Fa2004 16.3337-3 p yawing moment due to roll rate Rolling wing induces a change in spanwise Aoa, which changes the spanwise lift and drag Distributed drag change creates a yawing moment. Expect higher drag on right(lower on left )- positive yaw moment There is both a change in the lift(larger on downward wing be- cause of the increase in a)and a rotation(leans forward on down- ward wing because of the larger a).- negative yaw moment In general hard to know which effect is larger. Nelson suggests at for a rectangular wing, crude estimate is that Nn≈pUSb(-)<0 Nr yawing moment due to yaw rate Key in determining stability properties- mostly from fin Positive r has fin moving to the left which increases the apparent angle of attack b △ f Creates increase in lift at the tail fin by △L )fS/CLn,△a Creates a change in the yaw moment of N=-△r=-p(U1SCr7 P(UOS Cl <0 Key point: positive yaw rate= negative yaw moment. LN P r>0<0Fall 2004 16.333 7–3 • Np yawing moment due to roll rate: – Rolling wing induces a change in spanwise AOA, which changes the spanwise lift and drag. – Distributed drag change creates a yawing moment. Expect higher drag on right (lower on left) → positive yaw moment – There is both a change in the lift (larger on downward wing be￾cause of the increase in α) and a rotation (leans forward on down￾ward wing because of the larger α). → negative yaw moment – In general hard to know which effect is larger. Nelson suggests that for a rectangular wing, crude estimate is that 1 Np ≈ ρU0 2 Sb(−CL) < 0 2 8 • Nr yawing moment due to yaw rate: – Key in determining stability properties – mostly from fin. – Positive r has fin moving to the left which increases the apparent angle of attack by rlf Δαf = (U0)f – Creates increase in lift at the tail fin by 1 ΔLf = ρ(U0 2 )fSfCLαf Δαf 2 – Creates a change in the yaw moment of 1 N = −lfΔLf = −2 ρ(U0)fSfCLαf rl2 f 1 – So Nr = 2ρ(U0)fSfCLαf lf − 2 < 0 – Key point: positive yaw rate ⇒ negative yaw moment. L N p < 0 ? r > 0 < 0