FR2994686A1 - Method for determining floatability of rotary wing aircraft, involves connecting float to fuselage, and transversely moving float away from fuselage to increase stability of aircraft according to aircraft inclination - Google Patents

Abstract

The method involves connecting a float (15) to a fuselage (2) of an aircraft (1) by a connection device (20) to authorize transverse displacement of the float with respect to the fuselage, where the float is in initial position when the aircraft rests on water in a stable position. The float is transversely moved away from the fuselage to increase the stability of the aircraft according to the inclination of the aircraft from the stable position toward the float. The float is approached toward the fuselage when the aircraft is returned to the stable position. An independent claim is also included for a system for determining floatability of an aircraft.

Description

The present invention relates to an aircraft buoyancy method, an aircraft buoyancy system, and an aircraft equipped with a buoyancy system. Therefore, the invention lies in the technical field of buoyancy systems for landing and stability afloat of an aircraft, and more particularly a rotary wing aircraft.

Such a buoyancy system contributes to the floatation and stability of an aircraft during a landing. The buoyancy system can be used in particular during a ditching, to allow evacuation of the occupants of this aircraft. All devices dedicated to passenger missions in maritime areas are equipped in principle with such a buoyancy system. Certification regulations also specify that an aircraft must be able to land and be stable on the water with its buoyancy system. Stability must be proven for water-free surface conditions and wind levels that are defined in these certification regulations. These water-free surface states are also referred to as "sea state" thereafter, and apply to any liquid surface. The term "ditching" also covers the position of an aircraft on any water-free surface, whether on the sea or a lake, for example. A buoyancy system may comprise floats whose deployment is controlled either by the pilot and / or the co-pilot, or by automatic triggering notably by means of one or more immersion detectors. These floats may comprise bags inflated by an explosive or electric deployment means for example. For example, EP 0193265 B1 discloses a buoyancy system provided with inflatable flotation bags which are attached to a landing gear. The document US 2003/0057322 also discloses a buoyancy system attached to a landing gear. A buoyancy system may also include non-inflatable structural floats. Flotation systems with floats attached to a fuselage of an aircraft are thus known. The present invention therefore aims to provide an aircraft with optimized stability following a landing.

The invention relates in particular to a method of buoyancy of an aircraft, the aircraft being provided with a buoyancy system comprising at least two floats arranged on either side of a fuselage of the aircraft. Such a fuselage extends longitudinally from a front end to a rear end, and transversely from a right side to a left side. Each float may be an inflatable float inflated by a deployment device, adapted prior to a landing, or a structural float. Therefore, to ensure the buoyancy of the aircraft, each float is connected to the fuselage by a connecting device allowing a transverse displacement of each float relative to the fuselage, each float being in an initial position when the aircraft rests on the aircraft. water in a stable position.

The term "stable position" is the position of the aircraft in the absence of waves, namely substantially the position in which the aircraft is resting on its fuselage on a horizontal ground. This position can alternatively be called "rest position" insofar as it is obtained when the aircraft rests on a substantially immobile water-free surface. When the aircraft tilts towards a float from this stable position under the effect of agitation of the free surface of the water, then this float is moved transversely of the fuselage to increase the stability of the aircraft by function of the inclination of this aircraft, and this float is brought closer to the fuselage when the aircraft returns to said stable position. On the water, the floats can therefore move away from the fuselage under the effect of the weight of the aircraft during a landing to increase the stability of the aircraft. In addition, the distance separating each float from the fuselage is a function of the inclination of this fuselage, and in particular of its roll angle. Consequently, the greater the inclination of the aircraft, the more a float is moved away from the fuselage. Moving away, a float then generates on the fuselage a more important moment tending to straighten the aircraft towards its stable position. For example, when the aircraft begins to roll under the effect of the movement of the water, at least one float moves relative to the fuselage. We then observe an optimization of the buoyancy system. Compared to a conventional aircraft, the floats may be small in size to withstand equivalent sea conditions. At iso-stability with respect to a conventional aircraft, the invention can therefore generate a gain in mass. Likewise, with equivalent dimensioning of the floats with respect to a conventional aircraft, the invention makes it possible to offer satisfactory stability for more penalizing sea states. As an illustration, the stability level of an aircraft can be multiplied by a coefficient greater than one and for example equal to two by moving the floats of the fuselage a distance equal to 300 millimeters.

