Method for controlling an aircraft capable of hovering and relative aircraft

A hovering aircraft comprising:

• a first engine;
• a second engine;
• at least one rotor operatively connected to the first engine and to the second engine;
• a transmission interposed between the first and second engines and the rotor including a first inlet connected to the first engine and a second inlet connected to the second engine;
• a plurality of sensors to measuring parameters associated with external conditions and conditions of components of the aircraft;
• a control unit (30, 33, 22) configured to:
• a) receive a series of sensed parameters from the plurality of sensors, the parameters including:
• i) an external temperature (OAT);
• ii) an external pressure, an external air density;
• iii and iv) heights of the aircraft above ground level and sea level;
• v) an angular speed of the rotor;
• vii) an indicated speed;
• viii) a torque delivered by the first and second engines;
• ix) an altitude above a minimum flight level;
• and x) a variometric speed (Vz),
• b) determine whether the measured parameters indicate one or more of the following conditions:
• i) the external temperature (OAT) is between a first operating value and a second operating value;
• ii) the external pressure is between a third operating value and a fourth operating value;
• iii) the external air density is between a fifth operating value and a sixth operating value;
• iv) a height above ground level is between 50 and 1000 feet;
• v) the height above sea level is between 50 and 1000 feet;
• vi) the angular speed of the rotor is between 0.85 and 1.15 times a nominal angular speed;
• vii) the indicated speed (IAS) is between 0.5 and 2.5 times a first speed in level flight for which the minimum power at the torque delivered by the first and second engines level and operating temperature is required;
• viii) is between 0.5 and 3 times a first torque necessary for a straight level flight at the first speed;
• ix) an altitude above a minimum flight level is between 50 and 1000 feet;
• and a variometric speed (Vz) is between 0.1 and 1 times a vertical speed of autorotation and 0.1 and 1 times a maximum variometric speed at the first speed,
• c) when it is determined that the conditions i) through are ix) fulfilled:
• c1) transition operation of the aircraft from a first configuration in which both the first engine is operating with first power (P1) and the second engine is operating with second power (P2) to a second configuration in which the first engine is made to operate a third power (P3) greater than the first power (P1) and the second engine is made to operate at a nil power value (P4), wherein the third power being equal to the sum of first power (P1) and second power (P2);
• d) when it is determined that conditions i) through ix) are not fulfilled and a difference between the measured parameters and at least one condition i) through ix) is greater than a minor anomaly, and the aircraft is operating in the second configuration:
• d1) perform a first automatic transition operating of the aircraft from the second configuration to the first configuration,
• e) when it is determined that conditions i) through ix) are not fulfilled and a difference between the measured parameters and at least one condition i) through ix) is within a tolerance considered to minor anomaly, and the aircraft is operating in the second configuration:
• e1) perform a second automatic transition of the aircraft from said second configuration to the first configuration, wherein the second automatic transition is slower than the first automatic transition.