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Ever wanted to get into or improve your aerobatics?


Peter Jenkins
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I have just started to look at this thread and have read most of it with interest.

There are some very good points here but also some which require questioning.

As a former twice F3A team member and once Btitish champion I feel that I am reasonably qualified to comment.

I do not attempt the current schedules because (a) I do not like them and (b) I am now too old but I still enjoy the manoeuvres which I used to do.

The method of trimming wing balance is sound but only works if you are truly flying directly downwind and push to a half outside loop on low throttle. Insides do not seem to work for some reason. This is the way I do it.

CG and thrustlines are not difficult to set up. Starting with the thrustline, with the canopy towards you pull to the vertical and see if it remains that way. adjust as necessary and a good starting point is 2deg. right.

I try to set CG so that at the end of a spin the model should stop after exactly one half turn when the controls are neutralised. Forget the climbing/ diving, if the model is set up to tail 0 deg., wing +1 deg., motor - 2 deg downthrust then this will be a good starting point for most. If using a very large prop, say on electric. then the right thrust may have to be greater.

I must totally disagree about using the inner servo hole and have seen much written about it. If you do this, then to get the required surface throw you must use an inner horn hole so any play/slop will be amplified. Try it and you will see what I mean. I once got a tip from Mike Birch which was to make the (then used) quick link connection loose so that the feeble servos of the day had a chance to centre. This is still viable since no matter what you pay for your servos they are only able to centre a surface if there is no resistance in the linkage. It is the slop here which is amplified by an inner hole, not the servo gear play. I now only use ball links (cheapo snap on at one end and screw on at the servo works fine). Quick links just grab the arms/horns and give a lot of resistance usually.

Don`t use snakes on controll surfaces since unless they are dead straight and are pinched along their length they will be sloppy. Use hard balsa or cabon tube.

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Posted by Algy Yates on 01/12/2013 12:11:44:

Something that is worth noting about servos. Most metal geared servos have a greater clearance machined into the gears than in the nylon one and so often have more backlash. I think that is why most F3A pilots use nylon geared servos.

My servo set up, even when using ball links, is to attach to the outer hole on the horn and then move the ball in on the servo arm until I have the required movement (especially if using normal clevises) as this reduced the effect of any play in the linkage (but it has no effect on the servo backlash or servo load).

I think Martin you and I are of similar thinking as I said above I always start with the outer most hole on the surface horn and only come in on the servo horn to get the range of movement at 100% rate to give the best torque and centre, in fact on a lot of my models I have fitted longer horns on the surface so that I can use the outer holes on the servo arms for the very reasons you give. Also as I said above this has no effect on the servo torque output or the backlash play but will reduce the play from the linkages.

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As an afterthought to the above just look at the enormously long rudder servo arms on almost any top 3D model. Modern metal geared digi servos will find that centre no matter what, which is why they `sing` and are of course necessary on these to cope with the load but are not favoured or required for F3A.

My Curare replica is fitted with quite cheap nylon geared analogue servos just for authenticity.

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I feel the need to explain why we should use the outer hole on the control surface horn, as there seams to be a lot of talk about using the innermost hole on the servo arm.

To start with as long as we maintain the same ratio between pivot point and connection point on both the servo arm and horn the amount of control movement for a given servo arm deflection will be the same. If we accept that as true then the amount of rotary force on the control surface is the same, as is the resolution of movement.

So why use the outer hole on the horn? Well there are several reasons, so lets look at the effect of having a horn twice as long:

  1. The point of connection on the servo arm is now moved out to twice as far from the screw so that we have the same control surface movement.
  2. The servo arm now only pushes on the rod with half the force but this reduced force is a bonus not a negative. Why?
    1. Well with the horn being twice as long the rotary force on the control surface is doubled, right back to what it was before.
    2. The reduced force means the load on the push rod is reduced by half so it can be lighter.
    3. The force on the servo mounting rubbers is halved so the distort under load less.
    4. The load on the push rod connectors / clevises in halved as well so wear is reduced or distortion of the ball links is reduced.
  3. The effects of any sideways movement in the servo, servo bearings or play in the linkage is halved on the control surface.

