Do you have trouble getting your airplane to track straight and level at any speed? Does your airplane display odd or undesirable behaviors during simple or complex maneuvers? So many trim issues and thrust problems could be solved easily with such a simple device called an Incidence Meter. This item I feel should be in everyone's inventory for building and setting up airplanes. While the device itself is simple, there are incidence meters on the market that aren't what I would describe as "user friendly".

But what is "incidence" and why was it so important? Incidence is the angle of the airplane wing between the reference line (also called the datum line) on the plane's fuselage along its longitudinal axis and the wing's chord. The wing's chord refers to the wing's cross section from the center of the leading edge to the tip of the trailing edge. Just about all kits and properly designed scratch built plans will show this line. If you are building an ARF, you won't have access to this information, but generally it's a straight and level line off of the stabilizer. There are plenty of exceptions to this general rule of thumb so always check with the original set of plans for the correct information.

When I decided to build my first kit, I did a lot of research on how to build an airplane. Many master builders and seasoned veterans of building all stressed the importance of building the correct thrust into the firewall and having the correct incidence on the wings. My first incidence meter was a model that used a suspended laser pointer that projected its beam onto a chart that delineated the degrees of incidence. I found this device cumbersome and hard to use. For starters, you have to setup the device which requires you to level the airplane in order to zero out the device. If you accidentally bumped your airplane, you'd have to start over. I also found that I couldn't achieve the amount of precision I was wanting. After using this device a couple of times, I put it back into the box never to be used again.

The 4-in-1 Incidence Meter from Hanger 9 is my personal favorite. There are more advanced meters on the market, but they are substantially more money. The Hanger 9 meter is easy to read and simple to use. It will help with assembly and fixing trim issues with your airplane.I searched on for other incidence meters that were friendlier to use. I came across the Incidence Meter from Hanger 9 which had one overwhelmingly positive feature; it was completely digital. In its most basic form, it's a digital inclinometer. No longer did I have to spend an evening leveling the airplane before I could use the meter. It has a button marked "acquire" which will zero out the meter and can be used to establish a new zero degree point. The meter also came with a clamp that can attach the meter to your control surface so you can read the throws of your control surfaces measured in degrees.

The more I used this device, the more uses I found for it. For example, I was attempting to install a vertical fin on an ARF I as assembling. However, the airplane had a rounded fuselage and was proving difficult to make sure the vertical fin was exactly 90 degrees to the horizontal stabilizer. All I had to do was put the meter itself on the horizontal stabilizer, zero it, and then place it on the vertical fin. It would tell me within the nearest 1/10 of a degree accurate to 90 degrees. The unit is sensitive so try hard to not to induce a false reading by applying excessive pressure to the surface you are trying to measure.

Another use for an incidence meter is when you are setting up a plane for the first time and you need to zero out your control surfaces and make sure they are identical. One example would be making sure the right aileron is at the exact same angle as the left aileron in relation to the wing chord. Simply install the meter with the correct incidence measuring bar onto the wing (attached from the leading edge to the trailing edge of the aileron) and take a measurement, then you can carry over the meter to the other size of the wing and take another measurement. By comparing the two numbers, you can see if your ailerons are identical. Naturally, you need to ensure that the airplane itself doesn't rock back and forth. I like to assemble the plane and put it on the ground to make sure nothing moves before I start taking measurements. By taking these quick and simple measurements, I have been able to maiden airplanes that require very little trim adjustments. If I did everything correct, it should be pretty close to neutral from the beginning.

After a crash, its not uncommon for the wing to break the wing mount. When rebuilding the mount, it's important to make sure you aren't inducing too much incidence otherwise the plane just isn't going to fly correctly.

Some airplanes have straight firewalls but still require a certain amount of right thrust be built into the engine mount. Hopefully you have a set of plans that tell you the correct number of degrees of thrust you must build into your airplane. This task can be done in less than a minute with an incidence meter. Just take a zero degree measurement off the vertical fin and then rest the device on the motor shaft. By shimming the engine mount, you can build into your airplane the correct number of degrees of incidence.

Even though an incidence meter's primary function isn't of much use to ARF builders, I have found that it offers enough additional features and ease of use to justify its purchase. By referring to our flight trimming guide, you can test your airplane trims and use this precise device to make the minor adjustments that are needed to achieve flying nirvana.