The invention relates to helicopters, especially helicopters equipped with emergency assistance devices to the lift in case of failure of a main motor.

2. BACKGROUND

A helicopter rotor typically includes a main lift and propulsion forming a rotary wing, set in motion by a drive chain comprising a main gearbox and at least one main engine, such as a turbine engine. The main gearbox of the helicopter's mission, in particular, to transmit the lift rotor efforts to the entire aircraft structure. A helicopter also comprises a counter-torque means which is often formed by a second rear rotor coupled to the drive train.

There are single-engine helicopters, that is to say helicopters which the drive train has only one engine. There are also multi-engine helicopters, especially the twin-engine helicopters or airplanes having three engines, that is to say helicopters which the drive train has multiple engines.

Whatever type of helicopter concerned (single-engine or multi-engine), a failure of an engine of the drive train reduces the power supplied by the drive train to the main rotor lift and propulsion of the helicopter, which may have adverse consequences for the helicopter and its passengers.

For example, in the case of a single-engine helicopter, a main engine power loss requires the pilot to perform a delicate maneuver autorotation for an emergency landing. Statistics show that in certain conditions, this maneuver can lead to a landing "hard", causing serious damage to the helicopter.

It has therefore been proposed, including the applicant, installed on the helicopter means capable of providing additional power very quickly, to secure the operation of a single-engine helicopter autorotation preventing tower drop of the rotor in any one of phases of the maneuver.

In the case of a multi-engine helicopter, it was also proposed, including the applicant, different solutions to bring extra power to maintain sufficient power at the helicopter's rotor. For example, one proposed solution is to inject fluid into the turbine in operation to temporarily increase the power and thus compensate for the loss or failure of an engine. Another solution is to mechanically assist turbines operated by an input of mechanical power on the gas generator of this turbine in operation. Another solution is to bring extra power directly to the rotor of the helicopter or the main transmission box of the drive train.

All proposed solutions for single-engine or multi-engine applications, designed to provide additional power to the drive train of the helicopter to make the final extra power at the main rotor, which limits the drop tower the rotor, and thus maintain sufficient lift to keep the helicopter in flight or at least slow the helicopter drop.

A drawback shared by these solutions is the fact that a fault on the drive train of the main rotor (main gear box, rotor pitch control, tail rotor, ....) can not lift not be compensated by a power supply. None of the solutions thus overcomes a fault on the drive train of the main rotor.

Furthermore, in the case of a multi-engine helicopter, it is necessary to

oversize the turbine in order to maintain the helicopter in the event of failure of one engine. These oversized turbine engines are penalizing in terms of weight and fuel consumption.

Furthermore, it has been proposed in US 4,676,457 A to equip the helicopter with integrated propulsion organs fuselage to limit the speed of the fall. However, regarding the solution to equip the helicopter additional devices to provide propulsion power surplus in case of need, it requires a more complex architecture of the helicopter and the drive train, and this adds to d especially the helicopter, which is also disadvantageous in terms of weight and fuel consumption.

The applicant therefore sought a new solution to overcome the disadvantages of known solutions.

3. Objectives of the invention

The invention aims to provide a helicopter which can generate a vertical thrust complement without using the drive train of the helicopter.

The invention also aims to provide, in at least one embodiment of the invention, a power surplus in the event of failure of an engine, independently of the drive train of the helicopter.

The invention also aims to provide, in at least one embodiment of the invention, a helicopter can maintain a certain level of sustenance, including in case of failure of the main lift rotor.

The invention also aims to provide, in at least one embodiment of the invention, such a helicopter is not penalized in terms of weight or fuel consumption.

4. Summary of the Invention

To do this, the invention relates to a helicopter comprising a structural frame, at least one main rotor lift and propulsion secured to said structural frame and a drive train for moving said main rotor comprising a power transmission gearbox and least one main engine.

A helicopter according to the invention further comprises a plurality of boosters attached to said structural frame and configured to be able to provide additional lift of the helicopter in the event of failure of the drive train of the helicopter.

A helicopter according to the invention is characterized in that each booster is mounted removably to the structural frame.

This additional lift allows notably to overcome a lack of power of the drive train in a critical situation.

Throughout the text, the structural frame of the helicopter refers to the rigid structure formed by rigid members such as frames, crossbars, uprights, caissons, arches, plates, etc. assembled together to form the cell of the helicopter.

A helicopter according to the invention can therefore overcome all failures of its drive train (power transmission gearbox, motor, rotor, etc.) and maintain a certain level of buoyancy by the implementation boosters attached to the structural frame of the helicopter. In other words, a helicopter according to the invention can generate a vertical pushing addition, in case of need, without involving the rotor lift and propulsion of the helicopter. Helicopter The boosters of the invention form an emergency assistance mechanism to lift the helicopter.

The boosters are independent of the drive train, they are not intrusive and does not change the behavior of the helicopter in normal circumstances. Similarly, they do not impose a helicopter design change.