All of this is a benefit if you are not using the less expensive servos and linkages but it also has a positive effect on the expensive ones. Even with very expensive bearing link control rod ends and £100+ servos there is a small amount of play (or they would be very tight and this would effect centring), any one saying otherwise are miss guided.

With any model you want to have your servo throw set to 100% or greater to get the best torque and resolution from your servo, you do have to be careful if you use anything other than the smallest amount of subtrim that you do not over drive you servo. If you set you servo throw down to say 50% to get the amount of movement you need the you are only getting half the torque and accuracy from the servo, this can have a big impact, with surface blow back and poor centring. This can be avoided by now moving the push rod connection in on the servo arm (or better still using an even longer horn).

Okay there are models which long horns are not suitable such as, slim winged gliders and scale models. So what can we do with these models well we may have to compromise by using more powerful servos, accepting lower servo resolution or spending a lot of cash on the very best linkages.

As well as the servo, horns and linkages, we have to ensure that our hinges are also up to the job and play or compressibility in these will reduce control surface accuracy. The last thing is also in all this we must make sure the servo mounting structure and main surface structure is sound and flex free, again long horns help with the latter.

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Thank you Martin for your wise words. What I am trying to do is to help get folks with standard aerobatic aircraft to get the best performance out of them. None, of the typical aerobatic aircraft has any built in adjustment for incidence and the only reason I put something in an earlier post was as an answer to a question.

Thank you and Algy for your inputs on servo set up but if I may I’d like to leave it there and crack on with some more trimming and setup issues.

I wanted to move onto spinning. Generally speaking if an aerobatic aircraft is reluctant to spin and enters a spiral dive instead, you need to shift the CG aft a bit more. Martin makes an interesting point on how he sets up his airframes for spin recovery and if you have an airframe with adjusters for incidence on the wing and tail then you might want to give that a go. I found on my Wot 4 that it took ¾ turn to recover from a spin once I had centralised the controls. You can, of course, apply opposite rudder to stop the spin faster. Whichever method you use, you are looking for consistency so that you can predict with confidence the repeatability of coming out of the spin. Now, the recovery from the spin in aerobatics makes a big difference to the way the spin looks to a spectator. Quite a few people are keen to get the aircraft out of the post spin dive and into level flight asap. This is a good idea if you are close to the ground, but for deliberate spinning you will be quite high. I’ll cover the full manoeuvre later on but for the moment what we are looking for is a vertical dive followed by a gentle pull out to level flight.

The other demon of a hurried pull to horizontal is that you run the risk of having the wing enter a “high speed” stall. The wing has a fixed angle of attack at which it will stall. If you fly fast and have sufficient elevator power, you can pitch the wing up, or down, to reach the critical angle of attack at which the stall occurs. So, speed, or lack of it, is only one part of the stalling story. The real answer is that when the wing reaches its maximum angle of attack at which the airflow remains attached it will stall regardless of the speed of the aircraft. That is, other than the speed needs to be higher than the stalling speed identified by slowing down gradually until the amount of lift needed to support the weight of the aircraft requires the wing angle of attack to exceed its critical angle of attack – the normal stalling speed.

For models without any incidence adjustment, a truly vertical dive can be achieved by mixing a tad of down elevator to the fully closed throttle position. Again, I would recommend that you assign this mix to a switch until you think you have the mix correct. Even then, you might wish to turn off this mix so that when you are landing with a fully closed throttle you don’t get a small amount of down elevator being fed in just when you don’t want it. Why would you want to have a truly vertical dive? Well, it looks a lot better than a hurried pull out and, if you wanted to go on to fly in competition, that’s what the judges would be looking for so you might as well start practising it this way from the word go.

