Do twin engine airplanes have increased roll stability? Do twin engine airplanes with counter rotating props have increased roll stability?
Imagine a gust of wind hitting the airplane from the front right quarter.
The gust hitting the front of the plane first would yaw the plane to the left, before the rear vertical stabilizer can counter the yaw, the airplane will then roll to the left as the right wing sees more lift.
With a twin engined aircraft, the left engine would counter that yaw.
If less yaw, would that mean less roll, and therefore more roll stability?
Is this correct thinking?
If not, what can be done to increase roll stability besides using a maximum dihedral of about 6 deg and the addition of ventral fins, and wing sweep?
You're imagining the wind coming from the right, pushing the nose to the left. That doesn't happen. In fact, this is much more likely to push the nose to the right, because the vertical stabilizer, being a large panel that's far from the center of mass, creates a larger torque. This phenomenon is called &quot;weathervaning&quot;, and is a huge concern for tailwheel planes and seaplanes particularly.
But, to get to the actual question: You are correct in thinking that, if a plane is yawing to the left, the outside wing is going to generate more lift, causing it to roll left. But, no, having multiple engines on an airplane will not stabilize it in either roll or yaw. For all the thrust from the left engine is doing to counter the yaw, the right engine's thrust is balancing it out, so a twin engine will not be any more stable than a single engine, all else being equal.