Active flow control vs conventional control surfaces

[F-2]

I’m curious about active flow control and it’s advantages and disadvantages vs conventional control surfaces

US researchers show active flow control works on tailless aircraft | Aerospace Testing International

Active Flow Control uses jets of air to maneuver an aircraft

www.aerospacetestinginternational.com

Another advantage of active flow control is that it has the potential to allow for maneuvers that are impossible with conventional controls, including very fast turns and the ability to fly at angles that would cause conventional controls to become ineffective.

Is active flow control the next step in flight controls? | Aerospace Testing International

Active Flow Control could become an important tool in the aerospace engineer’s toolbox

www.aerospacetestinginternational.com

If an aircraft’s wings have rounded trailing edges, air will follow their curvature – a tendency known as the Coanda Effect. Blow air over the top of a rounded trailing edge and you create a downward wake. Blow air from below and you create an upward wake. The wakes can change the pitch of an aircraft, raising or lowering its nose just as flaps and elevators do. Left or right yaw motion, produced by rudders on conventional aircraft, is harder to create with pneumatic AFC, but it can be done by vectoring the thrust of an engine, essentially blowing or pulling exhaust gases to one side or the other.

https://www.electrofluidsystems.com/Scientific-Publications/Goksel-DGLR-2005-210.pdf

Paper on the subject

 

[red admiral]

It's academically interesting so there's been research on it for decades.

I've yet to see any real advantages besides the old school lift enhancement through blown surfaces, and thrust vectoring for manoeuvre at high angles of attack - which is what your first quote is getting after. Many people wouldn't class these as whats really meant by active flow control.

There are definitely cons e.g. all the valves and pipes that take up airframe volume and add mass; e.g. safety for what happens when something breaks - loss of engine rapidly leading to loss of control is not good

So to me its a pretty niche area for the moment that you could use for some very specific design problems

 

[robunos]

My thought was that if this technology could replace moving control surfaces, it could reduce structural weight and complexity (offset of course by the additional weight and complexity of the active flow control system), and impove LO . . .

cheers,
Robin.

 

[red admiral]

From the studies I've seen that go into that sort of integration detail (very few) then the flow control system turns out quite heavy and very complex, and takes up lots of volume (e.g. bigger heavier draggier wing to carry the same fuel) and so doesn't appear very attractive

But it's probably the safety side that's the real killer for having a system sufficiently reliable without single point failures

And then you look at the technical risk side and realise that "we" already have a good understanding of developing, producing and supporting conventional aerodynamic control surfaces.

So it feels like maybe only in some niche applications to supplement conventional aerodynamic controls