TECHNICAL FIELD

The present invention relates to seaplanes , i . e . aircraft capable of taking off and landing on water .

BACKGROUND OF THE ART

Seaplanes have been used for few decades especially in areas where no airports or roads may be found, but lake or other water area is present . Like landplanes , the seaplane comprises a rigid fuselage and wings attached to the fuselage . The plane may liftoff when the lifting force overcomes the gravity and other resisting forces pulling the plane downwards . Typically, the li fting force is achieved with the wings ( the shape of them) and adj usting angle of attack of the wings during the acceleration .

To accelerate and take of f a seaplane , the thrust ( of a propeller for example ) must overcome forces of hydrodynamic or water drag, and the angle of attack must be adj usted so that the seaplane may liftoff from water . For adj usting the angle of attack, the bottom of the fuselage is typically curved so that the plane position may be changed by applying back elevator pressure for lowering the tail towards the water, while avoiding hitting the tail to the water . I f the tail hits the water, it wi ll create stronger res istance and appreciably retarding the take off . However, such curved bottom causes negative lifting force and to overcome this extra negative lifting force , it must be compensated by increasing the lifting force of the wings . Increased lifting force on the wings increases the aerodynamic drag . Larger drag is detrimental to cruising operation . OBJECTIVE OF THE INVENTION

The obj ective of the device is to alleviate the disadvantages mentioned above .

In particular, it is an obj ective of the present device to provide a seaplane having a structure that is optimal for take off as well as for cruising .

SUMMARY

According to a first aspect , the present invention provides a seaplane compri sing a fuselage , at least two wings fastened to the fuselage , wherein the fuselage comprises two fuselage sections , a front fuselage and a back fuselage each having a bottom surface , arranged successively in axial direction of the fuselage , and the wings are fastened to the front fuselage , and hinge means pivotally interconnecting the front fuselage and the back fuselage for vertical movement relative to each other about a lateral axis .

The advantage of the device is that the seaplane may be adj usted to hydrodynamically and aerodynamically optimal positions for cruising in the air and take off from water .

In an embodiment of the device , the front fuselage and the back fuselage are each watertight .

In an embodiment of the device , the front fuselage and the back fuselage are partly overlapping each other .

In an embodiment of the device , the front fuselage has a front end and a back end, and the hinge mean are ar- ranged between the front end and the back end of the front fuselage.

In an embodiment of the device, the back fuselage has two positions, a runway position and a cruise position, having a different back fuselage angle a in relation to lateral level, which angle a is adjustable.

In an embodiment of the device, the seaplane comprises a damper for dampening a sudden movement of the back fuselage from runway position to cruising position.

In an embodiment of the device, the back fuselage angle a is from -5 to 35°.

In an embodiment of the device, the back fuselage comprises a tail fin having a horizontal stabilizer, which vertical angle [3 is adjustable.

In an embodiment of the device, the vertical angle [3 of the horizontal stabilizer is adjustable in relation to the back fuselage angle a for compensating the change of the angle a of the back fuselage.

In an embodiment of the device, the horizontal stabilizer is adjusted mechanically, electrically, hydraulically or pneumatically.

In an embodiment of the device, the back fuselage comprises an adjustable aerodynamic fairing arranged on top of the back fuselage, which has two positions, a cruising position and a runway position, so that in the cruising position, the fairing is extending from the back fuselage.

In an embodiment of the device, in runway position, the fairing is against the back fuselage. In an embodiment of the device , in cruising position of the back fuselage , the bottom surface of the front fuselage and the bottom surface of the back fuselage are at the same level , for forming uniform aerodynamic surface .

In an embodiment of the device , between the bottom surface of the front fuselage and the bottom surface of the back fuselage , a step is formed when the back fuselage is not in the cruising position .

In an embodiment of the device , the step is extending towards the center of the front fuselage .

It is to be understood that the aspects and embodiments of the invention described above may be used in any combination with each other . Several of the aspects and embodiments may be combined together to form a further embodiment of the invention .

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings , which are included to provide a further understanding of the invention and constitute a part of this specification, illustrate embodiments of the invention and together with the description help to explain the principles of the invention . In the drawings :

Fig . 1 shows the seaplane in cruising position,

Fig . 2 shows the seaplane in runway position,

Fig . 3 shows the seaplane in crui sing position , wherein the hori zontal stabili zer position is adj usted by push-pull cable , Fig. 4 shows axonometric view the seaplane in cruising position with fairing lifted, and

Fig. 5 shows axonometric view the seaplane wherein the front fuselage and the back fuselage are separated.

