Side slip angle command SCAS for aircraft

• US 4,094,479 A
• Filed: 03/25/1977
• Issued: 06/13/1978
• Est. Priority Date: 01/29/1976
• Status: Expired due to Term

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Sperry Rand Corporation (Unisys Corporation)
• Inventors: Kennedy, Thomas W. Jr.
• Primary Examiner(s): Kunin, Stephen G.
• Application Number:
  US05/781,226
• Time in Patent Office: 445 Days
• Field of Search: 235/150.2, 235/150.22, 244/17.13, 244/177, 244/178, 244/179, 244/184, 244/185, 244/189, 244/196, 244/197, 318/586
• US Class Current: 244/179
• CPC Class Codes: G05D 1/0816 to ensure stability

Abstract

A yaw axis stability and command augmentation system (SCAS) particularly applicable to STOL type aircraft includes three primary control terms proportional to side slip angle, side slip angle rate and rudder pedal force, wherein side slip angle rate is synthesized from measures of yaw rate, bank angle and lateral acceleration. These primary system feedback terms are supplied to the rudder electro-hydraulic secondary actuator which is positioned in accordance with their sum. The system serves to provide improved automatic damping of the Dutch roll modes, to suppress aircraft motion transients in yaw and roll under engine failure situations, to provide automatic turn-coordination in maneuvering flight, and to provide a side slip angle command capability to improve manual control precision in approach and landing under crosswind and lateral wind shear conditions.

Claims

1. In a yaw axis stability and command augmentation system for aircraft having a manually actuated rudder controller and a primary and secondary rudder actuator means for positioning the rudder to command a substantially steady state side-slip angle attitude of said aircraft proportional to a substantially steady state force on said manually actuated rudder controller, the combination comprising,

(a) means for supplying a first signal proportional to the side slip angle of the aircraft, including substantially steady state values thereof,

(b) means for supplying a second signal proportional to the force applied to said manually actuated controller including substantial steady state values thereof,

(c) summing means responsive to said first and second signals for supplying a control signal in accordance with the difference therebetween, and,

(d) means supplying said control signal to said secondary actuator for positioning said rudder in accordance therewith, thereby commanding said substantially steady state side-slip angle attitude of said aircraft proportional to said substantially steady state force on said manual controller.

2. A yaw axis SCAS as set forth in claim 1 further including

(a) means for supplying a third signal proportional to the rate of change the side slip angle of the aircraft, and

(b) means for supplying said third signal to said summing means for modifying said actuator control signal in accordance therewith to thereby further position said rudder to damp undesired yaw oscillations of said aircraft.

3. The yaw SCAS as set forth in claim 2 wherein the means for supplying said third signal includes

(a) means responsive to craft yaw rate for providing a signal in accordance therewith,

(b) means responsive to craft bank angle for providing a signal in accordance therewith, and

(c) means responsive to the algebraic sum of said yaw rate and bank angle signals for supplying said third signal.

4. The yaw SCAS as set forth in claim 3 further including,

(a) means responsive to craft airspeed for providing a signal in accordance therewith, and

(b) means responsive to said airspeed signal for varying the magnitude of said bank angle signal in accordance therewith.

5. The yaw SCAS as set forth in claim 1 further comprising,

(a) means responsive to craft airspeed for providing a signal in accordance therewith, and

(b) means responsive to said airspeed signal for varying the magnitude of said actuator control signal in accordance therewith.

6. The yaw SCAS as set forth in claim 1 wherein the means for supplying to said signal includes low pass filter means having a time constant such as to suppress spurious high frequency rudder controller force signals.

7. The yaw SCAS as set forth in claim 1 further including means responsive to craft airspeed for providing a signal in accordance therewith and wherein the means responsive to said second signal includes means responsive to said airspeed signal for varying the magnitude of said second signal in accordance therewith.

8. The yaw SCAS as set forth in claim 1 wherein the means for supplying said first signal includes low pass filter means having a time constant such as to suppress spurious high frequency sideslip angle signals.