Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
AIRPLANE WITH AN AFT-FUSELAGE MOUNTED PROPULSIVE EMPENNAGE WITH INTEGRATED CONTROL SURFACES
Document Type and Number:
WIPO Patent Application WO/2017/146579
Kind Code:
A1
Abstract:
Airplane comprising a fuselage with an empennage, wherein the fuselage is provided with wings and comprises a propulsion system (6) with propellers, wherein the propulsion system is integrated with the aft-fuselage mounted empennage forming a propulsive empennage. The 'propulsive empennage' preferably comprises two ring wings (7), each forming a duct wherein each duct is provided with at least one propeller mounted in the duct. The two ring wings are mounted symmetrically on sides of the fuselage.

Inventors:
VELDHUIS LEONARDUS (NL)
VAN ARNHEM NANDO (NL)
Application Number:
PCT/NL2017/050116
Publication Date:
August 31, 2017
Filing Date:
February 24, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
UNIV DELFT TECH (NL)
International Classes:
B64C11/00; B64D27/02
Domestic Patent References:
WO2012102698A12012-08-02
Foreign References:
FR1478457A1967-04-28
DE19919626A12000-11-02
FR985498A1951-07-19
DE1481629A11969-03-20
FR2929591A12009-10-09
FR2905356A12008-03-07
US2948111A1960-08-09
FR2899200A12007-10-05
FR2899200A12007-10-05
FR1478457A1967-04-28
Attorney, Agent or Firm:
VAN BREDA, Jacques (NL)
Download PDF:
Claims:
CLAIMS

1. Airplane (1) comprising a fuselage (2) provided at its aft (3) with stabilizing features (7, 10}, and wherein the fuselage (2) is provided with wings {4, 5) and comprises a propulsion system (6) with propellers, wherein the propulsion system (6) is arranged at the aft (3) of the fuselage (2) where the propulsion system (6) is integrated with the stabilizing features (7, 10), and wherein the propulsion system (6) comprises at least one ring wing (7) forming a duct, wherein at least one propeller is mounted in the duct, characterized in that in the duct and mounted behind the at least one pro¬ peller as seen in flight direction a control vane or vanes (10) are provided.

2. Airplane according to claim 1, characterized in that the propulsion system (6) comprises two ring wings (7), each forming a duct wherein each duct is provided with at least one propeller mounted in the duct.

3. Airplane according to claim 1 or 2, characterized in that there are horizontal control vanes and vertical control vanes.

4. Airplane according to any one of claims 1 - 3, characterized in that the control vane or vanes (10) are mounted in the ring wing (7) or ring wings and span partly or wholly a region between an imaginary centre line of the ring wing or ring wings (7) up to an inner surface of the ring wing or ring wings (7) .

5. Airplane according to any one of claims 1 - 4, characterized in that the control vane or vanes (10) are integrated in the ring wing (7) so as to embody trailing edges (13) of the ring wing (7).

6· Airplane according to any one of claims 1 - 5, characterized in that the control vane or vanes (10) are deflectable .

7. Airplane according to any one of the previous claims 1 - 6, characterized in that the two ring wings (7) are mounted symmetrically on sides of the fuselage (2).

8. Airplane according to claim 7, characterized in that a space between the ring wings (7) mounted on sides of the fuselage (2) is spanned by a wing construction (9).

9. Airplane according to any one of the previous claims 1 - 8, characterized in that the ring wing (7) has leading edges (7" ' ) with morphing capability to enable providing the ring wing (7) with a geometry which is optimal to maximize duct performance for specific flight conditions.

10. Airplane according to any one of claims 1 - 9, characterized in that the leading edges {!''') of the ring wing (7) are deflectable so as to provide that an inner diameter of the ring wing (7) or ring wings is adjustable.

11. Airplane according to any one of the previous claims 2 - 10, characterized in that the ring wing or ring wings (7) are asymmetric with a lower chord that has a greater length than an upper chord of the ring wing or wings (7) .

Description:
Airplane with an aft-fuselage mounted propulsive empennage with integrated control surfaces

The invention relates to an airplane comprising a fu- selage provided at its aft with stabilizing features, wherein the fuselage is provided with wings and comprises a propulsion system with propellers.

