I recently put my slightly tail heavy Astro Hog into a flat spin for the first time. Full up, right rudder, right aileron, low throttle after a couple of turns of a regular spin, I cross-controlled the ailerons to the left. Instan flat spin. After saying "Oh, wow!" I decided it was time to recover - It didn't! Full throttle, down elevator, left rudder, nothing. Just kept spinning. It plopped down in tall grass with minor damage. Now I want to know just what it takes to recover from a flat spin. More power? A bit of weight on the nose? The flat spin is pretty, but I don't want to repeat this performance[&o]!

Later... Kenny

Move the c.g. forward.

HI SMALL RC! Check your rudder linkage to make sure that it can't wimp out, especially in push mode. A plane that has a small rudder might not have the authority to stop the planes' momentum. Ample rudder area above and below the fuselages thrust line is helpful for inducing, and getting out of flat spins. A goodly amount of rudder throw will help also. You might think about installing a larger rudder, even counterbalanced per whatever proven example you can use to get an idea of proportion. Those flat spins are fun, huh? Setting up your ailerons to act as flaperons when coupled to the elevator will flatten those spins out even more!

You could try putting the ailerons back into the spin to the right, this helps on recovery by bringing the angle of attack of the two wings closer together again... Most of the time the power needs to be on to recover with a model... I had the engine quit during a flat spin with a model and it was completely unrecoverable... but you may try pulling power back to see what happens... the other technique you could try is rocking it with the elevator (full down-full up- full down-full up) this is what the F-16 does to recover from a spin, or I should say that's what it's computer does.

But to be safe move the cg foreward to the suggested position before attempting the next flat spin... that has the greatest impact of all.

Ty

I put three different Chipmunks into inverted flatspins. None of them came out. I read where the Harvard pilots were told to bail out in inverted flatspin as they wouldnt come out. I think it was because the centre of lift was to far ahead of the CG in the inverted flatspin and the elevator didn't have enough authority to pull it out.

As mentioned by Ty, "Pro-Spin" aileron is what you have to train your quickly panicking brain & thumbs to remember. Release all controls first; shove the ailerons smoothly over to the direction you kicked the rudder in to enter the spin; calmly ()wait 2 or 3 rotations; THEN try opposite rudder. Power seems to help as well.

'Course, moving the CG forward will help as the others have said but where's the excitement in that?

Some designs just will not recover -
there is plenty of fact to back this up
In models - conventional tractor types - typically they are sport/trainers with limited surface throws and aft CG setups.
Visulise what is happening - and where the center of rotation is located.
In most cases there is no air movement aligned with
"flying" attitudes.
My little flat fuselage & flat wing foamies are the easiest types to recover as they have mucho drag and very little weight.
The opposite setups are the worst -
very little side area and/or balanced side area front to rear on the fuselage - does nothing to make the thing want to go back to being an arrow---
you can actually make em climb in a flat spin.

smallrc - I don't know if this was the problem with recovering your Hog from the spin, but I can verify combatpigg's assertion here. My second R/C plane had NyRods that I failed to anchor anywhere in the fuselage. The clevis was hooked to the underside of the elevator. I was flying inverted one day at many hundred feet when I decided to do a half inside loop to recover. It went straight into the ground and at the time I thought it was radio interference. It wasn't until much later that I realized the pushrod had collapsed under load.

I have had the same experiance that some kits will and others won't. With my big Cap, you just let go of the controls, with my little bashed telemaster with a pull-pull rudder linkage, you go pick up the pieces.

I love spinning... some planes will flatten out nicely once they're rotating by -easing- out the pro-spin aileron. Take it out too quickly and the spins stops.
Others go right on down into the ground. These have the c.g. too far aft.
My racing HOB T-6s suffer this way. The "good" c.g. for racing is too far aft for violent manuvering.
Going from up to down elevator can change things in an interesting maner also.

