Mcdonnell Douglas Helicopter Company

Sperry Rand Corporation

Mcdonnell Douglas Corporation

The Boeing Company

Sperry Corporation

Stephen S Osder

Daniel A Nyhus

Donald G Caldwell

Thomas L Thompson

David C Mossman

A method of stabilizing a jet-powered tri-mode aircraft as the aircraft travels in a helicopter mode, a compound mode, and a fixed-wing mode is disclosed. The method includes receiving a plurality of velocity vector component values and velocity vector commands derived from either (1) a number of pilot operated controllers or (2) a commanded array of waypoints, which are used for fully automated flights, and a rotor speed reference value, which is decreased with increasing forward speed to unload the rotor, thereby permitting conditions for stopping the rotor in flight. Stabilization of the commanded velocity vector is achieved in all modes of flight using blended combinations of rotor swashplate controls and aerodynamic controls such as elevons, canards, rudders, and a horizontal tail. Stabilization to the commanded velocity vector includes a plurality of control constraints applied to the pilot stick controllers that prevent penetration of envelope limits.

Enhanced flight control systems and methods for a jet powered tri-mode aircraft

The present invention comprises a feedback-controlled braking apparatus that applies a modulated braking force that smoothly decelerates a rotating shaft such that it comes to rest at a precise location. According to a preferred embodiment of the present invention the rotor hub of a rotor/wing aircraft is coupled to a hydraulically actuated friction brake, such as a conventional disk brake. The disk brake caliper is supplied with fluid pressure from an electrically actuated servo valve which, in turn, is controlled by an electronic controller. A sensor monitors the angular position and velocity of the rotor main shaft. The velocity and position information is provided to the controller, which modulates the brake pressure as required to bring the rotor to a stop at exactly the right orientation relative to the aircraft. By providing active brake control, the present invention enables the rotor of a rotor/wing aircraft to be decelerated and stopped smoothly and precisely in the desired position in the minimum time possible.

Active brake control for rotor/wing aircraft

The disclosed flight control system includes a rotor blade speed monitor for monitoring the rotor blade speed of the jet powered tri-mode aircraft and for outputting a rotor blade speed command. The flight control system also includes an aircraft attitude controller for controlling the aircraft attitude of the jet powered tri-mode aircraft. Weighted rotor blade attitude stabilization commands and weighted aero surface attitude stabilization commands are output from the aircraft attitude controller to distribute power, control, and lift between the rotor blade and the aero surfaces. Relative weights of the weighted rotor blade attitude stabilization commands decrease with increasing aircraft travelling velocities, and relative weights of the weighted aero surface attitude stabilization commands increase with increasing velocities. A rotor blade lift controller receives the weighted rotor blade attitude stabilization commands and the rotor blade speed commands, and positions the rotor blade swashplate to adjust lift and control according to these commands. An aero lift controller receives the weighted aero surface attitude stabilization commands and deploys the aero surfaces to generate lift and control according to the received weighted aero surface attitude stabilization commands.

Flight control system for jet powered tri-mode aircraft

An apparatus for compensating for spatial phase angle phase errors in the flapping angle oscillations of a rotor blade is disclosed. The apparatus receives a measured aircraft roll and a measured aircraft pitch. Gyroscopic moments resulting from these measured rolls and pitches are determined, and compensating gyroscopic moments are then generated and summed with commanded pitch and roll accelerations. Flapping angle phase lags of the rotor blade swashplate are added to the summed signals to cancel any flapping angle phase leads, caused by changes in aircraft or rotor blade speed caused by installation configurations of the rotor blade swashplate.

Rotor blade swashplate-axis rotation and gyroscopic moments componsator

Rotor blade swashplate-axis rotation and gyroscopic moments compensator

A failure of any one of three swashplate actuators of a helicopter rotor blade is detected. Once such a detection is made, the position of this nonfunctional swashplate is locked and measured. The inputted commanded swashplate collective position, commanded swashplate x-axis rotational position, and commanded swashplate y-axis rotational position are then passed to a failure-mode control matrix. The failure-mode control matrix computes swashplate actuator commanded positions for the two operable swashplate actuators so that aircraft attitude control is maintained. These two swashplate actuator commanded positions instruct positional movement of the rotor blade swashplate to thereby meet the commanded swashplate x-axis rotational position and the commanded swashplate y-axis rotational position which will control attitude. A quasi-swashplate-collective-position corrector computes the quasi-swashplate collective position that will occur because of the successful control of the aircraft's attitude. The swashplate-collective-position corrector then generates an amount of rotor blade lift attainable with a computed rotor blade speed change to compensate for any difference between the commanded swashplate collective position and the quasi-swashplate collective position. A closed loop vertical velocity controller refines the predicted rotor speed change that is commanded to correct for the loss of collective control.

