How to use Flaps?

[mtuhoop24]

My next plane is going to be scale and rather large........it comes with flaps and I am excited to use them. The only problem is that I am not sure how.

How do I use them for taking off?

How do I use them for landing?

Any help would be great!

Thanks!

[pd1]

mtuhoop24,
Flaps increase drag and lift.

The more flaps are deflected the more lift they produce.

Flap use is primarily for steepening descents without increasing airspeed.

Partial flaps aid in takeoff because they also increase the wings lift.

If the plane your building is a high wing, deploying flaps will probably cause the plane to pitch up.

If the plane is a low wing the flaps will probably cause the plane to pitch down.

I say probably because there are a lot of exceptions.
It's best to test the planes reaction to flaps up high, and limiting the flap amount.

Flap affect the rate of speed change in the airplane when they are down.
The plane will slow a lot faster with flaps than without flaps.

If you let the nose of the plane come up with reduced power, it is easy to slow down more than expected and stall.

Flaps also lower the stall speed, but if you fly at or just above the new stall speed the plane can slow quickly and stall.
Keep the nose down with flaps until you get used to the airplane.

All that said, flaps can be a lot of fun.

Paul

[mtuhoop24]

Thanks Paul...

This will be a Cessna with a 65" wing span! I can't wait to give it a try!

[pd1]

Thanks Paul...

This will be a Cessna with a 65" wing span! I can't wait to give it a try!

On the full sized Cessna's flaps around 10 to 15 degrees Gets the plane off the ground sooner.

But stalls with that amount and a little power are pretty sharp.

Landing: The early Cessna's used 40 degrees. Most have been limited now to 30 degrees.
The planes didn't do a good go around with that much flap.

If you retracted the flaps all at once, the plane landed anyway.
The most amount of flaps that I know of was the L-19 Birddog, it has 60 degrees.

Why don't you post pictures while you're building it.

Pictures are always nice.

Paul

[Sparky Paul]

You probably won't need flaps for takeoff.
Landing, they do look neat.. BUT!!!
With my Kadets, full flaps and full power do not go together!
Full flaps and full power results in a pitch up that can not be stopped with the elevator!
Power must be reduced and the flaps pulled up to get the nose down.
Normal landing procedures don't need a lot of power, but go-arounds do, so be careful.

[MikeMc]

On the full sized Cessna's flaps around 10 to 15 degrees Gets the plane off the ground sooner.
Correct, and just to add more details...

Most people will use this setting with RC with a normal takeoff which is incorrect when applied to full scale light aircraft, and would most like result in a stall and crash immediately after takeoff. Typically works with RC due to excess power.

Flaps are coupled with a large amount of elevator from the very beginning of the takeoff roll to perform a "short field takeoff". As soon as the plane is airborne the nose is pushed down to level flight to increase airspeed and then shortly after the flaps are removed. Afterwards normal climb-out is resumed with no flaps.

[mtuhoop24]

Are the flaps applied gradually? I have them on the gear toggle of my DX7. When I hit the toggle they go down. When I hit the toggle they go up. No gradual.......just fulll up or full down.

How is this suppose to work.

Thanks.

[Gnascher]

Are the flaps applied gradually? I have them on the gear toggle of my DX7. When I hit the toggle they go down. When I hit the toggle they go up. No gradual.......just fulll up or full down.

How is this suppose to work.

Thanks.

In the "real world" flaps come down slowly. In a full scale aircraft, if the flaps were deployed as quickly as our servos deploy them, the experience in the cabin would be unpleasant. Similar to pressing the brakes on your car real hard (I'm purposely not saying "slamming on the breaks", because it's probably not quite THAT bad). Additionally, it would probably cause undue stress on various parts of the aircraft. In an airliner, even though the flaps deploy slowly, you can definitely feel the braking effect if you watch for it when the pilot begins adding flaps on his landing approach.

