Ailerons as Flaps

[Martin McIntosh]

I used to fit drag brakes to fast F3A models in order to get down on small patches. They were 75mm chord and 150mm span, fitted close to the wing root top hinged at 1/3 chord with as close to 90deg movement as you can get. Use brass tube bearing with soldered tinplate hinges, a mini servo since the load is balanced to almost zero, and any pitch change should be no problem with a computer radio. Make the top surface from 1/16 ply or thin ali, with 6 large holes forward of the hinge to give more drag. Very fidely to make and fit, but well worth the effort.

[Peter Miller]

Just to put in my twopennorth. Strip ailerons can be used as flaperons with some degree of safety. Using inset aierons out at the tip as flaperons is a NO-NO because they generate tip stalls.
Common full size practice on STOL aricraft is to lower the flaps and droop the ailerons slightly thus creating effective washout on the wing.
From what I have read the glider boys drop the flaps and raise the ailerons, i.e. Crow braking.
Flaps coming down generate more lift than drag as they start but the ratio changes the further down that they go.
Trim change can vary from model to model. My Fletcher Defender would pitch nose up slightly as the flaps started to come down and from then on the trim did not change. My Midget Mustang shows no trim change at all. The first time I tried the flaps at a great height I thought I must have twiddled the wrong knob as nothing obvious happened.
When the model got lower I could see that I had full down flap and all that happened was that the model slowed down.

[Evan Pimm 2]

As Pete says, if you have outboard (inset, normal, whatever) ailerons then moving them down as flaps will break your model. What happens is you lower them for landing, increasing both camber and AOA of the outboard sections of the wing. The model slows and you set things up for landing. Then you need to line up on the runway, straighten up the wing, whatever, and you use aileron to do it, naturally, we all do, it's how we fly. One aileron goes up a bit, the other goes down. It don't take a scientist to figure out what will happen next. As well as the extra drag of the one going down, and less from the up going one yawing the model the wrong way, the down going one, supposed to raise the wing tip, makes it fall down. Now do the same thing with up going ailerons (`crow braking'). Now it all starts to make sense. If you want to get into a small field then drag control, allowing a steeper, slower approach is what you need, not `extra lift' or any other strange stuff, you need extra drag so you can control the glide slope of the model without increasing the airspeed of the model. Anything that will do that, and inboard split flaps do it quite nicely, is what is needed.
Evan.

[Steve Hargreaves - Moderator]

Thanks Evan.....your theory does sound extremely interesting & on the face of it common sense, however just to lob a metaphorical hand grenade into the mix, the closet theorist in me would worry that a very steep approach would effectively mean a high alpha approach which would increase the risk of a catastrophic stall.

My theory is this; Since a wing doesn't know or care which way, direction or what ever the aircraft is travelling it is only interested in its angle of attack (alpha) to the oncomming airflow...without this it cannot fly. By definition a steep approach is a high alpha one as the oncoming air is approaching from under the aircraft. As an example (& I know the numbers are ridiculous but lets just go with them to illustrate the point) lets say you approach in dead still air at 45 degrees....the oncoming air is meeting the wing at 45 degrees hence your angle of attack is now 45 degrees. From this we can deduce that the steeper the approach the higher the angle of attack, the more likely to exceed the critical value & stall.....

(Stands well back & awaits the Surface to Air Missiles)

PS I have to admit the theory is not mine but comes from "Stick & Rudder" which is an excellent read for those interested in how aircraft fly (although it is fairly heavy going on the tchnical theory side)

[Alistair Taylor]

An old copy of radio modeller I had sitting on the top of the pile dealt with this in a response to a reader question (anyone remember Pete smoothy?).

The advice was that in a high wing model, lowering the flaps would drop the nose, in a low wing model the opposite was true - lowering the flaps would raise the nose. I'm not ure how the aerodynamics work to do this, and I suspect it does vary from model to model.

RM advised using small amounts of flap for takeoffs (10degrees), as per full size practise, and larger amounts for landings (20 degrees). This echos what Peter Miller says about the drag increasing, as more flap is used.

