FULL AUTHORITY FLY-BY-WIRE PEDAL
This application is a divisional application of U.S. patent application Ser. No. 11/354,687, filed on Feb. 15, 2006 now U.S. Pat. No. 7,644,893.
BACKGROUND OF THE INVENTION 10
The present invention relates to an anti-torque tail rotor system, and more particularly to a small displacement pedal system for a full authority Fly-By-Wire (FBW) flight control system. 15
The majority of helicopters utilize a single main rotor assembly and an anti-torque tail rotor assembly. The tail rotor assembly has proven to be efficient and reliable for providing lateral thrust to counteract induced torque generated by the main rotor assembly and to provide yaw directional control of 20 the helicopter in hover, transitional, low, and high speed flight regimes.
Control of the anti-torque tail rotor assembly is conventionally achieved through a relatively large displacement pedal system which provides control proportional to pedal 25 displacement. The pilot must typically constantly manipulate the pedals to coordinate changes in power, bank angle or speed. This may significantly increase pilot workload.
When an autopilot is incorporated, the pedal position is synchronized to the autopilot which results in frequent move- 30 ment of the pedals. As the pedals are often utilized as footrests to stabilize the pilot, autopilot movement of the pedals may be uncomfortable or otherwise distracting.
Fly By Wire (FBW) flight control systems are emerging as state of the art in control of rotary-wing aircraft. FBW permits 35 a wide range of improvements that contribute to pilot workload reductions. FBW pedal systems have heretofore only translated the relatively large displacement of the pedals into digital commands which provide yaw directional control. Although significant benefits are realized with FBW flight 40 control systems, conventional relatively large displacement FBW pedal systems have not utilized FBW flight control systems to full advantage as the pedal system remains essentially conventional.
Accordingly, it is desirable to provide a Fly-By-Wire 45 (FBW) pedal system for an anti-torque tail rotor system which is integrated with a full authority FBW flight control system to reduce pilot workload and thereby lead to a more capable aircraft.
SUMMARY OF THE INVENTION
A pedal system particularly tailored for a Fly-By-Wire (FBW) flight control system according to the present invention includes a double gradient linkage assembly. The double 55 gradient linkage assembly includes a spring system and a damper system to provide a double gradient force feeling to the pedal dynamics of the pedals.
The double gradient force feeling improves yaw axis (azimuth) control of the aircraft by significantly reducing the 60 workload for the pilot because control is only required when a change in the yaw axis state is demanded. At all other times the pilot relaxes input on the pedals and the FBW flight control system provides the required stability and coordination. 65
Since only minimal displacement inputs are required for such a pedal system, the travel of the pedals may be exceeding
compact, preferably on the order of +/-1.25 inches of travel. Pilot workload is thereby significantly reduced through reduction in both the frequency and magnitude of aircraft control inputs. Applicant has determined that to take full advantage of such minimal travel requires the pedal system to have a double gradient force feeling which provides a centering force to facilitate aircraft/pilot integration. More specifically, the double gradient force feeling provides approximately 40 lbs/in for the first 0.2 inches of the 1.25 inches of pedal travel then reduces to approximately 20 lbs/in.
The pedal system is of reduced system weight as the mechanisms between the pilot and control servos are eliminated as well as the mechanical interconnections between the pilot's stations. The pedal system also simplifies the mechanical design which reduces parts count and increases reliability. Furthermore, the flight control system is reduced in complexity as the need for trim modules which would normally position the pedals according to a proportional flight control feedback system may be eliminated.
The present invention therefore provides a Fly-By-Wire (FBW) pedal system for an anti-torque tail rotor system which is integrated with a full authority FBW flight control system to reduce pilot workload and thereby lead to a more capable aircraft.
BRIEF DESCRIPTION OF THE DRAWINGS
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:
FIG. 1 is a general perspective view an exemplary rotary wing aircraft embodiment for use with the present invention;
FIG. 2 is a block diagram of the anti-torque tail rotor system;
FIG. 3 is a perspective view of a pedal system according to the present invention;
FIG. 4 is a schematic representation of a double gradient force feeling to the pedal dynamics provided by the pedals according to the present invention;
FIG. 5A is a perspective view of a pedal system in a first position; and
FIG. 5B is a perspective view of a pedal system in a second position.
DETAILED DESCRIPTION OF THE PREFERRED
FIG. 1 schematically illustrates a rotary-wing aircraft 10 having a main rotor assembly 12. The aircraft 10 includes an airframe 14 having an extending tail 16 which mounts an anti-torque tail rotor system 18. The main rotor assembly 12 and the anti-torque tail rotor system 18 are driven through a transmission (illustrated schematically at 20) by one or more engines (illustrated schematically at 22). Although a particular helicopter configuration is illustrated in the disclosed embodiment, other anti-torque systems such as ducted fans and propulsors will also benefit from the present invention.
Referring to FIG. 2, the anti-torque tail rotor system 18 is driven through an aircraft flight control system 24. The aircraft flight control system 24 is preferably a full authority Fly-By-Wire (FBW) flight control system 24 that utilizes signals to convey pilot intentions to the flight control servos. In the FBW flight control system 24, a pilot provides input through FBW yaw flight control logic 28 and thence the anti-torque tail rotor system 18. Preferably, the FBW control