Proper way to trim an a/c
Morning everyone, At one point I somehow stumbled on threads on the best way to trim an a/c. Unfortuneately I did not book mark the threads, so I am soliciting advice on the best way to trim out. I am sure that there are hundreds of ways to skin that cat, but just some general guidelines would be appreciated. Should it make a difference, the a/c in particular is a sport aerobatic model. Thanks in advance. Rick</p> |
RE: Proper way to trim an a/c
Here are a few general guidelines I would recommend:
Make sure the wings, stabilizer and fin are aligned as squarely as possible. Look for any warps or twists in the wing. These are probably most visible when viewed from the back. Straighten the wing if necessary. Wing and stabilizer incidence should be set as recommended by the manual or indicated on the plan. Ensure that the COG is set as recommended for the first flights. This may later be adjusted to obtain better flight performance. Generally, it is set at about 28-30 percent of the wing chord starting at the leading edge. AUW of the plane should be within the recommended limits. Make sure all the control surfaces and trim tabs are as neutral as possible before attempting any flights. One exception to this might be a couple of clicks of up elevator trim to aid the climb and improve the glide a bit. It is probably best to pick a calm day to trim, if possible. Look for any tendencies to veer either right or left with the sticks neutral. It should not climb very steeply with moderate power, nor should it be very difficult to hold the nose up with the elevator. A few clicks of trim should be all that is necessary to correct any minor deviations. Control should be smooth, responsive and predictable. Anything worse than that probably indicates a structural or mechanical problem that needs more attention. Your goal is to achieve straight-ahead, level flight at a moderate power level with your hands off the sticks or with very little intervention. |
RE: Proper way to trim an a/c
Check this trimming table:
http://nsrca.us/all/flying/177-trimchart.html .......and this search for related RCU threads: http://search.rcuniverse.com/search....hwhere=subject |
RE: Proper way to trim an a/c
<div id="vbglossarattach">Trimming your plane
by Ed Anderson aeajr on the forums Your having problems flying your plane. Your problems may be your flying or it may be that the plane is out of trim. If it is out of trim or if any of the components can move around inside the plane, all your skills will be used fighting these problems, not flying the plane. Here is how we will find out. If you have an experienced pilot to help you with this, all the better, but you can do this on your own if you have patience. When I coach new pilots, we spend a lot of time trimming the plane first. I may fly it 10 times before I give them the sticks. It must fly properly or they have little chance of success. Balance If the plane is not properly balanced everything else is a waste of time. I want you to recheck the balance of your plane. This must be done at home where there is no air movement. All components, and especially the battery you are going to fly, need to be in the plane to check the balance. If you don't know how to check balance, tell me, but I am going to assume you know. This link may help you confirm you are doing it right. Balancing <font color="#0000ff">http://www.rcuniverse.com/magazine/article_display.cfm?article_id=84</font> More tips on balancing <font color="#0000ff">http://www.rc-airplane-world.com/balancing-rc-airplanes.html</font> Make sure all components are in the proper place and well secured. If the battery or any other components can move around, they can move the CG of the plane enough to throw off the handling, especially in a turn, on climb or in a loop, etc. Stuff has to stay put. NOTHING is allowed to move! Balance it to dead center of the recommended point. Dead center. Not nose heavy, not tail heavy. Dead center! Good enough is NOT good enough. Get it right on that spot!!! You might need to add tiny amounts of weight. Or you might remove weight by ripping a bit off a piece of foam you are using to hold something in place. Whatever you do, I want that plane balanced dead center of the recommended range. This is normally a very conservative spot and may actually be slightly nose heavy. It usually is, but that is the starting point we will use. Dead center! ( OK Ed, Dead Center! I get it! ) Surface trims If you have flown the plane already, then I want you to look at where you set your trims on the radio. With the plane is the air, all trims on your radio should be centered. If they are not, then I want you to adjust your surfaces at the control rods before you fly again so that you can center all your trims. Remember this MUST be done with the battery connected and the radio on. If you have three clicks of left rudder trimmed on your radio to get the plane to go straight, then measure how much the rudder moves when you move the trim to center. Now adjust it back at the control rods/lines so that it sits in that position with the trim centered. This will give you maximum trim capability in the air. If you have not flown it, make sure all surfaces are aligned with the fixed parts with the trims centered. The plane and radio MUST be on to do this. Trim centered and all surfaces aligned. Take your balanced and correctly trimmed plane to the field. Do a range check! If you don't know how to range check, look in your manual for your RTF plane or in your radio manual for all others. If you still don't know, tell me! Check all surfaces and all components again to be sure all is well. Now get ready to launch. I want you to pick as calm a day as you can find but at least on a day when the wind is under 5 mph and not gusty. For a slow stick or anything like a slow stick, under 3 mph please. Put a freshly charged battery in the plane, preferably the one you used to balance it. Check for smooth motor operation. Make sure the prop is on tight and turning in