Incidence question

[poulsbobill]

Ok be gentle... i have been flying a long time but this never come up before as i am now scratch building.

The question... Can the angle of incidence of the stab relative to the wing be adjusted by trimming the elevator in flight? I have read many ideas on what angle of incidence should be...but can't i just adjust it through the elevator trim on the Tx? In other words do small amounts of elevator and the stab/wing incidence do the same thing?

Thanks to all

Bill

[murmur]

Yep, it's the same thing. The incidence between the stab and the wing should be set so that with zero elevator, you get a "reasonable" trim angle-of-attack on the wing. What's "reasonable"? Something that gives around 1G lift from the wing at a mid-range airspeed. That way, you'll have maximum authority available from the elevator for changes to G-level, either way from 1G.

The general rule: incidence between the stab and wing determines the angle-of-attack of the wing for zero elevator. Elevator movement simply changes the wing angle-of-attack one direction or the other from that set by the stab/wing incidence.

Dave

[MarkusN]

In other words do small amounts of elevator and the stab/wing incidence do the same thing?
Yes and no.

On a full flying stab they are completely equivalent, since trim DOES change tail incidence.

On a flapped stab, however, trimming gives you a cambered section. Same net result, AOA of zero lift of the tail is changed accordingly, but:

- there is a drag penalty
- you may lose some usable lift range at the extremes.

The latter can become a problem if design of your plane is critical and can result in loss of pitch authority at one extreme of the flight envelope.

[poulsbobill]

Thank you Gentlemen!!!!

Bill