Can't get INTO flat spin

[Tony Kenny]

Whilst practising for my A, I've been getting a bit adventurous and managed various manoeuvres, just the basics aileron role, flick role, stall turn, loop.

The 2 that I just can't get just yet are the cuban 8 and a flat spin. I can get into a spin of sorts, get on a stall, throw the sticks in opposite corners and cork screw my way down, I'm using this to practice pulling out of that in the direction I want, rather then just thanking my lucky stars I got level before the ground came up! This practise turned out to be very useful when I had a battery leap out and become a pendulum, sending me into a spin, which I managed to rescue, just in time to aim is straight and level into a tree!

But, I'm trying to get myself into a flat spin and to learn how to get out of that.

Any suggestions, please?

[Dave Bran]

It may be in your wording, but how exactly are you entering a normal spin?

[Mr.B.]

Tony,

First, a couple of things. If the aircraft is cork screwing down it's not spinning it's in a spiral dive. And you said "sticks in the corners" you should (for the B test) enter the spin using elevator and rudder only. Spins result from stalling one wing. Therefore the entry must be right on the point of stall. Get high. Really high. reduce power. Keep pulling elevator to stop the nose dropping and slow the aircraft then just before it stalls add full rudder and pull the rest of the elevator if there is any left. It make take half a turn to a turn to develop into a full spin. For the B test you can add alieron now to keep it in the spin. The aircraft will rotate around it's CofG and not crock screw. Difficulty entering the spin can be because a)CoG to far forward b)not enough elevator throw c) entry to fast. Some models spin better one way than the other.

What model are you using?

Good luck.

[J D 8]

Hi Tony, First thing is what aircraft are you flying? While most will spin some types will not get into a true spin where the aircraft rotates about its center point somewhere near the center of gravity. Anything else as you have noted is just a tight spiral dive or corkscrew.

A normal spin can be described as an aircraft rotating about it's center in a nose down attitude. With most models releasing the controls to center is all that is needed to stop the spin and then elevator to pull up into normal flight.

A flat spin is when the aircraft rotates about it's center with the nose and tail level. This type off spin may well need opposit to the direction of spin control input using rudder,aileron and down elevator to recover. With some full size types pilots have to rock the aircraft out of the spin using bursts of engine power.

I have a flying wing that sometimes goes into a flat spin during sharp manouvers but with no rudder recovery is not possible and one just has to power down and let it rotate to the ground. Cheers John.

[Bob Cotsford]

'opposite corners' makes it sound as though you are giving opposing rudder and aileron. Try keeping the ailerons at neutral and the throttle open a crack. The extra airflow over the tail surfaces willl give them a little more authority to hold the model in the stall and yaw it. Adding ailerons in the same direction as rudder will speed up the spin.

[John Muir]

A lot of sport models are set up with a 'safe', i.e. forward CG. If you need a lot of down elevator to keep the plane level when it's inverted, it is difficult to roll without loads of elevator input or it won't spin properly, then try moving the CG back by adding weight to the tail.

There's a really good thread on this forum somewhere about trimming for aerobatics and is well worth finding. A well set up model makes it all so much easier.

You might also need to set up high rates on your transmitter to give you as much elevator and rudder movement as you can get for spins and flicks as well. Some models just don't like to spin and need a bit of encouragement.

[extra slim]

Just me... I enter from height, stalled, full up elevator, left aileron, 1/3 power, left rudder, once spinning, blend the aileron out back to centre whilst adding more power, probably up to 2/3rds and sometimes just past centre and a tad right aileron.. rearward CG and lots of elevator throw help alot.. as everyone says, some models are better at it that others..

[john stones 1 - Moderator]

Opposite corners ? you inverted ?

[Denis Watkins]

Flat spin Tony? If you get chance to fly with me, I have an Hangar9 F22 Raptor circa 2007,

At a certain wind speed, flying the crosswind part of the circuit at full chat

It will breakaway sideways and fling itself into a flat spin, that scares the life out of me.

Luckily, with the huge twin vertical fins, this rotation looses momentum very quickly,

Then all you have to do is let it gain speed to pull out of the resulting stall.

I suspect it maybe too windy to fly it on these occasions, as in a breeze, this does not happen.

Edited By Denis Watkins on 10/10/2017 12:09:09

[Martin Harris - Moderator]

The other week I couldn't get out of a flat spin!

