Oh Good Grief!
Is this what you're saying to yourself as your heart sinks into your stomach realizing your beautiful day just turned into crap? Yes you, the beginner or aspiring novice pilot, just screwed up, and it's going to cost you some money, time, and effort to get back on track. If it happens often enough, and for some once is enough, you'll say the hell with it and give up. Why do you think all those 4-channel radios are for sale on eBay?
The purpose of my little bit of prose is to save you some grief at the flying field ensuring that you'll at least be able to take off. For my thoughts on quickly and efficiently becoming an R/C pilot read Mr Akimoto's Fabulous and Free RC Training Course.
I consider the biggest mistake that most beginners make is not adequately preparing themselves and their planes before they head out to the flying field. You're probably going to hit the field on an instruction night when there are likely too many students and too few instructors. Also many instructors have to make a living, so they show up in the evening leaving just a few daylight hours for instruction. Why waste their time with problems that you could have solved on your own?
Probably one of the most frustrating experiences for most flyers is a balky engine. The little sucker just won't run! I'll confine my remarks to the OS 40 LA which occupies the motor mount of most 40 sized trainers. The Max operations manual covers just about anything one might want to know about setting up, starting, and maintaining it. It tells you how to mount the engine, proper installation of the fuel delivery system, selection of a propeller, what fuel to use, and so on. It's all good and valuable information, and the novice should carefully read and study the manual.
Small glow plug engines are notorious for being cranky and hard to get along with when they're new, but their attitudes quickly change after a couple tanks of fuel. In any case, don't attempt any take offs until you're sure your engine will run reliably. The best way is to tune it on the ground until you're confident it has gone through an attitude adjustment.
Begin by opening the needle valve two turns from a seated position and prime the carburetor. Simply open the throttle all the way and with your thumb over the opening, turn the prop over a couple of times. Next, attach the glow igniter and using an electric starter with the throttle partially open, crank the engine. It should start, but you may have to repeat the procedure a couple of times. When it does start, run it full bore until you empty the tank. Fill the tank for a second run, start the engine, and crank in the needle valve until the engine just begins to two cycle. You're now ready to begin flying. On each subsequent flight, lean the engine a click or two until you reach the point Max calls optimum RPM. This is a point 15 to 45 degrees from maximum RPM, or the leanest needle valve setting where the engine reaches it highest RPM. You'll know when you have reached it, because past it the RPM will drop off abruptly.
OS engines won't run reliably at their leanest setting or maximum RPM. Also you needn't concern yourself with trying to precisely adjust the needle valve for the optimum RPM. Just make sure you run on the rich side of maximum RPM.
Suppose your engine just won't start? First, leave the needle valve alone. It isn't the problem. The problem is either spark or fuel. Check the glow plug. It should glow a bright orange. Next, is the engine getting fuel? If it isn't, the fuel delivery system is screwed up. The fuel lines are improperly installed, they have leaks or holes, or there is some dirt plugging them or the needle valve up. You can easily check the clunk by moving the fuselage about its roll axis. The clunk is OK if it clunks.
Before every take off, run your engine up to maximum RPM to check its operation. Does it sound a little weak? Try leaning the engine out a click or two. Run the engine up again and carefully listen to detect the change in RPM. I have found that the initial optimum setting of the needle valve is usually OK, but temperature and humidity changes might require a minor re-adjustment (either richer or leaner) from time-to-time. In any case, this requires experience so proceed slowly and carefully when tuning the engine.
Finally, one last item regarding the engine. Don't screw around with the idle or air bleed adjustment. The factory setting is close enough, but if you're a perfectionist and want to waste the afternoon, you most certainly should. Instead, set up the idle with the EPA (end point adjustment) on the throttle servo. Adjust it, with the trim centered, so the throttle fully opens and is cracked open about an 1/8" at idle. You can shut off the engine with the trim.