This method may also have one or more of the following characteristics. For example, the two floats being separated by a wheelbase distance, the wheelbase distance is increased when said aircraft moves away from said stable position.

By moving the floats towards which the fuselage of the aircraft is inclined, the wheelbase distance is increased so as to optimize the stability of the aircraft according to the state of the sea. ditching, one can move the floats away from the fuselage to place them in the initial position.

The floats can be placed against the fuselage in flight to minimize their aerodynamic drag. On the other hand, during the landing, the floats are moved away from the fuselage to increase the stability of the aircraft on the water. The distance can be achieved before contact of the aircraft on the water, and / or following such contact under the effect of the pressure of the water on the floats.

This variant is all the more interesting when the aircraft is equipped with structural floats likely to degrade the performance of the aircraft in flight. In addition, one can tend to maintain the floats in the initial position using a return means. This return means can be used to control the movement of the floats relative to the fuselage. This return means may consist for example of jacks or springs. A stop on this return means can also block too close bringing the floats against the fuselage, while allowing their spacing. In addition to a method, the invention furthermore relates to a buoyancy system implementing this method. The invention therefore also relates to a buoyancy system of an aircraft, this buoyancy system being provided with at least two floats adapted to be arranged on either side of a fuselage of the aircraft. Each float may be an inflatable float, inflated by a deployment device adapted prior to a landing, or a structural float. Each float may be arranged below a plane passing through the floor of the cabin of the aircraft. In addition, the buoyancy system comprises a connecting device allowing a transverse displacement of each float relative to the fuselage, the connecting device including at least one float pivot arm for connecting each float to a structure of an aircraft.

For example, the connecting device includes two pivoting arms by float to optimize the attachment of the float to the rest of the aircraft. Each pivoting arm can then be articulated to a structural frame of the aircraft in at least one attachment point. The swivel arms provide a degree of freedom for each float to move relative to the fuselage to increase the stability of the aircraft according to the state of the sea. The buoyancy system may further include at least one of the following features: . Each pivoting arm may comprise a retaining bar provided with a hinge means to be articulated to a structure of an aircraft. Therefore, the retaining bar extends from a first end provided with the hinge means to a second end. According to a first variant, a float is attached to the second end, possibly by a hinge. In contrast, according to a second variant, each pivoting arm 20 may also comprise a connecting bar connecting the retaining bar to a float. A pivoting arm is then an articulated arm provided with a retaining bar which is articulated to a connecting bar. Consequently, since the retaining bar extends from a first end provided with the articulation means to a second end, the connecting bar is then articulated at the second end and secondly fixed to a second end. float.

The connecting device may also include a return means which is articulated to the pivoting arm and adapted to be articulated to a structure of an aircraft. This return means makes it possible to return the pivoting arm to an initial position, and to favor the return of the aircraft to the stable position. In addition, this biasing means makes it possible to connect a pivoting arm to a second fixing point. According to the variant, a return means comprises a piston cylinder or a spring for example. Alternatively, the buoyancy system further comprises a spacing means to separate each pivoting arm of the fuselage prior to a landing. For example, the floats are sealed structural compartments that are contiguous to the fuselage in flight. Prior to landing, the spacing means places each float in an initial position separated from the fuselage. These spacing means may comprise a piston cylinder also acting as a return means. It is then possible to inject a fluid into the piston cylinder to move a float away from the fuselage before landing. The invention also relates to an aircraft equipped with a fuselage and a buoyancy system, this buoyancy system being provided with at least two floats able to be arranged on either side of the fuselage. The buoyancy system is then of the type described above.

The invention and its advantages will appear in more detail in the context of the description which follows with exemplary embodiments given by way of illustration with reference to the appended figures which represent: FIG. 1, a schematic view of an aircraft according to FIG. FIGS. 2 to 4, views explaining the method according to the invention and the operation of the buoyancy system, FIG. 5, a view presenting a variant without link rod. The elements present in several separate figures are assigned a single reference. Note that three directions X, Y and Z orthogonal to each other are shown in the figures.

The first direction X is called longitudinal. The term "longitudinal" is relative to any direction parallel to the first direction X. The second direction Y is said to be transverse. The term "transverse" is relative to any direction parallel to the second direction Y. Finally, the third direction Z is said to be in elevation. The expression "in elevation" relates to any direction parallel to the third direction Z. FIG. 1 shows an aircraft 1 according to the invention.