A helicopter of the invention also allows mounting the boosters only when necessary. In particular, it is possible that the boosters can equip different helicopters. For example it is possible to have some boosters to equip a plurality of helicopter helicopter fleet. For each mission, the boosters are mounted on the helicopter fleet selected for this mission. During a subsequent mission, if another

helicopter is selected, the same propellers can then first be removed from the aircraft and mounted on the newly selected helicopter.

A helicopter according to the invention exhibits improved safety over the known helicopters.

Furthermore, in the case of a multi-engine helicopter, the invention renders obsolete the need to oversize the motor to compensate for a possible failure of a turbine engine. The specific consumption of the main engines is improved.

Advantageously and according to the invention, the structural frame comprises upper frames arranged in the vicinity of the main rotor lift and propulsion, and boosters are secured to the upper frames.

According to this advantageous variant, the boosters are attached to senior the structural frame arranged in the vicinity of the main rotor. These executives transmit the vertical forces to lift the helicopter airframe. The arrangement of the thrusters at the upper part of the helicopter allows the structural frame to limit the risk of rolling or loss of control during activation of the thruster.

Advantageously and according to the invention, the boosters comprise pyrotechnic devices.

According to this advantageous variant, propellants implement pyrotechnics. These pyrotechnic devices used to generate very quickly without extensive nevertheless present a significant bulk. These pyrotechnic devices comprise for example a solid propellant gas generator, an ignition of the solid propellant device, electrically controlled and connected to a timing calculator of the ignition device and a gas ejection nozzle.

Advantageously and according to the invention, the boosters are configured to be able to each provide the same propulsive power and they are arranged and oriented on the structural frame such that they exert pushing forces according to intersecting directions in a single point, said point of convergence.

Advantageously and according to this variant, the focal point is arranged in the center of the rotor in the plane of the rotor blades, so that the resulting extra propellant thrust forces is vertical, and applied on top of a mat rotor.

This arrangement and orientation of the thrusters used to generate a resultant of the buoyancy forces. In addition, the torque applied to the structural frame is zero at the convergence point, which eliminates the risk of inducing a rotation of the helicopter due to the thrusters.

Advantageously and according to the invention, the focal point is the helicopter's center of gravity.

Advantageously, a helicopter according to the invention further comprises a control unit connected to each booster and configured to control the activation of each booster in the event of a fault on the drive train of the helicopter.

This control unit is for example a helicopter control electronic computer (known by the acronym EECU). This calculator is for example integrated in the control device of the engines known by the acronym FADEC for Full Authority Digital Engine Control. The control unit can also be connected to the altitude of the helicopter detection devices, such as an altimeter, for automatically controlling the activation of thrusters once a critical altitude is reached in conjunction with a failure detected on one of the turbine of the helicopter. In this embodiment, the control unit is configured to automatically activate boosters to approach the ground.

According to an advantageous variant of the invention, the helicopter is equipped with four boosters regularly distributed over the structural frame.

The invention also relates to a helicopter, characterized in combination by all or some of the features mentioned above or below.

5. List of Figures

Other objects, features and advantages of the invention will appear on reading the following description given by way of non-limiting and which refers to the appended figures in which:

- Figure 1 is a schematic view of a helicopter to be equipped with an emergency device for assisting the airfoil to form a helicopter according to an embodiment of the invention,

- Figure 2 is a partially cutaway schematic view of a helicopter according to an embodiment of the invention

- Figure 3 is a partially cutaway schematic view of a helicopter according to another embodiment of the invention.

6. Description of an embodiment of the invention

In the figure, the scales and proportions are not strictly complied with, for purposes of illustration and clarity. Throughout the following detailed description with reference to the figures, unless otherwise specified, each helicopter element is described as it is arranged when the helicopter is horizontal. This arrangement is shown in Figures 1 to 3.

In addition, the elements identical, similar or analogous are designated by the same references in all the figures. Finally, the longitudinal, transverse and vertical terms are used as non-limiting with reference to the trihedron L, T, V as shown in FIGS. The longitudinal direction corresponds to the main direction of the helicopter.

1 shows a helicopter comprising a structural frame 5. This structural frame 5 is shown in dashed lines in Figure 1. This frame format the cell of the helicopter and includes upper frames 6, uprights 7, 8 of the lower frames, sleepers, etc. assembled together to form the cell of the helicopter.

The helicopter also comprises a main lift rotor 10 and integral drive the structural frame 5. The rotor 10 is coupled to the blades 9 of lift and propulsion. The helicopter also comprises a drive train for moving the main rotor 10. The drive train comprises a box 11 of power transmission and two motors 12a, 12b key.

