Canards have been used for different reasons, all modern fighter designs that have them do so for agility reasons, same with LERX's as you know, but
the SAAB Viggen used them purely for STOL operation.
As to advantages over LERX, I can only think of 1 at the moment (its 5am here and I just got up 'cos I can't sleep,
) and that is that they are
operated as control devices in their own right while LERX are fixed meaning that while LERX increase the instantaneous turn rate of an aircraft (which
is why the RAF had them incorporated onto the AV-8B for example) a canard is also useful in roll pitch and yaw. When I'm more awake I might be able
to do better and I may even find a site to link to
Just thought, aircraft with LERX also normally have a tailplane too, unlike which a canard generates lift and allows for a greater payload/range or a
smaller lighter wing depending on the requirement, a smaller and lighter still wing is afforded by FSW but that brings with it many problems related
to aeroelastic properties and structural strength so the delta canard has been seen for several years now as a happy medium.
[edit on 26-11-2005 by waynos]
