Ed

Do flaps really create lift on a high wing monoplane, or just drag to slow it down. I can understand how it might assist ground effect on a low winger, but on a high winger such as a Super Cub, does it really add lift when flaps are set to 15, or 45 degrees ?

Ed

vertical grimmace

My Feedback: (1)

Increasing camber to the airfoil section increases lift. Regardless of where the wing is. So yes, they do. Drag does also increase.

sensei

Yes to lift and drag both... No need to go into the full text book explanation on a topic that has been proven for decades.

Bob

FlyerInOKC

My Feedback: (6)

The short answer is if Flaps just caused drag and no lift the landing speed would have to go up instead of slowing down when the flaps are deployed.

Ed

Thank you for your answers gentlemen. Could flying then at partial flaps for an entire flight, perhaps 5 - 10%, be beneficial when flying a heavily loaded plane from point A to point B ? And is this normally done ?

Ed

BobH

My Feedback: (2)

A small amount of flaps are often used for take offs. Especially on shorter fields. This was a standard full scale practice with many fighters.

Example: the Seafire used the same flaps as the Spitfire. They were either all up or all down. To create extra lift from the carriers wooden wedges were fashioned and slid under the flaps. This gave them sufficient lift to get off the carrier. Once high enough they fully deployed the flaps and jettisoned the wedges.

I doubt flaps would be used for an entire flight. Burning off fuel would make the plane lighter during the trip.

Charlie P.

Flaps change the overall shape of the wing chord and have the effect of an increase in angle of attack = more lift. They also create more drag.

TheVought F-8 Crusaider (jet) went one step furtherby tipping the whole wing to get even moreangle of approach,

pimmnz

No, chaps, flaps DO NOT CREATE LIFT. As suggested, flaps change the camber and drag of a wing...Lift is determined by the weight of the airplane and whatever acceleration is acting upon it at the time. All the flaps do is affect the airspeed and power required to achieve the lift the pilot/airplane requires at that time.
Evan, WB #12.

BobH

My Feedback: (2)

I'll just say that flaps themselves don't create anything.. this is true.. But by changing the camber of the wing the properties of the wing are changed. A pretty complete explanation is here : http://en.wikipedia.org/wiki/Lift_(force)

invertmast

My Feedback: (23)

Well this is the first I have heard in 100+ years of there being aviation...

Flaps themselves could technically be said as not to do anything except change the Chord line, Chamber and in some instances the total wing area (fowler flaps) when the flaps are extended. This change of airfoil characteristics is what modifies the lift generated by the wing section.

Increase the AoA (by modifying the chord line, not changing the AoA) increases the lift generated.
Increase the chamber of the airfoil and lift is increased
Increase the wing area and the amount of lift is increased.


So with that said, since you cannot change any of those items (other than the AoA) with a conventional "rigid" airfoil without the use of some sort of high lift device (flaps, slats, slots, LE flaps, krueger flaps, slotted flaps, fowler flaps, etc etc etc) Flaps are in fact responsible for Increase the lift generated by a wing section.


Every aircraft I have flown in real life, when flaps are extended, the AoA must be reduced to keep the aircraft from climbing.. Why, b/c the amount of lift being generated by the wing has been increased due to the flaps being extended.

Its just like when you apply an aileron input. The downward moving aileron causes the wing section to increase the amount of lift being generated, and the upward moving aileron causes that wing section's lift to decrease, giving you a roll in the direction you demanded.

vertical grimmace

My Feedback: (1)

This is also why a steeper approach, with a nose down attitude is usually seen with the heavy metal warbirds. The need to decrease angle of attack.

Invert is spot on.

pimmnz

OK, look at it this way...if flaps CREATE LIFT, then applying them to a stationary wing should make that wing lift. Obviously not. Try that again, in a real situation...on approach, clean wing, aircraft descending...lift just slightly less than weight. Apply flaps, continue descent...lift just slightly less than weight...no overall change in the amount of lift generated...things that might change...airspeed, power, angle of descent. You can do this for any part of the flight..accelerated and non accelerated...again, flaps, by themselves do not create lift...you actually have to do something with the airplane to appreciate that flaps modify the wings ability to generate lift...but on their own...you cannot create lift with flaps.
But then...it's all just how you use the language...
Evan, WB #12.

nine o nine

My Feedback: (1)

This is sounding like the old "downwind turn argument". Ever flown a Cesna 152? Extend 15deg flaps on the downwind while reducing power and retrimming to aproach speed. Reduce power a bit more on base but add more flap during the turn and the AC remains at the same attitude and airspeed but altuitude is lowering...no retrimming required because now we've created lift AND some drag. Last flap, to 30 Degrees on final.... much more drag but still no retrimming. Airspeed is stable with just a bit of power management to stay on desired glide path (wind corrections). Soooo.... flap USAGE creates lift and a bit of drag at low deflection, a bit more lift and significantly more drag at more deflection, and mostly drag at high deflection.
Experiment with different flap settings on your model with reduced power settings...adjust power and trim (use an elevator mix if available) as necessesary for the desired attitude. Mitch CFII/CFMEI/CFIG/CFISES

tailskid

My Feedback: (34)