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The final piece of trimming I wanted to cover at this stage is checking whether you need aileron differential. As most of you know, when you use the ailerons to bank the aircraft the down going aileron increases lift and drag while the up going aileron decreases lift and drag. So, you get more drag on the wing that is on the way up causing the aircraft to yaw away from the direction of turn. This is called adverse yaw and can be corrected by either applying rudder manually or else mixing rudder to aileron. However, another, and better, way of eliminating adverse yaw is to introduce differential to the ailerons - the down going aileron travels less distance than the up going aileron so eliminating the imbalance in drag between them.. Before the advent of the computer radio this had to be done by introducing manual fixes and you can still do the same today. However, most of today’s computer radios have an in-built function called differential and you could use this function to address the adverse yaw function.

But how do you check for adverse yaw? Well a good way is to fly the aircraft towards you and to pull to a vertical climb very close to you and then to do a half roll rapidly. Watch which way the nose of the aircraft is pointing at the end of the half roll. You may have to do this several times and have a friend to observe the flight path as well. Let’s say after establishing a true vertical climb, you perform a half roll to the right. If the flight path remains truly vertical, you have no need of differential. If the flight path is dragged to the right as you look at what will now be the topside of the aircraft, then the left wing (with the down going aileron) has too much drag so you need to reduce the amount of down aileron on that wing.

Do the same for a roll to the left and observe the aircraft flight path carefully again to determine whether the right wing’s aileron needs its travel adjusted. Land, and adjust the differential function, or if you don’t have that then use the ATV to reduce the throw of the down going aileron. Go and repeat the exercise until you can roll left or right without any deviation of the flight path.

I’ll cover setting up the aircraft for knife edge later on as I think you might like to get onto actually flying aerobatics next. However, you should return to trimming at regular intervals either to check that all is well or else to make some adjustments that you feel are necessary to address an issue you are having with performing a manoeuvre.

I hope you will set up your aircraft as I’ve described above as it will make a great deal of difference to how it feels when you fly it. It’s much nicer and can feel like a completely different aeroplane than the way it may be flying currently.

In the next post, I’ll cover where you should be flying if you are following a precision aerobatic schedule. 3D flying will be quite different and I hope that someone who knows about this will either chip in or start a new thread if they prefer.

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Peter - I've just had a funny feeling of deja vu (see my earlier posts).

On a more relevant note, do the scale competition pilots use this system to trim out their aircraft? I'm thinking here of an accurate scale model of, say, a P51 Mustang. It's taken umpteen thousand hours to design, build, finish and detail. The pilot is probably just glad it flies at all. But would he benefit from trimming in the sense we are discussing here? I've seen some models (at the Nats for example) that appear to be a bit of a handful to fly. It wouldn't be as easy to trim out some of the undesirable tendencies as it would with an F3A type, if only because any adjustment to the engine thrust line would put the spinner out of place compared to the cowl, but it could be done. Any thoughts?

Graeme

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Hi Peter

Like Martin MacIntosh , I noticed this thread a few days ago, so watched with interest. I regret (!) having to have stood on a draughty airfield practising F3A aeros when it could all have been avoided if I'd had a computer radio !

The nearest Martin and I got to "advanced technology" was rate switches on aileron and/or elevator. My normal flying was on both low rates. High rate elevator for spins, and high rate aileron for upward rolls.

I noticed you recently mention adverse yaw and using aileron differential. Good idea on some aeroplanes. But why would you employ differential when the model has a symmetrical wing section, with centre hinged ailerons ? The more up that down aileron logic doesn't work when the model is inverted, which is about half the time.

The nearest I'd get to alleged adverse yaw would be to make sure both ailerons are not displaced up or down from centre, which could cause any rolls to be slightly barrelled, either pos or neg. Certainly this is something I'd check for.

My 10 penn'orth so far.

David

.

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Hi Graeme,

Trimming scale models is different as they don't spend so much time upside down and you would not want to fly your model Lanc up a climb at 45deg then roll inverted to see if the CofG is in the right place. That side CofG is the first place to start and then the thrust line. Down thrust is judged normally by looking for signs of climb or dive under power and vice versa as the throttle is closed.

