Aeronautics and astronautics – Aircraft – heavier-than-air – Airplane and helicopter sustained
Reexamination Certificate
1999-10-01
2001-07-17
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Airplane and helicopter sustained
C244S056000, C244S066000, C244S130000
Reexamination Certificate
active
06260793
ABSTRACT:
The invention relates to improvements, particularly with regard to the aerodynamics, made to a convertible aircraft with tilting rotors which is capable of operating in aeroplane mode and in helicopter mode, and comprising at least one fuselage, a fixed wing system comprising at least two wings extending laterally on either side of the fuselage and, in helicopter mode, a rotating wing system comprising at least two rotors, each having a substantially vertical shaft erected above a respective fixed wing and mounted so that the shaft can pivot on this fixed wing about a pivot axis arranged transversely to the fuselage, the shaft pivoting towards the front of this fixed wing in order to switch from helicopter mode to aeroplane mode, in which case the rotors act as propellers.
The invention more specifically relates to a convertible aircraft with tilting rotors of the type in which the shaft of each rotor is driven in rotation about itself by a front reduction gear unit of one respectively of two transmissions, each also having a rear reduction gear unit linked to the corresponding front reduction gear unit as well as to one respectively of two engines, each supported respectively on one of the two fixed wings, and to an inter-connecting shaft linking the two transmissions so that the two rotors can be driven in rotation by either of the two engines in the event that the other engine fails, the shaft of each rotor, the corresponding transmission and the corresponding engine being housed respectively in one of two articulated pods or nacelles, each comprising a front part which pivots about the pivot axis on a fixed rear part fixed respectively to one of the two fixed wings and in which the corresponding engine and at least a part of the rear reduction gear unit of the corresponding transmission are housed, the front reduction gear unit thereof and corresponding rotor shaft being housed in the pivoting front part of the pod and being mounted so as to pivot with said front part relative to said rear part and said corresponding wing.
In a convertible aircraft with tilting rotors of the type outlined above, it is extremely desirable, not to say indispensable, to provide the greatest aerodynamic continuity possible between the two parts, one articulated on the other, of each pod, regardless of the flight configuration (aeroplane mode or helicopter mode) and it is necessary to avoid having too many orifices or discontinuities between the cowlings of the pivoting front part and the stationary rear part of each pod when the corresponding rotor is in helicopter mode and more particularly in aeroplane mode when the aircraft reaches much higher speeds.
The basic problem underlying the invention is that of improving convertible aircraft With tilting rotors of the type described above so as to guarantee an aerodynamic continuity in the different flight configurations adopted by each articulated pod in order to reduce turbulence and other aerodynamic problems and to prevent foreign bodies from getting into orifices or discontinuities in and/or between the cowlings of the two articulated parts of each pod.
Accordingly, one objective of the invention is to improve convertible aircraft with tilting rotors of the type outlined above so that the discontinuities and/or orifices between the cowlings of the two articulated parts of each pod can be substantially closed off using a small number of moving components, thereby enabling the aerodynamic continuity to be substantially preserved and/or reestablished without adding to the mechanical complexity, which would necessarily lead to an increase in mass and cost, and in a manner more conducive to meeting various practical requirements than solutions proposed in the prior art.
To this end, the invention proposes that the pivoting front part of the pod should have a bottom fairing in aeroplane mode, which is extended towards the rear and towards the interior of the rear stationary part of the pod by means of a curved cowl, the concave aspect of which is turned towards the pivot axis and at least partially curved and axisymmetric (of revolution) about this pivot axis, so that when said pivoting front part of the pod is pivoted into helicopter mode, the curved cowl will substantially provide aerodynamic continuity between the bottom fairing, arranged towards the front of the pivoting front part of the pod in helicopter mode and the front of a bottom fairing of the rear stationary part of the pod. This will duly ensure a substantially geometric continuity of the bottom face of the two articulated parts of each pod both in aeroplane mode and in helicopter mode, which will promote aerodynamic continuity along this bottom face.
Further, to advantage, a swivel-mounted flap is mounted by a front edge so as to pivot about a pivot pin substantially parallel with the pivot axis on a rear portion of a top fairing of the pivoting front part of the pod in aeroplane mode so that this swivel-mounted flap will provide substantial geometric and hence aerodynamic continuity on the pod between said rear portion of the top fairing of said pivoting front part and a front edge of a top fairing of the stationary rear part of the pod in aeroplane mode, whereas, when converting from aeroplane mode to helicopter mode, the swivel-mounted flap is displaced, at least at its rear edge, on said top fairing of said stationary rear part of the pod, against which top fairing this swivel-mounted flap is applied in helicopter mode. As a result, in aeroplane mode, this swivel-mounted flap closes off the free space between the rear edge of the top fairing of the pivoting front part of the pod and the front edge of the top fairing of the stationary rear part of the pod, whereas in helicopter mode, these two respective rear and front edges of the top fairings of the respective pivoting front and stationary rear parts of the pod may be substantially contiguous, practically the entire surface of the swivel-mounted flap being applied against the top fairing of the stationary rear part of the pod, thereby producing geometric and hence aerodynamic continuity along the top face of the two pod parts, in aeroplane mode and helicopter mode alike, due to the pivoting action of this unique flap on the pivoting front part of the pod.
Advantageously, the swivel-mounted flap is retained against the top fairing of the stationary rear part of the pod due to the fact that the swivel-mounted flap is permanently elastically biassed and/or retained by at least one stop against said top fairing of said stationary rear part of the pod.
With regard to the curved cowl of the bottom fairing of the pivoting front part of the pod, this curved cowl may advantageously comprise at least one part which is in the shape of a cylinder portion, the axis of which coincides with the pivot axis, in particular a central part, and/or at least one part of a spherical shape centred on said pivot axis and in particular the lateral parts.
In order to simplify the design of the pivot pin enabling the front pod part and the corresponding rotor shaft as well as the front reduction gear unit of the corresponding transmission to pivot, in supporting the pivot pin on either side of said pivoting front part of the pod, and whilst avoiding an overhanging mounting yet retaining good aerodynamic continuity, at least in aeroplane mode, the pivoting front part of the pod advantageously pivots between two inner sides of two fixed front lateral extensions of said stationary rear part of the pod, each fixed front lateral extension being delimited at the front by a front face, preferably at least in part substantially curved and axisymmetric about the pivot axis and covered, in aeroplane mode, by a rear face, preferably of a substantially matching shape, on one respectively of two front lateral portions of said pivoting front part of the pod.
In one simple embodiment, the inner sides are flat sides, substantially perpendicular to the pivot axis and between which a central rear portion of said pivoting front part of the pod is pivotally mounted.
To guara
Balayn Frederic
Magre Eric
Best Christian M.
Eurocopter
Jordan Charles T.
Piper Marbury Rudnick & Wolfe
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