FR2629045A1 - Light aircraft structural layout - has two main bulkheads interconnected by main bream allowing rearward positioning of engine and wing spar - Google Patents

Abstract

The light aircraft has a primary structure consisting of a front (11) and rear (10) transverse bulkhead joined axially by a main channel section beam (12) e.g. fabricated in reinforced fibre composite materials. The engine is mounted centrally in the fuselage suspended from the rear bulkhead (10). The propeller is driven by a shaft (13) and reduction gearbox (14) mounted on the forward bulkhead (11). The main landing gear is mounted on the rear bulkhead and retracts into the rear fuselage space. The front. wheel retracts under the main axial beam below the driveshaft (13). The main wing spar is also attached to the rear bulkhead and the pilot and passengers sit in a cockpit between the two bulkheads (11,10). ADVANTAGE - The structural layout improved safety and visibility for the pilot by allowing a slender nose to be used with a rearward location of the wing. (20pp Dwg.No.15/15)

Description

FRENCH REPUBLIC Publication no .: 2,629,045 (to be used only for

  the NATIONAL INSTITUTE reproduction orders)

INDUSTRIAL PROPERTY

  OF INDUSTRIAL PROPERTY National registration number: 88 04049 PARIS

  (Int CI4: B 64 C 1/06, 1/26, 25/04; B 64 D 29/04.

  A1 PATENT APPLICATION

  Date of filing: March 22, 1988. (D Applicant (s): MOUNIER-POULATFrancois. FR.

) Priority

    Inventor (s): François Mounier-Poulat.

  4 Date of public availability of the

  application: BOPI "Patents" n 39 of September 29, 1989.

  (Y References to other national documents appearing

  rentés Q Holder (s): _ Agent (s) Light aircraft architecture with central engine.

  (5 Light aircraft architecture with central engine and propeller

pulsating or traction.

  The invention relates to an architecture allowing the use of a central engine by grouping in a compact volume 2 the connections between passenger compartment, powertrain, wing and

landing gear.

  It is characterized by a structure formed by two transverse partitions limiting the passenger compartment, 10 and 11 connected by q- a central beam 12. On the rear partition 10 are fixed

  the wing, the engine, and the landing gear mechanism. The hour - - -

  lice tractor is mounted on the output shaft of a reducer I 14, fix. on the partition 11 and driven by a shaft 13 located in the central beam. The retractable undercarriage in the

  Ut fuselage is independent of the wing.

  û 'Aim of the invention: simplification of construction in the case of using a central motor, improvement of comfort and

of security.

  V, De JilD sale of the booklets l rl'MPRIMERIE NATIONALE, ': 7. rue de la Convention - 75732 PARIS CEDEX 15 State of the art:

  Conventionally, the architecture of the light aircraft corresponds

  Most often lays one of the following two provisions: Fremiere disposition (see figure 1): The "passenger compartment" has two or four seats, -repere 1- (to simplify the presentation, the explanatory figures will only be made in the case two places) is located in the central position, the engine 2 being at the front of the aircraft and driving a towing propeller 4. The fuselage 3 of frustoconical shape in its rear part is equipped with a tailplane whose role is to stabilize i 'airplane in pitch (elevators), and yaw (rudder). The wing 5 which performs the vertical lift function is arranged longitudinally so that its "aerodynamic focus" is close to the center of gravity of the assembly, generally a little behind it. The landing gear is generally composed of a so-called main gear 6 comprising two wheels arranged symmetrically with respect to the plane of symmetry of the aircraft and a little behind the center of gravity, often retractable in the thickness of the wing by pivoting around articulation axes located in the wing, and a front wheel 7 located in the front part of the fuselage and

  often retractable in this one.

  Second arrangement (see FIG. 2): In this variant, the motor 2 is in the central position, the passengers in the front position I and the propeller 4 at the rear end of the fuselage, driven by a drive shaft 8. The position longitudinal of the wing is not changed from the center of

gravity of the whole.

  Preliminal remark: The case of "4 places" can be naturally extrapolated from the case "2 places" by lengthening the passenger compartment, we will only represent in the figures

the case of the two-seater side by side.

Description of the Invention:

  The main structure is characterized by 3 elements which cooperate to ensure the main connections between the different functions: _ the passenger compartment, _ the engine unit, the propeller, or propeller, the wing, _ the landing gear,

the fuselage empenne.

