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Center of Gravity (CG)
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You must set your CG before continuing. If you change the CG location of your plane, you will have to re-run the trimming steps to compensate.

Many pilots get very confused when thinking about CG. It doesn’t need to be that way, because it is really very basic.

1. For your first flight, set the CG where the plane manufacturer tells you to. Then throw the instructions away. The numbers they give you are to get you in the ballpark, but that is all they are good for. Period! I cannot count the number of pilots that obsess on the numbers and lose perspective of what is important; namely, we are trying to get the plane flying right. You don‘t measure that on the ground, but in the air. Once you get the plane flying, you are going to tell where to put the CG by the way the it acts.

2. Fly the plane around at about throttle, which is where you will be flying your level lines in competition. Trim it so it tracks absolutely level. (Be sure you have set your trim steps to 1 unit) Now roll the plane inverted and see how much push it takes on the elevator stick to hold level inverted flight.

A. If it takes stick travel or more, the plane is too nose heavy (CG to far forward). Land and move equipment aft to adjust the CG back. On a big plane it will take a lot of shift to alter CG. On a smaller plane, not so much. Other symptoms of nose heavy include:

- You cannot stall the airplane for a spin entry. It instead gently lowers its nose and descends without a “break” into a stall.

- You run out of elevator in the flare and find the plane nosing over, even with full aft stick.

- Snap rolls do not break.

B. If it takes no push to hold level flight, or if it climbs when you let go of the sticks, The you are tail heavy (to aft CG). CAREFULLY land! You need to move equipment forward to move the CG forward. Other symptoms of tail heavy include:

- The plane will not fly level. A single unit of trim is enough to go from climbing to descending.

- The plane seems to “dart” up and down so it is impossible to fly a smooth maneuver.

- Snap rolls are “wallowy”, with a very aggressive break. It is difficult to exit the snap precisely.

- During landing the plane flares itself, to the point of stalling if you do not physically push the nose back down.

3. The goal is to gradually move weight aft in the plane (move the CG aft) until the plane starts to demonstrate one or more of the tail -heavy symptoms. Then move it back forward until the symptom goes away and you are perfect!

Let’s move on to the next step.

 

On to Setting Elevator Travel

 

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