The biggest problem of a true scale model is that the tail area is often too small to give good stability if the CofG is wrong, so most models of that type therefore need the CofG further forward than ideal this can leads to them running out of elevator on landing. Also if a true scale model is built the speed range becomes more critical (as air will not scale down with the model), so at the point of a nice round out to land it is easy to pull just little too much elevator and stall. A further problem is with WW2 war birds that they often have tampered wings that are more prone to tip stall. Lastly with the Clark Y type wing section averse yaw in a prominent feature and so good use of rudder or rudder mixing is needed along with aileron differential.

To get around these problems you will find some scale models have a slightly forward of scale rake on the UC, extra washout on the wings and a slight increase in tail size. There is though no argument that trimming will make a big difference to a scale model.

Hi David,

With the old aerobatic models with 0-0-0 set up aileron differential was not much of an issue it only starts to show a need once the wing has a positive incidence but the amount needed is very small compared to a high wing Cub.

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Hello David

Thank you for your comments.

I know your first comment is slightly tongue-in-cheek. Even with the best trimmed model it is jolly difficult to fly the perfect schedule and that only comes with years of practice. However, this thread is not really aimed at the F3A pilot but rather the club pilot who is interested either in starting aerobatics or in doing rather better aerobatics with his standard club aerobat. It offers some help and guidance if you do have an F3A airframe as well regardless of size and the gizmos on it.

As regards differential, I did say pull the aircraft to the vertical at which point it matters not whether you are upright or inverted. There may, or may not, be any difference between the two ailerons but this at least eliminates any that might be there. That helps our budding aerobatic pilot by removing even a small deviation caused by the model's behaviour.

Depending on your view, we are either blessed or cursed with computer radios. It seems a pity not to use the full range of capability that resides in our hands and we can now get help where you and Martin had to use mechanical measures to resolve aberrant behaviour by the aircraft. Interestingly, the latest A380 jet's flight control system reacts to the pilots input for roll by including rudder, elevator and power without him having to put them in himself! Advanced fighter aircraft do exactly the same with the pilot telling the computer what he wants and the computer providing the required manoeuvre that is always kept within the flight envelope.

Of course, you don't need to do any of the stuff I'm describing here, but I found it helped me and so I thought I'd share this with others. You can go off to the specialist aerobatic forums and read all about it there but there are, I suspect, many on this forum who don't want to do that. Some may choose to pursue that course in the future and I'd be jolly happy if they did but you don't need to want to fly competition in order to fly nice looking aerobatics with a nicely trimmed airframe that gives you great pleasure.

Please do keep your comments coming especially if I get something wrong - I am not a fount of all wisdom.

Peter

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Peter, your doing well.

This might not be for those planning to fly competion but it is worth reminding those who are reading this thread that, should they change their minds and dip a toe into the competion seen then a well trimmed model is a very good start.

Also that if they have practiced aerobatics with their trimmed sports model, then they will have all they really need to have a go. The clubman schedual only needs a sports model and a bit of practice to get a good score, models such as the Wot 4, Acrowot or Extra. It is also worth noting that whatever aerobatic meeting they go to, they will learn a lot by talking to others, looking at how thing should and shouldn't be flown and finally that they will never be looked down on even if they come last but supported and helped to improve, by pilots such as your good self.

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Hi Peter

Interesting thread.

You mention the hardships of dinosaurs (like me) having no fancy radio facilities. We managed quite well, so we just got on with the flying !

Fact is you need a really "straight" well designed model. I don't believe you can make a good-flying model out of a second rate or twisted model however hard you try. I still have Lightnings 2 and 4 in my cupboard. I remember the first flight of #3 model. It was unbelievable, and needed virtually no tweaks apart from minor throw alterations. Flew as if on rails. (It was so good Ken Binks eventually borrowed most of the design and called it a Pacemaker !!).

You draw a parallel between A380 's automated aids, and models. I'm very sceptical about airliners that do all the thinking for the pilot. Recent events prove you still need to be able to revert to basics when all the fancy stuff calls it a day, or ties you in knots.

