Some thoughts about "dialing in" a plane... :)

Hi everyone -

Now that I have pretty much dialed in another plane, I thought it would be a good time to post my process for how I like to dial in my planes to have the best setup and chance of long term success and enjoyment.  This post will probably take longer to write than the process takes itself, but hopefully there will be a few tidbits that might be of use to you.  As the old saying goes, "the devil is in the details" and being and old Air Force operator, I am big on processes and checklists... :)

Another caveat that I should add is that though some of these points might seem painfully obvious, sometimes in my rush to get a plane to the field to get flying, I have missed them and paid the price.  In the almost two years since I started scratch building park jets, I have maidened over 40 planes, most of them successfully, but often not without moments where I lost a few thousand heartbeats in panic!  And at my age, I can't afford to lose too many more heartbeats to self induced stupidity... :/

So like many things with my planes, it starts with the build, I try to build as light as I can but still keep my planes strong and hopefully durable.  Ensuring the control surface hinges are secure, that control horns are lined up as close as possible so that the holes are directly over the hinge, pushrods and other linkage components are in good condition and secure and that all the electronics, motor, ESC, RX and servos have been bench tested before installation in my plane.  All common sense stuff, but there have been times in a rush to get a plane finished I have missed one of these steps and like having a poor foundation on a house, it has cost me at the field.

Once I do have my servos installed in the plane, I discipline myself to let the glue on them completely dry so that as I am connecting the pushrods, etc I don't work them loose or weaken the glue joint before it has hardened.  Again, lesson learned!

I currently run a Turnigy er9x radio system, so I am able to do the bulk of the initial configuration of my radio setup through my PC which saves considerable wear and tear on the buttons of the radio.  I run through everything to ensure that I haven't put in any subtrim or other weird travel adjustments that might affect me getting my plane setup with a clean slate right from the start.

 Before doing much of anything else when hooking up my system, I always ensure I re-bind the Tx and Rx.  Then I set the throttle points on my ESC.  Even if I have used this ESC before, I always do this, especially if I am using a different receiver than I used with the ESC in the past.  It is a bit anal, but it gives me the confidence of knowing that my ESC is set properly for this setup.

Your ESC might be different, so check the manual if you have one either in paper on online to see if setting the throttle points might be different.  I think the lion's share of ESCs are the same for this setup.  I use Turnigy Plush ESCs from HK, 40A with my Focal Price motors and 60A with my NTM 2700 motors.  Before starting to set the throttle points, I will connect my ESC to the programming card to double check that all the other settings on my ESC like brake (I fly with mine off), timing, etc are all where I want them to be.  If the brand of ESCs you like to use has a programming card, I would highly recommend picking one up.  The Turnigy one for example is about $8 and for the cost, it saves a lot of hassle with doing it through the transmitter and gives me the confidence that my ESC is going to do what I want it to.

Setting throttle points is normally done before I put the prop on the motor, just in case something crazy happens, I don't have my plane fly off the table or worse yet hurt myself with a prop that is suddenly spinning at 30,000 RPM.  The motor is connected to the ESC for this process, so I turn on my transmitter, advance the throttle to full or 100%, then connect the battery to the ESC.  I then should hear one beep followed by two beeps in quick succession, I then chop the throttle to zero and I normally hear one beep, followed by 3 beeps for the number of cells in my lipo and then a single beep letting me know the throttle points have been set.

So now I should have all the gear installed and connected.  I use a throttle cut safety switch on my transmitter to ensure I don't accidentally advance my throttle while I am playing around with the sticks, if you don't have this feature or don't feel confident your motor won't start up unexpectedly, you can leave the prop off while going through the process of checking all the control surfaces.

So all my servos are now in the correct configuration and channels on my receiver and it is time to fire things up and see where we are at.  I connect my battery and wait for everything to initialize.  Often the control surfaces won't be perfectly centered, so I first check that I have all my trims at zero, then I mechanically center them with the quick connects I like to use or you can use whatever you have like adjustable clevis, etc to ensure the control surface is as close to dead center as you can get it.