DETAILED DESCRIPTION

A seaplane is an aircraft that is capable of taking off and landing on water, i.e. they use the water as a runway. Seaplanes may be divided into subclasses: floatplanes (having slender floats under the fuselage) and flying boats. The present device is a seaplane and the structure is most optimal for flying boats but it may be also used in floatplanes. In a flying boat, the main source of buoyancy is the fuselage, which acts like a hull of a ship or a boat in the water. This is achieved by shaping the underside of the fuselage hydrodynamically to allow water to flow around it.

Figure 1 shows a seaplane 1 comprising a fuselage 2 and wings, which are fastened to the fuselage. The fuselage is a hollow body having a bottom surface, i.e. underside. The fuselage is elongated part extending in axial direction between the nose and tail of the plane. The fuselage comprises two sections, a front fuselage 3 and a back fuselage 4, which are arranged successively in axial direction of the fuselage. The front fuselage 3 and the back fuselage 4 are separate components which are attached to each other to form the fuselage of the seaplane 2. The seaplane comprises hinge means 7, which are pivotally interconnecting the front fuselage 3 and the back fuselage 4 for vertical movement relative to each other about lateral axis. With the hinged structure, the seaplane fuselage 2 may be adjusted so that the angle a (marked in figure 2) of the back fuselage 4 in relation to the lateral level may be adjusted independently from the front fuselage 3. Therefore, the angle of the back fuselage may be adjusted for different scenarios, e.g. for take off and cruising, to have an optimal aerodynamic and hydrodynamic shape for each scenario. Thus, there is no need for compromise and the resisting forces for different scenarios may be minimized.

The back fuselage angle a may be -5-35°. Optionally, the minimum angle may be zero degrees. Optionally, the maximum angle may be 10°, 20° or 30°. Optionally, the range of angle a may be between any of the minimum angles and maximum angles defined above.

In figure 1, the seaplane is in a cruising position, wherein the angle of the back fuselage is zero, i.e. there is no angle between the front fuselage 3 and the back fuselage 4 and the bottom surface of the front fuselage 5 and the bottom surface of the back fuselage 6 forms a uniform aerodynamic surface. In this position, the negative lifting force created by the bottom surface is minimal and, thus, the needed lifting force for flying is also minimal. This helps saving energy needed for flying.

In figure 2, the seaplane is in a runway position, wherein the angle of the back fuselage is more than zero. The said angle is marked with a in figure 2. By pivoting the back fuselage 4 to the angle a, the bottom surface of the fuselage forms a curved shape, and the tail of the seaplane may be lowered towards the water by applying back elevator pressure without hitting the water surface with the tail. At the same time, the support of the seaplane is transferred to the wings from the fuselage and the seaplane may liftoff. After liftoff, the angle a, and the seaplane, may be adj usted to the crui sing position as seen in figure

1 .

The hinge means 7 may compri se pins extending from the side walls of one fuselage section and holes in the side wall s of the other fuselage section . The pins may extend outwards or inwards from the side walls of a fuselage section . Instead of pins , one fuselage section may comprise a shaft that i s arranged between the side walls of the fuselage section . For example , the side walls of front fuselage 3 may comprise pins that are perpendicular or essentially perpendicular to the axial direction of the fuselage , and the side wall s of the back fuselage 4 may comprise holes that are fastened to the pins of the front fuselage 3 . Optionally, the back fuselage 4 comprises said pins that are perpendicular or essentially perpendicular to the axial direction of the fuselage , and the front fuselage 3 comprises holes that are fastened to the pins . The holes or pins in the back fuselage may be arranged on the tips 15 of the back fuselage 4 ( seen in f igure 5 ) . Optionally, one of the fuselage sections comprise a shaft arranged between the side wall s of said fuselage section , and the side wal ls of the other fuselage section comprises holes that are fastened to the shaft .

The front fuselage 3 has a front end and a back end in axial direction . The hinge means 7 in the front fuselage 3 may be positioned so that they are between the front end and the back end . The hinge means 7 may be positioned at a distance from the back end of the front fuselage 3 so that when the back fuselage is pivoted, i . e . the seaplane is adj usted to the runway position, a step 14 is formed between the back end of the front fuselage 3 and the back fuselage 4 . The step 14 may be formed towards the center axis of the front fuselage 3 . When the back fuselage 4 is adj usted to the cruising position (angle a is zero) the step 14 disappears, and the uniform aerodynamic bottom surface is formed. The height of the step 14 may be whatever is hydrodynamically required for liftoff. The height of the step 14 may be 0-10% of the width of the step. Optionally, the height of the step, in runway position, may be 40, 85 or 100 mm.

The front fuselage 3 and the back fuselage 4 may be fastened to each other so that they are partly overlapping. For example, the back fuselage 4 may be fastened to the front fuselage 3 so that the front fuselage 3 is partly inside the back fuselage 4. Optionally, the back fuselage 4 may be fastened to the front fuselage 3 so that the back fuselage 3 is partly inside the front fuselage 4. With the overlapping structure, the hinge means 7 may be positioned between the front end and the back end of the front fuselage 3 and at a distance from the back end.

