Question about flaps....

[NY3D]

I have been flying sims for about 15 years(right after I came back from Kuwait.)And noticed that all flight sims vary when it comes to the deployment of flaps.It's not very clear to me,even after all these years,what it is that flaps do,some sims have them,some dont.But my concern is that sometimes(not often)I forget to lower my flaps before take off,and still manage to get the bird off the ground.Can an aircraft in real life take off without deploying the flaps?Im not a real pilot,however Im just curious as to what role flaps play in take off and landing.At what alttitude should I retract my flaps after take off.I mostly fly the SU-27 and 33. If anyone knows of a link or any tips it would really make things easier for me.One final question....how does one perform this "Cobra" maneuver???? In any case thanx a million guys:cool:

[Colt40Five]

I'll have a go...I'm sure someone will be along to correect me shortly :)

 

Basically flaps increase lift. With enough runway to get up to speed any plane can take off without flaps (well except cases where the A/C design prevents certain AOA's due to tail scrape).

 

They're really more important for landing, as you must maintain a generally low speed with a proper angle of attack and sink rate. also important for taking off with a short roll or heavy load (like taking off from carrier where you don't have full flying speed when you leave the ramp).

 

to perform the Cobra, maintain about 400km/h, pull back on the stick kind of sharply, and hit [K]. The Cobra is a scripted maneuver in LO, which means once you meet the requirements to do it, a script takes over and performs the maneuver.

 

Hope this helps!

[NY3D]

flaps.

 

Interesting concept. It becomes more clearer the way you explained it,the manuals sometimes confuse me more than anything else.thanx for the minute buddy.:icon_supe

[RvETito]

You should first press the K key and then pull on the stick. At least this is closer to what they do in real life- disable the AOA limiter(i.e. pressing the K key in Lock-On) and pulling full back.

 

As for the flaps- yes, their major function is to increase lift at low speed and thus helping take-off and landing. But they could be quiet useful in dogfight also, like going into scisors for example. At least I use them. But you can notice than on the Su-27 they deploy automaticaly on high AOA along with the slats. This isn't indicated on the configuration display though, I just noticed it from the outside view.

[Nate Dogg]

The effects that flaps have on an aircraft are that it increases lift. The more stages (10, 15, 30 degrees) of flaps you take the more lift is generated. However as more stages are taken the more airflow is disrupted to create the lift thus increasing drag, ie slowing you down.

Using flaps is a great benifit for landing as you can obtain a lower nose attitude (see more of the ground) at a certain speed than you can without using flaps.

Flaps are used in takeoff, but it really depends on the specific aircraft. Taking off without flaps will generally require a higher speed as less lift is being generated by the wings without the use of flaps. However using full flaps will decrease the acceleration of the aircraft as more drag is acting on the plane.

 

Flaps can be taken or retracted at any altitude, it all depends on the airspeed and the aircraft. Obviously taking flaps at high speed will put lots of force on the flaps themselves and may damage or destroy the structure of the flaps/wing. In general aviation the airspeed indicater will tell you all the speeds for certain things like stall speed, max speed for flaps and so forth.

 

I hope this explains the use of flaps and when the benifits of flaps can be used.

cheers

[dynamocl]

Essentially lift (the upwards force an aerofoil creates) is created by the wing of an aircraft.

 

It does this (as is currently believed) by a phonomenon called the Bernoulli principle. Essentially (without too much physics), in a uniformed flow (water or air) if the volume is kept constant but the speed of the flow is increased, pressure will decrease in relation to the increase of speed. What does this have to do with flaps? well just stick with me...

 

Aircraft wings are generally curved. The reason for this shape is to change the path of the airflow. The top surface of the wing is a convex curve, the underneath can be convex or flat. Now imaginetwo "air particles" travelling towards a wing (or a wing travelling to them). One particle will travel over the wing, the other underneath. In order for these partcles to remain the same distance apart (horizontally), the top particle must travel faster (as it has further to go to keep up due to the curvature of the wing). Hence the air over the top surface of the wing has a faster speed than the air flow beneath. By using Bernoulli's ideas, it is clear that the air under the wing has a relativly higher pressure than teh air above. This difference in pressure causes a force (as the higher pressure tries to get to the lower pressure), this upwards force is called lift, and what allows planes to fly.

 

Again what does this have to do with flaps?

 

Well you already have the basics to put the theory together. Essentially flaps are surfaces at the trailing (back) edge of a wing. When extended they increase the curvature of the wing. Are you following whats going on....?

 

So, as the shape of the wing changes, gets more curved, the air flow at the top edge gets faster (has a bigger curve to travel). Hence pressure under the wing increases, hence pressure gets higher = creates more lift.

 

BAsicly, the flaps change the shape of the wing, causing more lift to be generated (and also decreases the aerodynamics and increases drag - slows you down).

 

So flaps what do they allow you to do? Fly slower and generate more lift - so for slower speeds the wings still work (decrease stall speed).

 

Using them at takeoff lets you get airborne at slower speeds (like taking off into the wind). And for landing - same again you can stay airborne at slower speeds with more flaps.

 

Of course this is a simple (yup, really) view and it does get more complex. But I hope this basic understanding of principles of flight answers your question.

[Mako]

Essentially lift (the upwards force an aerofoil creates) is created by the wing of an aircraft.

 

...