Kenny,

Let me see if I can summarize.
1. Check your controls. Put in full rudder, hold it and try to move the rudder with your hand. Do this both ways. Do the same for elevator. Fix any direction that flexes.
2. I have flown a lot of flat spins, including some to the ground, both intentionally and not intentionally. I like the CG back myself because the plane does better tricks. You are going to need the engine running at, I think, full power. For the most part, the only air flow you have over the controls is from the prop blast. Keep the power up or add it.
3. Try going back to normal spin controls at full power, then release to recover. Most all models will come out of a normal spin by releasing the controls.
4. Try opposite rudder. This is what I use first if releasing doesn't work.
5. Try full down at full power. The idea is to blow the tail upwards so the plane gains speed going down and flies out of the spin. I have used this a lot, too.
6. If the plane's nose gets down, use opposite aileron to stop, you may just be rolling. This happens on a heavy plane sometimes.
7. Lastly, yell out, "Did you guys see that."

Ty, You're a long way from college in Daytona Beach and RC Online.

Saw a few fullsize Chipmunks and Quite a few more Tigermoths with fuselage strakes on the side of the fuselage at the root of the stab. Supposed to help pull out of a flatpin. Search ( tigermoth) and i'm sure they'd show up. Might be worth trying on a model to see if it works,, or doesn't.

Had a plane stuck in a flat spin that wouldn't come out. WhenI ran out of options I used the spoilers and had a last minute recovery. After that it was the only way it would recover
B-

Thanks to every one for the advice on my flat spin problem. Sounds like most of you agree that the tail heavy-ness is a major contributing factor. I'll try going forward with the CG and make some of the other suggested corrections and try again.

Later... Kenny

I love to fly all of my big bipes, (1/4 scale and up) into an inverted flat spin. My best is a custom modifieed ULTIMATE. I find that the one thing I need the most to get out of the spin is POWER. Lots of pitch so that you have huge amounts of air moving across the control surfaces. By the way my ULTIMATE spins within its own wingspan.

Ed_Moorman's point 3 is the flat spin recovery technique that should do the trick.

Not all aircraft will come out of a flat spin directly. Try going back to normal spin controls (in the direction of the flat spin, e.g. for an upright flatspin to the left that will be full up elevator, full left rudder and in some cases full left aileron) and then wait until the flat spin becomes a normal spin (it may also require a little bit of juggling with the throttle, but in most cases I have simply returned the throttle to idle). The hairy part is to wait for the flat spin to revert into a normal spin, it may take several turns to do so. After the aircraft is spinning normally one can use standard spin recovery techniques.

/Red B.

OK guys here's how it works,

When you are in a flat spin you have gyroscopic procession, p-factor, and gyroscopic slipstream acting on your airplane. Now, we all know that the reason one we are spinning is because one wing is stalled out more that the other. We put aileron into the direction of rotation to further increase the stall in the already stalled wing. Now that that's covered let's talk about added power. All of that power you are adding is simply increasing the gyroscopic procession and actually forcing the tail down. I am fortunate to have access to a Christen Eagle and Extra 300 full scale at Mark Anton airport located in Dayton, TN. One of the top aerobatic pilots (and my instructor) Tim Bastian, flys IAC (International Aerobatic Club) competition and this is his preferred method of recovery. It's called the PARE approach.

Power off.

Ailerons neutral

Rudder opposite the direction of spin

Elevator down (if in an upright spin) or Elevator Up (if in an inverted spin)

In any case get the nose pointed toward the ground.

The opposite rudder and elevator should be applied simultaneously. Rotation should break within a half turn. I Promise.

See ya,

Dan Payne

I teach in the Pitts S-2B, and Extra 300 full size, plus compete in unlimited in my Pitts S1S, and I absolutely agree that the PARE recovery works every timein a full size. However, models often take power to recover from flat spins. I flew models well before I flew full size, and I had the engine quite a couple times during a flat spin... both times the plane spun to the ground even with full opposite rudder and full down elevator.

At the flight school I work for ALL private pilots are taught spins before they solo... I do quite a few of these spin lessons for the other instructors students. So far I've had about 4 students with modeling backgrounds, one of which competed in IMAC for quite some time, all of them thought that they should use power during the spin recovery because of their modeling backgrounds. The differences are pretty extreme between full size and models... The mass distribution, wing loading, and definately the power loading are all very different. If an Extra 300 weighed 800 lbs instead of 1500, and had 600 horsepower instead of 300 it would probably come close to a typical model. In fact Wayne Handley could do a power on Recovery from a flat spin in the Raven which came close to a model in power loading.

