flight controls

This message from "Derek Marshall" <derek@derekmarshall.com> brought to you by EFLIGHT!

I wonder if anyone could explain how 3-axis flight control is managed by
a) rudder/elevator, b) v-tail elevons or c) mixed-aileron only (flying
wings). It seems in all these cases control is maintained only through
pitch and yaw or pitch and roll but never by pitch, yaw and roll
together. Yet these rc planes (3 channel types) seem to be quite nimble
and totally oblivious to the fact that they do not, in theory, have 3
axis control.

Allowing that the above types of craft do in fact seem to have 3-axis
control, I wonder if anyone has an opinion on which of the three types
is better (a relative word, I know, but perhaps each has a strength
depending on each situation). Please enlighten.

Derek


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This message from Doug Ingraham <dpi@rapidnet.com> brought to you by EFLIGHT!

On Fri, 5 Dec 2003, Derek Marshall wrote:

> This message from "Derek Marshall" <derek@derekmarshall.com> brought to you by EFLIGHT!
>
> I wonder if anyone could explain how 3-axis flight control is managed by
> a) rudder/elevator, b) v-tail elevons or c) mixed-aileron only (flying
> wings). It seems in all these cases control is maintained only through
> pitch and yaw or pitch and roll but never by pitch, yaw and roll
> together. Yet these rc planes (3 channel types) seem to be quite nimble
> and totally oblivious to the fact that they do not, in theory, have 3
> axis control.
>
> Allowing that the above types of craft do in fact seem to have 3-axis
> control, I wonder if anyone has an opinion on which of the three types
> is better (a relative word, I know, but perhaps each has a strength
> depending on each situation). Please enlighten.

It depends. If I can only have 2 of the three I would choose
aileron/elevator for almost every plane I can think of. The one situation
that comes to mind is shooting touch and goes. In this one case I would
choose rudder/elevator because this would allow (more easily) a steerable
nose gear or tailwheel for ground handling.

The way it works is you don't need yaw control if you can use your
ailerons to bank and then elevator to pull the plane around the corner.
You never simply yaw the aircraft through a turn keeping the wings level
anyway. If you use rudder/elevator you are dependent on yaw roll coupling
to initiate the roll and then the elevator is used to actually make the
turn. To complete a turn you again use the rudder and yaw roll coupling
to level the wings. Yaw roll coupling can be so good as to be almost
invisible or painfully slow. If painfully slow then rudder/elevator is
not a good choice for control.


Doug Ingraham
Rapid City, SD USA




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