Landing/take off flaps

[seesul]

I have a question for pilots as Flyboy etc.:
what is a different between landing and take off flaps?
is it always the same flap and the only difference is the angle of its inclination?

thanks

 

[FLYBOYJ]

Hi Roman;

A very broad question. Some aircraft have flaps that are utilized for mainly landing only. Other have provision in their pilots' manual to deploy flaps (5-10 degrees) for short field take off. Other aircraft have a take off flap setting (again 5-10 degrees) under normal conditions, and have landing flap settings up to 30 (or more) degrees. For example - A Cessna 172 has no flap setting on normal take off but does have a 10 degree setting for short field take offs. The L-29 has a 10 degree flap setting on all take offs and up to a 30 degree flap setting on landing. Airliners have specific flap and spoiler settings for take off and landings that vary in with each aircraft.
Hope this answers your question!

 

[Nostalgair]

Hi,

As FLYBOYJ rightly commented, it's a pretty broad question. Anyway, here's a little more input in a very simplistic sense.

A primary purpose of all flap is to increase the wings' amount of lift. i.e. it's ability to fly. In the take-off and landing phase it is particularly useful in allowing flight at lower speeds, leading to shorter take off and landing distances. (Always useful )

A common comeback is that, "If they increase lift, why not fly with flaps extended all of the time??" The reason being is that they also cause resistance to the airflow,or 'drag', which is not ideal for most phases of flight. For take-off and landing the trade off is acceptable.

FLYBOYJ is on the money about landing flap normally having a greater degree of extension relative to take off flap settings, which is often zero on light aircraft.

Also, on more complex wings take-off 'flaps' can be found on the front, or 'leading edge', of the wings. These 'leading edge devices' can be slats, flaps, etc. Also used in the landing phase, for take off they are usually extended in unison with the take-off setting of the 'trailing edge' flaps at the rear of the wing. Once again they are retracted after take off.

The photo below is not the best, but it was all I had at hand. It shows the extension of 'lift devices' on both the leading and trailing edges of the wing on this Boeing 737-300)

As mentioned, this subject can get very complex, so I've skirted the edges.I hope it helps.

Cheers

Owen

 

[seesul]

Thank you Joe and Owen!

this is what I wanted to know. Thank you for your description.

 

[seesul]

one question more- i´m writting with my daughter in my arms, so very quickly- tail wheel lock/unlock- is it so, that the tail wheel is unlocked during taxing and locked during take off and landing?

 

[Crumpp]

Yes tailwheel is unlocked during taxi and locked during TO.

 

[FLYBOYJ]

and locked during TO.

Oh I hope so!

 

[Nostalgair]

Hi again,

Once again it depends upon the aircraft type.

If you have a lockable tailwheel, it is unlocked for taxi, but locked in line for take off. Some tailwheels have a mechanism that locks the tailwheel on take off when the stick is held back, the normal position for commencement of the ground roll. When the stick moves forward and the tail comes up, the tailwheel unlocks.

Others, like the Tiger Moth were designed with a tailskid. My Tiger (below)was modified with a tailwheel and it was purely castoring with no means of locking it.

Cheers

Owen

 

[FLYBOYJ]

Nice plane!!!

I maily fly 172s and these days Supercubs. We have Scott tailwheels on ours.

 

[Crumpp]

If you have a lockable tailwheel, it is unlocked for taxi, but locked in line for take off.

Key word being IF.

I fly a Decathlon on occasion which is free castering. I like it as it is very maneuverable. You just need a longer TO run.

My "family" plane has a castering nosewheel with differential braking. Just the opposite, LOL.

Beautiful Tiger Moth Owen!

All the best,

Crumpp

 

[Crumpp]

Also, on more complex wings take-off 'flaps' can be found on the front, or 'leading edge', of the wings. These 'leading edge devices' can be slats, flaps, etc. Also used in the landing phase, for take off they are usually extended in unison with the take-off setting of the 'trailing edge' flaps at the rear of the wing. Once again they are retracted after take off.

Good explaination. Allow me to expand and clarify a few things please.

Depends on the LE device if they are retracted or not. Some are used continuously like the fixed slots on the Swift for example.

Others, like my aircraft, have such things as Handley-Page automatic slats. These are deployed by the wing when needed without any input from the pilot.

TE flaps work primarily by increasing the camber of the airfoil and altering our Angle of Incidence. This allows the pilot to lower the nose to see and the wing to develop the needed lift at a lower velocity. Don't think of these Leading edge or Trailing edge devices as "high lift". They are not. Lift only meets the amount of force required and in level flight equals weight whether our flaps are deployed or not. The TE flap allows for an increase in the coefficient of lift the wing is capable of producing but reduces the Angle of Attack our wings maximum coefficient of lift occurs. The net effect is too reduce the usable Angle of Attack of the wing.

Flap performance depends on L/D ratio. Generally speaking in the first few degrees a TE flap will develop its greatest lift benefits for the least drag penalty. At full deflection our lift benefit is high but our drag penalty is at its greatest. This means our aircraft is limited in the maneuvering it is capable of achieving. In other words it will not turn its best Rate of Turn. Additionally deploying flaps lowers load factor limitations on the airframe.

So there are very good reasons why WWII fighter pilots did not drop full flaps to try and outturn each other as it just would not work!

These devices are "high coefficient of lift devices". Some devices energize or add energy to the boundary layer as well. This means they induced turbulent flow with is also high lift flow and requires more energy than laminar flow. Turbulent flow also produces more drag.

All the best,

Crumpp

 

[Nostalgair]

Hi Crumpp,

A very thorough response. I was trying to keep it fairly simple, so I did skim over such things as slots and slats, grouping them together as leading edge devices. (The Tiger Moth above also has lockable, automatic slats)

...and unfortunately the Tiger Moth has gone to a new home. I have something a little less exotic and more practical in the hangar now. (...for the moment)

Cheers

Owen

 

[Crumpp]

I was trying to keep it fairly simple

Don't worry; I had you pegged as someone who could speak knowledgably on the science of flight from reading your post. If I didn't you would have definately known it too. I have a very short fuse with BS'ing.

The challenge was to let you know I understood you were just keeping it simple and convey the fact I was only expanding upon your explanation.

It was not to come across as correcting you.

How did I do?



All the best,

Crumpp

 

[Nostalgair]

No sweat Crumpp.

I enjoyed reading your post, it's well put.

Cheers

Owen

 

[seesul]

Thank you friends!
Beautiful Tiger Moth Owen