The present invention relates to an aircraft with rear mounted engines, in which the engines are mounted at the horizontal tail plane of the aircraft. Background of the invention

The rear mounted installation of the engines in an aircraft is preferred in certain cases, for instance, when installing ultra high bypass ratio engines, propeller engines and/or contra rotating open rotor (CROR) engines. In these cases, due to the high diameter of the engines and/or the noise they produce, or just because it is preferred to have a clean wing, a rear mounted installation is sometimes preferred. In these aircraft, the horizontal tail is usually moved to the top of the vertical tail, this configuration being known as a "T-tasi".

The mounting of the engines to the aircraft is usually achieved via conventional huge pylons on the rear portion of the fuselage of the aircraft. These pylons do not perform any other function apart from sustaining the engines. Some proposals, as the ones disclosed in GB 2445555 A or WO 98/21092 A1 , provide aircraft in which the engines are located towards the aft of the aircraft, close to the tail end.

GB 1 1 12924, referred to Improvements in or relating to Aircraft ^" , discloses an aircraft including a main wing having trailing edge flaps guided in the wing for chordwise motion relative thereto, and a tail assembly having horizontal and vertical control surfaces and at least two power driven propellers supported by the tail assembly, the propellers being positioned on both sides of the longitudinal axis of the aircraft in the vicinity of the rear of the wing so that in the rearwardly deflected position of the flaps the rear edges of the flaps are closely adjacent the lower part of the propeller-disk area, said horizontal and vertical control surfaces being positioned so that the slip stream of the propellers sweeps over said surfaces.

These prior art configurations provide different aircraft in which the engines are mounted in the rear part of the aircraft. However, it is desirable to have an aircraft with rear mounted engines and with control surfaces located at the rear part of the aircraft which can provide an improved efficiency of the control surfaces.

Summary of the invention

Therefore, the object of the invention is to provide an aircraft with rear mounted engines that can provide an improved efficiency of the control surfaces.

The invention provides an aircraft with rear mounted engines, comprising a vertical tail plane and a horizontal tail plane, in which the engines are mounted on top of the horizontal tail plane, such that the horizontal tail plane comprises an inner fixed part attached to the fuselage of the aircraft, the inner fixed part comprising an elevator, and two outer movable parts, each one of the outer movable parts being located at each side end of the horizontal tail plane which is furthest away from the fuselage of the aircraft, such that both the inner fixed part and the outer movable parts are at least partially subjected to the flow coming from the engines when they are in use.

The configuration of the horizontal tail plane, in conjunction with the fact that the engines are located on top of the horizontal tail plane, allows an improved efficiency of the control surfaces located at the rear part of the aircraft.

In effect, with this configuration the elevator and the movable parts of the horizontal tail palne are blown with flow coming from the engines, so the aircraft can be trimmed in an improved way, reducing the drag considerably. This effect can be specially improved during take-off and landing.

Besides that, by positioning the engines on top of the horizontal tail plane of the aircraft, when it rotates for take-off or landing the risk of impact of the engines with the ground is eliminated. This problem is particularly important for aircraft with long fuselage and engines at the back. Other advantageous embodiments will be described in the dependent claims. Brief description of the drawings For a more complete understanding of the present invention, it will be described below in greater detail, making reference to the attached drawings, in which:

Figure 1 is a front perspective view of an aircraft of the invention.

Figure 2 is a rear perspective view of an aircraft of the invention. Figure 3 is a front view of an aircraft of the invention.

Figure 4 A is a plan view of an aircraft of the invention.

Figure 4B shows a detail of the rear part of the aircraft of figure 4A.

Figure 5A is a side view of an aircraft of the invention.

Figure 5B shows a detail of the rear part of the aircraft of figure 5A. Figure 6 is a rear perspective view of a second aircraft of the invention.

Figure 7 A is a plan view of a second aircraft of the invention.

Figure 7B shows a detail of the rear part of the aircraft of figure 7A.

Figure 8A is a side view of a second aircraft of the invention.