  These three structural elements (see FIG. 3) are: a central partition 10 located behind the passenger compartment, approximately perpendicular to the longitudinal axis of the aircraft and perpendicular to its plane of symmetry, a front partition 11 substantially parallel to the partition 10, a central beam 12 connecting these two partitions, of rectangular or trapezoidal section widened downwards. The whole of this basic structure 10 + 11 + 12 is made so as to withstand the loads and constraints corresponding to the use of the device while guaranteeing good rigidity. By way of nonlimiting examples, the following embodiments may be cited: the assembly 10 + 11 + 12 is made of composite materials

  sandwich type (known combinations of aaDellie nest.

  foams or balsa between thin sheets of light metal, or glass-fiber resin laminate, or other kevlar, carbon tilers, etc.). cloIns 10 etl can include a tubular reinforcement (flat trellis) possibly reinforced by sandwich materlaux, and the central beam can be

  made of sheets and profiles of iegers alloys.

  These variants are in the known field of art.

  Motor 2 is located behind the central bulkhead. fig. 4.

  In the case where the aircraft uses a propeller propeller at the front end of the fuselage, its movement output is on the front. The engine torque is transported by a transmission shaft 13 iongituainai has inside the central beam 12 and connected to a reducer 14 fixed on the structural partition before 1Il. The reducer produced according to a known technique v gears, smooth, striated or notched belts, .chalne silent type * HYVO ", etc.) comprises a propeller output shaft parallel to the input shaft 51,1 'spacing between these two shafts being such as to allow sufficient ground clearance to be obtained from the propeller blades (4) during

taxiing on the ground.

  The seats 15 are arranged symmetrically with respect to the central beam 12 which can advantageously serve as an armrest and be of an evolving section to promote the ergonomics of the passenger compartment. The fuselage part comprised between the two structural partitions, and in particular the part lower than the main torque seen from above, serves as reinforcement for the structural assembly 10 + 11 + 12, and ae

  passenger protection, as shown in Figure 5.

  It is advantageously made of materials capable of great impact resistance and great rigidity; for example a working wall made of sandwich materials is well suited; the filling of these sandwich floor fillings can be of variable thickness to optimize their protective role and

the ergonomics of the passenger compartment.

  All the partitions 10 and 11, the central beam 12 (Figures 3,4 and 5) and the outer walls thus constitute a structural nacelle acting as a cabin and on which are fixed: _ the power unit: .motor 2 transmission 13, reducer 14 and propeller, _ the landing gear, described below, _ the wing 5,

the rear part of the fuselage.

  The engine and the rear part of the fuselage, C which can be produced according to known techniques, either in working covering, or with a lattice structure and covered covering), are fixed on the central partition. The engine can be fixed to the central wall, for example by a tubular frame, as is usually the case in conventional assemblies. The front engine mounts can be

  fixed on or very close to the central partition.

  In the case of use of rear propellant propeller, there is no longer a re-reactor nor a propeller at the front end. No propeller shaft in the central beam: its engine power is transmitted to the rear propeller. by a drive shaft 8 driven by 1harriere or engine

as in the diagram in Figure 2.

  FIG. 6 shows a layout of the connections between engine and structure which is particularly advantageous in the case of a front propeller, and which is part of the invention. In this arrangement, the engine assembly 2 is supported at three points, two of these points being located on either side of the engine at 16 and 17. The crankshaft at the engine carries at its front end a flywheel 18; this flywheel being disposed in a casing 19 which may contain a declutching mechanism (common arrangement in automotive technology) and which has a lower extension 20 situated approximately in the vertical plane containing the axis of the crankshaft and which has at its front end an articulation fixing 'a known type, silentbloc or other, 21, which plays the role of the trolsieme engine attachment point. This trolsleeme attachment point can be located inside the central beam 12. The other two engine supports, 16 and 17, are connected as shown in FIG. 7 to the central bulkhead 10, each respectively by a trelllls structure in pyramid shape, 22 and 23. The connection between the rear part of the fuselage and the central bulkhead is carried out in a non-original way, and known in aeronautical construction, for example by a lattice structure, or by the external working coating, or a combination of the two The wing, the flexural strength of which is mainly ensured by its main spar, according to a technique widely used in aircraft construction, is fixed to the main bulkhead of structure: O. FIGS. 8 and 9 illustrate two possible variants: the extensions of the longitudinal beams of the aisle can be integrated into the main partition (fig. 8), or else, the longitudinal beams can be

  fixed to fittings 26 integral with the partition 10, fig. 9.

  The secondary attachment of the wing at the level of a false rear spar (known conventional arrangement) can be connected either to the working fuselage wall, or to the trelllls structure connecting the main bulkhead to the part

  fuselage back, still on engine support frame.

