Jester241

I just posted this in the "beginner lounge" were I usually hang out,but you guys would be a very good place to post this also.....so here it is. What do you guys think? Thanks!.............



Ok,I fly off a short paved runway with an equally short approach to it that requires loosing alot of altitude quickly making it hard to slow down for landing. You have to clear the tops of the trees first,then dive down and hope you can get slowed down enough to land on the pavement and not overshoot it into the rough(hard on cowls and props). So I want to experiment with either spoilerons or flaperons on my Big Stick .60,then maybe my little sukhoi 31,and if all goes well I could use is on my new edge 540. So, if I do decide to try this.....what would you pros recommend? I'm kinda leaning toward spoilerons because I heard the plane wont glide as far. Its easy to glide the whole length of our runway if your going too fast. But I'm not sure if spoilerons would slow me down as much as flaperons. I also hear flaperons can cause tip stalls more,but this is likely the least of my worries as I usually cant get slowed down that far if I wanted too,lol. So,what do you think considering my short approach and having to loose alot of altitude in a short distance?

crasherboy

I am in the process of building a big stick 60 from scratch. This is what I have done ,I widened the ailerons 1/2' and added[inboard] flaps .I had to rearrange things a bit,but I am quite sure it will come in real slow and easy with the flaps full down. I have an RCM Funster that is about the some size,but some heavier ,and it will come in SLOW and steep to. Where I fly I have plenty of room ,but there may be places that I might fly where I may not have so much room. If you were to put your aileron servos out in the wing[2] it would not be to hard to add flaps ,you could use one servo in the middle to operate them. That way you would not have the problem that flperons sometimes give. That is my 2 cents.

AirWizard

My Feedback: (3)

You might want to learn how to Harrier. Then you can slow the plane down and land.

franklin_m

Jester,

Have a little background in aerodynamics, am a graduate (and former instructor) at the Navy Test Pilot School. In additon to about 2000 hours in tactical jets, some work as a developmental test pilot, and I'm also a huge RC flyer. Before I'd tackle your problem, I'd ask if you indulge me a bit so we can be sure of some definitions first. BLUF (Bottom line up front): I'd go with flaperons.

Spoilerons are aerodynamic devices on the top of the wing that have really only one function. They kill lift. Used differentially, they can be used to roll an airplane (A-6 Intruder and the EA-6B Prowler both use them). Used together than can function as direct lift control, killing lift uniformly across a lifting surface. While it's true that they also add drag, this is small in comparison to the amount of lift they kill. They also produce yaw when used differentially, but this is often good, as it produces proverse yaw (into the turn) vice the traditional adverse yaw when using ailerons to roll.

Flaperons are aerodynamic devices on the trailing edge of the wing that can either increase lift differentially or in tandem. Differentially they increase up lift on one wing, but simultaneously create down lift on the other wing. In typical applications (equal amounts trailing edge up as well as down), they produce some decent amount of adverse yaw (away from turn). This isn't to say that it can't be mixed out, designed out, or some other solution, just know that it's there. However, what flaperons buy you that spoilerons don't is the ability to add some lift, while creating uniform drag, while they're used together. The "Flap" part of the flaperon allows you to increase lift a little (to compensate for slower airspeed) while increasing drag.

Going to your specific problem, I don't think spoilerons are the solution because they're mostly lift killers. On a sailplane, they're great for the application you describe (commonly used for that purpose), I'm thinking flaperons are a better solution. That said, flaperons are not a sure fire solution either. On the stick, they'll be just fine (I used them on the Sig Somethin' Extra), but on the Edge, I think you're buying yourself more problems. Not saying they won't work, just with the tapered wing that's also relatively thin, you run a decent risk of stalling the wing across the span...suddently and all at once. I've got a large Staudacher that does that, annoying as crap. It'll be flying a nice and pretty nose high approach until I get just a hair slow, then POW, the nose drops and it plows in. Fun to watch...were it not me.

