Flight control system hardover monitor with provisions for preventing nuisance alarms

Claim 2

A monitor for an aircraft control system, comprising: first means for sensing the position of an aircraft attitude control surface and for providing a first signal corresponding to the sensed position; second means for sensing the force exerted by a pilot of the aircraft on a member which actuates the aircraft control surface and for providing a second signal corresponding to the sensed force; third means for sensing the force applied for automatically actuating the aircraft control surface and for providing a third signal corresponding to the sensed force; monitoring means; and actuating means connected to the first, second and third means and to the monitoring means, said actuating means responsive to the first signal when said signal corresponds to a control surface hard-over position for activating the monitoring means, responsive to the second signal when said signal corresponds to a predetermined force for inhibiting activation of the monitoring means, and responsive to the third signal when said signal corresponds to a predetermined force for inhibiting activation of the monitoring means.

Claim 3

A monitor for an aircraft control system as described by claim 1, including: fourth means for providing a fourth signal corresponding to the pitch rate of the aircraft, and the activating means connected to the pitch rate signal means for activating the monitoring means when the pitch rate signal is other than zero.

Claim 4

A monitor for an aircraft control system as described by claim 2, wherein the first, second, third and fourth signals have a.c. components and d.c. components, and the activating means includes: means for providing a d.c. bias signal; means for combining the d.c. bias signal and the second signal to provide a fifth signal having a.c. and d.c. components; detector means connected to the fifth signal means for providing a d.c. signal if the a.c. component of the fifth signal predominates and for providing an a.c. signal if the d.c. component predominates; means for combining the first and fourth signals and the signal from the detector to provIde a combined signal having a.c. and d.c. components. detector means connected to the combining means for providing an a.c. signal if the a.c. component of the combined signal predominates and for providing a d.c. signal if the d.c. component predominates, indicating a hardover control surface failure mode; and means connected to the last mentioned detector means and responsive to the d.c. signal therefrom for activating the monitor and responsive to the a.c. signal therefrom for inactivating the monitoring means.

Claim 5

A monitor for an aircraft control system as described by claim 2, wherein the fourth means includes: a vertical gyro for providing an a.c. signal corresponding to the pitch attitude of the aircraft; means for demodulating the a.c. signal and for providing a d.c. signal; means for providing an a.c. reference signal; filter means connected to the demodulator and to the a.c. reference signal means and responsive to the signals therefrom for providing a signal having a.c. and d.c. components; and means for partially differentiating the d.c. component of the signal to provide the fourth signal.

Claim 6

A monitor for an aircraft control system as described by claim 1, wherein the first means includes: means for providing an a.c. signal corresponding to the control surface position relative to a predetermined position; means for demodulating the a.c. signal and for providing a d.c. signal corresponding to control surface position; means for providing an a.c. reference signal; means connected to the demodulator and to the reference signal means and responsive to the signals therefrom for providing a signal having a.c. and d.c. components; and means for partially differentiating the d.c. component of the signal to provide the first signal.

Claim 7

A monitor for an aircraft control system as described by claim 1, wherein the second means includes: means for providing an a.c. signal corresponding to the force exerted by the pilot of the aircraft; means for providing an a.c. signal corresponding to the force exerted by the co-pilot of the aircraft; means for combining the force signals to provide a combined a.c. signal; means for demodulating the combined a.c. signal to provide a d.c. signal independent of the sense of the force exerted; means for providing an a.c. reference signal; means for combining the a.c. reference signal and the d.c. force signal to provide a signal having a.c. and d.c. components; and means for partially differentiating the d.c. component of the signal to provide the second signal.

Claim 8

A monitor for an aircraft control system as described by claim 1, wherein the third means includes: means for providing an a.c. signal corresponding to the force applied for automatically actuating the aircraft control surface; means for demodulating the a.c. signal for providing a d.c. signal independent of the sense of the force; means for providing an a.c. reference signal; and filter means connected to the demodulator and to the a.c. reference signal means and responsive to the signals therefrom for providing the third signal having a.c. and d.c. components.