Rudder hinge angle vs. engine-out control

[Brian Jackson]

Greetings.

More of an academic question before I start laying out the final empennage design for my 'Bee build.

Though many tails I've seen have a near-vertical hinge line running perpendicular to the keel, I've been tempted to rake the hinge line slightly forward. (This is to be a separate rudder and vertical stabilizer rather than an all-flying tail.) The reasoning being more rudder authority in an engine out vertical descent. My concern however is if this would introduce an unwanted nose-down pitching when the rudder is deflected at full power since the prop blast on the angled rudder surface would tend to impose a lifting force on the tail.

I'm sure this has been discussed somewhere, and I don't want to assume I am smart enough to predict the behavior of an item with so many hidden attributes. If anyone has experience with this topic I would be grateful for their opinion. Thank you kindly.

 

[Mayfield]

Hi Brian,
Although there are exceptions, control coupling is generally not the best idea.
Aileron/rudder coupling is fairly common (Beech T34, etc.) and the ruddervators on some of the Bonanza series aircraft work ok.
Pitch/yaw coupling, however, would seem to be an unnecessary complication.
I have had a few engine outs over the years and I have never resorted to a vertical descent in that situation.
I believe an overhead spiral to a "key" position is probably a better technique.
Jim

 

[Brian Jackson]

Hi Brian,
Although there are exceptions, control coupling is generally not the best idea.
Aileron/rudder coupling is fairly common (Beech T34, etc.) and the ruddervators on some of the Bonanza series aircraft work ok.
Pitch/yaw coupling, however, would seem to be an unnecessary complication.
I have had a few engine outs over the years and I have never resorted to a vertical descent in that situation.
I believe an overhead spiral to a "key" position is probably a better technique.
Jim

Thank you, Jim. I appreciate your insight very much. That was kind of the answer I expected since other designers have not done things that way. This is an example of something looking reasonable on paper but having unintended consequences. Will be sticking with a conventional tried-and-true design.

Thanks again for taking the time to answer. Cheers.

Brian

 

[Tyger]

I agree that vertical descents will not be your first choice during an engine out, but neither will you likely be doing major rudder inputs at full power. Or at least I never do... 😇