That's a fixable problem if you want, there's things on full size aircraft called stall strips, that you can add to the leading edge inboard section of the wing. They're small sharp triangular chunks (think tristock) attached spanwise to the leading edge. They're sharp, so they make turbulent air on the inboard section, causing it to stall before the tips, and therefore make it a bit more gentle (unless you really get slow). I've toyed with trying that with mine, more as an experiment, but just haven't gotten around to it. Of course, the more crap, excuse me, aerodynamic fixes, you put on an airplane, the more it indicates that it's "design challenged" or has some nasty characteristic that the designer didn't anticipate.

You've humored me for long enough. I'd go with flaperons, but would also recommend you experiment with flying slow. Do it at altitude, and do it a lot. You will get a feel for how slow you can go.

Probably a lot more than you ever wanted to know, but hey, had some time so I thought I'd chime in.

Frank

BMatthews

This has been a popular topic but the short Reader's Digest version is

Tip or strip ailerons? Use spoilerons.

Tip ailerons with center flaps is best as then you can set up crow. But if this is an aerobatic model then that's out since you won't have room for the flaps since the whole trailing edge is aileron. So spoilerons it is.

da Rock

The straight wing on the Stik is going to be easier to fly near the stall. Wings with no taper to the chord naturally stall from the root.

Tapered wings naturally stall from the tip. The stalled portion having the leverage afforded by the span has more and quicker result, a roll in the direction of the most stall. Landings are seldom directly into the gusting breeze. So stalls during landings are seldom symmetrically balanced, and tapered wing stalls usually produce quicker and more pronounced results.

The Stik will be the better testbed to work out your solutions. The tapered wing, designed for aerobatics models should benefit more.

da Rock

BTW, "diving in to the landing" usually increases airspeed. Explore other techniques until you've got the test setup working. You may find that pilot technique works as well.

For example, fly the base leg toward the end of the runway, not perpendicular to the runway. It flattens the "dive angle" and gives you more distance to slow the airplane.

Steve Steinbring

Just put some stall strips on an airplane as a test bed that was pretty snap happy. So far so good seems to be working well controlling that tendency. I need to do a little more airwork up high to see all the results. Been looking at putting together a 72" Cap 21 kit thats been around in storage for probably 15yrs that the stall strips should work well to tame its reputation of snapping.

Side slipping is a handy technique to loose some altitude as well. I'd advise getting up high to practice the maneuver a bit and see how your airplane reacts.

xlr82v2

My Feedback: (1)

I'd advise going with Flaperons, and learning how to fly your airplane at low airspeeds. Learn what power setting it takes to maintain minimum flying speed... Don't be tricked into thinking that groundspeed equates to airspeed. If it takes 3 clicks of throttle stick travel above idle to maintain altitude at minimum controllable airspeed, then this power setting will always work, whether you're flying upwind, or downwind... your airspeed will always be the same assuming that you have the same trim setting set on the flight controls... if you change elevator trim, it will require a power setting change. What I'm saying, is learn to fly your airplane to it's maximum potential, and fly with pitch and power... groundspeed (how fast the airplane APPEARS to be travelling to your eyes) is not a direct indicator of airspeed. Learn to fly pitch and power.

The reason I don't recommend spoilerons, is, just as Franklin M said, spoilerons are lift killers... which means, when you have your "spoilerons" deflected, it will actually require more airspeed to maintain the same amount of lift (1 G)... to keep your airplane from falling out of the air. Since you'll have a higher airspeed, then you'll also have a higher groundspeed when you touch down, which you'll have to then dissipate before you run off the end of the runway.

Flaperons will allow you to maintain the same amount of lift (1 G) at a lower airspeed which will result in a lower groundspeed at touchdown, which directly equates into a shorter ground roll.

Don't be fooled into thinking that the wing of an aircraft in a stable, unaccelerated descent is producing less lift than the wing of an aircraft in stable, unaccelerated level flight, or even in a stable, unaccelerated climb. In all three instances, the wing is producing lift equal to the weight of the aircraft (1 G). So, if you're killing lift with spoilerons, you'll need a higher airspeed to maintain that 1 G of lift...

