# How do the actuator loads (e.g. for the ailerons) vary between different flight phases?

Assume the hinge moment is given as

$HM = 0.5\rho v^2*C_{h\delta} \delta*S*c$

$\rho$ = air density

$v$ = air speed

$C_{h\delta}$ = Hinge moment coefficient

$S$ = Control surface area

$c$ = average surface chord

the resulting moments / actuator loads are mainly influenced by the aircraft's altitude (air density $\rho$), speed $v$ and the control surface deflections $\delta$. (AoA is neglected to keep it simple)

Can there be anything said about the actuator loads regarding different mission types or flight phases? E.g. does cruise (high altitude and speeds, small surface defelctions) cause higher actuator loads than approach (low altitude, low speed, larger surface delections).

I was planning to use X-Plane to investigate this, but as far as I know it will only output the rudder's deflections, not the hinge moment itself.

• @Frederico, thanks for your comment. Actually i didn't because i do not have any reliable data concerning the rudder deflections ($\delta$). Of course I could generate some data by simulation (X-Plane) - but I'm not sure how realistic this approach will be... – Henrik Feb 28 '17 at 14:01
• Notice that the the hinge moment is proportional to dynamic pressure ($\frac12\rho v^2$) and deflection ($\delta$) and so is the aerodynamic force on that control surface. – Jan Hudec Mar 1 '17 at 21:08