The model is a rather rare pattern ship (Priory Models Supernova) which I acquired part built from a deceased member's estate...it had gone unwanted and sat in our clubhouse for months. I took pity on it when various mumblings about a bonfire were heard as it seemed too good to destroy. I located most parts except the rudder and canopy and made a "that looks about right" rudder based on a sketch in the build notes (no plan available).

I've been delighted with the model but it has always required a full spin recovery procedure (Throttle closed, ailerons central, full opposite rudder, stick forward until the spin stops) to come out of a flat spin (enter spin, increase throttle to full while feeding in opposite aileron) and taken at least a couple of turns to recover. However, a few weeks ago I entered a normal spin and it flattened itself - spin recovery was ineffective, tried blipping the throttle as well but it disappeared from view into the neighbouring corn field.

Luckily, this was fully grown maize and there was only minor damage to the fuselage so a repair took very little time. As the C of G was a bit of a struggle to get far enough back with the 120 4 stroke I'd fitted, I thought that was unlikely to be the cause. The model was carrying a second receiver battery on the C of G as I was using it to test a newly bought (described as unused and no evidence that it wasn't) Jeti "powerbox" intended for my current build so was slightly heavier than usual. My thoughts turned to rudder blanking so I made a new rudder with more area and extending further back.

I conducted some careful testing (hopefully at a point where the wind would have drifted it back to the corn "mattress" should the worst happen) starting with normal spins and progressing to deliberate flat spins - the model was transformed and spins stop on command from all conditions.

So, back to the point, you can see that small changes can make a big difference to spin behaviour. How is your model set up? C of G on or forward of the recommendation? Rudder and elevator at a conservative setting? I always ignore instructions calling for small movements of the rudder - look at the available movement on full size - the angles on the elevator inner ends are there to provide the necessary range...

It's perfectly possible for a fully developed spin to be very nose down - as long as the elevator is holding the angle of attack of the inside wing above stalling, the nose can be pointing down at any angle so don't assume you're in a spiral dive.

Check the C of G and if it's on the recommended point or forward of it and the model is stable in pitch consider adding a small amount of weight to the tail (most designers err on the safe side). A simple test is to see how much elevator is required to maintain level flight inverted (starting with the model trimmed to fly level in normal flight) - most models should require a small input of down elevator. None or even some up indicates a rearward C of G and a good hard push means it's too far forward.

Once you're happy with the C of G, you can start increasing the elevator movement progressively until the model behaves as you want it to.

Edited By Martin Harris on 10/10/2017 12:46:32

[Tony Kenny]

Hi All,

Some great advice again, thank you. To clarify, I was putting in full rudder, opposite aileron and full up elevator. Turns out the instructions I was flying on my sim's tutorial was for a spiral dive but they called it a spin. That certainly explains why I wasn't getting into a spin!

I'll try the suggestions on the simulator and get used to it before trying it on a real model and with this one, I might just buddy up with the club instructor first, just in case!

The aircraft I've been trying this on mostly was a mini switch and I think I got brave enough to try it on my shiny new Dynam Smart, can't remember for sure, probably blocked it out

Martin, sounds like you had a lot of fun! I'm looking forward to those times as I gain more experience!

[Tony Kenny]

I've tried all of the above on several planes in the sim, on full realism, but the best i can get is a tight turn on a downward spiral with the nose slightly downwards. It almost looks as if I'm trying to enter the spin either a fraction too early and the wings still have lift, or, a fraction too late and both have lost lift and i enter a slight dive which recovers airspeed and therefore lift.

Is this a particularly difficult point to judge or and I still missing something? I bet it's a lot easier with the real thing, especially when it's not desired!

[extra slim]

Check CG and ele movement on the SIM model.. I'd of thought it is that..

[John Bisset]

Generally speaking, in the real thing a true flat spin only occurs with the CG well back towards its aft limit in machines with particularly powerful elevator and rudder effectiveness. Adding engine power can encourage a normal spin to go flat in some types, rather as Martin describes. The sensation is then of being thrown forward in the cockpit. Not particularly enjoyable in my opinion even when done deliberately and especially unpleasant if unexpected - as once happened in a two seat sailplane I was flying. Fortunately that was at height in wave and eventually full spin recovery plus airbrake to try to disturb things worked.

With the CG well forward, many machines, both model and full size, develop what you describe; a spiral dive which may at first feel like a spin.

Mr B's description of how to enter a spin works well for both models and many full size machines. My old style Wot4 spins nicely if I have the elevator and rudder throws on max rates. I haven't tried to get it to flat spin, suspect it would need careful addition of tail ballast to encourage that. (Again as Martin said)

Edited By John Bisset on 10/10/2017 22:23:39