The seaplane may comprise limiters, which limits the pivotal movement of back fuselage 4, i.e. limiters defines the range of angle a. The limiters may be mechanical components, such as shaft or pins.

The seaplane may comprise a dampener, which is configured to dampen the sudden pivotal movement of the back fuselage 4. For example, if the pivoting mechanism breaks, the back fuselage would fall to the cruising position. Such sudden movement could cause huge aerodynamical force to the seaplane, which could break the plane further or even drop the plane. The damper would absorb the impact of the back fuselage, in case of sudden movement, and further damages may be prevented.

The seaplane comprises a tail fin 8 having a horizontal stabilizer 9 for providing horizontal stabiliza- tion for the seaplane. The horizontal stabilizer 9 has a vertical angle [3, i.e. set angle, which may be adjustable. The vertical angle [3 may be adjusted independently or it may be adjustable in relation to the back fuselage angle a for compensating the change of the angle a of the back fuselage. The vertical angle [3 may be adjusted automatically in relation to the back fuselage angle a or it may be adjusted manually. It may be adjusted mechanically, hydraulically, electrically or pneumatically. For example, the vertical angle [3 may be adjusted by using push-pull cable 16, i.e. cable capable of transfer forces in both push and pull mode of operation, by using mechanical means, i.e. rods or shafts with pivoting levers, or by using electric or hydraulic actuator. In each cases where the vertical angle [3 is adjusted manually, the vertical angle [3 is adjusted by the user in the cockpit. The adjusting means may be used by pedals, buttons and/or controller arranged in the cockpit.

In figure 1 and 2, the seaplane comprises mechanical means to adjust the vertical angle [3. The mechanical means comprises a first rod 11 connected to the front fuselage 3 and extending towards the tail of the seaplane. The other end is fastened to a pivoting lever 12 which is connected to a second rod 13. The other end of the second rod 13 is fastened to the horizontal stabilizer 9 for adjusting the vertical angle [3. The axial movement of the first rod 11 is transferred to perpendicular movement of the second rod 13 by the pivoting lever 12. In figure 3, the mechanical means to adjust the vertical angle [3 comprises push-pull cable 16, which is connected between the cockpit in the front fuselage 3 and the horizontal stabilizer 9.

The seaplane comprises at least two wings, which are extending in opposite directions and are in perpendic- ular direction to the fuselage. Optionally, the wings may extend in direction that is not perpendicular to the fuselage, i.e. they may be angled in relation to the fuselage. The seaplane may comprise more than two wings arranged in different positions in the seaplane.

The seaplane may comprise a fairing 10 arranged on top of the back fuselage 4. The fairing 10 is used for eliminating the aerodynamic discontinuity formed on the upper surface of the fuselage when the back fuselage 4 position is changed. The fairing 10 is a sheet or wing having a front end and a back end, and which is arranged partly around the top surface of the back fuselage 4. The fairing 10 may be pivoted so that the front end is lifted from the surface of the back fuselage while the back end stays connected to the surface. The fairing is adjustable so that the position may be adjusted in relation to the back fuselage position. In cruising position, the front end of the fairing 10 is lifted (seen in figure 1) while the back end stays in connection to the back fuselage 4. This eliminates the aerodynamic discontinuity which is formed on top of the fuselage 2 in this position. By lifting the front end of the fairing 10, the upper surface of the front fuselage 3 and the fairing forms aerodynami- cally continued structure, which creates fewer vertical forces to the plane. In runway position, i.e. when the back fuselage is pivoted, the front end of the fairing 10 may be lowered so that the whole fairing 10 is engaged with the top surface of the back fuselage 4. The fairing 10 may be automatically adjusted in relation to the back fuselage 4 angle a, or it may be adjusted manually. The fairing may be seen in figure 4, where the seaplane is in cruising position and the fairing, the top part of it, is lifted. The front fuselage 3 and the back fuselage 4 are each watertight structures. Thus, when the seaplane is in the runway position, the water cannot enter inside the fuselage sections. The water may enter the space between the fuselage sections, but it will drain during the liftoff. Thus, there is no need for sealing the whole fuselage, especially the connection between the fuselage sections.

In an embodiment, the seaplane is a flying boat.

Although the invention has been the described in conjunction with a certain type of device, it should be understood that the invention is not limited to any certain type of device. While the present inventions have been described in connection with a number of exemplary embodiments, and implementations, the present inventions are not so limited, but rather cover various modifications, and equivalent arrangements, which fall within the purview of prospective claims.