# Novice aerodynamic questions

• SubZer0
So, in summary, these equations can be used to calculate the dynamics of an aircraft with a dihedral wing during sideslip, but taking into account the specific wing geometry and other factors.Inspiration for beginner books in this field:"Aerodynamics for Engineers and Scientists" by H.M. Green and "Aerodynamics for Scientists and Engineers" by L.J. Sussman.f

#### SubZer0

Hi all,

Just a generalised question about rolling moments generated by an aircraft with a dihedral wing during sideslip. Are there any equations which relate (generalised) the sideslip angle of an aircraft with a dihedral wing and its rolling moment? I would like to be able to calculate the amount of roll generated as a result of some degree of sideslip induced by rudder action alone.

I would, inevitably, want to use this roll angle to calculate the turning angle and rate of an aircraft. But prior to that, I want to be able to calculate the amount of rudder (and induced sideslip) which will result in a specific bank angle.

Ideas? Inspiration? Any recommendations for books for beginners in this field?

Thanks!

I had high hopes for this forum, but no gurus on here. ;)

The problem is that in aerodynamics, almost nothing can be generalized. To my knowledge, this is not one of the things that can.

There are radio control models that use dihedral and rudder for turning (no ailerons). There is a contest class for gliders that only allows rudder, elevator, and spoilers; try doing a web search for RES radio control to see if you can find any useful info.

As boneh3ad said, very little can be generalized about aerodynamics, and unless I'm forgetting something, he's right that this is not one of the things for which a generic answer exists. It depends on the exact wing geometry, wing position, fuselage shape, and other factors, and as a result, it is usually either done with complicated computer codes or (ideally) with wind tunnel and flight test results.

There is no big problem about general answers to questions like "what is the point of dihedral wings", at the qualitative level of "if you yaw left then this force gets bigger, this one gets smaller, so this happens".

But turning that into equations to predict the dynamics of a particular aircraft design is not generalizable. At best you would end up with a "general" equation containing a bunch of unknown constants, and you would still need to do the detailed modelling to find their numerical values.

AlephZero said:
At best you would end up with a "general" equation containing a bunch of unknown constants, and you would still need to do the detailed modelling to find their numerical values.

And the key word here is "at best". It would likely be an equation so ridiculously complex (if it was one equation) that it would be entirely unuseful.

Hi all,

Thanks for the replies. There are indeed semi-generalised "rigid body" equations relating to aerodynamics, which are specialised through parameters. I wasn't asking the question of whether aircraft aerodynamics can be "predicted" through these equations, just whether they existed, and in this case, the equations relating to sideslip angle, lift, etc, exist, but taking into account specific aerodynamic properties which can be ascertained through (a) flight testing, (b) wind tunnel studies.