Figure 8B shows a detail of the rear part of the aircraft of figure 8A. Figure 9 shows a detail of the rear part of the perspective view of the aircraft of figure 6, in which the outer part of the HTP is in a different position.

Figure 10 shows a detail of the rear part of the aircraft of figure 6, in which the outer part of the HTP is in a different position.

Figure 1 1 shows a detail of the rear part of the aircraft of figure 6, with the flow coming from the engines. Figure 12 shows a detail of the rear part of the aircraft of figure 1 , with a fairing in the gap between the inner and outer part of the horizontal tail plane.

Detailed description of the invention

The figures show two embodiments of aircraft of the invention: a first aircraft 1 (figures 1 to 5B and figure 12) and a second aircraft V (figures 6 to 1 1 ).

In both aircraft 1 , 1 ' the engines 2, 2 ^' are mounted in its rear part. The aircraft 1 , 1 ' have a single vertical tail plane (VTP) 3 and a horizontal tail plane (HTP) 4, and the engines 2, 2' are mounted on top of the horizontal tail plane 4, as can be seen in all the figures.

The horizontal tail plane 4 comprises: an inner fixed part 5 attached to the fuselage 8 of the aircraft 1 , 1 ', the inner fixed part 5 comprising an elevator 7, and two outer movable parts 6, each one of the outer movable parts 6 being located at each side end of the horizontal tail plane 4 which is furthest away from the fuselage 8 of the aircraft 1 , 1 ', In this way both the inner fixed part 5 and the outer movable parts 6 are at least partially subjected to the flow coming from the engines 2, 2' when they are in use, as can be seen in figure 1 1.

The inner part 5 must be rigid enough to support the weight of the engine 2, 2 ^' . This is also favoured if there is no cut-out in the fuselage 8 and hence there is less loss of rigidity as normally does in current HTP configurations.

The outer part 6 can be attached to the inner part 5 at the rear spar of the inner part torsion box through a shaft 9 that can be used as a pivot to rotate the outer part 6. The shaft 9, that protrudes from the inner part 5, can be perpendicular to the fuselage 8 (see figures 9 and 10). It can also have other angles with respect to the fuselage 8. The inner part 5 can be attached to the fuselage 8 through a kind of piano junction as done for instance in the ATR wing.

This configuration of the HTP 4 also allows having a simple VTP 3 instead of the current T- tail that most of the configurations with rear mounted engines have, which has a considerable reduction on VTP weight.

The engines 2, 2' can be attached to the top surface of the horizontal tail plane 4 by means of pylons, in a similar way as done when the engines 2, 2' are attached to the wings in other aircraft configurations.

The vertical tail plane 3 can be in a forward position with respect to the horizontal tail plane 4, which can be an important feature. In effect, for CROR engines where certification authorities require to protect the engine to engine debris, the VTP 3 can be used as a shielding not penalising so much the configuration since the VTP 3 is decoupled from the HTP 4. So if the VTP 3 is placed in a forward position with respect to the HTP 4, this HTP 4 remains at its optimal position. This is not the case if the tail arrangement is a T-tail where the HTP is on top of the VTP.

The engines 2, 2 ^' used in the aircraft 1 , 1 ' of the invention can be ultra high bypass ratio engines, propeller engines or contra rotating open rotor engines.

The outer movable parts 6 of the horizontal tail plane 4 and the elevator 7 of the fixed part 5 of the horizontal tail plane 4 can be moved by means of actuators. Since the elevator 7 is blown, it can achieve larger maximum lift force before stall and this can reduce the take-off field length and reduce landing speed. But trimming the aircraft 1 , 1 ' with only elevator 7 is very draggy.

As a complement of the elevator 7 are the outer parts 6 which are at least partially blown and can improve much more the effect on take-off and landing. But on the other hand they can be used to trim the aircraft 1 , 1 ' much better than with the elevator 7, reducing considerably the drag. To achieve this, the possible gap between the inner part 5 and the outer part 6 must be minimised while the outer part 6 is rotating. To cover this gap a fairing 10 is provided, which can be embedded in the engine nacelle 1 1 . Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering this as limited by these embodiments, but by the contents of the following claims.