Such an airplane configuration is commonly known from practice. Typically, such an airplane is provided with aerody- namic parts at its aft forming an empennage to provide longitudinal and lateral control and to provide stability to the aircraft. The propellers of the conventional airplane are commonly mounted on the wings, which requires a minimum height at which the wings must be mounted to the fuselage. Conversely the propeller diameter is restricted by the aircraft dimensions, which limits the effective thrust that can be provided with wings mounted propellers.

It is an object of the invention to reduce the weight of the airplane and to improve its fuel efficiency.

It is a further object of the invention to reduce the noise footprint of the airplane, both on the ground and in the fuselage interior.

It is still a further object of the invention to improve stability of the airplane in specific flight conditions and to make the aerodynamic surfaces of the airplane that provide it with stability less sensitive to aerodynamic stall.

It is still a further object of the invention to improve on safety aspects that are specific to propeller airplanes .

Yet another object of the invention is to provide the airplane with a propulsion system with propellers having comparatively high thrust output.

The invention specifically relates to an aircraft comprising a propulsion system which is arranged at the aft of the fuselage where the propulsion system is combined with the stabilizing features at the aft of the airplane. This opens the way to combine several features of the airplane that are anyway required for the airplane's functionality and safety, and enables to gain benefits, such as a reduction of the over- all weight of the airplane, a reduction of noise and an improved fuel efficiency.

FR 2 899 200 and FR 1.478.457 each disclose an airplane comprising a fuselage provided at its aft with stabiliz- ing features, wherein the fuselage is provided with wings and comprises a propulsion system with propellers, wherein the propulsion system is arranged at the aft of the fuselage where the propulsion system is integrated with the stabilizing features, and wherein the propulsion system comprises at least one ring wing forming a duct, and wherein at least one propeller is mounted in the duct. FR 1.478.457 further discloses vanes at the outer circumference of the duct.

In a first aspect of the invention in the duct and mounted behind the at least one propeller as seen in flight direction a control vane or vanes are provided. The surfaces of said vane or vanes contribute to the longitudinal and lateral control capability of the aircraft, particularly when there are horizontal control vanes and/or vertical control vanes. Suitably the propulsion system comprises two ring wings, each forming a duct wherein each duct is provided with at least one propeller mounted in the duct and the said control vane or vanes.

Beneficially the control vane or vanes are mounted in the duct or ducts behind the propeller or propellers as seen in flight direction. This particular position adds to the fuel efficiency of the plane by making use of the swirling motion of the flow behind the propeller to produce a reduced drag or thrust force on these control vanes and thereby effectively reducing the propeller swirl losses.

Furthermore, the position of the control vanes behind the propeller and the aft location of the vanes relative to the duct allows for a thrust vectoring capability of the control vanes by deflecting the propeller slipstream which results in a net force on the vanes.

The control vanes can be used as aerodynamic brakes by deflecting the said slipstream symmetrically with respect to the fuselage symmetry plane, thereby effectively reducing the need of additional aerodynamic surfaces for aerodynamic braking. This functionality enhances the capability of steep descent of the airplane which is particularly helpful in accepting the airplane for use in densely populated areas.

One further beneficial feature is that the particular position of the propeller relative to the ring wing and con- trol vanes results in a higher dynamic pressure experienced by the construction at the aft of the airplane. In normal operating condition the increased flow speed results in reduced in ¬ duced losses, whereas it further causes that the control vanes are more effective in comparison with their operating in a free stream flow. Furthermore, in the case of severe wing stall which may result in a separated wake adversely affecting the aft construction, and in the case of flow separation on this construction, the induced flow field by the propeller results in increased effectiveness of the stabilizing features of the airplane which provides enhanced stability and controllability .

In a preferred embodiment the control vane or vanes are mounted in the ring wing or ring wings and span partly or wholly a region between an imaginary centre line of the ring wing or ring wings up to an inner surface of the ring wing or ring wings .

In an alternative embodiment the control vane or vanes are integrated in the ring wing so as to embody trailing edges of the ring wing. Deflection of the vanes in this embod- iment results not only in an aerodynamic force acting on the vanes, but also in forces acting on the remainder of the ring wing. This effectively increases the aerodynamic forces acting on the aft construction of the fuselage. Accordingly the manoeuverability of the airplane in case one engine fails is maintained at a higher level than without this feature.