This aircraft comprises a fuselage 2 extending longitudinally from a front end 3 to a rear end 4. In addition, the fuselage 2 extends transversely from a left side 5 to a right side 6, and in elevation of a lower part 7 to an upper part 8. The lower part is conventionally provided with a landing gear, while the upper part can carry a lifting rotor 9 or propulsion. The lower part may include a boat bounded in particular by the floor of a cabin and the outer casing of the fuselage. This aircraft 1 is provided with a buoyancy system 10 according to the invention in order to be able to fish. Such a buoyancy system is provided with at least two floats 15 arranged on either side of the fuselage 2 of the aircraft. Thus, a first float is disposed on the side of the left flank of the aircraft, while a second float is disposed on the side of the right side of the aircraft. Floats can be paired. Therefore, the floats of a pair can be arranged symmetrically on either side of an anteroposterior plane of symmetry of the aircraft in a stable position of the aircraft.

For example, the aircraft comprises a single pair of floats 15. Each float can be arranged near the boat of an aircraft to keep the aircraft afloat. The floats may be inflatable floats by a deployment device of the buoyancy system. According to another variant, the floats are structural floats. The floats can then for example comprise mobile hollow compartments.

According to the invention, each float 15 is movable relative to the fuselage, in particular in a transverse direction. Therefore, the buoyancy system has a connecting device 20 connecting each float 15 to a structure of the aircraft, such as a structural frame of this aircraft. This connecting device offers a degree of freedom to each float to allow a transverse displacement of each float tending to move or bring each float of the fuselage. This connecting device 20 comprises at least one pivoting arm 25 which pivots relative to the fuselage. Thus, each float cooperates with at least one pivoting arm 25. Two pivoting arms are used according to the example shown. Therefore, the two pivoting arms can be connected to each other by a conjugation bar 100. Each pivoting arm 25 is articulated to a structure of the aircraft in at least one fulcrum, such as a fulcrum P1 of a structural frame for example. Therefore, each pivoting arm is provided with a retaining bar 26. The retaining bar 26 extends from a first end 26 'to a second end 26 ", whereby the first end 26' is provided with a hinge means 50 which is articulated to a structure of the aircraft According to the variant of Figure 5, the second end 26 "can be attached to a float. However, the second end 26 "is articulated or fixed to a connecting bar 27 according to the variant of FIG. 1. The connecting bar is then fixed to a float 15. Each connecting bar is substantially tangent to a float, in For example, this architecture allows the pivoting arm to conform to the shape of the fuselage when the pivoting arm is folded.

Furthermore, each pivoting arm can cooperate with a return means 28. Each return means then extends from a bearing point P2 of the aircraft to a pivoting arm, for example, the return means is articulated to the retaining bar 26, near the second end 26 ".

This return means may comprise a piston cylinder or a spring. Any variable length means can be used. In addition, the connecting device 20 may have a spacer means. This spacing means then has the function of removing a float from the fuselage to place it in a position called "initial position" prior to a landing. In addition, the spacing means may instead press a float against the fuselage in a position called "flight position" following a takeoff, in the context of a variant provided with reusable floats.

The spacing means and the return means may constitute an equipment only. Figures 2 to 4 explain the method according to the invention implemented by this buoyancy system 10. With reference to Figure 2, the floats 15 are deployed 25 prior to a landing.

When the floats are structural floats, it is understood that the floats are permanently deployed, and in particular prior to a landing. On the other hand, the situation differs in the context of inflatable floats. According to this variant, the buoyancy system is provided with a deployment device for inflating the floats. Therefore, the deployment device inflates the floats before a landing. During a flight, the floats can be contiguous to the fuselage 10 2 of the aircraft, to minimize aerodynamic drag. This characteristic is all the more interesting when the floats are structural floats permanently deployed. According to this variant, it is possible to slightly separate each float from the fuselage before landing. Indeed, the greater the wheelbase distance D between two floats 15, the greater the stability of the aircraft on the water is important. The floats can be separated from the fuselage by spacing means of the buoyancy system. With reference to FIG. 3, during a landing, the floats 20 are in a so-called "initial position" position to make the aircraft stable on a water-free surface that is flat. The aircraft is then in a position called "stable position". In the initial position, the floats are slightly spaced from the fuselage. Indeed, during the landing, the weight of the aircraft associated with the buoyancy force tends to move the floats of the fuselage in a transverse direction along the arrows F0. Note that the retaining bar 26 of each pivoting arm has angulation with gravity while the connecting bar remains substantially parallel to gravity. Referring to Figure 4, when the free water surface is agitated, the aircraft tilts depending on the waves.