One more note, gyroscopic reaction from the prop only flattens the spin when in an upright spin with left rudder, or an inverted spin with right rudder... Going the other way gyroscopic reaction drags the nose down and accelerates the spin... which is more dangerous then a flat spin in my opinion.

Lets address spins a little more...Did you all know, that in Full-Scale competition a flat spin is scored just the same at 60 degrees nose down as it would be completely flat? OK, now we are getting somewhere. 60 degrees nose down spinning is considered flat in full scale. this is per IAC regulations. Correct me if i'm wrong aero sport ty but i believe those are still standard rules.
The Full scale Extra 300 is 1380 lbs empty weight, and with only 300 horse it is an awesome performer. We generally get 3600 FPM climb rate with two people and full fuel, where as your average 150 horse 172 would be lucky to get 1000. The Extra's spin rate just accelerates when power is applied. The best spin you can get out of one is inverted full forward left stick and right rudder to break into it, then gradually push the stick (while maintaining full forward) to the right putting the ailerons into the spin. Go full power and it will flatten out extremely nice. The exact same technique works excellent in models as well. It will take an extremely powerful engine in a full scale to blow it out of a spin. Now, most people cannot understand why jets have a hard time getting out of a spin. That is because of gyroscopic procession (A characteristic of all rotating bodies, when a force is applied to the outside of a rotating body, parallel to its axis of rotation, the rotating body tilts 90 degrees in the direction of rotation from the point where the force was applied) acting on a jet is so great. What gyroscopic procession does is actually holds the tail of your airplane down. Reducing power reduces the gyroscopic procession, and applying control forces to counteract the direction of rotation gets things straight and level again. In an Extra you might be getting 15,000-25,000 pounds of gyroscopic force in a spin at full power. A jet generates almost 90,000 pounds at idle. Therefore when you get in a spin in a jet, you got your hands full and your best options are to plug in the burner maximizing thrust and actually blowing the airplane in to flight again. Also, please remember that it takes two turns for a spin to fully develop. So always remember that if things look crazy in the first turn it's time to go PARE. Another important point I would like to address is called yaw coupling or a moment of inertia. Many full scale pilots got into trouble by placing their batteries in the tail of their Pitts while trying to balance them after putting bigger engines in them. Kinda like we do in our models with battery packs right? Well, making it tail heavy by adding weight in that tail creates a moment of inertia when you begin to spin. Before you do that, consider the fact that you may or may not have enough rudder to break that moment of inertia that is going to build from rotation of that extra weight in the tail of your airplane.
Just my .02 worth,

Dan Payne
Hangar A Aero Services
Dayton, TN

Neutralize all surfaces, let the plane dive a little to build up some speed, use a little aileron to get your exit line correct, pull elevator and return to normal flight

It's hard to imagine anyone trying to trim their model so it WONT SPIN[:'(]! If you power off any of my planes in a spin you will make the recovery a sloppy mess, and with nuetral ailerons you clean up the spin, but that's not the key to recovery. Pointing the nose down is the #1 on the "to do" list. If the tail of the plane has too much angular momentum for the rudder to overcome, a panicked pilot might give up on opposite rudder if it doesn't work right away. The key to recovery is to have a plan , and stick to your guns, because it might take a few seconds for the corrective measures to work. The lighter the plane, the easier the recover.

Talking just about models and not full scale. What you have is the airplane at 60-80 degrees angle of attack with a really big yaw rate. Think about how a modern model that does 3D maneuvers is flying. They can be fly (although the surfaces are fully stalled they still create lift along with a boat load of drag) and be controllable at 60-80 degrees angle of attack using just the prop blast over the tail surfaces. This includes roll, pitch and yaw. The ailerons are usually full span and the tail surfaces are big. Since the prop blast is all you have to work with (well almost) they have to be big.