Jezmo

The neat thing about spoilerons is they kill lift as stated. In order to get the lift back the angle attack is increased causing greatly increased drag and slowing the plane in the process. There are lots of ways to increase drag but I have my Big Stick set up to have either spoilerons or flaperons depending on which way I flip the three position switch. I can get the plane MUCH slower with spoilerons as compared to flaperons. Yes we have a VERY short runway and approach at one of our fields here in the Houston area and that's where the spoilerons first showed their worth to me. When I switch on the spoilerons my plane will come down in a very high alpha attitude and it is quite stable as compared to flaperons which seem to make it very unstable as it approaches stall. Just my two cents.

mjfrederick

Yes, the spoilers will cause the airplane to present a much larger profile to the oncoming wind and provide a lot of drag, but spoilers should be used for a normal glide slope landing with an airplane that just won't slow down no matter what (i.e. too much pitch on the prop causing too fast of an idle speed). In this particular situation, flaps are the proper solution. The purpose of flaps is to allow a steeper glide slope (which this person needs to avoid trees) without an increase in airspeed.

Jezmo

I didn't clarify that I was referring to model types where full length ailerons are used as both spoilers and ailerons or flaps and ailerons hence spoilerons or flaperons. When used as flaperons they cause a tendency for a wing tip to stall abruptly and can cause a seriously fast roll condition that can't be corrected soon enough if the plane is too low to the ground when it occurs. (ouch!!!) That's my reasoning for preferring to use them in spoileron mode as it tends to reduce the tendency for a tip stall. It really shines when the crosswinds are strong and gusty. For the record, I have been doing this spoileron flaperon mix on my Big Stick 60 with a Saito 91 for about six months.

crasherboy

After reading all the posts here ,I still say rearrange the wing a little and do outboard ailerons with inboard flaps on your big stick 60. As to other models I can not say .

BMatthews

Full span flaperons are best avoided. I've tried them on two models and in both cases dropping the flaps more than around 45 degrees results in a total loss of aileron control. And I do mean total. In fact lowering them to 60'ish degrees and then inputting aileron deflection on top of that and you get a reverse bank and extreme adverse yaw of the tail.

This is avoided if you go with spoilerons where the ailerons deflect upwards. The roll function remains positive and you add the required drag via a higher angle of attack as mentioned by jezmo. The stall speed will still be the same or very close to the same. It'll just make a whole lot more drag to produce the lift.

xlr82v2

My Feedback: (1)

45 degrees of flap is rather extreme, especially with full span flaperons... Cessna 150's had 40 degrees of flap available, but Cessna reduced this to only 30 degrees on the 152 because people were getting themselves into trouble with the 40 degrees (couldn't climb, could barely maintain S&L with full flaps extended).

With full span flaperons, you only need 10-20 degrees maximum... they are very effective, and you still have very good roll control with ailerons.

I use full span flaperons on my Hangar 9 UltraStik 60... when I get home I'll measure what deflection I have set up... I'm quite happy with them... and no trim change when you drop the flaperons on the UltraStik 60. No tendency to "tip stall" either, no more than with flaperons up.

Shoe

One issue I've had with flaperons is the abrupt change in roll response when the down-going aileron hits full deflection. The F-18 gets around this by doubling the rate of the up-going flaperon when the down-going flaperon hits the "stop" (there's also some minor change to stabilator scheduling). I haven't figured out how to set this up R/C yet.

Jezmo

In my humble opinion it isn't worth cutting up the plane and adding the extra weight of the servos to drive the inboard flaps. Besides, I'm very satisified with the performance when using the spoileron setup on my Big Stick. I also mix in a little elevator when I switch them on so the plane doesn't require any stick input to remain in a level attitude.