A further preferable feature is that the ring wing has leading edges with morphing capability to enable providing the ring wing with a geometry which is optimal to maximize duct performance for specific flight conditions.

Suitably therefore the leading edges of the ring wing are deflectable so as to provide that an inner diameter of the ring wing or ring wings is adjustable.

As mentioned the propulsion system of the airplane comprises at least one ring wing forming a duct, wherein at least one propeller is mounted in the duct. Although it is known that a propeller mounted in a duct generally increases the efficiency of the propeller, large propellers which are required for the propulsion of an airplane are generally not ducted due to the associated disadvantages in terms of flight performance including added weight of the duct and aerodynamic drag of the duct in cruise condition. Embodying the duct as a ring wing results however in a reduction of induced drag of the stabilizing features compared with conventional empennage geometries. Furthermore the presence of a so-called propeller induced pressure field can even result in a net thrust force acting on the ring wing. The combination of functions of the duct by embodying it as a ring wing providing an aerodynamic stabilizing surface, and its function as a duct for the pro- peller results in an offset of common known disadvantages. The known increased aerodynamic drag of large ducts in some flight conditions and the added weight of a duct in comparison with an unducted propulsion system is thus off-set by the advantage that the invention provides in replacing a conventional empen- nage on the aft of the airplane by a ring wing shaped duct.

Furthermore, the position of the propulsion system at the aft region of the fuselage results in a reduced noise level experienced in the cabin of the airplane due to the propulsion system being positioned in downstream direction.

Another advantage is that it is not required to add structural strength to particular zones of the fuselage which would otherwise be required in an open-rotor propulsion system at such zones of the fuselage which are susceptible to possible penetration of debris in case of a disintegrating propel- ler. The associated debris from a propeller blade failure is confined by the strengthened inner region of the duct and hence a pressurised cabin is intrinsically protected by the duct .

It is further preferable that the two ring wings are mounted symmetrically on sides of the fuselage. Since the ring wings can be mounted relatively close to the fuselage, the manoeuverability of the airplane is improved in comparison with the conventional airplane in the situation that one of the propellers and/or related propulsion systems disfunc- tions. Accordingly the required handling qualities and stability margins which are required for certification purposes can be met with lower impact on the aerodynamic sizing of the sta ¬ bilizing features of the airplane of the invention than are typically necessary in a conventional airplane configuration.

In some embodiments it may be beneficial that a space between the ring wings mounted on sides of the fuselage is spanned by a wing construction. This optional additional wing may add to the rigidity of the construction.

One further beneficial feature is that the ring wing or ring wings are asymmetric with a lower chord that has a greater length than an upper chord of the ring wing or ring wings. This improves the noise shielding particularly with reference to the ground above which the airplane flies. Addi ¬ tionally, the relative contribution of the ring wing or ring wings to the longitudinal respectively lateral stability and control of the airplane can be selected by an asymmetric upper and lower chord length of the ring wing. Similarly, the aero ¬ dynamic and noise shielding characteristics of the ring wing can be carefully selected by an asymmetric chord distribution of the ring wing or ring wings when viewed from the top.

One further beneficial feature is that the position of the propeller relative to the ground is relatively high so that when the airplane is manoeuvring on the ground safety is increased in comparison with conventional propeller airplanes.

The invention will hereinafter be further elucidated with reference to the drawing of an exemplary embodiment of an airplane according to the invention that is not limiting as to the appended claims.

In the drawing:

-figures 1A - 1C show a first embodiment of an airplane according to the invention in isometric view, side view and top view, respectively;

-figures 2A - 2D show a first exemplary embodiment of a propulsion system of the airplane according to figures 1A - 1C in detail in respectively an isometric view, a second isometric view, a rear view and a cross-sectional view according to line A - A in figure 2C;

-figure 3 shows a rear view of an exemplary second embodiment of a propulsion system of an airplane according to the invention;

-figure 4 shows a fourth exemplary embodiment of a propulsion system of an airplane according to the invention in side view.

-figure 5 shows a variation in the ring wing of the propulsion system of an airplane according to the invention;

-figure 6 shows a second embodiment of an airplane according to the invention; and

-figures 7A - 7D show a fifth exemplary embodiment of a propulsion system according to the invention in isometric view, side view, rear view and front view respectively.