So now that all my surfaces are dead center, I check that they are moving in the correct direction.  I always pay close attention that they are moving in the correct direction and not just a quick waggle of the sticks to ensure they move.  Ailerons are the worst culprit of this, I still see guys at my field give the sticks a quick waggle, take off and then realize that although their ailerons were moving, they were going the wrong way, so left is right, right is left...you get the picture...it often results in a short walk of shame after cranking the plane into some immovable object... :(

Since I have a very easily programmable transmitter, I will also fine tune my elevons and ailerons to ensure that when I pull full up on the elevator that both elevons are equal.  If one comes up a bit further than the other, every time I pull up in a loop, it will roll at the same time and cause other issues of imbalance in handling.  Fortunately with the er9x, I have huge flexibility in mixing and programming, so this is very helpful in achieving the control surface throws I am looking for.  I will also use a ruler to ensure that my ailerons travel the same distance to prevent my plane rolling faster one way than the other.  All a bit anal, but well worth it.  My personal choice for starting throws and expo is 70% throws on aileron and elevator with 50% expo on the elevator input and 60% throw on the aileron.  For the rudders, I start with 100% throws and 50% expo.  I don't bother with low and high rates, just personal preference.

So after a quick check to ensure all my hinges, control horns, servos and linkages are good and secure after all the adjusting, I get ready for battery placement as long as I have already installed my prop and ensured it is running in the right direction.

Unless I specifically know that a certain plane is always going to have the center of gravity (CofG) ahead or behind what is marked on the plans, I balance my plane using the stock CofG per the plans.  I also find this is easiest to do at home in the house so that no wind will affect my plane balancing properly.  I use a fully charged battery so that when I get it balanced, I just leave that battery in until I am ready to maiden it at the field.  I like to have my plane balance right on or perhaps very slightly nose heavy, maybe about 10 degrees nose down for the maiden.

When I get to the field, I like to take one plane that I am already very comfortable with and fly that a couple times just to get my brain and thumbs warmed up.  Even after over 40 maiden flights, I still get nervous flying a new plane for the first time and find that if I put a couple batteries through a plane that I am familiar with, it helps calm my nerves and gets things warmed up.

I normally launch my planes with about 45-50% throttle and then just climb away gradually until I am up at about 100 ft off the ground (at least two mistakes high, whatever altitude that is supposed to be...:/) and then keep it out in front of me so that I can figure out what trim it needs.  I do this by flying it perpendicular to me (so that I am looking basically at the side of the plane as it flies by) and then center the right stick so I'm "hands off" (I fly mode 2) and seeing what it does and adding trim accordingly until when I let go of the stick it pretty much flies straight and level without control input.  I normally just trim in the roll and pitch (aileron and elevator) axes, I don't worry too much about the rudder, I just check them regularly to ensure they are always dead center and not causing me trim issues.

Then once I have completed that first flight, the fine tuning begins.  I am always in search of the ability to fly my plane balanced and straight and level with no trim input if I can, I find it just allows my planes to fly better and I am not dragging around any deflected control inputs because of trim.  Although not always possible, this is easiest done on the calmest day possible so that wind is not a big factor in me getting my plane trimmed the best way possible.

I find it easiest to solve the trim one axis at a time and I normally start with pitch.  If the plane was nose heavy, I move the battery back slightly.  If it was tail heavy, I move it forward.  Not that this is a hard and fast rule, but I find most planes that 1/4" of battery movement (with a 2200 battery anyway) is equal to about one click of trim, but I do this very gradually.  Then for the next couple flights, I just keep flying and adjusting the battery backwards or forwards until I get it to the point of zero trim in the pitch.  Sometimes I will even land a couple times during a flight, make an adjustment, continue on.  In drastic cases if I can't get it down to less than one or two clicks of trim (which I can live with if I absolutely have to), I will try to move my ESC and/or Rx forward or aft to help achieve that neutral balance.