AlistairT

[Steve Hargreaves - Moderator]

I'm sure this is good advise but I think we need to be a little careful when comparing our models to the full size. Specifically on power to weight we have a huge advantage. Being a disciple of NASA most of my models will climb vertically from a take-off run...try that in yer Cessna & see how far you get!!! Of course if you happen to have a Euro Fighter at your disposal then you can disregard that last comment!!!!

The point is though that all this power makes us lazy & rather than allowing the wing to actually work & fly as its designer intended we tend to drag our models around & rely on all that power to get us through the manouever, or at least I do. This is something a full size pilot cannot do. Hence when we cut the power & glide into land we become like the full size pilots & if we forget we don't have a huge fan to pull us along & start taking liberties with the aircraft they bite.

I was reading recently that someone had put a "black box" in a model & recorded a max of 16G!!! That means that yer average 7lb Acrowot effectively weighed...er...112lb!! Thats a lot for some balsa to support but then structural failure is pretty rare. How many full size aircraft are rated to 16G? (Apart from the fact the pilot would be unconcious long before 16G was reached)

Personally I put a lot of my rubbish landings (& flying generally) down to my habit of swapping between aircraft...I always take 2 or three models to the patch & after flying my fun fly & taking outrageous (aerodynamic) liberties with it I always find my flying of other more "scale" models (Extra, Sukhoi etc) suffers & I'm convinced its because, subconciously, I try & fly 'em like a fun fly!!!!

[Alistair Taylor]

I know exactly what you mean steve :)

I switched back to my electric Tucano after flying a TT V-bat (slippery profile, very lightweight, excellent pitch and roll response), and doing cuban-ish type manoeuvres, and was GUTTED at the tucanos slow roll rate, poor elevator response etc etc etc.

If only my brain had the same model memories as my TX....

AlistairT

[Evan Pimm 2]

Steve,
The `Steeper approach, high AOA' thing actually means that the nose of the model is pointing down more, without the model increasing speed. The AOA doesn't change from a normal approach, but the pitch trim change can be, as alluded to, quite large. My Curare goes nose up quite strongly, needing a decent change in both engine speed and trim to stay `S&L' whereas the FW 190 I fly has no noticeable pitch change with flap extension at all. Whether a model will go nose up or nose down depends on much more than just wing position, and even models of the same design can't agree, it's one of those SIAS things...
Evan.

[Steve Hargreaves - Moderator]

Its certainly an interesting theory Evan....not one I'd ever thought of so I will definitely give it a go....I think I need a float plane at the moment though...weathers just been awful so I have to get my Aeromodelling fix from t'internet !!!

[Evan Pimm 2]

Yeah, been persisting down here too, and cold but it is the middle of winter so I guess you can't expect too much from nature at the mo. Floatplanes are one of those wonderfully romantic things that everyone seems to have a soft spot for, I have a 1/4 size Brandenburg W29 thats been languishing out in shed for a few years, needs to be overhauled and re-introduced to the air, funny thing, it took off so well from grass that it never got its feet wet for the four or so years it flew before being stored. Wonder if I should, just for old times sake...
Evan.

[Peter Miller]

Get it out to fly from water, that will guarentee a drought, just like making snow skis ensures a snow free Winter

[Evan Pimm 2]

And putting the batts on charge guarantees wind and rain in the morning...
Evan.

[Steve Hargreaves - Moderator]

Evan, you're not from "down under" are you??? Here in Blighty we hear you guys fly inverted all the time.....maybe thats why the up moving aileron works for you guys....??!!!

[Peter Miller]

I had an Australian engine once. At least I think it was Australian because every model that I put it in tried to get home the short way.

[Evan Pimm 2]

Certainly not Sir, `Downunda' refers to those uncivilised excommunicated ex Poms called `Aussies'. We here in New Zealand are the very antithesis of that sort. And as for inverted flying, well even your water goes down the plug hole the wrong way...!
Evan.