  The main landing gear is attached to the main bulkhead; the wheel / ground contact forces are introduced into the main structure only at the level of this partition 10; for example in a simple realization of landing gear using a flexible transverse blade, the blade connected to the wheels would be supported on two supports directly fixed on the main partition. This example has no other purpose than to show that the structure of the nacelle-cockpit makes it possible to receive directly the fixing of a non-retractable simpie landing gear. However, the design of this structure according to the invention makes it possible to associate therewith the advantageous original reaiisation described below, FIGS. 10 and following and which forms part of the invention. Each wheel 30 is mounted on a spindle axle rigidly connected to a Dras 31 pivoting around a-axis xx 'which is part of a support 32. this latter being able to' itself pivot around a second axis yy close to the main partition 10 and perpendicular to the plane of symmetry of the aircraft. The axes xx 'corresponding to each wheel are parallel to each other and parallel to the plane of symmetry of the airplane. The bearings dCe plvotement of the mobile support 32 around the axis yy 'spotted at 33 and 34 are fixed on the structural partition and can be more than two. The mobile support 32 (see figure it) comprises a part 35, dlrlgee towards the low when the landing gear is in the extended position, and on which are arranged two articulations 36 and 37. On the other hand, each wheel support arm 31 has at its lower extremlté a part offset downwards and inwards , 39, as shown in FIG. 11, and which contains a joint 40. The joints 36 and 40 are connected elastically; the elastic element symbolized in FIG. 11 by a spring ensures the suspension function of the half landing gear. The offsets of the articulation 40 relative, on the one hand to the wheel axle, (b), and on the other hand to the axis of the suspension arm, (a), are such that the force of tension between the joints 36 and 40 is opposed to the bending force of the arms 31, which can then be reallsatlon lighter and more economical. During the landing gear retraction operation, a rotational movement of the suspension arms around the axes xx is controlled. This rotation of an angle (a), see FIG. 12, brings the two wheels of the main train closer together; It can be operated by one or more hydraulic cylinders such

  as for example 42 and 43 directly commanding the Dras 31.

  It can also be carried out, on each side, by a jack included in the connection between the two joints 36 and 40; this connection then taking the form of a telescopic and elastic connecting rod as shown in Figure 13 which shows between the connections 36 and 40: a telescopic cylinder 41, the rod of which penetrates into the cylinder when a pressurized fluid is introduced in 42, and leaves when the cylinder is not under pressure, pushed by a spring 43, this cylinder being mounted in series with an elastic suspension element 44, which may be a metal or elastomeric spring. When the link 36-40 does not include a rotation control verln (a) around xx-, it can keep the arrangement of FIG. 10; the room of the verln not being supplied; it can also be achieved by connecting the suspension spring 44 to the articulation 36 by one or more flexible cables which accompany the movement to the arm 31 during the return of the landing gear. The rotation of angle ca) around the axis xx- constitutes a first phase of the retraction operation: it is followed by a second phase which is a rotation at an angle (b) around the axis yy of support 32,

  the two phases of rotation being able to overlap.

  After the retraction operation, the whole landing gear is in the arrangement of Figure 14. The angle rotation (b) around the axis yy'du support 32 can be performed by means of hydraulic cylinder or any other known device, the locking in the low position of the support 2 is ensured by a conventional compass device on the landing gear, not shown for lightening

the figures.

  The front structural partition may optionally serve as a support for an auxiliary lifting and stabilizing surface as used in aircraft of the so-called "duck" formula; the connection between this surface and the partition 11 can be

  similar to that of the main wing and bulkhead 10.

  I It can also have a non-planar surface while

  ensuring the same structure function.

?

BENEFITS PROVIDED BY THE INVENTION

  _ Slmpllclté and compactness of a single structure, rlgide and light, providing a good protection to the passengers and receiving directly the principal components of the aircraft. Comfort of the passengers by the extended position authorized by the vlsibillte which is the consequence of: the tightness of the front part of the fuselage, (no engine bulk at the front), 10. the advanced position relative to the wing ; the lower noise level of the rear engine; In the event of a forward hitch, it is possible to keep the advantages of the propeller at the same time as the advantages of centering the central engine; - - safety by visual surveillance on the ground, - blowing of the tail surfaces allowing better control of the aircraft, - protection of the engine against these projections of the wheels, frequent causes of damage, in the case of propellers propellants,

  - increased ground clearance of the landing heiice -

  smoothing, (known problem with propelling propellers>, - increased safety in the event of an emergency evacuation in flight with a parachute, Whatever the position of the propeller, front or rear: Safe by improving the front visibility to the fact of the the front of the fuselage allowed by the size of the reducer smaller than that of the engine, Improvement of aerodynamic performance by reduction of the aisle / fuselage interaction tralnee due to the median position of the wing, position allowed by the design particular of the main landing gear independent of the wing: _ Simplification of construction of the wing, for the same

ra i son.

  _ Simplification of the connection: main landing gear / structure, _ In the case of a rear propeller, increased safety by design of the passenger compartment with central beam

and front structural bulkhead.

