Hi all! I am taking an online course on aerial robotics and am currently on the topic of linearizing a 2-D quadrotor dynamic model. See slide (link below): The equations under "linearized dynamics" are derived using the equilibrium hover configuration (e.g. y = y0, z = z0, Φ0 = 0, u1,0 = mg, u2,0 = 0) and the fact that at hover, sin(Φ) ~ Φ and cos(Φ) ~ 1. So, linearized y_ddot = (-u1/m)*sin(Φ) = (-mg/m)*Φ = -gΦ This makes sense to me. But how come z_ddot isn't 0? and Φ_ddot isn't 0? Shouldn't z_ddot = -g + (mg)/m*(1) = 0? Φ_ddot = (0)/I_xx = 0? Thank you!