I can live with being called old-fashioned !

David

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Graeme

I shudder to think of what goes through one’s mind as you commit several thousand hours of work to flight for the first time. I don’t know how the scale brotherhood goes about the trimming process but remember that they are hampered by a thing called scale and the fact that airflow behaves differently depending on, amongst other things, a number called the Reynolds Number. You can just take it that true scale aircraft, unless they are quite big, and I mean a wing chord of at least 1 mtrs or more, will not perform like the full size unless you make some changes to the shape. The latter is not what scale models are about so our scale brethren, unless they are flying giant scale models, have their hands full with what looks like a beast of a model when the full size was nothing like as nasty!

Only read further if you want to know a little bit more about Reynolds Number - the paras below are not mandatory reading! They are also rather simplified because I’ve forgotten a lot of my aerodynamics!

The Reynolds number is a ratio between inertial forces and viscous forces. The inertial forces are made up of local air density (ρ multiplied by the velocity of the airstream (v) multiplied by a typical length (L) typically the wing chord. The local temperature and air pressure also affect density and viscosity. The viscous forces are made up of the local air density .  Provided you have used consistent units (i.e. metric or imperial) you end up with a non-dimensional number i.e. there is nothing left of metres/sec, meters etc as they just cancel out between the top line and the bottom line. Remember to use velocity expressed as metres/sec and length as meters otherwise the sums don’t work

So the Reynolds number = ρvL
                                            μ

In rough terms this equates to 60,000 x velocity x Length

For most full size aircraft this number in in excess of 1.5 million at its lowest and around 8-9 million at the upper end. For a model aeroplane with a 0.25 mtr chord wing and a flying speed of 30 mph we get approx. 200,000. If we up the chord to a full 1 mtr, we get a Reynolds No of approx. 800,000. That’s why big models fly better than little models.

The important thing about the Reynolds number is that we can use it to predict how the airflow in the layer of air right next to the wing, called the boundary layer, will act. This is also affected by the roughness of the surface of the aerofoil so you would get a different effect with a wing beautifully covered in Solarfilm from one covered in sand paper.

The important number is around 750,000 roughly. Below that figure the airflow over the body remains laminar – in other words the streamlines remain as streamlines without any mixing. This is excellent at the beginning of the aerofoil as the pressure is dropping and the flow speeding up. However, once past the thickest part of the aerofoil, the pressure has to start rising and laminar flow does not like this and so breaks away from the surface.

You can play little tricks with laminar flow and the free flight glider boys used to use a turbulator (a piece of thing string which they stuck parallel to the leading edge of the wing) fixed fairly close to the leading edge. As the laminar flow meets this obstruction, it transitioned to turbulent flow (there was mixing between the layers so this boundary layer becomes thicker). In this case, covering the leading edge in fine sand paper actually helps!

Above the magic 750,000 the airflow may start off laminar but rapidly turns turbulent. A turbulent boundary layer is much more resilient when it gets past the thickest part of the wing – the area where the airflow is fastest, and then needs to slow down as the wing thins towards the rear. In the language, a turbulent boundary layer is more able to cope with an adverse pressure gradient than a laminar one.

So with a scale model you do not get the lift or control response that you would expect on the full size aircraft. This is also why a bigger model flys so much better than a small model.

Edited By Peter Jenkins on 05/12/2013 19:16:39

Edited By Peter Jenkins on 05/12/2013 19:17:34

Edited By Peter Jenkins on 05/12/2013 19:18:34

Edited By Peter Jenkins on 05/12/2013 19:19:45

Edited By Peter Jenkins on 05/12/2013 19:20:20

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Hi David

I agree that a good straight airframe is the best way to proceed. However, the average club modeller will be using an ARTF and while many are made to a high standard there are a number that are not. You also have airframes, Wot 4 for example, that have a number of less desirable aerodynamic qualities that a bit of mixing allows us to overcome to an extent. I certainly wouldn't choose to use a doctored Wot4 if I had a more specialist aerobat in my hangar. Having said that, I thoroughly enjoy flying my doctored Wot4 as it is so much fun even though it's hard work getting to it to do large aerobatic manoeuvres. But not everyone has a better aerobat available to them and hence the hints on how to use the electronic equipment that we are now blessed with.

