wing tip stalling.

[Peter Lee]

A question about stalling.
I have noticed in a couple of planes that the stall without flaps is quite level laterally , but with flaps the stall speed is lower, but a wing may drop.
Since the flaps are closer to the fuselage and the aerolons at the tips I would expect the tips, at a lower incidence than the lowered flaps, to stall later.
Am I missing something?

[WLIU]

Your question contains its answer. Lower incidence and Angle Of Attack means flying. Higher AOA means stalling. Putting the flaps down increases the both the camber and AOA of the inboard part of the wing.

A wing drops because the pilot is not using rudder appropriately. Nothing to do with the flap deployment unless the flaps are not rigged to deploy equally. Some pilots might get distracted by the change in aircraft behavior during flap deployment and let their feet get out of sync.

Best of luck,

Wes
N78PS

[Peter Lee]

Sorry to be obtuse- to avoid a tip stall one builds in "wash-out", ie. the tips are at a lower aoa than the wing-roots. Lowering flaps must enhance this effect?
I suspect my flaps are not lowering symmetrically so you may have supplied the answer- will check....
Thanks, Peter.

[martymayes]

Not all airplanes have twist built into the wing and they stall quite symmetrically regardless of flap position.

I don't think you are being obtuse, but I do think with a few simple experiments your hypothesis can be proven false.

[mikevictor]

My two cents: lowering the flaps doesn't increase aoa in the inner portion of the wing, but increases camber, that gives you more CL and more CD. The trick is the same thing lowers the critical aoa. Slats have the effect of an increased CL and critical aoa, thats why flaps are located in the inner part of the wing and slats usually in the outer part. Also, the stall in a straight wing will start at the root an progress towards the tip. Washout is not necessary in theory, but some planes, especially those used in primary training may have this feature implemented, just to be more forgiving. One example of this is the Piper J3.

[Peter Lee]

Right, gotcha! I was assuming that lowering the flaps increases aoa. Thanks both.

[WLIU]

Well, if you change the wing camber by extending flaps, the wing chord line, which is the reference for AoA, changes. So for that section of the wing, the relative wind does not change, but the AoA in reference to the chord line does change. So the inner section of the wing and the outer section of the wing are now experiencing different AoA's.

Once you start adding "stuff" to a wing, the calculations get more complicated.

Best of luck,

Wes
N78PS

[mikevictor]

Well, if you change the wing camber by extending flaps, the wing chord line, which is the reference for AoA, changes. So for that section of the wing, the relative wind does not change, but the AoA in reference to the chord line does change. So the inner section of the wing and the outer section of the wing are now experiencing different AoA's.

Once you start adding "stuff" to a wing, the calculations get more complicated.

Best of luck,

Wes
N78PS

You're right, thanks

[LooneyBird]

Sorry to piggy back this question here, but it seems like a good topic are. Washout that is mentioned, is that from 0 reference or from the wing root reference. So if I have 2 degrees of washout at the tip, is that from 0 degrees, or is that 2 degrees from the 1 degree aoa that the wing root has.

Thanks,
Josh

[cub builder]

Sorry to piggy back this question here, but it seems like a good topic are. Washout that is mentioned, is that from 0 reference or from the wing root reference. So if I have 2 degrees of washout at the tip, is that from 0 degrees, or is that 2 degrees from the 1 degree aoa that the wing root has.

Thanks,
Josh

Washout is the angular measurement of the cord at the wing tip vs the cord at the wing root. In your case, you have 2° twist in your wings.

Your 1° reference is the angle of incidence between the wing root and the longitudinal axis of the fuselage, often times referenced to the longerons.

AOA is a dynamic in-flight measurement of the wing to the relative wind.

-Cub Builder