 

Aircraft wings are generally curved. The reason for this shape is to change the path of the airflow. The top surface of the wing is a convex curve, the underneath can be convex or flat. Now imaginetwo "air particles" travelling towards a wing (or a wing travelling to them). One particle will travel over the wing, the other underneath. In order for these partcles to remain the same distance apart (horizontally), the top particle must travel faster (as it has further to go to keep up due to the curvature of the wing).

 

Using the Bernoulli Effect to explain how a wing produces lift presents some major (and mutliple minor) quandaries.

 

1) Um...Why are these two particles required to remain the same distance apart? Are they like, married or something?

 

2) If it is the curved upper (in normal flight) surface of the wing which is producing lift courtesy of Bernoulli, how can an aircraft fly inverted? With the curved surface now on the "bottom" it would seem that the aircraft would plummet.

 

3) Consider a symetric airfoil. If the Bernoulli effect were the cause of lift it doesn't seem that this design would produce much lift since the air molecules would (assumingly) feel a need to accelerate equally in order to reach the trailing edge at the same moment. There would be no pressure differential.

 

My admittedly limited understanding is that, while the correlation between velocity and pressure can be observed with a wing in flight it is almost more of an effect rather than a cause of lift. Most of the lift is produced by a simple action/reaction situation. The wing pushes air down (due to angle of attack) and is thus experiences an upward force. The curved surfaces (on top and/or bottom) simply allow this to happen at higher angles of attack without airflow separation.

 

Flaps exaggerate the downward motion of the air and thus increase lift (at a cost of a great increase in drag).

[Bublik]

Actually even a flat door would produce lift at positive angles of attack :)

 

http://www.av8n.com/how/htm/airfoils.html

 

http://www.av8n.com/how/htm/airfoils.html#sec-fluid

[Guest IguanaKing]

An aircraft flying inverted is not actually flying at all...it is simply moving across the sky on pure kinetic energy.

 

As for the concept of lift, don't think of it so much in terms of air molecules as this statement "Nature abhors a vaccum". ;) The air molecules are all rushing to fill the same void, so the one with the greater distance to travel, travels faster. The faster speed of the upper stream of air creates its own vacuum, and air beneath the wing pushes upward in an attempt to equalize that void. Try taking a glass of Coca Cola or other dark beverage, put a straw in it, and blow across the top of the straw. You will see the liquid in the straw rise slightly, and have just witnessed Bernoulli's theories in action. Better yet, take one of those water bottles with a straw built into the top, fill it to almost full (leave a little air space at the top), then screw the top on tightly. What you have done is to seal the current air pressure at your location into the top of that bottle. Put the bottle into a holder in your vehicle and drive into the mountains. Soon, at sufficient altitude, you will have water coming out of the straw on its own. Again...Bernoulli's principle at work. ;)

[Bublik]

Another link from the same site:

http://www.av8n.com/how/htm/spins.html#sec-coanda-fallacy

I could not explain it better myself :)

[Bublik]

An aircraft flying inverted is not actually flying at all...it is simply moving across the sky on pure kinetic energy.

 

and the only reason aircraft can take off is the curvature of the Earth :biggrin:

[Guest IguanaKing]

An inverted wing is no longer producing lift...so I'm not sure how that applies to the situation. :D

[Weta43]

The fact that a wing generates some portion of its lift through a simple reaction to the air it is deflecting doesn't rule out the genration of lift through Bernoulli Effect. Nor does it stop the flaps generating the bulk of their lift from simply deflecting the air, while as a secondary effect increasing the Bernoulli Effect. An aircraft that's wings generate lift towards the more curved side can fly indefinately upside down if the engines, hdraulics & pumps run upside down by putting the wing at a sufficiently high angle to gaining reactive lift from the deflected air & overcome the opposimg Bernoulli Effect, just as a wing slill generates lift at very high angles of attack where there is no laminar flow over the wing

[Mako]

Ha! Yes indeed, a stalled wing continues to produce lift (in mass quantities) as long as there is any airflow at all. The real problem with loss of laminar flow over the upper surface is the huge increase in drag rather than a loss of lift. That's what causes you to stop flyin' and start fallin'. L/D is the key to flight!

[Bublik]

An inverted wing is no longer producing lift...so I'm not sure how that applies to the situation. :D

 

It does produce lift inverted at sufficiently high negative angles of attack.

 

CL - the coefficient of lift depends on AoA of the wing almost linearly (for moderate AoAs.)

 

So for negative alphas CL is negative. Lift = (CL*S*rho*v^2)/2.

In inverted flight the "Lift" axis points down (to the ground), so negative lift in this coordinate system points up.

 

There are aerobatic pilots out there performing turns, loops and what not inverted.

[33 309th_Hedgehog]

Here some Diagrams how flaps operate on A-10A in LOMAC:

 

[Guest IguanaKing]

It does produce lift inverted at sufficiently high negative angles of attack.

 

CL - the coefficient of lift depends on AoA of the wing almost linearly (for moderate AoAs.)

 

So for negative alphas CL is negative. Lift = (CL*S*rho*v^2)/2.

In inverted flight the "Lift" axis points down (to the ground), so negative lift in this coordinate system points up.

 

There are aerobatic pilots out there performing turns, loops and what not inverted.

 

DOH!!! I guess I should just stick to avionics discussions. :icon_toil

 

Thanks for the correction. :D