Adding Flaps in a Chandelle

[TMetzinger]

Ah, ain't Primacy grand...

 

[denverpilot]

I'm still convinced that flaps provide more lift than drag at low flap settings, especially fowler flaps. Once you go past the first 10 or 15 degrees you start adding more drag than lift.

Okay, if that's your assertion, come up with a way to prove it. Design a test you can fly at altitude.

(In other words, I think the instructors in the thread are correct, but I'd love to see you "teach" yourself in a safe environment before your assumption kills you.)

Here's a big hint from super high Density Altitude takeoff procedures taught in many mountain flying courses, paraphrased by me...

"All takeoffs during the flight portion of this course shall be made without flaps. If the takeoff cannot be made without flaps, since adding flaps will only increase drag and slow acceleration, the departure will be delayed until temperature and wind allow for a safe departure from the mountain airport."

 

[dmccormack]

I'm still convinced that flaps provide more lift than drag at low flap settings, especially fowler flaps. Once you go past the first 10 or 15 degrees you start adding more drag than lift.

You are still confused...

Sure, the percentage of lift v drag shifts at different flap settings.

But you don't "lift more" because you have 10 degrees of flaps.

 

[RoscoeT]

I'm still convinced that flaps provide more lift than drag at low flap settings, especially fowler flaps. Once you go past the first 10 or 15 degrees you start adding more drag than lift.

I don't have a dog in this one, but put aside the arguments and what you're conviced of, and do some actual testing of angle and rate of climb with flap/no flap. The flight test engineers have already done this a long time ago to acheive type certification, but you can always do it again.

 

[kgruber]

Don't beavers use a positive flap setting for a normal climb?

I'm still convinced that flaps provide more lift than drag at low flap settings, especially fowler flaps. Once you go past the first 10 or 15 degrees you start adding more drag than lift.

Yes. DHC-2 Beaver has climb flaps. I flew an amphibian model professionally in Alaska. There are other oddballs but not light aircraft we fly in the US.

If you still think 10° flaps will help your climb in a 152, go out and experiment. It will be a good lesson. Time a 2,000 foot climb. One at 55 KIAS no flap, the other at 54 KIAS 10° flap. Report back. I'll buy the beer in either case.

 

[dell30rb]

But you don't "lift more" because you have 10 degrees of flaps.

A 152 wing with 10 degrees of flaps at a constant airspeed is going to create more lift than a wing with 0 degrees of flaps at the same airspeed. The wing with 10 degrees of flaps will also have more drag.

Flaps are by definition a system for increasing lift. If you just wanted to increase drag, you would use spoilers.


As for the 2000 foot climb, I think 55 kts and no flaps will win. Because Vx is 55kts and no flaps (as you correctly pointed out). I'll probably try it anyway.

My idea is that by adding some flaps at the end of a chandelle, increasing your lift and lowering the stall speed, you can continue your climb a bit longer than you would clean.



Not sure of the source as I have never heard of this site before, but here is a comment from an article on flaps.

http://www.experimentalaircraft.info/flight-planning/aircraft-lift-augmentation-devices.php

Lift/drag ratio (L/D) is also reduced when full flaps are extended. Normally, flap settings between 0 - 25° will noticeably increase lift more than drag, ideal for take off. Flap settings beyond 25° will increase drag much more than lift, ideal for landing and steep approaches.

 

[dmccormack]

A 152 wing with 10 degrees of flaps at a constant airspeed is going to create more lift than a wing with 0 degrees of flaps at the same airspeed. The wing with 10 degrees of flaps will also have more drag.

Flaps are by definition a system for increasing lift. If you just wanted to increase drag, you would use spoilers.

Ahh -- "constant airspeed."

Which means you need to add power to maintain that constant airspeed with 10 degrees of flaps vs no flaps, correct?

 

[dell30rb]

Ahh -- "constant airspeed."

Which means you need to add power to maintain that constant airspeed with 10 degrees of flaps vs no flaps, correct?

Yes! I explicitly said it would increase drag. Flaps increase both. It sounds like you are trying to tell me that they only add drag.

 

[dmccormack]

Yes! I explicitly said it would increase drag. Flaps increase both. It sounds like you are trying to tell me that they only add drag.

Maybe this will help:

A wing produces two types of drag: induced (the cost of the production of lift) and parasite (the air being pushed aside, etc).

Flaps increase the camber of the wing, allowing the same amount of air to be pushed on at a slower speed.

That's all.

As you increase the camber, you increase the drag. So there is a cost. You must make up that cost with more thrust.

Therefore, at full power, a Cessna 15x/17x series airplane will climb higher, sooner, with no flaps than with flaps.