Reconfigurable helicopter flight control system

A device and method of back-up fly by wire control, especially useful in fly by wire systems when a failure mode is encountered. The problem of back-up system controllability with the type of compliant sidestick which has minimal displacement and returns to zero upon release of the control force is solved by reducing the authority of the sidestick to a fraction of full authority actuator position capability, to provide good control sensitivity. Full authority actuator position control is provided by automatically activating a trim integrator when the sidestick reaches its displacement stops.

Back-up fly by wire control system

An apparatus and method for controlling the flight of a helicopter, in which the pilot commands vehicle state changes, embodies several significant advances to the helicopter control art. Among these are control decoupling to reduce undesired helicopter responses in other axes to pilot inputs in one axis, task oriented control modes which are selected automatically, and automatic control of engine torque and rotor speed constraints. Novel task oriented control modes include independent control of heading and ground track at low speed and turn rate and flight path angle control at higher speeds. Control decoupling is achieved through a combination of force/moment decoupling and open loop prediction methods. Vertical control, traditionally accomplished with collective only, is accomplished in this system with a combination of longitudinal cyclic and collective control, increasing vertical response performance and minimizing engine power change demands. These flight control automation methods were designed to enable the use of small displacement, multi-axis controllers for full envelope helicopter control; the system provides dramatic pilot work load reduction for any of wide range of pilot manipulator configurations.

Automated helicopter flight control system

Apparatus for controlling channel equalization in a monitored dual servo channel aircraft automatic flight control system, in which the limits of the equalization control are responsive to the commanded input signal to the control surface. Rate feedback means responsive to the output velocity of each channel are differentially summed and integrated to provide the signals for equalizing the dual servo channels. Limiter means responsive to the commanded input signal varies the limits of the equalization signals to allow very tight error detection thresholds of the system monitor without causing nuisance trips in situations where the system's normal tolerances are large.

Dynamic equalization system for dual channel automatic pilot

The outputs of a pair of linear accelerometers are utilized to provide measures of craft vertical acceleration and body axis pitch angular acceleration. The pitch angular acceleration signal is integrated to provide a measure of body axis pitch rate. The pitch rate signal is in turn integrated to provide a measure of body axis pitch attitude. An earth referenced pitch attitude sensor provides a measure of earth referenced pitch attitude and through a rate taker a measure of earth referenced pitch rate. The earth referenced sensor is utilized to calibrate out errors and effectively align the linear accelerometers so that in the event of a loss of the earth referenced sensor, the calibrated accelerometers have adequate accuracy to compute pitch rate and pitch attitude within the long period bandwidth needed to provide the stability augmentation function for a relaxed static stability aircraft. The earth referenced and body axis pitch rate signals are blended and the earth referenced and body axis pitch attitude signals are blended whereby steady state differences therebetween are washed out through a long time constant washout, the earth referenced signals dominating in the steady state. The linear vertical acceleration and angular acceleration signals and the blended pitch rate and pitch attitude signals are combined in a control law to drive the craft elevator servo. Failure of the earth referenced attitude sensor results in a graceful degradation of the control law to washed out body axis attitude and attitude rate control.

Stability augmentation system for relaxed static stability aircraft

The servomotor outputs of two substantially identical servo channels, are connected through a differential mechanism to position an attitude control surface of an aircraft in response to common or separate, normally identical, command signals applied to the respective channels. Position and rate feedback means responsive to the movement of the control surface and each servomotor provides position and rate feedback signals to their respective channels. The primary position rate feedback term for each servomotor channel is derived from the position feedback means rather than from a servo tachometer to increase the stiffness of the output in resisting the motions commanded by a failed servo channel and to improve fault detection capability by increasing the difference velocity between a good and a failed channel. Improved electrical equalization means, to allow more effective or lower velocity mismatch between the two servo channel motors, is provided wherein the equalization includes limits, which are varied in response to the input command. Also, monitoring with fault isolation is provided employing an estimate of surface position whereby the system is provided with fail operational characteristics.

Dual servo automatic pilot with improved failure monitoring

A dual channel, fail-operative automatic flight control system is disclosed in which each channel includes a totally monitored digital computer for operating upon sensor input data to provide command signals to the aircraft surface control actuators. The operative program for each computer is repetitively executed to effectively provide continuous control. The program is organized into a plurality of tasks to be performed by the computer with program segments associated with the respective tasks and a program routine for determining that all of the tasks have been completed for each program iteration. If non-completion of a task is detected, the program enters a failure routine which stops execution of the program. The program also includes a routine for generating a dynamically varying pattern in accordance with the continuously reiterated execution of the program. The system includes a detector for determining that the correct pattern is being generated and shuts down the system upon detecting a failure of the computer to generate the correct pattern. All of the instructions of the computer instruction repertoire operatively utilized in the system are employed to control the program flow whereby failure of an instruction to operate properly will cause the program to flow into an abnormal path thus causing the task completion program routine to indicate failure and stop the computer. Additionally, the system utilizes further techniques such as dual data and program memory banks to perform redundant computations, all of the techniques in combination providing an automatic flight control system with two autonomous fail-passive channels, the two channels providing a fail-operative system.

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Scottsdale, AZ, United States of America

Stephen S Osder