Now think about the Hog. It has small full strip ailerons and relatively small moveable tail surfaces. However a good prop blast across the surfaces that are there will help. You can use the ailerons deflected into the spin direction to roll the airplane. Although you use the deflection to help get the rates up to enter the flat spin it also changes the angle of attack to a sideslip angle as the airplane rolles about the airplane body axis, reducing the airplane angle of attack and increasing the sideslip angle. The directional stability is more effective in recovery and full down elevator in the prop blast and rull rudder opposite the yaw rate will give a nose now and anti spin moment.

You end up with an airplane going to a lower angle of attack where the vertical tail and rudder is more effective and it will literally roll out of the spin. It does require a good prop blast though.

Whether or not the airplane will stay in a spin depends a lot on the directional stability of the airplane, Cnbeta, yawing moment with respect to sideslip angle. I had a shoulder wing model (bought from a friend that built better than I did) with what looked to me like a small vertical tail. It flew nicely though and would spin and flat spin on command. I thought I would dress it up with a canopy right over the wing. The CG was the same since the canopy was right over it and the weight was the same (just a piece of very thin plastic). The canopy lowered the Cnbeta of the airplane and the next time I tried the flat spin it would not come out. The ailerons were conventional located and could not get any prop blast over them. A landing in high weeds next to the field saved the airplane.

I removed the canopy and things were back to normal. The extra area forward of the vertical tial lowered the Cnbeta. The change wasn't much, but enough.

The same thing happens with a CG change. The Cnbeta is lower with an aft CG and the rudder moment arm is lower which will keep you in the flat spin. Go forward with the CG and both items change to a favorable value to let the airplane pull out.

Full sized airplanes are a different horse, as some of the writers noted the inertial effects of the prop are significant where as our relatively little (with respect to the airframe) props don't do much in that regard. Perhaps a geared electric power plant turning a really big prop would act similiar to their larger brothers.

Here's a thought... when u originally balanced you model, was it nose heavy or tail heavy? if it was tail heavy, where did you mount the weight to balance it?

Reason i'm asking, i learned about a guy who balanced his full scale plane with a bowling ball in the tail area of the plane. Even though his plane ended up within CG limits, when he put it in a flat spin, the centrifugal force of the weight being so far towards the tail put him in a flat spin that he ended up crashing from.

Thats a new use for a bowling ball! Actually what happens is that the moment of inertias go up. You can write a big hairy equation that defines a steady state flat spin and in it is included the moments of inertia of the airplane about the 3 body axes. Increasing his yaw and pitching moment of inertia by one bowling ball, along with a move aft shift in CG, put him over the edge.

He would have been better off balancing with a higher weight closer to the CG. The moment of inertia is a direct function of mass and the square of the length. The link below gives the methods of determining several common moments of inertia. The fuselage is like the first one. For an irregular body like a fuselage with motor, person, construction and bowling ball you would do each piece separately.


http://www.physics.uoguelph.ca/tutor...e.inertia.html

Flydenfeld

The situation with the full scale pilot spinning into the ground is exactly what I described a few posts back. I DON'T CARE WHETHER IT IS A FULL-SCALE OR A MODEL AIRPLANE THE SAME RULES APPLY REGARDLESS! People with full scale airplanes that put a bigger engine on them use to put their batteries in the tail of their airplanes to balance them out. We do exactly the same thing in our model airplanes, RIGHT? Yaw coupling, which is basically a derivation of a moment of inertia is what kills people. Think about it, when you get an airplane spinning, you're getting a weight spinning in the tail of your aiplane. If your airplane does not have enough rudder to break this moment of inertia, you are SCREWED. This is the way things work Lanterman. I have seen full scale pilots die from this. Yes it does depend on the length of your fuselage. The longer the fuselage the more rudder authority needed. The shorter the fuselage the less. Granted, the number of rotations per minute can also play a key role in the moment of inertia as well. All I am saying, is that if a 18-20 lb battery in a 1500 lb airplane makes a difference like what I have described above, think about what your 1/4 lb battery is doing in your 6lb airplane.

Dan Payne
Chattanooga, TN