I absolutely think we have it easier today - I cannot begin to imagine how people flew aerobatic schedules using reeds!

Thanks for your comments - keep them coming. BTW, I only got into F3A flying at the age of 61 and in my youth built my own MacGregor single channel valve Rx and Tx. It was not a huge success! I then built a Remcon 6 from the kit of bits and that didn't work too well either. Today, we can buy some amazing quality and capability for so much less.

Peter

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Interesting about the scale factor. When I first flew a comp. I had a `Clipper` with about 63" span then upped the basic design to 67 or 69" when I started to use retracts, same motor used. The result was a much better model even though it weighed tons more.

I have built the Tony Nihuis 44, 62 and 72" Spits. The 62 handles just as you would expect a Spit to do and catches me out occasionally. The 72 is much better and flies round loops rather than being dragged by the motor.

The puzzling thing is that the tiny 44" outflies both on miniscule power (OS26FS) despite a weight of 3lbs 10oz with retracts and a four servo wing with two of them (heavy MG) behind the cg against a plan weight of 2lbs 6oz and is almost impossible to stall even with full up applied. It just mushes like a delta and a spin is difficult to induce. The cg is as per plan.

This defies all the theories.

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Martin

Are Tony's Spits exact scale or has he designed them to fly well while looking like a Spit? If the latter, then that would explain why they fly so well. As regards your last point, I'm sure that with the advances there are in computational fluid dynamics today there would be an aerodynamicist who would be able to work you why your little Spit seems to fly fly the way it does. Trouble is they would have to use a very expensive computing set up to give you the answer - but you would get one! They guys I used to work with were responsible for some amazing aerodynamic fixes for some of today's iconic aircraft.

Peter

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On the differential theme, many of us added a little of this by putting the horn slightly in front of the hinge line (small ammount of positive wing incidence used-not zero-zero) in contrast to what I read in the mag by someone who suggested that it should be behind. On paper that would seem right but in practice it does not work.

In my opinion it is best to start with this configuration mechanically, as everything else on the model should be, then use the computer tranny to fine tune. This way you maximise the servo torque and centring.

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Martin - they way I've introduced differential mechanically is the way it's done on simple full size aircraft. Instead of having the servo horn at 90 deg to servo centre line, I place it so that you get more linear movement to up aileron and less to down aileron. In fact, when you look at the geometry of a mechanical servo with a rotary output, as built you get more linear movement around neutral and less towards the end of the movement. That's useful when setting up differential. I believe, but I've not tried it myself, that if you set expo at 35% (to soften movement around neutral) you get a true linear output on the control surface. In other words as you move the stick you get a true representation on the control surface. Some trigonometry would prove this easily.

Rick Tee - I must say that I had an Aresti 40 till my thumbs screwed up! In those days I'm not sure I'd have noticed whether it had adverse or proverse roll! Thanks for letting me know.

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Right, we’ve got our aircraft trimmed – remember trimming never stops! – and now we want to fly aerobatic manoeuvres. First of all, where should you fly these manoeuvres? Typically right in front of you is best as you get the best view of the manoeuvre and so do your mates! You can choose to just fly a single manoeuvre and then reposition to come the other way for the next manoeuvre. When you are first learning a manoeuvre that’s probably quite enough complication. As you get more practiced and more confident you can, if you want, put in manoeuvres as part of your turn around at each end of the field – hence the term turn around schedule you may hear bandied around. Oh, and there’s that word schedule! But remember, you set the pace at which you wish to develop your aerobatics, although it’s always helpful if you have a more experienced mentor at hand or a group of you to help and encourage each other.

