Hovering

[AuddieD2015]

I can get a rocket to hover. I can get one to land at or below 1 m/s.  I even have success inching to a flatter spot without a catastrophe. The second I try to do this with an airplane or hovercraft, there are more flips than there are at gymnastics competition. I have gotten as close to the vessel as zoom will allow to align the center of thrust with the center of mass. Flip. I use only one tank of fuel because I am only trying to get it to work at this point but the flipping is almost immediately and rather hard so I don't think tank drainage is the cause. There's no time for anything to drain. 

I have tried a single engine at the center of mass. I have tried 4 engines in an X spread out around the center of mass. I have watched/read every tutorial I can find and mimicked them the best I can but most of them are outdated and many versions lower than current. I have even tried mods. CKAN says they are current but I can't make them work. Every single time, mods or not, it immediately flips. I turned to Breaking Ground propellers instead of engines. They flip, flop, and spin if they even have enough power to lift off and use electricity faster than I can generate it. Again, I have watched/read every tutorial I can find. 

I guess my question is simply, is it even possible anymore?  Why is a rocket easy but a  hovercraft is seemingly impossible? I know it used to work because I see the videos of it.  

[Coyote Foxtrot]

The center of thrust of a rocket is far from the center of mass which allows it to have a strong torque do to having a large moment arm. When it comes to aircraft it is likely a lot closer so when it comes to control, the method used needs to be quick to adjust and drastic.

As an example a VTOL aircraft I made was design with three jet engines with two in the back and one up front and there is a net torque with a tendency to pitch up. It has this tendency to reduce complexity so only one mechanism is needed to entirely block any thrust from the front engine causing a strong pitch down movement. The engines always remains at full thrust and a part physically blocks the thrust.

There is a big trade off I make with hovering designs as in reducing the needed control systems I reduce how much I am able to correct any movement.