the right direction. If you are hand launching, launch it into the wind, at full throttle with a good solid level throw ( not up ) and get your plane out at least 50 feet before you touch any up elevator. Always hand launch into the wind and level. Now fly it up slowly and get it to height, at least 100 feet ( say double tree height where I live) and preferably higher. Get it well up wind from you. At no time do I want the plane over your head or behind you. Keep it at least 50 feet in front of you, upwind. No stunts today. Do this by making gentle turns around the field till you get it high and flying into the wind and going reasonably straight. Now, smoothly take the throttle back to HALF throttle. Be sure the plane is flying straight and level, and take your hands off the sticks and watch the plane. It should proceed fairly straight and either hold height or lose it in a graceful/gradual fashion. Unless this is a 3D aerobat, it should not be climbing! Visualize it as a small boat on a river of water. It will bob up and down a little, and shift left and right as the air currents and waves float by, but it should continue to fly. Let it float on the river of air. It will bob left and right as the waves of air come past but it should not dive, or snap left or right into a roll. The wind may push it into a gradual turn, let it, but it should continue to fly with little or no input from you. Resist the temptation to correct it unless it is going out of control. Let it fly! If this will not work, if the plane can not maintain flight without your constant input, your plane is out of trim. All your efforts to learn to fly it will be thwarted by this. You need to work on the balance and trim of the plane or it is going to behave badly. Land it, adjust surfaces and do it again. See how she flies. This is your "gold standard" for making sure the plane is right. Spend at least a couple of hours on this. Looks good? OK, move the CG slightly forward and do it again. Better? Or does it tend to dive now? Move it back slightly. Better? Or does it tend to climb and stall? You may get it right very quickly but be prepared to spend some time with this. I have spent 2-3 hours trimming till I was totally happy. Do it until the plane no longer needs your constant attention to fly. Your plane knows how to fly if you set it up right. It does not need you to fly it! How are you doing? Is the plane flying on its own? Good! Now! Do the same but turn the motor completely off. The plane should still fly in an unpowered glide. If it stalls immediately and starts to dive, power up and save it. You probably have too much up elevator trimmed into the tail. This will cause the plane to want to climb all the time. With the motor off, it can't climb, so it will stall and drop. The motor will mask this situation. That is why we are doing it in a glide now. You need to trim a little down into the elevator and try it again. To what extent it will glide depends on the plane but the Easy Star, T-hawk, EZ400, the e-starter, slow sticks, Magpie, Aerobirds, and other light wing loaded planes should be able to still fly straight and lose altitude in a graceful manner. Even if you are flying a high wing loading plane, you should still be able to do this. After all, the 5, 10, 20, 40+ pound glow and gas planes can be landed "dead stick" with no motor. Boeing 767s can be landed with the motors off. Your small electric should glide very well and practically land itself! Now that you have spent a day at the field trimming your plane, now that it can fly without you, now you can learn to fly your plane. Now it will behave as it should. This exercise may not seem like the fun you had planned for the day, but it will teach you more about your plane, how it flies and how you can fly it than anything else you will do. Trying to learn to fly a poorly trimmed plane is frustrating and typically hard on plane and pilot alike! When the plane is in a glide, you should still be able to exercise full control. The only thing you can't do is climb. The response may be sluggish as there is less air moving over the control surfaces, but you should still have control! When I started to fly gliders I learned more about flying electrics because I learned not to depend on the motor to power me out of trouble and to overcome a poorly balanced and poorly trimmed plane. Also during this trimming process you will convince yourself that you do not need to constantly interfere with the plane and thus you will tend to overcontol it less and less. The plane "knows" how to fly. Let it fly! This is what I am suggesting you do, for just a little while. Get that plane flying so well that you don't need the motor to fly it. Then, and only then, will you know that the problem is you and not a poorly trimmed, poorly balanced plane. At that point you can make progress and become master of the skies! I hope you find this helpful. Clear skies and safe flying! OTHER RESOURCES Forces in Flight <font color="#0000ff">http://adamone.rchomepage.com/index4.htm</font> Stability <font color="#0000ff">http://adamone.rchomepage.com/index5.htm</font> Stall and Spin <font color="#0000ff">http://adamone.rchomepage.com/index6.htm</font> Balancing <font color="#0000ff">http://www.rc-airplane-world.com/balancing-rc-airplanes.html</font></div> |
RE: Proper way to trim an a/c
Ed,
You are the man!!! That was one of the posts I referred to in my OP, low and behold it was one of yours.... :-) I can't wait to get my a/c out tomorrow and get them trimmed up properly. Thanks Again for all of your help and advice Rick |
RE: Proper way to trim an a/c
<font color="#00265e" size="2">Lnewqban</font>
The trim chart is also what I was looking for. I remembered seeing a version of that chart that helped with the balance of the a/c in various attitudes. I have printed a copy and I will be taking it along with me tomorrow. Thank you very very much for your info! Rick |
All times are GMT -8. The time now is 09:28 AM. |
Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.