When you finally get airborne, how are you going to know when the fuel tank is close to empty? You don't want to make any dead stick landings into Grandma's pumpkin' pie coolin' on the window sill. Get yourself a kitchen timer and attach it to a clothes pin with double-sided tape. You then can then clip it onto your antenna. I have mine set for 16 minutes (for an 8 ounce tank), and I turn it on as soon as the engine starts. I usually fly half throttle, and I have plenty of fuel left to land when the timer beeps zero.
Don't try starting your engine with a chicken stick. You'll have a heart attack before it cooperates. Get yourself an electric starter. Also forget about starter panels for field boxes. You want your starter and glow igniter to both be portable, so you don't always have to drag your plane over to the field box to get power. Hobbico has a nice starter where the battery is contained in a case that attaches to the starter housing.
Next throw away that spinner that came with your pretty RTF and get a prop nut that accommodates a starter cone. Make sure you use a prop washer with the prop nut too. Great Planes (GPMQ4642 or GPMQ4630) makes a very nice one in either brass or aluminum for $6.49. You will also have to replace your starter insert with one made for the prop nut, and that'll cost you a few more dollars. You'll then be relieved of being boinked by a propeller flying off when you try to start your engine.
Another item while you're at the front end, is adjusting the prop to be horizontal on the compression stroke of the engine. This will save you many broken propellers. Wooden propellers have many merits but durability isn't one of them when they come into contact with some object. Get a Screw Master G/F propeller. Although these "plastic" props will break too, they stand up very well to abuse like those less than perfect landings.
Balance that propeller! Get yourself a Top Flite Propeller Balancer for about $20. I can't think of a more important item for long engine life and reducing vibration and stress on the airframe and Rx. The benefits are enormous like not shaking the hardware loose on the airframe and engine. Have you ever wondered how those screws that held the muffler on came loose?
There is an art to properly balancing a propeller, and very few people know how or have the patience to do it correctly. The field geezers will tell you it isn't important, but they are dead wrong. I will tell you how to do it. You want to achieve two states of balance: horizontal and vertical. If you do this, you'll find the propeller will remain stationary at any point on its 360 degree circle.
Do the vertical first by removing material with a small mill file from the heavy side of the hub. I combine this with adding weight to the light side using clear nail polish. Note on the backside, there are 45 degree circular slots you can pour some nail polish into. After you get the prop to stand on its end, you'll want to get it to remain stationary in a horizontal position. I usually do this by adding nail polish to the front side of the light blade. You can also remove material from the front side of the heavy. Whatever you do, don't remove or add material to the back side, or you'll change the pitch and airfoil. The prop is now balanced.
After a few flights, do you see a brown stain where the muffler bolts to the engine? This flange joint will leak, so smear a little bit of clear silicone sealant on the muffler and engine flanges before you bolt them together.
OS mufflers have a habit of coming apart due to losing the nut on the end of the long rod that holds them together. If it happens, you're done for the day. You'll never find the nut, rod, or the end of the muffler. To eliminate this frustration, I just put a drop of thin CA (or red thread lock) on the nut which will soak into the threads. I never plan to take it apart, and if I do, I'll have to use CA debonder.
Sometimes the plane will get so far away that the only way you can tell if it's coming or going is to make a turn. Is the plane going away from or towards you? Give it right aileron and if it goes right, it is away, but if it is left, it's towards.
Do something to change the covering to help you distinguish the top from the bottom of the wing. Clearly being able to tell the top from the bottom will tell provide more information about the attitude of your ship.
Take some red rags to the field. After each flight, wipe off the goop from the exhaust. It will make your plane easier to clean up when you're ready to go home. Also, if you don't, it'll be like picking up and trying to hold onto a greased pig especially if you use a full synthetic fuel.
When you rubber band down your wing, don't put ten on each side. Just use three, so when the wing hits the ground, it comes off without damaging itself.
After every flying session, you should plan on doing some home maintenance. Check every screw on the engine to ensure it's tight. Do the same on the rest of the plane checking control horns, servos arms, landing gear, wheels, and any place there is a screw or a nut holding something together. Also check the hinges to see if any have failed and don't forget the keepers on the clevises.
Now get out there and nail those landings!
Ciao,
Mr Akimoto