Aeronautics and astronautics – Aircraft – heavier-than-air – Helicopter or auto-rotating wing sustained – i.e. – gyroplanes
Reexamination Certificate
1998-10-06
2001-09-18
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Helicopter or auto-rotating wing sustained, i.e., gyroplanes
C244S00700B
Reexamination Certificate
active
06290171
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for controlling a helicopter hybrid countertorque system, said hybrid countertorque system comprising a countertorque rotor associated with at least one turnable aerodynamic steering surface, such as a fin flap or a fin which is fully turnable. It also relates to a helicopter equipped with such a control device.
It is known that in a helicopter equipped with a single main rotor providing lift and propulsion, the fuselage tends, as a reaction to the torque exerted by said main rotor, to turn in the opposite direction to the direction of rotation of the latter. It is also known that in order to combat the reaction torque to which the fuselage is subjected, it is conventional to provide an auxiliary countertorque rotor capable of generating a transverse thrust and the rotation of which is driven off the source of motive power of the main rotor. Thus, the auxiliary countertorque rotor taps off some of the power from this power source.
This therefore means that, as far as helicopter performance is concerned, it is advantageous for the auxiliary countertorque rotor to be assisted in its function of providing the fuselage with countertorque lateral stabilization.
DESCRIPTION OF THE PRIOR ART
As is mentioned, for example, in patent U.S. Pat. No. 2,818,224, it is possible, to these ends, to unload said countertorque rotor in translational flight, using an aerodynamic thrust exerted on a fin provided toward the tail of said helicopter. Such thrust is usually obtained by choosing a cambered profile for the fin and by setting this fin at a certain angle with respect to the plane of symmetry of the fuselage. However, for a fixed design of fin, the thrust thus obtained when the helicopter is flying with zero yaw depends only on the dynamic pressure of the air on the fin and can therefore not be altered. As the countertorque force to be exerted varies differently as a function of the speed, and as a function of other flight parameters, this means that optimum unloading of the countertorque rotor is, in practice, possible only in one single flight scenario.
To avoid the drawbacks and limitations that arise in using such a fixed unloading fin, it is possible to employ a fin flap, the orientation of which is adjustable.
As regards the way in which such a fin flap is controlled, there are various so-called deterministic concepts of control law, that is to say ones which cause a turning of the fin flap as a function of known flight-scenario parameters and which is adapted to the desired objective (according to an awareness model) This type of control, although attractive in principle, is, by nature, not well able to withstand changes to the external aerodynamics (carriage of external stores for example) and requires in-flight optimization if the awareness model proves imprecise.
It will also be noted that another drawback of a countertorque rotor lies in its induced drag, which may reach as much as half of the thrust at high speeds, and in the induced noise which is liable to be very troublesome.
SUMMARY OF THE INVENTION
The object of the present invention is to overcome these drawbacks. The invention relates to a device for controlling a helicopter hybrid countertorque system which makes it possible to reduce the thrust of the countertorque rotor (and therefore improve the helicopter performance and/or reduce the cost of the flight), and the induced noise and drag, and which in addition makes it possible to keep authority for controlling the helicopter in terms of yaw at all points in the flight envelope.
To this end, according to the invention, said device for controlling a hybrid countertorque system is intended to counteract the torque induced by a main rotor providing a helicopter with forward propulsion and with lift, and which comprises:
an auxiliary countertorque rotor which is controllable and exerts a lateral countertorque thrust; and
at least one aerodynamic steering surface which is controllable and generates transverse countertorque lift, is noteworthy in that it comprises control means:
for controlling, as a matter of priority, said aerodynamic surface so that it generates lift which represents at least part of a first control command, which part can be executed by said aerodynamic surface; and
for controlling said auxiliary rotor in such a way that the combined action of said aerodynamic surface and said auxiliary rotor represents a command for controlling the helicopter in terms of yaw.
Thus, by virtue of the priority control over said aerodynamic surface, preferably a fin flap or an entirely turnable fin, the device in accordance with the invention makes it possible to cancel or at the very least minimize the thrust of the auxiliary rotor, while at the same time exerting the required control in terms of yaw, this making it possible to reduce the induced noise and drag and to improve the helicopter performance.
In addition, the invention makes it possible to keep, or even to improve, the authority of the control of the helicopter in terms of yaw, at all points in the flight envelope.
Incidentally, said first control command corresponds, according to the invention:
either also to said helicopter yaw control command, which means as a consequence, when said aerodynamic surface is capable of executing said first control command in full, that in equilibrium, all of the countertorque action is provided by said aerodynamic surface and that said auxiliary rotor then exerts zero thrust;
or to an order which is determined on the basis of the difference between said yaw control command and a reference command that represents reference control of said auxiliary rotor, so that in equilibrium, said auxiliary rotor exerts a thrust that represents said reference control. Of course, if said reference control corresponds to the control that generates zero thrust, this again amounts to the previous scenario (the auxiliary rotor exerts no thrust and all of the countertorque action is exerted by the aerodynamic surface).
Furthermore, according to the invention, said yaw control command may:
either represent the action exerted by a pilot of the helicopter on a rudder bar, which allows the device in accordance with the invention to be fitted to a conventional helicopter with a mechanical flight-control system;
or be determined by a calculation unit, on the basis of the actions exerted respectively on a collective stick and on a rudder bar by at least one pilot of the helicopter. Said calculation unit may, in particular, correspond to a fly-by-wire control system.
In a first advantageous embodiment of the invention, which is an essentially mechanical embodiment, applied to a helicopter comprising at least one rudder bar for controlling the helicopter in terms of yaw and a linkage connected to said rudder bar and to a member for operating the auxiliary rotor, said control means advantageously comprise a bellcrank with two branches, incorporated into said linkage and intended to split the movement of the linkage between said branches so that it can be transmitted, a first of which branches is connected mechanically to a member for operating the aerodynamic surface, and the second of which branches is mechanically connected to the member for operating the auxiliary rotor, the mechanical link between said second branch and said member for operating the auxiliary rotor being elastically constrained.
In this case, said elastic constraint advantageously has a neutral point which is adjustable.
It will be noted that an appreciable loss in control responsiveness at low speeds may occur, with the appearance of a dead control range.
To overcome this problem, the present invention presents a number of different solutions.
In a first solution, adjustable stops which limit the movement of the mechanical link between the first branch of the bellcrank and the member for operating the aerodynamic surface are provided.
Preferably, means for adjusting said stops as a function of the helicopter speed are also provided in order to greatly limit or even co
Delisle Valery Lionel
Dequin Andre-Michel
Barefoot Galen L.
Eurocopter
Marshall Gerstein & Borun
LandOfFree
Device for controlling a helicopter hybrid countertorque system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device for controlling a helicopter hybrid countertorque system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device for controlling a helicopter hybrid countertorque system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521524