Figure 2 is a schematic view of a helicopter according to an embodiment of the invention obtained from the helicopter of Figure 1. This view shows a broken away to show the upper frames, uprights, lower frames, cross etc. of the structural frame 5. The helicopter further comprises bodies and elements described in connection with Figure 1, four thrusters 21a, 21b, 21c, 21d extra fixed on the frames 6 of the upper structural frame 5. Each propellant is configured to provide custom additional lift of the helicopter in the event of failure of one motor 12a, 12b of the main helicopter.

Propellants are for example pyrotechnics comprising a solid propellant gas generator, an ignition device and a solid propellant gas ejection nozzle. Any other type of propellant can be used for the implementation of the invention.

Preferably, all thrusters are identical and are configured to be able to provide the same power. They are removably fixed on the upper frames 5 of the structural frame 5, for example by clamps with screw and nut type system. In addition, they are directed downwardly so that they exert a thrust force downwardly. The thrust produced by each engine 21a, 21b, 21c, 21d is shown schematically in Figures 2 and 3 by an arrow referenced with the letter P.

According to an advantageous embodiment, the lift contribution of each thruster is moderated. To do this, the propellant is configured so that the maximum power it can produce either the order of 20% of the maximum power of a main engine of the helicopter, and this for a period of the order of 30 seconds. The thrusters are only intended to slow the fall of the helicopter for a short time, near the ground and not to ensure a continuation of the flight in case of failure of one or more main engines of the helicopter.

Figure 3 is a schematic view of a helicopter according to another embodiment of the invention wherein the thrusters 21a, 21b, 21c, 21d booster are arranged and oriented on the structural frame 5 so that they exert pushing forces P according to directions intersecting at a single point, said convergence point. This is referenced by the letter C in Figure 3. The view of Figure 3 also shows a broken away to show the executives, amounts lower frames, cross, etc. of the structural frame 5. In the embodiment of Figure 3, the point of convergence C is arranged at the center of rotor blades 10 in the plane 9. According to this embodiment, pushing forces of the resultant P thrusters 21a, 21b, 21c, 21d of

Activation of propellants can be controlled from a control unit connected to each booster and configured to control the activation of each booster in the event of a fault on the drive train of the helicopter.

This control unit may also be connected to a device for detecting the altitude of the helicopter such as an altimeter or any equivalent device. This control unit can also be manually controlled by the pilot during the mission if needed, for example in case of emergency to avoid an obstacle or form evasive action to enemy fire.

According to an advantageous variant, the axis of thrust thrusters may be steerable by means of the nozzle type component, to ensure the horizontal position of the helicopter.

The invention is not limited to the embodiments described. The invention also applies to a single engine helicopter. The invention may also comprise more (or less) of four boosters to provide emergency assistance to the lift.

Similarly, the detailed description describes thrusters provided on the executives of the structural frame of the helicopter. According to other embodiments not shown, the propellant can of course be arranged in any point of the structural frame, in particular on the helicopter skids.

CLAIMS

Helicopter comprising a structural frame (5), at least one rotor (10) main lift and secured propulsion said structural frame (5) and a drive train for moving said rotor (10) main comprising a box (11) power transmission and at least one motor (12a, 12b) main, further comprising a plurality of thrusters (21a, 21b, 21c, 21d) booster attached to said structural frame

(5) and configured to be able to provide additional lift of the helicopter in the event of failure of the drive train of the helicopter, characterized in that each propulsion unit (21a, 21b, 21c, 21d) is mounted booster removably to the structural frame (5).

A helicopter according to claim 1, characterized in that the structural frame (5) further comprises frames (6) arranged above the vicinity of the rotor (10) of the main lift and propulsion, and in that said propellers (21a, 21b, 21c, 21d) booster are fixed to said frames

(6) above.

Helicopter according to one of claims 1 or 2, characterized in that said propellers (21a, 21b, 21c, 21d) extra comprise pyrotechnic devices.

Helicopter according to one of claims 1 to 3, characterized in that said propellers (21a, 21b, 21c, 21d) are configured to extra power each provide the same propulsive power and in that they are arranged and oriented said structural frame (5) such that they exert pressure forces according to directions intersecting at a single point, said point (C) of convergence.

A helicopter according to claim 4, characterized in that said point (C) of convergence is arranged at the center of the rotor (10) in the blades of the plane (9) of the rotor, such that the resultant of urging forces of propellants booster is vertical and applied on top of a rotor mast.

A helicopter according to claim 4, characterized in that said point (C) of convergence is the helicopter's center of gravity.

7. A helicopter according to one of claims 1 to 6, characterized in that it comprises a control unit connected to each propulsion unit (21a, 21b, 21c, 21d) and extra configured to control the activation of each propellant (21a, 21b, 21c, 21d) extra in case of a fault on the drive train of the helicopter.

8. A helicopter according to claim 7, characterized in that said control unit is configured to automatically activate the thrusters (21a, 21b, 21c, 21d) complementing the ground approach.

9. A helicopter according to one of claims 1 to 8, characterized in that it comprises four thrusters (21a, 21b, 21c, 21d) extra regularly distributed on said structural frame (5).