As far as models go "bang-bang" flaps are fine ... some people even mix in some elevator to compensate for any pitch tendencies the flaps may induce. You probably won't notice any 'violent' action when engaging the flaps. I'm sure some people may have experimented with having proportional flap deployment ... or incremental (10 degrees, 20 degrees, 30 degrees, etc...), but I've never played around with flaps to that extent.

There are several manufacturers out there that sell devices that slow down a servo. If you wanted to slow down your flap deployment for a scale look you could employ this method. However, chances are you won't be able to see your flaps deploy in-flight anyway, so there's probably not much point except to show people how cool it looks when you're on the ground.

"Down" ... bzzzzzt ... "up" ... bzzzzzzzt ... "Oooh neat!" ... "Down" ... bzzzzzt ... "up" ... bzzzzzzzt ... "That's so cool" ... "Down" ... bzzzzzt ... "up" ... bzzzzzzzt ... .."Ok enough of that".

[mtuhoop24]

Thanks that helps. Great reply!

[MikeMc]

Correct, and just to add more details...

Most people will use this setting with RC with a normal takeoff which is incorrect when applied to full scale light aircraft, and would most like result in a stall and crash immediately after takeoff. Typically works with RC due to excess power.

Flaps are coupled with a large amount of elevator from the very beginning of the takeoff roll to perform a "short field takeoff". As soon as the plane is airborne the nose is pushed down to level flight to increase airspeed and then shortly after the flaps are removed. Afterwards normal climb-out is resumed with no flaps.
It was pointed out to me that I described a soft field take off, not a short field take off. Sometimes I should never speak. :blah:

[HX3D014]

In the "real world" flaps come down slowly. In a full scale aircraft, if the flaps were deployed as quickly as our servos deploy them, the experience in the cabin would be unpleasant. Similar to pressing the brakes on your car real hard (I'm purposely not saying "slamming on the breaks", because it's probably not quite THAT bad). Additionally, it would probably cause undue stress on various parts of the aircraft. In an airliner, even though the flaps deploy slowly, you can definitely feel the braking effect if you watch for it when the pilot begins adding flaps on his landing approach.

As far as models go "bang-bang" flaps are fine ... some people even mix in some elevator to compensate for any pitch tendencies the flaps may induce. You probably won't notice any 'violent' action when engaging the flaps. I'm sure some people may have experimented with having proportional flap deployment ... or incremental (10 degrees, 20 degrees, 30 degrees, etc...), but I've never played around with flaps to that extent.

There are several manufacturers out there that sell devices that slow down a servo. If you wanted to slow down your flap deployment for a scale look you could employ this method. However, chances are you won't be able to see your flaps deploy in-flight anyway, so there's probably not much point except to show people how cool it looks when you're on the ground.

"Down" ... bzzzzzt ... "up" ... bzzzzzzzt ... "Oooh neat!" ... "Down" ... bzzzzzt ... "up" ... bzzzzzzzt ... "That's so cool" ... "Down" ... bzzzzzt ... "up" ... bzzzzzzzt ... .."Ok enough of that".
I know that the JR PCM9XII has this as a programmable setting on its flap switch.
I set mine to about 3 seconds from up to down and the same for the way back.
It was also possible to have the Elevator come down to up and up to down in unison. Was kind of fun watching the flaperons move as ailerons whilst the flaps were being deployed.
You can also use flaps as a mix with elevator (Not usually done with a Cessna eh ;) but some aerobatic aircraft can benefit from it if it is your style.

All in all Gnascher pined it pretty well :)
Nice work Gnascher :)

<Edit Sorry that was supposed to have been;

All in all pd1 pined it pretty well :)
Nice work pd1 :)

No discredit there Gnascher ;)
Edit>

Bryce.

[simibill]

Are the flaps applied gradually? I have them on the gear toggle of my DX7. When I hit the toggle they go down. When I hit the toggle they go up. No gradual.......just fulll up or full down.

How is this suppose to work.

Thanks.

Why not have flaps controlled by the flap switch? That will provide a full and partial deployment.