(One neat feature of having seperate inboard flaps is being able to use crow mode as mentioned above. I still think I would rather save the weight, lighter is better IMHO.)

Red B.

IMHO using strip ailerons as either "flaperons" or "spolerons" is a stop-gap solution at best. I would recommend you split the ailerons so that you can use the inboard part as flaps. Modern radios almost always allow you to couple the surfaces electronically so that you can use both the inner and outer surface as ailerons, but only the inner part as flaps. The weight penalty is often insignificant compared to the gain in low speed performance.
Another suggesting is to learn how to sideslip the aircraft using crossed aileron and rudder inputs. If done correctly it is a very efficient (and also safe) method to steepen the glide path without speed increase. It works fine for almost all conventionally configured aircraft.

Jezmo

I agree with it being stop gap but I don't agree about the weight penalty. Yes side slipping is a great way to slow it down but sometimes you just want to make it easy and mindless, just flip a switch. Again, If you go split flaps/ailerons then crow mode is way cool, I just don't want the weight penalty of the extra servos. I already do a lot to cut weight and to add it back with servos would defeat my purpose. I guess each has his/her own point of view. Have a great one all.

racer-RCU

My Feedback: (14)

another thing to think about it pilot skill and comforatability, one person may love one set-up and another may not like it, one pilot may just have that special technique and another might not be able to handle it, i would say try both.....at altittude with recovery time....just see what works for you

rustypep

My Feedback: (6)

I also have the flaps and ailerons split on my ultra stick 40. I have crow, flaps, and full span ailerons assigned to various switches so I can play around with all of them in addition to flap to elevator to do tighter loops while maintaining full aileron control. The weight penalty is minimal for the extra servos but you do have to match them up well or they won't move as one unit when you turn on full span ailerons. My weight is just over five pounds with a fifty two stroke and she is a floater but not sure I would want to try full span flaps or spoilers using the ailerons on most planes unless it is in small amounts and/or has been stall tested at altitude. It sounds like he needs massive drag and control so crow would be an obvious choice with flaps maybe next depending on the airframe involved. It is very easy to drop down and steer a stick with rudder using crow or flaps. It is also very easy to come in with the nose high at low throttle and hit a small landing area. Lastly, think about your prop and idle speed. A larger diameter lower pitch prop will slow it down and help with braking. An idle speed set too high makes landing more difficult. Proper tuning will solve that problem. Good luck!

VeeAte

After reading this I have to ask....

Whats Crow??

Sorry I am new to flying and i understand flaperons and spoilerons, but have never heard of Crow.

da Rock

When the wing has two sets of surfaces, ailerons and full motion flaps, computer radios can do a trick called Crow. Those flaps are often capable of movement like the ailerons. They can often move as far up as they move down. But it's not required for the trick. Now for the trick.

The computer radio will let you flip a switch that suddenly changes center for the ailerons about halfway up and the flaps center about halfway down. The airplane then experiences a MAJOR braking effect. Yet the plane still responds to the TX aileron stick movement.

It has a benefit that there usually is no major pitch trim change. It also tends to calm whatever tip stalling tendency the airplane might have had as the change of the ailerons center gives the wing washout. MAJOR washout.

VeeAte

Awesome explanation. Thanks da Rock.

I was speaking to a member of our club about warbirds, specifically the P51 Mustang and he mentioned that these planes can benefit a lot from washout as they can have a tendency to tip stall rather easily. I have a P51 on the way and the wing has no washout.

So this might be a good way to overcome (somewhat) this tendency if set up correctly.

Thanks for your help.

emeraude

Hi , im facing the same problem on my flapless .15 sized cessna 180 .Landings are quite fast and require a long final approach.I was thinking some way to slow it down suffiently without stalling.I cant use flaperons as the ailerons are near the wing tips and cessnas have nasty stall habbits at too low an approach speed.Will spoilerons help instead ?.One other option i have in mind is to add jet style airbrakes on under side of the fuselage that can be deployed before landing .Any suggestions?