Shoe

Shaun,

Two things (well, at least two things) are likely to happen when you extend flaps. 1) you will very likely change the angle of attack for which the airplan is "trimmed". Any time a stable airplane is not at the angle of attack for which it is trimmed, it will try to return the trim angle of attack. According to linear aerodynamics, it will do this through its "short period" mode. I think the easiest way to visualize this is to think about an arrow that is moving through the air, but not quite alinged with the direction it is going. The arrow's tail feathers will try to align the arrow with its flight path. The arrow will typically overshoot the flight path several times before lining up. The period of one cycle is the "short period". 2) By extending flaps you will also likely change the aircraft lift coefficient at any given angle of attack. If you take a plane in level flight and make a small increase in it's lift coefficient, the extra lift will bend the flight path up. If the power isn't changed, the plane will slow down as it climbs. Most planes will continue to decelerate below the speed that would keep them level at the new lift coefficient. This means that their flight path will eventually bend back down. On the way down the aircraft will speed up and eventually begin to climb again. This periodic motion is what is called the airpalne's "long period" or "phugoid".

The short and long period motions can continue for many cycles (the long period can go on indefinitely for planes like the P-3), or "damp out" in less than a full cycle. A good pilot or flight control system (or some combination of the two) should be able to intervene when flaps are extended in order to keep porpoising to a minimum.

If you are looking at ways to minimize the amount of pilot input required to minimize porpoising, your best bet would probably be to look at a simple interconnect between the flaps and the horizontal stab. As you point out there may be an aerodynamic connection between the flaps and the stab. The idea is to electronically or mechanically "take out" some or all of this natural connection (a T-38 would pitch up uncontrollably at flap extension if not for a built-in "flap-slab" interconnect). More sophisticated automatic flight control systems can add artificial damping, but these typicall require sophisticated sensors (like rate gyros).

To answer your question, I don't think that slotted flaps would help much by smoothing ot the flow.