So, once I am happy with where my battery is for balance in the pitch, I mark the foam with a magic marker so that I can continually put the battery in the same place time after time.

Then I solve for the roll axis if need be.  I would say that with about 90% of my planes, I end up with the battery all the way over to the right to compensate for torque roll and roll is often the most difficult for me to get to zero trim.  Again, if I have one or two clicks of trim, I can live with that.  I am not a big fan of adding extra weight to a plane to get it to balance, but I will if I find that I need excess trim to get it to fly straight and level.

Then once I am happy with where I have put my battery, if it is considerably different from where it was in the pitch axis for the maiden flight, I leave the battery in and starting at the old CofG, I try to balance it again on my fingers (I like to do this with the plane upside down, just my technique) and keep moving the plane on my fingertips until it balances perfectly.  Again, this is easier done indoors if you can so no wind affects the plane.  Then I mark on the wing (normally I just put a little dent in the foam with a nail or make a little mark with a marker) where the true CofG is for that plane.  That way, if I decide I want to use a different size battery, I know where the plane needs to balance and I don't have to go through the process again.  As you have probably seen on my stock Mig29 V4, I ensure to label the marks in the battery bay so that I know where a 2200 battery goes and where a 1600 battery goes.  This prevents me from putting one where the other should go...again, lesson learned the hard way!

Within the first 6-10 flights, I also double check that all my control surfaces have stayed dead center with zero trim.  I have found that as hinges get broken in and linkages get worked in that sometimes the control surface can be off center slightly and I might end up trimming against that slight deflection.  Again, anal, but worth it in my experience.  Then I check my plane each time I take it to the field before the first flight of the day just to ensure nothing in the control surfaces has become loose, servos, pushrod connections, control horns, hinges, etc.

Then as I accumulate more flights with that plane, I will start to assess the requirement to adjust any throws and expo.  I rarely will adjust my expo from the start, but sometimes I will add more throw like I did with the Mig29 V4M3e3 to get it to fly close to scale and the way I like to fly.  If you like to fly more aggressively or more gently you can adjust accordingly.  Then I will also assess and adjust any flaps/spoilers I might be using for high alpha or landing or other such portions of the flight envelope.  This is simply trial and error to find what deflection of spoiler/flap/spoileron/flaperon might work best for a specific portion of the flight envelope where these special control surfaces may be utilized.  For things like high alpha, I might also temporarily adjust my battery position like I did on my stock Mig29 V4, I found that having it further forward was better for more steady high alpha.

I have several planes with over 100 flights on them and have found that sometimes over time, a plane seems to gain weight either in the nose or the tail.  I know this is not the case, but perhaps as the foam gets more flexible over time, it seems to affect the balance, so as your plane accumulates more flying time, you may have to readjust your battery position and once again determine the new CofG.

So if you are still awake after working through all this stuff, I hope at least some of it might be helpful to you or give you some other ideas to consider when dialing in your plane.  For the longest time I didn't really worry about it, I just flew with lots of trim and thought I had to live with it.  But as I started to improve and challenge my skills to fly more scale and more precise, I knew I had to get my planes setup to allow for this.  It makes a huge difference in how my planes fly and how predictable they become when I can trim and balance them as close to zero trim as possible.  Some planes dial in faster than others, but it is fun to go through the process and the rewards are worth the tedium...at least in my humble opinion.

Like many things in RC and especially scratch building planes, there are numerous ways to achieve the same goal, so I don't think for one minute I have presented all the answers or what might even be the right answer for how you like to fly.  Much of what I have written I have learned the hard way or borrowed from other folks at the field or in posts I have read in different forums, sometimes just trying new things can be fun and could be a breakthrough in helping with a particular process in your RC adventure.  Good luck!

Cheers,

Scott