Abstract: The present method and apparatus consists of storing past values of estimated IRU error and using these past values to update the coasting filter when switching from GPS to inertial mode. Through the storage of past IRU error estimates, it is possible to avoid misdirected guidance from an erroneous GPS signal. The MMR and ground station can require up to 6 seconds to identify a failed GLS signal.

Abstract: The present method and apparatus consists of storing past values of estimated IRU error and using these past values to update the coasting filter when switching from GPS to inertial mode. Through the storage of past IRU error estimates, it is possible to avoid misdirected guidance from an erroneous GPS signal. The MMR and ground station can require up to 6 seconds to identify a failed GLS signal.

Abstract: An airplane precision approach guidance system and method. The airplane precision approach guidance system includes: (i) GPS landing system (GLS) components (12) for receiving and processing signals from GPS satellites (30) and a GPS ground station (32) and generating a first set of velocities; (ii) an inertial reference system (IRS)(20) for generating a second set of velocities; and (iii) guidance software (24) for generating a cross-runway velocity and a lateral distance from runway centerline based on received runway centerline information and the generated first and second set of velocities. The airplane precision approach guidance system also includes flight instruments (26) and an autopilot system (28) for receiving and processing the information produced by the guidance software. The guidance software may be executed by a conventional airplane processor, such as the GLS processor, the IRS processor or the airplane's autopilot processor, or by a separate stand-alone processor.

Abstract: A plurality of inertial measuring unit (IMU) modules (41A, B, C and D) each comprising gyros and accelerometers (61, 65 and 67) for sensing inertial information along two orthogonal axes, are strapdown mounted in an aircraft, preferably such that the sense axes of the IMUs are skewed with respect to one another. Inertial and temperature signals produced by the IMU modules, plus pressure signals produced by a plurality of pressure transducer modules (43A, B and C) and air temperature signals produced by total air temperature sensors (45A and B) are applied to redundant signal processors (47A, B and C). The signal processors convert the raw analog information signals into digital form, error compensate the incoming raw digital data and, then, manipulate the compensated digital data to produce signals suitable for use by the automatic flight control, pilot display and navigation systems of the aircraft.

Abstract: A closed-loop controller for controlling the frequency of the power applied to a gyroscope synchronous motor to rotate the seismic mass (wheel) of the gyro so as to compensate for movement of the gyro case about the spin axis of the gyro is disclosed. The controller includes a sensor for sensing fluctuations in the current drawn by the gyro, said fluctuations being directly related to the fluctuations in the load angle of the gyro caused by movement of the gyro case about the spin axis. The current fluctuations create an analog voltage, which is amplified by several orders of magnitude. The result is used to modulate the frequency of the applied power so as to compensate for the load angle fluctuations caused by case movement about the spin axis. In essence, the controller reduces the frequency of the hunting mode of the gyro to a level below which movement of the gyro case about its spin axis has substantially no undesirable effect.