Now before we fly any manoeuvres practice what Ultimate put in his early post. Practice flying on a line, parallel to the runway in use. Try and arrange this so that you have an easily identifiable marker on the horizon right in front of you that you can see as you fly across the sky. For a 40-50 size model, aim to fly at around 50 meters away from yourself. That way, if you have a problem maintaining direction on, say, a loop, you don’t end up overhead and possibly into your no fly area! Also, don’t fly too low. Stay at around 100 ft or so. It makes a big difference to your adrenaline flow since if you make a mistake you have height in hand. We’ve all scared ourselves with the wrong input at the wrong time and you also stand a good chance of avoiding the dreaded sudden one point landing if you have that extra insurance of height.

It is quite difficult to fly a consistent line and that is the basic starting point for aerobatics. So, it is worth practicing flying to and fro 50 mtrs out at around 100 ft (sorry 30 mtrs!). If you train yourself to fly in an area bounded by a line 60 deg either side of straight ahead if you decide to take up flying in a competition you will not have to re-learn your flying technique. Again, try and pick a tree or other feature on or close to these two directions so that you can “see” your aerobatic box. In competition, the height of the box, by the way, is defined by a 60 deg line to the horizontal from the pilot’s position but that’s for later if you want to go there.

If you are relatively experienced in flying aerobatics, your end manoeuvres can be any combination of stall turn, half Cuban eight, half reverse Cuban eight etc or just a procedure turn. The procedure turn is a 90 deg outward turn, then a 270 deg inward turn to bring you back onto your chosen line. If you are new to aerobatics the procedure turn gives you time to collect your wits before returning in the other direction.

Since it is highly likely you will have a cross wind component to cope with try and set up the aircraft so that its track over the ground is truly parallel to your runway i.e. the aircraft is not blown in to you or out away from you. You do this by turning the nose of the aircraft as far into wind as necessary to achieve the ground track. This is where using the rudder to move the nose in or out is the way to go and why we trimmed the aircraft to eliminate any secondary effect of rudder. Why not just roll the aircraft you say? Well, you could do that but everyone can see that you’re doing that whereas gentle use of the rudder hides that fact. Also, you will be putting yourself in a good position if you ever to want to have a go at a competition because you lose points for not keeping the wings level! At the end of the day, it looks better if you use the rudder to achieve the required path over the ground. But you do need to use it gently and think about which way you need to move the rudder before getting airborne.

When you can fly that line at a consistent distance out and at the same height in both directions then we’ll move onto the next bit. Ah,well, we’d better move on after a few flights as it is quite difficult to do what I’ve just said – that’s where lots of practice comes in. Come back to practicing just flying this line from time to time as it will help you to become more accurate in your aerobatic flying.

The one thing I would urge you to do is to strive for accuracy. It is easy to do sloppy aerobatics but everyone will see that and you won't feel satisfied. If when you start your loop, your loop is way off centre, try to readjust it so that the loop is centred. That skill will be essential if you are aiming to achieve a B Certificate and it just looks better and shows that you have full control over your aircraft.

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Posted by Peter Jenkins on 06/12/2013 11:20:51:

Since it is highly likely you will have a cross wind component to cope with try and set up the aircraft so that its track over the ground is truly parallel to your runway i.e. the aircraft is not blown in to you or out away from you. You do this by turning the nose of the aircraft as far into wind as necessary to achieve the ground track. This is where using the rudder to move the nose in or out is the way to go and why we trimmed the aircraft to eliminate any secondary effect of rudder. Why not just roll the aircraft you say? Well, you could do that but everyone can see that you’re doing that whereas gentle use of the rudder hides that fact.

Just to add to Peters bit above, if you lean the model into the wind this will not help you as you go through say a loop. Imagine you are leaning the model towards you as the wind in on your back as you start the loop the model will want to come towards you, but the wind may keep it away but as you get towards the top the bank will now pull the model down wind away from you and the model will end up on a new line several meters further away. If you use rudder to hold the line, you will only have to increase or decrease the amount of rudder to keep the loop all upright and on the same line. It will all look a lot nicer and you may even find it easier.

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