control planes movements by ''fly by wire'' ?




of course many have heard of fly-by-wire
making many flight corrections
to stabilize the aircraft.

but...

actually, how many movements do control planes
(rudders, ailerons, elevators, elevons
and/or flaperon) REALLY move per second ?

because i've seen a fighter jet with
missiles/bombs, when it took off,
front wheel already off the runway,
while main landing gear still at the runway,
the elevator does moves up and down a bit
(at downward position),
showing fly-by-wire at work,
and i'm sure the pilot was not playing
with the control stick ;)


so...

whot do you think the approximate
ACTUAL max number of movement per second
for the control planes (full FBW) ?


thanks a lot ;)

On a fighter jet because it has such a small wing span the computer is constantly making correction to keep the aircraft stable. If it did not have this small wing span it would not be able to achieve the tight turns that it can do. If the series of systems that control this failed the aircraft would instantly become uncontrollable. On a larger plane such as the A-320 & up the movements r not as great due to a lot more stable wing. How ever these planes do have hydrolic assist & if that is lost it would become almost impossible to move control surfaces.

On fighter aircraft such as the F-16, F/A-18, F-22 etc. the flight control system typically updates the commands to the surface at about 80 to 100 times per second.

l guess there is a bit of ambiguity here. The frantic control surface deflection mentioned here is applicable only for Relaxed Static Stability (RSS) aircraft. Not all FBW aircrafts r RSS, especially the huge ones as they dont need the maneuverability.

Having said the above, l have to shamelessly state that l dont have an answer to ur question. The number of control surface deflection would be proportional to the magnitude of instability, i.e. the seperation between Aerodynamic Center & the CoG. As the aerodynamic center changes with the airspeed, the correction rate could vary.

And l am guessing that the movements u saw with the wheels down is not from the control law. It should be the pilot is doing.

The impulse & feedback to/from the FCC is non-stop, as in virtually instananeous. You can not tell it is happening. The input/output is nearly a solid line. The fluctuations that u saw in the tail of the aircraft r normal, & u really should not see much during takeoff. more during landing & then too, that is something that u take as a matter of pride as a pilot that u landed as smoothly & under control as is possible with the fewest control & throttle changes as possible. If u see the tail flapping around all over the place, someone is scrambling to ''save'' a landing from being a bouncer. Regardless. the movement u saw, was a result of the input from the pilot, not the computer over-riding him.