Me thinks Mitch has the experience

pimmnz

But mitch, if dropping flaps on final created more lift...you would not continue to descend...And more drag means you will slow down, unless you add power. It's the slowing down bit that's important...less airspeed, less lift. When i was learning to fly, as flaps were lowered, you juggle power and trim to maintain glideslope and watch the approach speeds...elevator is still the speed control, power still height control, and flaps just help steepen the glideslope...and you still got to come down...ahh well..
Fun, anyway!
Evan, WB #12.

cubcrasher

My Feedback: (6)

I can tell this one is getting good. I will keep an eye on it.[:-]

Ed

" But mitch, if dropping flaps on final created more lift...you would not continue to descend...And more drag means you will slow down, unless you add power. It's the slowing down bit that's important...less airspeed, less lift. " - Evan

Exactly right .................. Then for a given, or constant air speed, the flaps do create lift !

Ed

nine o nine

My Feedback: (1)

Aha! Slowing down on short final is good into the flare...loss of some airspeed means LESS lift from the entire wing regardless of flap position. You're right in that poiwer is your main altitude control but it's always a juggling between power application and flap position. In basic instrument training we teach a notch of flaps, a power adjustment for altitude control (usually to a specific rpm or manifold pressure number) and the lift component with the added flaps is balanced with a COMBINATION of longitudinal trim so that a specific airspeed is maintained. That's how instrument approaches in light planes are done, especially when timed turns to a specific heading heading (the runway maybe) at a standard rate is performed. Then simply with an appropriate POWER reduction, drag added by lowering the landing gear, if equipped, the plane will stay right on the glideslope with no pilot interference. Flaps don't get lowered any more until landing is assured. A go-around with full flaps could ruin one's day. That's why Cessna changed allowable flap from 40 to 30 degrees on training planes years ago. Students with their minds "swimming in glue" in a botched landing go-around couldn't climb over trees at the end of the runway even with full power....if they didn't have the flaps brought up from 40 to at least 30 degrees. I know...fulll scale flying doesn't always equate to models but the principles are the same. Lower rpm but add elevator by hand or mix as some flaps are lowered. Our model flying minds are governed by what we see but in a full scale we can feel or read the instruments. Again it's a juggling act and every approach might be different from the last due to any number of factors. That's why mucho practise in many weather environments is the best thing. Just don't get too low and slow before you're ready to put your bird on the runway. Power is your friend until the last bit of flare is there. Practise practise practise. My first instructor in a Cub taught me the three rules of landing approaches. #1. Keep the nose down #2 Keep the nose down #3 Keep the nose down.
Finally, a bit of flap adds some lift and a little drag. Drag takes over at some point as flaps are lowered more. Mitch Whewwww, I'm done.

F4u5

My Feedback: (81)

Only in flight

Dlavp47

I read an article that said flap setting determine lift and also drag it stated that 0 to 20 degrees create lift. 20 degrees and more create drag. hope this helps Dave L.

invertmast

My Feedback: (23)

A stationary wing doesn't create any lift either! In order for a wing to generate lift it MUST have airflow over it. If you take a steady state wing that is generating equal amounts of lift to the weight of the aircraft and apply flaps, the aircraft will pitch up and climb b/c of the increase camber and chord line AoA that was generated by extending the flaps. In order to reduce the tendency of this pitching up, you either reduce speed, or decrease AoA. The same thing will happen in a decent, apply flaps to a constant speed wing in a decent and it will increase its pitch angle and either stop or decrease the rate of decent.

Flaps are directly responsible for the increased lift the wing generates Because of the reasons i have already stated.

CMEL/CSEL/Instr./ A&P/CFI/CFII 3000hrs of King Air experience

sensei

There is no argument, and no need to reinvent the wheel either, flaps create drag and lift. It really is that simple...

Bob

Ed

" I read an article that said flap setting determine lift and also drag it stated that 0 to 20 degrees create lift. 20 degrees and more create drag. hope this helps Dave L. "

I think that David's post has a lot of merit. Too high a degree flap setting, above maybe 30 degrees, causes more drag then lift. So then a nominal setting such as 15 degrees, might be much more efficient at creating lift.

sensei

LOL... If you have enough power to produce enough thrust, in turn enough speed/energy to overcome the drag of lets say 30 degrees, or even 45, or 50 degrees of deployed flap, then you are producing lift now by accelerating that energy across the stabilized wing and deployed flaps, aren't you.

Now back off on the power and the drag of the deployed flaps overcomes and prevails by slowing the vehicle.

Bob

invertmast

My Feedback: (23)

If flaps didn't increase lift, then the stall speed of modern aircraft with flaps wouldn't be slower with the flaps extended than when the flaps are retracted... simple as that