Aircraft

A method of operating an aircraft (1), the method comprising:

• providing the aircraft (1) including:
• a fuselage (2) with a first longitudinal extension axis (A) between a nose (2a) and a tail portion (2b) opposite along said first longitudinal extension axis (A);
• a pair of half-wings (3) extending in a cantilever fashion from respective opposite sides of said fuselage (2) and transversely to said first longitudinal extension axis (A);
• a pair of nacelles (4);
• and
• a pair of rotors (5);
• each said rotor (5) comprising, in turn:
• a motor (6);
• a drive shaft (7) rotatable about a second axis (B);
• a hub (8) dragged, in use, into rotation by said drive shaft (7);
• a plurality of blades (9), which are articulated on said hub (8);
• said aircraft (1) further comprising a transmission (10) which transmits, in use, the power from said motor (6) to said drive shaft (7);
• said transmission (10) being a gear reducer and comprising:
• an external support casing (11);
• an input shaft (12, 12′) supported by said external support casing (11) and connected to said motor (6);
• and
• an output shaft (13) supported by said external support casing (11) and connected to said drive shaft (7);
• said external support casing (11) comprising a support element (16;
• 16′);
• said input shaft (12;
• 12′) rotating, in use, about a third axis (E, E′);
• said transmission (10) comprising a first coupling assembly (14) for coupling said input shaft (12) to said external support casing (11);
• said first coupling assembly (14) comprising a pair of oblique first rolling bearings (17;
• 17′) mounted so as to couple said input shaft (12;
• 12′) to said support element (16;
• 16′) in a rotating manner about said third axis (E, E′);
• said first rolling bearings (17;
• 17′) comprising:
• respective first races (18, 19;
• 18′, 19′) cooperating radially in contact with a first component (16, 12;
• 16′, 12′) defined by one from said support element (16;
• 16′) and said input shaft (12;
• 12′);
• respective second races (19, 18;
• 19′, 18′) cooperating radially in contact with a second component (12, 16;
• 12′, 16′) defined by the other from said support element (16;
• 16′) and said input shaft (12;
• 12′);
• and
• respective pluralities of rolling elements (20;
• 20′) adapted to roll on said first and said second races (18, 19;
• 18′ 19′;
• 19, 18;
• 19′, 18′);
• said aircraft (1) further comprising a pair of preloaded elastic members (21;
• 21′), which couple said first races (18, 19;
• 18′, 19′) to said first component (16, 12;
• 16′, 12′) respectively, axially and in an elastically yielding manner;
• wherein said pair of preloaded of elastic members (21;
• 21′) is arranged axially between said first races (18, 19;
• 18′, 19′);
• wherein said first component (16, 12;
• 16′, 12′) defines a pair of first shoulders (33;
• 33′) arranged axially between said pair of preloaded elastic members (21;
• 21′);
• said pair of preloaded elastic members (21;
• 21′) coupling said first races (18, 19;
• 18′, 19′) to said first shoulders (33;
• 33′) respectively, in an elastically yielding manner in an axial direction;
• wherein said first component (16, 12;
• 16′, 12′) defines a pair of second shoulders (35;
• 35′) respectively axially facing said first races (18, 19;
• 18′, 19′), so as to define respective axial end-stops for said first races (18, 19;
• 18′, 19′);
• said output shaft (13) being coupled to said external support casing (11) by means of a second coupling assembly (110), which comprises at least one second rolling bearing (111, 112);
• said first races (18, 19;
• 18′, 19′) being configured to float, in use, along said third axis (E, E′) in response to the application of an axial load on said first component (16, 12;
• 16′, 12′);
• and
• said transmission (30) further comprising a third coupling assembly (101) for rotatably supporting said input shaft (12, 12′) with respect to said external support casing (11);
• the method characterized by the steps of:
• transferring whole radial loads from said input shaft (12, 12′) of said third coupling assembly (101) by means of at least one third radial rolling bearing (102, 103) of said third coupling assembly (101);
• and
• transferring only an axial load from said input shaft (12, 12′) and said external support casing (11) by means of said oblique first rolling bearings (17, 17′).