Landing with flaps

[fearless]

Hi guys can someone enlighten me on flaps, does it matter if they are up or downwards on take off and landing?

[sihinch]

Putting flaps down effectively increases the camber of the wing which in turn increases lift. And drag. So in very simple terms, some flap down is good on take-off to increase lift (and reduce take-off speed) and lots of flap down is good for landing to allow your approach to be slower (without stalling.)

This is very simplified and doesn't explain the aerodynamics too much.

And most of our models don't require flaps for take off because the thrust to weight ratio is usually very good, and our models don't generally weigh that much (comparative to their size.)

So another rule of thumb - the bigger and heavier the aircraft, the more they will benefit from having flaps.

When flying along normally and cruising, flaps should be raised level with the trailing edge.

[fearless]

Thanks Simon,


I just wanted to know so I can use it on my jet because it a pretty big,  well to me anyways lolz. 
So just wondering what does flaps up do?

[Michael]

"Flaps up" are essentially used as spoilers on gliders and other airplanes to help planes descend faster, and to get out of thermals.

Never use 'flaps up' on a jet.

When using flaps down (a little bit of flaps for takeoff or to slow down, and more flaps to slow down on landing), you will have to be mind-full of the following:

1. You will have to mix in a little down elevator for each down flap position, maybe 2% for medium flaps down, and 4% for full flaps down, or else the plane will nose up, and could stall. Each plane is different and you will have to figure this out; you could check online to see what others have done.

2. Don't use more than 45 degrees down flaps. More does very little.

3. When using flaps when landing, unless the plane is just about to touch the ground, always keep the nose level or nose down, but never nose up; the plane can easily stall.

4. When using flaps, trim to fly level at approx. 1/2 throttle. Stay at half throttle until you're about to touch down.

Any comments, criticisms or corrections from anybody?

[Wingnutz]

Gonna weigh in on this one with the expectation that persons who know more than I will correct my inaccuracies and untruths.

Hi guys can someone enlighten me on flaps, does it matter if they are up or downwards on take off and landing?

Short answer...yes it matters.
Even in the RC world, it's a bit more complicated than that....I agree with Simon...flaps are pretty much unnecessary for RC take-offs.
But...sometimes flaps should be used and sometimes it's probably safer if they're not used or deployed only partially for landings.
Use flaps for landings if you have light winds and need added drag to slow the model on approach and can safely give away some manouevrability.
But, probably best to use no flap or partial flap at most if it's windy.
A headwind will decrease your ground speed on approach and landing, making slower stall speed of flaps less necessary or downright unsafe depending on the strength of the wind...the more wind you have, the less flap you need and the more airspeed you need to maintain manouevrability...this is really important if your model is an EDF (Fearless is your jet an EDF?) as there's no prop wash over the tail surfaces to help maintain control response.
In a gusty crosswind landing, using flaps is even more risky as flaps mask airflow over the tail surfaces and compromise tail surface authority...you need all you can get for crosswind landings.
As an aside, can flaps can be positioned up? (as against retracted to the normal trailing edge position) I thought gliders positioned ailerons up to create reflex (spoilerons) or ailerons up and flaps down to create crow and really put the brakes on.

[Michael]

I agree with Bill; don't use full flaps if you have a good head-wind.

[fearless]

Thanks fella's.

Yes it is a EDF Jet.  Maybe i'll just put the flaps DOWN 20% and gradually increase if needed with a little mix 1-2% of down elevator correct?
Also you suggested on a cross windy day not to use any flaps at all?
I never used flaps before this will be the first time.

[flying IT]

interesting question.

I will speak from full scale knowledge that I have found out does transfer to models.  Aeronautical rules don't change.  Simon, Micheal and Bill have given very good answers.  The negative bit about flaps is the large increase of drag, which means, to hold a plane level you will need to lift the nose, and trim accordingly (as per Micheal) with more flaps you drop.  You will fly slower though, and increase your lift.  Because you are in the realm of slow flight any sudden movements can cause the plane to drop out of the sky.

Use of flaps, on landing, usually was done turning onto base (the part just before turning to face the runway), usually somewhere around 10 to 20 degrees and then dropping 40 on final (if needed).

When doing a crosswind landing you are crabbing anyway,  I would sideslip if need be.

There is a maneuver called Canyon Turn  that requires about 10 degrees of flaps while turning.  If done right the wing tip is stationary

[Wingnutz]

Thanks fella's.

Yes it is a EDF Jet.  Maybe i'll just put the flaps DOWN 20% and gradually increase if needed with a little mix 1-2% of down elevator correct?
Also you suggested on a cross windy day not to use any flaps at all?
I never used flaps before this will be the first time.y

Fearless,
Fear the flap...well, at least try to understand flaps!
If this is your first flap experience, do some in-flight testing AT ALTITUDE before you use them on landing.
Fly the model straight and level at an altitude of three or four mistakes. Extend the flaps and see what happens. Some models will pitch up, Some will pitch down and some will maintain level flight.
If pitch changes with flaps, trim to level flight with a flap-elevator mix.


I have several models with flaps and I only extend flaps if there is no wind or extremely light wind. Never on a windy day and especially not if there's cross-wind.
Whatever else you do with your EDF model, maintain a brisk approach and touch down speed...and, have fun!

[Frank v B]

One thing that was not mentioned- if you come in for a landing and elect to pass, make sure you throttle up before retracting the flaps.  Speed has to compensate for lift loss when flaps are retracted.


Frank