Method and device for estimating an unwanted pitch moment of an aircraft, and applications to the pitch control of the aircraft

A method for controlling the pitch of an aircraft, comprising the steps:

• producing a command for controlled deflection of at least one elevator, in accordance with a standard control law, said controlled deflection command being representative of a manual actuation by a pilot, and applying to the aircraft an actual deflection command depending on said controlled deflection command, comprising the steps of:
• estimating an unwanted pitch moment by:
• determining current values of an angle of attack and of a pitch rate of the aircraft, and also an angle of deflection of at least one elevator of the aircraft;
• determining current values of coefficients forming part of a reference model of a longitudinal movement of the aircraft;
• calculating a pitch moment Δ{circumflex over (m)} the current values thus determined, using the following expression:
• Δ{circumflex over (m)}={dot over (q)}−mα*(α−αeq)−mq*q−mδq*δq
• where:
• q is the current value of the pitch rate of the aircraft;
• {dot over (q)} is the pitch rate derivative;
• α is the current value of the angle of attack of the aircraft;
• αeq is an equilibrium value of the angle of attack of the aircraft;
• δq is the current value of the angle of deflection of the elevator;
• and
• mα, mq, mδq are said current coefficient values;
• and
• sending to user means the pitch moment thus calculated, which represents an estimated unwanted pitch moment;
• calculating a compensation command, from the unwanted pitch moment thus estimated;
• and
• summing said compensation command and said controlled deflection command to form said actual deflection command which is applied to the aircraft.

A device for automatic estimation of an unwanted pitch moment of an aircraft, that is, a pitch moment which is not produced by an action by a pilot on a control stick, which has a disruptive effect and which is not wanted, said device comprising:

• first means for determining values of the angle of attack and of the pitch rate of the aircraft, and also the angle of deflection of at least one elevator;
• second means for determining current values of coefficients forming part of a reference model of a longitudinal movement of the aircraft;
• third means for calculating a pitch moment using the current values thus determined, said third means being formed to calculate the pitch moment Δ{circumflex over (m)} using the following expression:
• Δ{circumflex over (m)}={dot over (q)}−mα*(α−αeq)−mq*q−mδq*δq
• where:
• q is the current value of the pitch rate of the aircraft (AC);
• {dot over (q)} is the pitch rate derivative;
• α is the current value of the angle of attack of the aircraft (AC);
• αeq is an equilibrium value of the angle of attack of the aircraft (AC);
• δq is the current value of the angle of deflection of the elevator (3);
• and
• mα, mq, mδq are said current coefficient values;
• and
• fourth means for sending to user means the pitch moment thus calculated, which represents an estimated unwanted pitch moment.