Are Flaps Over Rated?

[mvivion]

Christina,

There is no way that you can "measure" actual angle of attack by looking out the window. For example, an F-15 in full burner can sustain a vertical climb. Would that then be a 90 degree AOA? Nope.

I would not disagree with your original assertion, that AOA is less with flaps, but I would disagree that you can judge AOA by going out and looking out the window. That is deck angle, not AOA.

MTV

 

[Christina Young]

I would not disagree with your original assertion, that AOA is less with flaps, but I would disagree that you can judge AOA by going out and looking out the window. That is deck angle, not AOA.

MTV

My point was that the exercise of seeing at what attitude you stall at both with flaps and without is still valid.

 

[Christina Young]

With 50 ft'rs at each end and a 600 ft. strip,thats a tight light strip by any standard.

A piece of cake with room to spare. Crash

I just thought that this would make for an interesting discussion on the different techniques that could be employed.

 

[Pico]

Don't have a whole lot to add here, but I believe the reason the 206 is flaps-restricted on floats is that it lands too "nose-down" with full flaps (as the center of lift is moved rearward on the wing), and there would be a risk of digging the front of the floats into the water.

At least that's the BS theory I was told about.....

If you subscribe to the Newtonian theory of lift rather than the Bernoulli theory, this movement of the center of lift, along with other effects of flaps, are more easily understood. It's just like putting your hand out the window of your car when moving.

 

[Steve Pierce]

Pico, Makes sence to me after landing 210s and knowing what that picture looks like on landing with full flaps.

 

[Fortysix12]

With 50 ft'rs at each end and a 600 ft. strip,thats a tight light strip by any standard.

A piece of cake with room to spare. Crash

My mistake, 75 plus'rs at the both ends. Is that still a piece of cake?

 

[mvivion]

Christina,

I would again suggest that "attitude" has very little to do with actual AOA.

MTV

 

[mvivion]

Oh, yeah, the 206 lands just fine with full flaps down. Not that I've ever tried that, by the way.

Sometimes mechanics forget to reset the flaps when the plane goes to floats :lol: .

MTV

 

[Erik]

...The cub wing with flaps retracted stalls at a higher AOA than it does with flaps deployed. If you don't believe me, it's easy enough to find this out for yourself in your own cub.

Lift is a function of both AOA and airfoil shape, among other things. The flaps are simply devices that change that airfoil shape...

The first chapter of Stick And Rudder seems to clear things up for me.

Paul

Christina,

Seems like you both hit the nail on the head ("lift is a function of both AOA and airfoil shape, among other things. The flaps are simply devices that change that airfoil shape") and miss completely ("The cub wing with flaps retracted stalls at a higher AOA than it does with flaps deployed. If you don't believe me, it's easy enough to find this out for yourself in your own cub."). I use Stick and Rudder as my resource (beautiful "understanding" text - I agree harneymaki).

Page 16 and 17 of Stick and Rudder discusses the "no-lift line", which is specific to each wing and is a reference line that must be used to accurately measure the angle of attack. The point here is that you must use the "no-lift line" to measure angle of attack, NOT the bottom of the wing. There are two illustrations on Page 17. One shows an inclined plane (the no-lift line) in the relative wind, illustrating a certain angle of attack. The next shows a dotted line representing a wing cross section containing the same inclined plane and showing the same relative wind. The bottom of the wing is shown at a completely different angle to the relative wind than the "no-lift line". In other words, even without flaps deployed, the bottom of the wing is the wrong reference for AOA measurements.

Christina,

Are you confusing Angle of Attack with deck angle? I believe, but one of the aerodynamic whizes on the site can address this better than me, that the Cub will reach a higher angle of attack with flaps deployed.

No, absolutely not. Try it for yourself! Go out and try a stall with no flaps, then one with flaps. Which one stalls with the higher AOA?

I would not disagree with your original assertion, that AOA is less with flaps, but I would disagree that you can judge AOA by going out and looking out the window. That is deck angle, not AOA.

MTV

My point was that the exercise of seeing at what attitude you stall at both with flaps and without is still valid.

Christina, I'm not convinced you get the point. You are supporting your assertion that flaps have a certain effect on AOA because you went out and verified it by looking out the window. But you can't see the no-lift line and therefore you can't see the angle of attack.

Now, since the stall occurs by definition when you have reached the critical angle of attack, and we all seem to agree that flaps decrease your stall speed, then flaps must increase critical angle of attack.

Erik

 

[mvivion]

You can drive an aircraft wing to critical AOA at ANY flight attitude. You can stall a wing going straight up, you can stall a wing going straight down. Looking out the window tells you very little about AOA.

MTV

 

[Aviator]

When it comes to AOA, What You See is not always What You Get

Forward hover: Horizon zero, AOA about 75

VTO: Horizon zero, AOA about -90

Cobra: Horizon about 75, AOA about 75

Vertical climb: Horizon about 90, AOA about zero

 

[diggler]

delete

 

[Jon B.]

I use flaps for take off, landing, crosswind, downwind, climbing, descending. When im in Alaska carrying a moose on each lift strut with my spoiler mesh wing covers on I even use them when cruising at 3500 lbs gross weight.

Girly-man! I *never* use flaps in my airplane. Oh, wait. I don't *have* flaps. Never mind...

Jon B. :lol: