Patent Application
20110168836
The present invention relates to an aircraft with propeller engines located at its rear part and more particularly to the pylons supporting said engines.
There are known commercial aircrafts (CBA vector 123, SARA, AVANTI, 7J7) powered with propeller engines located in the rear part of the aircraft supported by the fuselage by means of non-moving pylons.
One of the problems raised by this aircraft configuration is related to failure events such as a PBR (“Propeller Blade Release”) i.e. an event where a blade of one of the propeller engines comes off and hits the fuselage, a UERF (Uncontained Engine Rotor Failure), or any other “Large Damage” event. The design of said rear fuselage shall therefore take into account such events and guarantee its capability for maintaining stability and proceed to a safe landing, i.e. shall be an impact resistant and damage tolerant fuselage.
In the prior art, non-moving pylons attached to the rear part of the aircraft fuselage are basically made with metallic materials.
As it is well known, weight is a fundamental aspect in the aeronautic industry and therefore there is a current trends to use composite material instead metallic material even for primary structures.
The composite materials that are most used in the aeronautical industry consist of fibers or fiber bundles embedded in a matrix of thermosetting or thermoplastic resin, in the form of a preimpregnated or “prepreg” material. Its main advantages refer to:
In this framework, the present invention is addressed to the demand of non-moving engine supporting pylons made of composite materials to be attached to the rear part of an aircraft.
It is an object of the present invention to provide a supporting device made of composite materials to be attached to an aircraft fuselage part such as a non-moving pylon for an aircraft with propeller engines located at its rear part able to withstand failure events such as a PBR or an UERF event.
This and other objects are met by a device such a pylon attached to an aircraft fuselage part having a close transversal section of a curved shape comprising a skin and a plurality of frames, in which:
In a preferred embodiment, the central box has the same number of central spars than the number of interrupted intermediate frames, said central spars being located in the same fuselage section that said interrupted intermediate frames to provide them load path continuity. Hereby it is achieved a multi-spar pylon which is a fail safe for those considered failure events.
In another preferred embodiment, the attachment means comprise rows of tension fittings between, respectively, the upper and lower skins of the external boxes and the upper and lower skins of the central box with tension bolts crossing the fuselage skin; and rows of tension fittings between, respectively the lateral spars of the external boxes and the lateral spars of the central box with tension bolts crossing the fuselage skin. Hereby it is achieved an efficient piano-type union between the central and the lateral boxes that allows the full continuity of the fuselage skin.
In another preferred embodiment, the attachment means also comprise attachment fittings with bolts between the interrupted intermediate frames and the central spars of the central box. Hereby it is achieved an efficient union between the central box and the interrupted frames that allows the full transfer of loads between them.
In another preferred embodiment, the device is a pylon located in an aircraft rear fuselage supporting an aircraft propulsion system with propeller blades, having the central box within the mid fuselage section.
Other characteristics and advantages of the present invention will be clear from the following detailed description of embodiments illustrative of its object in relation to the attached figures.
In an aircraft 11 having a propulsion system 13 with propeller blades 15 attached to the rear fuselage 17 by means of an upstream pylon 19, the rear fuselage 17 shall be an impact resistant and damage tolerant fuselage.
The pylon 19 is a high loaded structure due to the big distance between the propulsion means 13 and the fuselage 17. Particularly, the interface between the fuselage 17 and the pylon 19 is affected by high torsional and bending moments and, in cases of crash landing and dynamic landing, to high thrust and vertical loads. On the other hand, the pylon 19 should be a structure suitable to be replaced in cases of very different events such as damages due to disc debris events, fire, fatigue failures or engine replacements.
As illustrated in
Following
The three boxes 41, 51, 61 are configured as multi-spar boxes with upper and lower skins 43, 45; 53, 55; 63, 65. Both the lateral spars 57, 59; 67, 69 and the central spars 58; 68 of said lateral boxes 51, 61 have a C-shaped configuration.
The lateral spars 47, 49 of the central box 41 have a C-shaped configuration and the central spars 48 of the central box 41 have a double T-shaped configuration (a suitable configuration for providing continuity to the intermediate frames 33′ interrupted by the central box 41).
The central box 41 is joined to the external boxes 51, 61 by means of:
The central box 41 is therefore joined to the external boxes 51, 61 by means of a so-called piano union.
The union between the central box 41 and the intermediate frames 33′ interrupted by the pylon 19 is made as shown in
In the embodiment just described the external boxes 51, 61 have C-shaped spars but the skilled man will readily understand that the invention is also applicable to boxes with Double T-shaped spars, X-shaped spars, Double Lambda-shaped spars, Double Pi-shaped spars, W-shaped spars, Omega-shaped spars, or even a corrugated spar box structure.
On the other hand, it can be noted that its central spars 58, 68 does not have any specific role in the union with the central box 41 in no-damage conditions so that its number and position depends only on dimensioning considerations regarding the external boxes 51, 61. In damage events, the mid spars have the role of closing the torsion boxes.
Regarding the central box 41, its lateral spars 47, 49 have the same C-shaped configuration than the lateral spars 57, 59; 67, 69 of the external boxes. Any other configuration of said lateral spars 47, 49 allowing a piano-type union such as Double T-shaped lateral spars, X-shaped lateral spars, Double Lambda-shaped lateral spars, Double Pi-shaped lateral spars, W-shaped lateral spars, Omega-shaped lateral spars, or even a corrugated spar box structure, will be acceptable.
The configuration of the central spars 48 in shape and position depends on the above-mentioned interrupted intermediate frames 33′ in order to provide the above-mentioned load transfer, that is, intermediate frames 33′ load continuity by means of said central spars 48.
It is considered that this structural design of the pylon 19 reinforces the rear fuselage 17 torsional strength to deal with a failure event such an event of detachment of a propeller blade 15 from an engine 13 causing the failure of a part of any of boxes 41, 51, 61 because the multi-spar structure of said boxes allows maintaining a closed box to withstand the torsion moment produced in said event.
Secondly it is considered that this structural design of the pylon 19 provides a reinforced interface with the fuselage for maintaining the aircraft stability in any failure event.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201030027 | Jan 2010 | ES | national |