Claims (3)

REVENDI CATI ONS.   1- Light aircraft structural assembly characterized in that the passenger compartment consists of three parts: b - a so-called central or main partition 10 behind this compartment, - a front partition 11, at the front end of this compartment , - a hollow central beam 12, connecting these two 11 partitions which can separate the left and right seats and-1 serve as an armrest; this set (10) + (11) + (12) being possibly reinforced by the fuselage walls in the parts where it is not open for access or visibility, so as to participate in the resumption of efforts , rigidity, and passenger protection; the rear bulkhead 10 being characterized by the fact that the following are fixed to it: - the main spar of the wing 5. where the flanges can either be bolted to terraces fixed to the partition, or else be an integral part of the structure said partition, - motor 2 or its support frame,   - the rear part of the fuselage or its supporting frame.   - possibly the main landing gear; _, 2- An assembly according to claim 1 characterized in that the motor 2 being disposed behind the main partition 10, its movement output is located on the front substantially in the plane this symmetry that the aircraft; the driving shaft (crankshaft) is extended to the front partition 11 by a transmission shaft 13, which can be in several sections, located inside the beam 12 connecting the two partitions of the main structure, and which drives a reducer 14 fixed on the front bulkhead, the latter being extended on the front 3 f by a propeller shaft 50, and having the function: - to drive the propeller 4 - to adapt the propeller speed & engine speed, - adapt the position of the propeller axis to the operating constraints (ground clearance); 4 <. the engine crankshaft being equipped with a flywheel 18 which can be part of a clutch mechanism making it possible to cut the engine-propeller connection, or of a hydraulic or powder coupler; the connection by the clutch mechanism or the coupler which can be separated from the flywheel of the engine, and in particular postponed   At the front end of the transmission 13.   _ 3- assembly according to claim 2 characterized in that the flywheel 18 and optionally the clutch mechanism or the coupler are contained in a housing 19 which has a lower extension 20 directed on the front and at the end which is placed a front engine support, 21, approximately in the plane of symmetry of the aircraft; this support 21 can be internal to the central beam 12 of the structure defined in I and fixed on it, and cooperate with two lateral supports of the engine, 16 and 17, each of these supports being connected to the central partition; the connection between this central partition 10 and the lateral supports of the engine, 16 and 17, is constituted by two pyramidal trellis elements, 22 and 23, the bases of which are rigidly fixed to the main partition 10, and the vertices of which converge   to the elastic motor supports 16 and 17.   4- The assembly of claim 1 characterized in that the motor 2 drives a propeller 4 located at one rear of the fuselage.   - Assembly according to any one of the claims   i to 4 characterized in that the front part of the central structural beam 12 is used to house, in the retracted position, the front landing gear, (strut and wheel); the joint may be on the front bulkhead, in the central beam, or on the housing reducer.   _ 6- assembly according to claim I characterized in that fixed on the rear bulkhead 10 the main landing gear, is formed by the combination of: - a support 32, pivoting during the operation of said landing gear, around d '' a horizontal transverse axis on bearings integral with the main partition 10, - two wheel-carrier suspension arms 31 articulated on the preceding support 32 around two parallel axes, approximately horizontal when the landing gear is in the taxiing position on the ground , and perpendicular to the transverse pivot axis of said support, and arranged symmetrically with respect to the plane of plane symmetry.   The two wheel carrier arms each pivoting around one of these parallel axes to ensure the suspension travel; each of the wheel arms 31 has an articulation 40 offset downward relative to the wheel axle and inwardly relative to the suspension arm and on which is fixed an elastic connection connected to the suspension spring; the position of the center of this articulation 40 being chosen so as to minimize the bending forces to which the suspension arm is subjected; the other end 36 of this elastic connection being articulated at a point of the pivoting support 32 cited in 13; this elastic connection can be achieved by a telescopic and elastic rod containing a hydraulic cylinder used during the retraction operation of the landing gear. The landing gear retraction movement combines the two previous rotations so that the arms read wheel carrier 31 in the retracted position are retracted into the fuselage along the lower part of the engine in the case of an inline engine , or below the engine in the   conventional light aircraft engine & flat cylinders.   7- assembly according to claim 1 characterized in that the propeller being propellant, the structural partition pianne 11, à1 'before the cockpit is replaced by Moon non-planar surface having the same structure raole.   _ 8- An assembly according to any of the claims   previous characterized in that the front structural partition 11 serves as a support for a stabilizing surface as used in aircraft of formula called "duck" the connection between this surface and the front partition 11 can be similar to that of the wing and of the partition main 10. 1/9 2629045   si 2/9 13 3 fihi Il '3/9 IIi // 2 4/9 OI i0 / 9 c lj 7/9 -2629045 7/9 42 43 kfAit / r L__ I ' 4.I 4I I tl // - 8/9 3k 6/6 M6z9z