As a result, as a function of the waves, the aircraft tilts and moves away from the stable POSO position of FIG. 3. When the aircraft tilts on one side of the aircraft, the floats present on this side of the aircraft move away from the fuselage. Thus, when the aircraft tilts along the arrow F1 on the side of the left flank 5, the float connected to this left flank 5 moves away from the fuselage along the arrow F2. Conversely, when the aircraft returns to the stable position POSO, this float is closer to the fuselage to return to its initial position POSINI.

Naturally, the present invention is subject to many variations as to its implementation. Although several embodiments have been described, it is well understood that it is not conceivable to exhaustively identify all the possible modes. It is of course conceivable to replace a means described by equivalent means without departing from the scope of the present invention.

Claims (14)

REVENDICATIONS1. A method of buoyancy of an aircraft (1), the aircraft (1) being provided with a buoyancy system (10) comprising at least two floats (15) arranged on either side of a fuselage (2) of the aircraft (1), characterized in that to ensure the buoyancy of the aircraft (1): - each float (15) is connected to the fuselage (2) by a connecting device (20) allowing a transverse displacement of each float (15) relative to the fuselage (2), each float (15) being in an initial position (POSINI) when the aircraft (1) is resting on water in a stable position (POSO), - when said aircraft (1) tilts towards a float (15) from said stable position (POSO), then this float (15) is moved transversely from the fuselage (2) to increase the stability of the aircraft (1) according to the inclination of this aircraft (1), and is brought closer to the float (15) of the fuselage (2) when the aircraft (1) returns to said stable position (POSO). 2. buoyancy method according to claim 1, characterized in that said two floats (15) being separated by a wheelbase distance, said distance is increased when said aircraft (1) away from said stable position (POSO). 3. Buoyancy method according to any one of claims 1 to 2, characterized in that during the landing, said floats (15) are moved away from the fuselage (2) to place them in said initial position (POSINI). 4. buoyancy method according to any one of claims 1 to 3, characterized in that one tends to maintain the floats (15) in said initial position (POSINI) using a biasing means (28). 5. Buoyancy system (10) of an aircraft (1), this buoyancy system (10) being provided with at least two floats (15) able to be arranged on either side of a fuselage (2). ) of the aircraft (1), characterized in that said buoyancy system (10) comprises a connecting device (20) allowing a transverse displacement of each float (15) relative to the fuselage (2), said connecting device Apparatus (20) including at least one float pivot arm (25) for connecting each float (15) to a structure of an aircraft (1). 6. buoyancy system according to claim 5, characterized in that each pivoting arm (25) comprises a retaining bar (26) provided with a hinge means (50) to be articulated to a structure of an aircraft ( 1). 7. buoyancy system according to claim 6, characterized in that each pivoting arm (25) comprises a connecting bar (27) connecting said retaining bar (26) to a float (15). 8. Buoyancy system according to claim 7, characterized in that said support bar (26) extending from a first end (26 ') provided with said hinge means (50) to a second end (26 ") ), said connecting bar (27) is articulated to said second end (26 "). 9. buoyancy system according to any one of claims 5 to 8, characterized in that the connecting device comprises a return means (28) articulated to the pivoting arm (25) and adapted to be articulated to a structure of a aircraft (1). 10. Buoyancy system according to claim 9, characterized in that said biasing means (28) comprises a piston cylinder. The buoyancy system of claim 9, characterized in that said biasing means (28) comprises a spring. 12. Buoyancy system according to any one of claims 5 to 11, characterized in that said connecting device (20) includes two pivoting arms (25) by float (15). 20 13. Buoyancy system according to any one of claims 5 to 11, characterized in that said buoyancy system (10) comprises a spacer means for spacing each pivoting arm (25) of the fuselage (2) prior to a landing . 25 14. Aircraft (1) having a fuselage (2) and a buoyancy system (10), this buoyancy system (10) being provided with at least two floats (15) arranged on either side of the fuselage (2), characterized in that said buoyancy system (10) is according to any one of claims 5 to 13.5