Whenever in the figures the same reference numerals are applied, these numerals refer to the same parts.

With reference first to figures 1A - 1C a first em ¬ bodiment of an airplane 1 according to the invention is shown comprising a payload carrying fuselage 2 with an aft end region 3, wherein the fuselage 2 is provided with wings 4, 5 and comprises a propulsion system 6 with propellers (not shown) , and wherein the propulsion system 6 is arranged at the aft 3 of the fuselage 2 where the propulsion system 6 is combined with stabilizing features 7, 10 of the airplane. The stabilizing features are preferably embodied by the ring wing 7, and control vanes 10 as are more clearly shown in figures 2A - 2D. The entire construction can be said to form a ^propulsive empennage' .

As figure 1A - 1C show the propulsion system 6 of the airplane preferably comprises two ring wings 7, each forming a duct wherein each duct is provided with at least one propeller mounted in the duct. It is also clear that the two ring wings 7 are preferably mounted symmetrically on sides of the fuselage 2 by means of a support strut 12 , as shown in figures 2A - 2C, or by a similar structure. Through said support strut 12 or through a similar structure systems that are required to rotate the propeller and control the control vanes 10 are guided.

Figures 2A-2D provide a detailed view of one ring wing 7 of the propulsion system 6. Although the propeller is not shown in the duct formed by the ring wing 7, it is per- fectly clear for the skilled person how to construe the duct with such a propeller.

Figures 1A - 1C show that in the duct or ducts at the back of the ring wing or ring wings 7 a control vane or vanes 10 are provided. This is more clearly shown in figures 2A - 2D, which also schematically shows in figure 2D that the control vane or vanes 10 are mounted behind the propeller or propellers as seen in flight direction. A possible location of the propeller in the duct formed by the ring wing 7 is indi- cated with the striped line 11. It may be recognized that the vanes 10 can contribute to the rigidity of the structure. The central core 8 can be used to house necessary components and systems to rotate the propeller and control the control vanes 10. The embodiment of the ring wing 7 shown in figure 2A - 2D is provided with horizontal control vanes and vertical control vanes. This need not be the only option however; figure 3 shows an embodiment in which the vanes 10 are regularly distributed in the duct formed by the ring wing 7 at a mutual angle of 120°, but any other even distribution of these vanes 10 can be used.

Turning now to the embodiment of the ring wing 7 represented by the striped line shown in figure 4, this figure shows that the duct (or ducts) may be shaped asymmetrically with a lower chord 7' that has a greater length than an upper chord 1' ' of the duct or ducts. This is beneficial for reducing sound that propagates during flight towards the ground.

Figure 5 shows that leading edges 1' ' ' of the ring wing 7 may be provided with suitable morphing to provide a geometry which is optimal to maximize duct performance for spe- cific flight conditions. Accordingly it shows that the leading edges T r ' of the ring wing 7 are deflectable so as to provide that an inner diameter of the ring wing 7 or ring wings is adjustable. This is symbolized with the broken lines in figure 5, which represent that the leading edges 7' ' ' are moved in- wardly to reduce the inner diameter of the ring wing 7.

Figure 6 shows another embodiment of the airplane 1 of the invention in which a space between the ring wings 7 mounted on sides of the fuselage 2 is spanned by a wing construction 9. An alternative to that embodiment is shown in figures 7A - 7D wherein the control vane or vanes 10 are integrated in the ring wing 7 so as to embody trailing edges 13 at the rear of the ring wing 7.

Figure 7B shows with reference to an upper one of the control vanes 10 that these vanes are deflectable. Another deflection of the control vanes 10 is shown in figure 7D with the dashed lines indicating the deflected control vanes. In this figure 7D, the lower and upper control vanes are deflected in upwards direction while the two control vanes on the sides of the ring wing are deflected towards the side.

Figure 7C shows the rear of the embodiment shown in figures 7A - 7D, which shows that the trailing edge 13 of the ring wing 7 does not have to be circular.

Although the invention has been discussed in the foregoing with reference to an exemplary embodiment of the apparatus of the invention, the invention is not restricted to this particular embodiment which can be varied in many ways without departing from the invention. The discussed exemplary embodiment shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment.