Vortex generators

Va is the speed at which
– the wing in clean configuration
– at the angle of attack that produces maximum lift
– generates a force that leads to an acceleration that is exactly the maximum permitted

Vs0 is the speed at which
– the wing in clean configuration
– at the angle of attack that produces maximum lift
– generates a force that is exactly the weight of the aircraft

so vortex generators lower the stall speed, they also lower Va. Which is a bad thing.

Thanks @Cobalt for the informations.

But can you explain why it is a bad thing ?
If you slow down, it will ok, isn’t it ?

They also state

Much smoother ride in turbulence

@PetitCessnaVoyageur,

Yes, you need to slow down in turbulence, and it will be ok. But most of us like going fast…

One thing I don’t know is if the effectiveness of vortex generators is speed dependent.

Cobalt wrote:

But most of us like going fast…

Oh, I understand !
In my case (slow SEP), it will be a discussion about 105 vs 110kt, no big deal.
Anyway, your remark was eye opening for me, about the “deep” meaning of Va and VS0.

Now that this discussion has been brought to the front again…

Much of the talk here is about lowered stall and landing speeds, but the reason I have put them on two PA31s is that they increase MTOW by 100Kg (-310) and 300lbs (-350) respectively.

That means that these aircraft can carry an extra person or two. That’s a big difference for a tiny, cheap mod.

The caveat is that they don’t increase either landing weight or zero fuel weight, so you need to be going places to take advantage, but that’s generally ok, as you rarely want eight people on a circuit detail (though it can be difficult for my London sightseeing charity flights.)

Timothy wrote:

Much of the talk here is about lowered stall and landing speeds, but the reason I have put them on two PA31s is that they increase MTOW by 100Kg (-310) and 300lbs (-350) respectively.

That means that without them, you can load 100kg more if you’re OK with the slightly increased rotation speed i.e. takeoff distance. It also means that the previous MTOM was not due to structural limitations but due to a certain takeoff distance target.

…be that as it may, we all feel a little constrained by the Limitations section of our AFM, don’t we? I mean, just a little, right?

When I did my North Pole trip, I checked that my Aztec flew satisfactorily following an EFATO at 120% MTOM, and I never had any doubt that it was safe to fly at that regime (off decent runways). I have little doubt that most aircraft have very conservative MTOMs.

But being able to fly with higher MTOMs according to an AFM supplement, with a clear conscience, is another matter, and very helpful.

Sure, just wanted to point out what that STC tells us about the MTOM. That’s important to understand if you ever get into a situation where you want to exceed it.

However, European operators are usually keener on STCs that reduce the official MTOM