[Steve Hargreaves - Moderator]

New Zealand??? Isn't that where there are 10 million sheep....3 million of whom think they are human!!!! Only joking...I'd love to see New Zealand...the terrain looks awesome...I hear the traffic is light & its generally like the UK was about 20 years ago; I mean, in a nice way...no drugs/guns or religious loonies trying to blow us up with car bombs!!!!

[Peter Miller]

I love that crack about ten million sheep, really made me laugh.
Seriously though, New Zealand does sound like a really civilized place. I corresponded with a friend there for several years until he moved back to the USA.
If it wasn't for the cost of living which I understand is high I might even think about moving outhter if I was a bit...a lot younger.

[Evan Pimm 2]

Yes, we have sheep... but as for the looneys, thats just something you see on telly. Guess we are a bit quiet that way, but then I wouldn't want to be living too close to some of the worlds neighbours. It's just the weather I'd swap for anyone elses...
Evan.

[Steve Hargreaves - Moderator]

Bit damp is it???

Can't be worse than the UK at the moment...we had a blistering April, a so so May & it has literally rained every day since beginning of June....floods....thunderstorms....just appalling...I have two models built & ready to test fly but no sign of any decent weather!!! Aaaarrggghhh!!!!

Peter, I've just received my August RCM&E & your CAP21 is very tempting.....looks lovely...could be just the excuse I need to buy a 30 Four Stroke...how do you think it would go with one or am I better sticking to a 30 2-stroke do you think

[Peter Miller]

The Cap 21 has a SC 32 two stroke. I think you may be getting mixed up with my Fournier RF7 in Simon Delaney's column.
They keep saying a .25 for the CAP 21. Well, it would be quite nice with that engine but the .32 is needed for thr sustained knife edge.
If you go with the .25 KEEP IT LIGHT.
A 30 FS would NOT be very good at all.

[Len Ward]

Forgive me if I go back to basics,but ,using aelerons as flaps can reduce the effectiveness of the aeleron.Can I with due humility suggest that you try controlling the speed with the stick and the rate of decent with the throttle.Obviously the 2 interact but if the plane is set up at the right hight on approach the wonders can be achieved on short landings by using the throttleto vary rate of decent?
Len

[Evan Pimm 2]

Too true, too true, but then you need to have been taught by a knowledgeable instructor, have a properly set up model, know the theory and practice of the thing, and have the discipline to just go out and do zillions of circuits...What? This is a model flying forum...?

And they say that Sunday will be sunny and calm, yeeah.
Evan.

[Flanker .]

I have a nice pattern ship that has a nasty habit of flicking to a spin if slowed up too much with elevator. I use flapperons with great effect and no problems. You do need to take your time setting it up in order not to stall one of the servos but full aileron control is available all the time even at maximum deflection, about 6/7 mm down (I think) after experiments at hight I added a little up elevator mix to compensate for a downward trim change. This set up allows nice steep approches (sp?) and IN MY CASE removed the tip stall flick tendancy at low speed. All my aircraft have this set up, even bi planes, it is brilliant, do it. Also v importent. USE YOUR RUDDER to control turning in finals, and airleron to control any wing drops, much safer. The BEST way to learn this is with a SHOCKIE every one should own one, they bring your skills on like nothing else esp this rudder thing.

[Steve Hargreaves - Moderator]

Thanks for that Flanker...interesting to know....I'm going to try the UK way (ailerons down) & the Down Under way...(ailerons up!!!) & see what happens....just as soon as we get a dry day that is!!!

[Flanker .]

Cool, though I would not recommend ailerons up, thats more glider stuff, known as reflex.
Also of note is that it is fine if only one aileron moves in the flaps down position, on my aircraft once the flaps are down there is no more travel left. This is fine, i've used this set up for over 10 years with no snags.

Thing is with them down you get more LIFT at a lower SPEED with more DRAG which is ideal on the landing approach, you may need to use more power though esp just before the flair. Very necessary on my big bipe just before touch down to avoid a bumpy landing. Have fun mate.